Biomedical subjects

Q Jin

Publications and source records attributed to Q Jin.

At least 19 recordsLinked to original sources

PubMed2005

Current concepts in periodontal bioengineering.

Repair of tooth supporting alveolar bone defects caused by periodontal and peri-implant tissue destruction is a major goal of reconstructive therapy. Oral and craniofacial tissue engineering has been achieved with limited success by the utilization of a variety of approaches such as cell-occlusive barrier membranes, bone substitutes and autogenous block grafting techniques. Signaling molecules such as growth factors have been used to restore lost tooth support because of damage by periodontal disease or trauma. This paper will review emerging periodontal therapies in the areas of materials science, growth factor biology and cell/gene therapy. Several different polymer delivery systems that aid in the targeting of proteins, genes and cells to periodontal and peri-implant defects will be highlighted. Results from preclinical and clinical trials will be reviewed using the topical application of bone morphogenetic proteins (BMP-2 and BMP-7) and platelet-derived growth factor-BB (PDGF) for periodontal and peri-implant regeneration. The paper concludes with recent research on the use of ex vivo and in vivo gene delivery strategies via gene therapy vectors encoding growth promoting and inhibiting molecules (PDGF, BMP, noggin and others) to regenerate periodontal structures including bone, periodontal ligament and cementum.

Animals↗

PubMed2002

[The hemolytic site of the basic phospholipase A(2) from Agkistrodon halys pallas].

The gene of the basic phospholipase A(2) from Agkistrodon halys Pallas (BPLA(2) )was mutated site-directedly by polymerase chain reaction (PCR) and the residue Arg(34) of the encloding protein was substituted by Glu and Gln respectively. The mutant gene has been cloned into the expression vector pBLMVL2 and has been expressed in E.coli RR1 effectively. The protein was produced as insoluble inclusion bodies. After partial purification, the inclusion bodies were denatured and renatured into active form, and the renatured recombinant protein was purified by gel-filtration. The expression product has the same enzymatic activity as the denatured-refolded BPLA(2) and its hemolytic activity dropped distinctly, which suggest that the basic residue Arg(34) of BPLA(2) is a crucial amino acid residue during the process of hemolysis.

Agkistrodon↗

PubMed2001

Role of the Hrp pilus in type III protein secretion in Pseudomonas syringae.

Bacterial surface appendages called pili and needle-like filaments are associated with protein and/or DNA transfer to recipient plant, human, or bacterial cells during pathogenesis or conjugation. Although it has long been suspected that pili function as a conduit for protein or DNA transfer, direct evidence has been lacking. The Hrp pilus of Pseudomonas syringae is assembled by the type III secretion system. We used an in situ immunogold labeling procedure to visualize the extrusion of an effector protein, AvrPto, from the tip of the Hrp pilus, providing direct evidence that a bacterial pilus can function as a conduit for protein delivery.

Antibodies, Bacterial↗

PubMed2001

Catalytic asymmetric allylic C-H activation as a surrogate of the asymmetric Claisen rearrangement.

[reaction: see text]. Tetrakis[N-[4-dodecylphenyl)sulfonyl]-(S)-prolinato]-dirhodium [Rh2(S-DOSP)4] catalyzed decomposition of methyl aryldiazoacetates in the presence of alkenes results in allylic C-H activation by means of a rhodium-carbene induced C-H insertion. The resulting gamma,delta-unsaturated esters are equivalent to products that would be traditionally obtained from an asymmetric Claisen rearrangement. Highly regio- and enantioselective C-H insertions can be achieved, and in certain cases, good diastereocontrol is also possible.

Journal Article↗

PubMed2001

Total syntheses of thiocoraline and BE-22179 and assessment of their DNA binding and biological properties.

Full details of the total syntheses of thiocoraline (1) and BE-22179 (2), C(2) symmetric bicyclic octadepsipeptides possessing two pendant 3-hydroxyquinoline chromophores, are described in which their relative and absolute stereochemistry were established. Key elements of the approach include the late-stage introduction of the chromophore, symmetrical tetrapeptide coupling, macrocyclization of the 26-membered octadepsipeptide conducted at the single secondary amide site following disulfide formation, and a convergent assemblage of the tetradepsipeptide with introduction of the labile thiol ester linkage in the final coupling reaction under near racemization free conditions. By virtue of the late-stage introduction of the chromophore and despite the challenges this imposes on the synthesis, this approach provides ready access to a range of key chromophore analogues. Thiocoraline and BE-22179 were shown to bind to DNA by high-affinity bisintercalation analogous to echinomycin, but with little or no perceptible sequence selectivity. Both 1 and 2 were found to exhibit exceptional cytotoxic activity (IC(50) = 200 and 400 pM, respectively, L1210 cell line) comparable to echinomycin and one analogue, which bears the luzopeptin chromophore, was also found to be a potent cytotoxic agent.

Animals↗

PubMed2001

A simple flow-injection on-line clean-up system for microwave plasma-torch atomic emission spectrometry.

A simple flow injection (FI) on-line clean-up system has been developed for microwave plasma-torch atomic emission spectrometry (MPT-AES). A non-selective strongly acidic cation-exchange resin was used to achieve the goal of "on-line clean-up". Ag and Zr, which form halogen-complex anions in halide acid media, and Cr, Mo, and P, which exist as acid group anions or acids (neutral) in acidic solution, were determined and the interfering matrix cations were removed on-line. Satisfactory analytical results were obtained from some practical samples by use of this procedure.

Journal Article↗

PubMed2001

Visualization of secreted Hrp and Avr proteins along the Hrp pilus during type III secretion in Erwinia amylovora and Pseudomonas syringae.

Pili are required for protein and/or DNA transfer from bacteria to recipient plant or bacterial cells, based on genetic evidence. However, it has never been shown directly that the effector proteins or DNA are localized along or inside the pili in situ. Failure to visualize an association of effector proteins/DNA with pili is the central issue in the debate regarding the exact function of pili in protein and DNA transfer. In this study, a newly developed in situ immunogold labelling procedure enabled visualization of the specific localization of type III effector proteins of Erwinia amylovora and Pseudomonas syringae pv. tomato along the Hrp pilus, but not along the flagellum or randomly in the intercellular space. In contrast, PelE, a pectate lyase secreted via the type II protein secretion system, was not associated with the Hrp pilus. These results provide direct evidence that type III secretion occurs only at the site of Hrp pilus assembly and that the Hrp pilus guides the transfer of effector proteins outside the bacterial cell, favouring the 'conduit/guiding filament' model.

Animals↗

PubMed2001

The Saccharomyces cerevisiae MUM2 gene interacts with the DNA replication machinery and is required for meiotic levels of double strand breaks.

The Saccharomyces cerevisiae MUM2 gene is essential for meiotic, but not mitotic, DNA replication and thus sporulation. Genetic interactions between MUM2 and a component of the origin recognition complex and polymerase alpha-primase suggest that MUM2 influences the function of the DNA replication machinery. Early meiotic gene expression is induced to a much greater extent in mum2 cells than in meiotic cells treated with the DNA synthesis inhibitor hydroxyurea. This result indicates that the mum2 meiotic arrest is downstream of the arrest induced by hydroxyurea and suggests that DNA synthesis is initiated in the mutant. Genetic analyses indicate that the recombination that occurs in mum2 mutants is dependent on the normal recombination machinery and on synaptonemal complex components and therefore is not a consequence of lesions created by incompletely replicated DNA. Both meiotic ectopic and allelic recombination are similarly reduced in the mum2 mutant, and the levels are consistent with the levels of meiosis-specific DSBs that are generated. Cytological analyses of mum2 mutants show that chromosome pairing and synapsis occur, although at reduced levels compared to wild type. Given the near-wild-type levels of meiotic gene expression, pairing, and synapsis, we suggest that the reduction in DNA replication is directly responsible for the reduced level of DSBs and meiotic recombination.

Alleles↗

PubMed2001

Use of monozygotic twins in search for breast cancer susceptibility loci.

We have used Swedish monozygotic twins concordant for breast cancer to study genetic changes associated with the development of breast cancer. Because loss of heterozygosity (LOH) at a specific genomic region may reflect the presence of a tumour suppressor gene, loss of the same allele in both of the twins concordant for breast cancer may pinpoint a tumour suppressor gene that confers a strong predisposition to breast cancer. DNA samples extracted from the matched tumour and normal tissues of nine twin pairs were analysed for allelic imbalance using a set of microsatellite markers on chromosomes 1, 13, 16 and 17, containing loci with known tumour suppressor genes. The two main regions, where more twin pairs than expected had lost the same allele, were located at 16qtel', including markers D16S393, D16S305 and D16S413, and at 17p13, distal to the p53 locus. Our results show that the monozygotic twin model can be used to suggest candidate regions of potential tumour suppressor genes, even with a limited number of twin pairs.

Adult↗

PubMed2001

[Survey of 3-monochloropropane-1,2-diol in soy sauce and similar products].

A survey of 3-monochloropropane-1,2-diol (3-MCPD) in soy sauce and other similar products available in China has been completed. Thirty samples of soy, oyster sauce and other sauces were purchased from six supermarkets in Beijing during March and April 2000 and analysed using a validated method of analysis by capillary gas chromatography with mass spectrometric detection. The UK Food Advisory Committee (FAC) has advised a level of 0.01 mg/kg for 3-MCPD. Following reports that high levels had been detected in some brands of soy sauce in China. 3-MCPD was undetectable with a detection limit of 0.01 mg/kg in 15 of the 30 samples analyzed in the survey, with a further 4 samples (13.3%) containing very low levels of between 0.01 and 0.02 mg/kg. However, 5 samples (16.7%) contained 3-MCPD levels above 1 mg/kg.

Chemosterilants↗

PubMed2001

Geometry of carriers controlling phenotypic expression in BMP-induced osteogenesis and chondrogenesis.

BACKGROUND: The effect of the geometry of extracellular matrices on bone morphogenetic protein (BMP)-induced osteogenesis has not been systematically studied. Geometry is crucially important for the scaffold in bone and joint tissue engineering. The purpose of this study was to elucidate principles of geometry of matrices in designing new scaffolds and matrices for use in reconstruction of bone and joints. METHODS: More than ten biomaterials with different geometries, including a unique device of honeycomb-shaped hydroxyapatite, were combined with BMPs of recombinant (rhBMP-2) or natural bovine origin (S300 BMP cocktail) and implanted subcutaneously into 4-week-old Wistar-King rats. The implanted pellets were removed at 1-4 weeks and analyzed for bone and cartilage formation by histological and biochemical methods. RESULTS: BMP-induced bone and cartilage induction was highly dependent on the geometric properties of the carrier. Some carriers such as porous particles or blocks of hydroxyapatite induced osteogenesis directly, without detectable chondrogenesis, whereas other carriers such as fibrous glass membrane induced cartilage exclusively. Still other carriers induced mostly cartilage followed by bone formation. Solid particles of hydroxyapatite and fibrous glass membrane with too tight a meshwork did not induce bone or cartilage. The optimal pore size for bone-forming efficacy in porous blocks of hydroxyapatite was a diameter of 300-400 microm. In straight tunnel structures with various diameters in honeycomb-shaped hydroxyapatite, tunnels with smaller diameters (90-120 microm) induced cartilage followed by bone formation, whereas those with larger diameters (350 microm) induced bone formation directly within the tunnels. CONCLUSIONS: BMP carriers were classified into three types: bone-inducing, cartilage-inducing, and cartilage-bone-inducing. From the analysis of causative factors inducing osteogenesis and chondrogenesis in the BMP system, we concluded that the geometry of the carrier is crucially important and vasculature-inducing geometry should be considered in designing effective scaffolds for bone formation. We propose a classification of geometry of the artificial extracellular matrices that is useful for designing a scaffold for tissue engineering of bone and related tissues. CLINICAL RELEVANCE: Conventional requisites of the BMP carriers for clinical use have mainly concerned the affinities of carriers with cells and biomolecules and their mechanical strength. The vasculature-inducing geometry of carriers adds a new criterion in designing systems for effective bone and joint reconstruction. The geometries of porous structures-their sizes, continuity, and straightness as verified by hydroxyapatite in this study-will be applicable for other biomaterials for clinical reconstruction therapy.

Animals↗

PubMed2001

[Early postoperative complications of choledochal cyst excision and reconstruction of biliary tract].

OBJECTIVE: To study the early postoperative complications of choledochal cyst excision with reconstruction of the biliary tract. METHODS: In last 10 years, 173 patients aged from 27 days to 14 years (mean = 2.4 years) were operated on with procedures of choledochal cyst excision and biliary tract reconstruction by jejunointerposition between the liver hilum and duodenum or Roux-en-Y hepaticojejunostomy in our hospital. Amongst these 173 patients, 16 were found to suffer from postoperative complications. Therefore, their clinical data were retrospectively analyzed, and the prevention and treatment of the early postoperative complications discussed. RESULTS: The morbidity of early postoperative complications was 9.3% (16/173). The early complications included biliary leakage in 10 patients, wound dehiscence of abdominal wall in 3, hepatic failure in 1, pancreatic fistula in 1, and postoperative enteric intussusception in 1. The morbidity of early postoperative complications in infants younger than 1-year old was significantly higher than that in children(chi 2 = 15.78, P < 0.01). However, there was no significant difference in the morbidity of early postoperative complications between patients undergoing biliary tract reconstruction by jejunal segment interposition and those undergoing that by Roux-en-Y hepaticojejunostomy (chi 2 = 0.07, P > 0.05). The total mortality in all the operated patients was 2.3% (4/173). Three patients died from biliary leakage and 1 from postoperative hepatic failure. CONCLUSIONS: Biliary leakage, wound dehiscence of abdominal wall and hepatic failure are major early postoperative complications. The morbidity in infants younger than 1-year old is higher than in children. The preoperative treatment of biliary tract infection, hypohepatia, and surgical skills during operation should be emphasized. Reoperation for biliary leakage should not be delayed and mycotic cholangitis after biliary leakage needs more attention. Tension suture in the fascial space of the abdominal wall is useful for the prevention and treatment of abdominal wall dehiscence.

Adolescent↗

PubMed2001

[Characterization of rpoB mutation in rifampin - resistant clinical Mycobacterium tuberculosis isolates from China].

OBJECTIVE: To elucidate the characterization of rpoB mutation in rifampin - resistant clinical isolates of Mycobacterium tuberculosis isolates from China. METHODS: 588 bp DNA fragment of rpoB gene including 81 bp code region (rifampin resistance determination region, RRDR) was sequenced. 242 strains of Mycobacterium tuberculosis, including 193 rifampin - resistant strains and 46 rifampin - susceptible strains and 3 artificially induced rifampin - resistant strains were sequenced. RESULTS: 89.1% (172/193) rifampin - resistant strains had rpoB gene mutations in RRDR, no mutation was found in rifampin - susceptible strains. 46.1% rifampin - resistant strains had mutations located at 531-Ser; 17.1% strains had mutations located at 526-His; Combinative mutation rate was 12.4%; 4 strains had synonymous mutations; No deletion or insertion mutation was found among all strains. High level rifampin resistant strains (250 microgram/ml rifampin resistant) had higher mutation frequency at 531 - Ser than low level rifampin resistant strains (50 microgram/ml rifampin resistant) (P < 0.05). CONCLUSIONS: About 90% rifampin resistant clinical strains of Mycobacterium tuberculosis from China had rpoB mutations; 531-Ser and 526 - His were the most common positions to be substituted, the added mutation rate was about 46%; High level rifampin resistant strains had a higher frequency of 531-Ser mutation than low level rifampin resistant strains; No insertion or deletion mutation was found in these specimens; DNA sequencing is significant in drug choosing for tuberculosis treatment.

Antibiotics, Antitubercular↗

PubMed2001

[Determination of Pd, Pt and Au by microwave plasma torch atomic emission spectrometry using an on-line clean-up].

In this paper, in the presence of Li+, Na+, K+, Ca2+ and Mg2+, determinations of Pd, Pt and Au by microwave plasma torch atomic emission spectrometry (MPT-AES) using an on-line clean-up were studied. It was shown from the experiments that these interfering matrix elements might be removed with the strong acidic cation exchange resin. The method was applied to the analysis of some practical samples and the results obtained were satisfactory.

Cation Exchange Resins↗

PubMed2000

Single nucleotide polymorphism analyses of the human proliferating cell nuclear antigen (pCNA) and flap endonuclease (FEN1) genes.

The products of proliferating cell nuclear antigen (PCNA) and flap endonuclease (FEN1) genes are multifunctional proteins that are involved in DNA replication and damage repair. Yeast models suggest association of mutant forms of PCNA and FEN1 with genomic instability. In our study, we have determined the single nucleotide polymorphisms in human PCNA and FEN1 genes. We sequenced the coding region and adjacent noncoding region of both the PCNA and FEN1 genes in 120 alleles (60 individuals). In the PCNA gene, we detected 9 sequence variants with Hardy-Weinberg allele frequency ranging from 0.008 to 0.088. No polymorphism was detected in the FEN1 gene. The sequence variants in the PCNA gene included 7 intronic single nucleotide polymorphisms (SNP) and 2 synonymous exonic SNPs. All the intronic SNPs were located in introns 1 and 4, which contain several regulatory elements involved in the control of PCNA gene expression. Six of the 7 intronic SNPs showed complete linkage disequilibrium. We confirmed this allelic linkage disequilibrium by allele-specific PCR sequencing. We genotyped 117 additional individuals belonging to 3 population subgroups using the PCR-RFLP method. Finally, to see if the detected polymorphisms are associated with any cancer type, we genotyped cases with melanomas (37 cases), breast cancers (118 cases) and lung cancers (100 cases). We did not find statistical difference in frequency of polymorphism in any cancer type compared with healthy controls, although in breast cancer the frequency was low. Our results suggest that the coding regions of the PCNA and FEN1 genes are highly conserved when compared with other DNA repair genes. The potential of some of the detected intronic polymorphisms to effect regulation of the PCNA gene expression remains to be determined.

Alleles↗

PubMed2000

Design, synthesis, and biological evaluation of fluoronitrophenyl substituted folate analogues as potential inhibitors of GAR transformylase and AICAR transformylase.

The examination results of a novel series of potential inhibitors of glycinamide ribonucleotide transformylase (GAR Tfase) and aminoimidazole carboxamide transformylase (AICAR Tfase) are reported. These agents incorporate an electrophilic fluoronitrophenyl group that can potentially react with an active site nucleophile or the substrate GAR/AICAR amine via nucleophilic aromatic substitution.

Animals↗

PubMed2000

Synthesis and evaluation of 1,2,8, 8a-Tetrahydrocyclopropa[c]pyrrolo[3,2-e]indol-4(5H)-one, the parent alkylation subunit of CC-1065 and the duocarmycins: impact of the alkylation subunit substituents and its implications for DNA alkylation catalysis.

The synthesis of 1,2,8,8a-tetrahydrocyclopropa[c]pyrrolo[3, 2-e]indol-4(5H)-one (CPI), the parent CC-1065 and duocarmycin SA alkylation subunit, is detailed. The parent CPI alkylation subunit lacks the C7 methyl substituent of the CC-1065 alkylation subunit and the C6 methoxycarbonyl group of duocarmycin SA, and their examination permitted the establishment of the impact of these natural product substituents. The studies revealed a CPI stability comparable to the CC-1065 alkylation subunit but which was 6x more reactive than the (+)-duocarmycin SA alkylation subunit, and it displayed the inherent reaction regioselectivity (4:1) of the natural products. The single-crystal X-ray structure of (+)-N-BOC-CPI depicts a near identical stereoelectronic alignment of the cyclopropane accounting for the identical reaction regioselectivity and a slightly diminished vinylogous amide conjugation relative to (+)-N-BOC-DSA suggesting that the stability distinctions stem in part from this difference in the vinylogous amide as well as alterations in the electronic nature of the fused pyrrole. Establishment of the DNA binding properties revealed that the CPI-based agents retain the identical DNA alkylation selectivities of the natural products. More importantly, the C6 methoxycarbonyl group of duocarmycin SA was found to increase the rate (12-13x) and efficiency (10x) of DNA alkylation despite its intrinsic lower reactivity while the CC-1065 C7 methyl group was found to slow the DNA alkylation rate (4x) and lower the alkylation efficiency (ca. 4x). The greater DNA alkylation rate and efficiency for duocarmycin SA and related analogues containing the C6 methoxycarbonyl is proposed to be derived from the extended length that the rigid C6 methoxycarbonyl provides and the resulting increase in the DNA binding-induced conformational change which serves to deconjugate the vinylogous amide and activate the alkylation subunit for nucleophilic attack. The diminished properties resulting from the CC-1065 C7 methyl group may be attributed to the steric impediment this substituent introduces to DNA minor groove binding and alkylation. Consistent with this behavior, the duocarmycin SA C6 methoxycarbonyl group increases biological potency while the CC-1065 C7 methyl group diminishes it.

Alkylating Agents↗

PubMed2000

Total synthesis of ningalin B utilizing a heterocyclic azadiene Diels-Alder reaction and discovery of a new class of potent multidrug resistant (MDR) reversal agents.

A concise, efficient approach to the total synthesis of ningalin B (1) based on a heterocyclic azadiene Diels-Alder strategy (1,2,4,5-tetrazine-->1,2,-diazine-->pyrrole) ideally suited for construction of the densely functionalized pyrrole core found in the natural product is detailed. Examination of the natural product and a number of synthetic intermediates revealed that while lacking inherent cytotoxic activity, many reverse the multidrug-resistant (MDR) phenotype, resensitizing a human colon cancer cell line (HCT116/VM46) to vinblastine and doxorubicin at lower doses than the prototypical agent verapamil.

Animals↗