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Biomedical subjects

Q Yu

Publications and source records attributed to Q Yu.

At least 163 records · Page 9Linked to original sources
PubMed1999

[Humoral immune response in mice to hybrid nucleic acid vaccines containing Plasmodium falciparum merozoite surface protein 1 block 17-based gene].

AIM: To analyse the humoral immune response in mice to nucleic acid vaccines (VR1012/HG-MSP1-17 for intracellular expression or VR1012/TPA/HG-MSP-17 for secretion) containing Plasmodium falciparum merozoite surface protein 1 (MSP1) 17 block gene and gene fragment of several T cell epitopes from MSA1, MSA2, RESA, IL-1 and TT. METHODS: BALB/c or C57BL/6 mice received three times intramuscular immunization with 200 micrograms/100 microliters or 100 micrograms/100 microliters of VR1012/HG-MSP1-17 or VR1012/TPA/HG-MSP1-17 per mouse each time. Anti-HG or anti-MSP1-17 antibodies were monitored by indirect ELISA. RESULTS: BALB/c and C57BL/6 mice immunized with 100 micrograms/100 microliters of VR1012/HG-MSP1-17 per mouse raised significantly anti-HG and anti-MSP1-17 antibodies, but the levels of antibodies were not high. BALB/c mice immunized with 200 micrograms/100 microliters of VR1012/HG-MSP1-17 per mouse raised higher anti-HG antibodies but not anti-MSP1-17 antibodies. BALB/c mice immunized with 200 micrograms/100 microliters of VR1012/TPA/HG-MSP1-17 per mouse raised low level of anti-HG antibodies only. CONCLUSION: VR1012/HG-MSP1-17 is more immunogenic than VR1012/TPA/HG-MSP1-17.

Animals↗
PubMed1999

[Analyses of central serous chorioretinopathy from indocyanine green angiography].

PURPOSE: To compare and analyse the characters of Indocyanine Green Angiography (ICGA) and Fundus Fluorescein Angiography (FFA) in Central Serous Chorioretinopathy (CSCR) and explore its pathological significance. METHOD: 35 cases of CSCR were examed with Heidelberg Retina Angiography. Simultaneous images of ICGA and FFA were analysed. RESULTS: Among the 35 cases, 29(83%) revealed more lesions in ICGA than in FFA. The lesions appeared in FFA were all associated with ICGA changes. CONCLUSION: The increasing of choroid hyperpermeability is an early change, which causes the overlying RPE dysfunction and structural damage. Some points related to the laser and medical treatment to CSCR were also discussed.

Angiography↗
PubMed1999

[Analysis of surgical reconstructions of canal and middle ear via "direct entrance" approach in 53 ears with congenital aural atresia].

OBJECTIVE: To recognize the indication of surgical reconstruction via the "direct entrance" surgical approach (superoanterior surgical approach) for congenital atresia of the external acoustic canal and malformations of the middle ear. METHODS: A series of 53 ears operated on via the superoanterior surgical approach during 10 years from January 1988 to December 1997 was analyzed. RESULTS: The tympanic cavity was encountered without difficulty in 52 ears. Facial paralysis occurred postoperatively in one ear, which recovered after two months. The hearing improvement was observed in 45 ears (84.9%), of which 24 ears had hearing improvement greater than 30 dB and the air-bone conduction gap was within 15 dB (45.3%). A long-term (1-9 years) follow-up of 25 ears demonstrated that the hearing levels in 18 ears were kept unchanged. Postoperative stenosis of the canal occurred in one ear of a 2 years-old child. CONCLUSION: Based on the scanning images of the temporal bone by high-resolution computed tomography before the operation, the authors classified the bony structures of the paths of external acoustic canals into four types. Our results indicated that the selerotic and the diploetic paths of external acoustic cmeati could be indications for the "direct entrance" surgical approach, whereas the mixed type, either containing a little small cells or diploetic bone in sclerotic bone, might be suitable for this surgical approach also.

Adolescent↗
PubMed1999

[Diagnosis of skull base dieases using three dimensional computed tomography]

OBJECTIVE:To explore the value of three-dimensional (3D) computed tomography (CT) to diseases of the skull base.METHODS:Twenty-five cases with various skull base diseases were examined with 3D CT.All cases received surface shaded display (SSD) method for reconstruction and analysis of 3D reconstruction images in showing the change of skull base bones.RESULTS:In 4 cases with skull base fractures,3D CT demonstrated the fracture lines which were not showed by skull plain films,and provided more informations than those in axial scans.In 15 cases with skull base diseases and 6 cases with trigeminal neuralgia,3D CT helped plan the preoperative approach or the postoperative follow up evaluation,treatment. CONCLUSION:3D CT which based on two dimensional CT scan was very useful for skull baseimaging.

Journal Article↗
PubMed1999

[CT findings in the recurrent oral maxillofacial tumors eroding the central skull base]

OBJECTIVE:To domonstrate the CT manifestations of the recurrent oral maxillofacial tumors invading the middle skull base.METHODS:CT detections with axial (37 cases) and coronal (26 cases) scans were performed in thirty-seven patients who suffered from the recurrent oral maxillofacial tumors.All lesions were proven histopathologically.RESULTS:Four patterns of the central skull base erosion showing on CT images were encompassed:1.resorption of the outer cortical margin (5 cases);2.resorption of both outer and inner cortical laminae (24 cases);3.enlargement of the ovale foramen (3 cases);4.combined of sclerosis and resorption of the skull base (5 cases).The sphenoid greater wing involvement by the recurrent lesions was more frequently seen in our series (36 cases).Twenty four patients with the recurrent lesions were identified as following intracranial structures affected:the cavernous sinus (n=16),temporal lobe (n=15),and pituetary (n=1).CONCLUSION:It is believed that involvement of the intracranial structures is in close relationship with the aforementioned erosive patterns of the central skull base.The role of CT examination for evaluating the oral maxillofacial recurrent lesions invading the central skull base is very important.

Journal Article↗
PubMed1998

Structural organization of the human TOP2A and TOP2B genes.

Eucaryotic topoisomerase II is an essential nuclear enzyme involved in processes such as chromosome condensation, chromatid separation, and in the relief of torsional stress that occurs during DNA transcription and replication. In cells from vertebrate species, there are two forms of the enzyme, designated alpha and beta. Human topoisomerase IIalpha (TOP2A) is encoded by the TOP2A gene on chromosome 17q21-22, and human topoisomerase IIbeta (TOP2B) is encoded by the TOP2B gene on chromosome 3p24. The protein products of these two genes are important cellular targets of several drugs widely used in the treatment of many human cancers, and a variety of mutations in TOP2A have been associated with the development of drug resistance. In the present study, we have defined the intron-exon structures of TOP2A and TOP2B. TOP2A is approx. 30kb whereas TOP2B is at least 49kb. TOP2A and TOP2B contain 35 and 36 exons, respectively, and both genes contain a high proportion of class 0 introns. Alignment of the amino-acid sequences of the two proteins indicates that the intron-exon organization of the two genes is highly conserved, except for the regions encoding the extreme NH2 and COOH termini of the proteins. These findings suggest strongly that the vertebrate isoforms evolved by duplication of an ancestral gene. Mutations in TOP2A associated with drug resistance show clustering in exons 12, 13, 19-21 and 34-35. Knowledge of the genomic organization of TOP2A and TOP2B will be useful for detection of mutations in clinical samples from patients with drug-resistant malignant disease.

Amino Acid Sequence↗
PubMed1998

Methionine ligation strategy in the biomimetic synthesis of parathyroid hormones.

In biological systems, both proteolysis and aminolysis of amide bonds produce activated intermediates through acyl transfer reactions either inter- or intramolecularly. Protein splicing is an illustrative example that proceeds through a series of catalyzed acyl transfer reactions and culminates at an O- or S-acyl intermediate. This intermediate leads to an uncatalyzed acyl migration to form an amide bond in the spliced product. A ligation method mimicking the uncatalyzed final steps in protein splicing has been developed utilizing the acyl transfer amide-bond feature for the blockwise coupling of unprotected, free peptide segments at methionine (Met). The latent thiol moiety of Met can be exploited using homocysteine at the alpha-amino terminal position of a free peptide for transthioesterification with another free peptide containing an alpha-thioester to give an S-acyl intermediate. A subsequent, proximity-driven S- to N-acyl migration of this acyl intermediate spontaneously rearranges to form a homocysteinyl amide bond. S-methylation with excess p-nitrobenezensulfonate yields Met at the ligation site. The methionine ligation is selective and orthogonal, and is usually completed within 4 h when performed at slightly basis pH and under strongly reductive conditions. No side reactions due to acylation were observed with any other alpha-amines of both peptide segments as seen in the synthesis of parathyroid hormone peptides. Furthermore, cyclic peptide can also be obtained through the same strategy by placing both homocysteine at the amino terminus and the thioester at the carboxyl terminus in an unprotected peptide precursor. These biomimetic ligation strategies hold promise for engineering novel peptides and proteins.

Amides↗
PubMed1998

[Preparation of morchella liquid by submersed fermentation and and analysis of its nutrient contents].

Natural morchella esculenta fruits were collected and its spores were isolated to get pure mycelium. Morchella liquid was prepared by submersed fermentation technology. The quantitative analysis showed that the liquid is relatively high in nutrient contents and several kinds of other essential components. The nutrient contents of the liquid are as follows (g/L): carbohydrates 63.1, reduced saccharide 25.6, protein 8.3, dry material 104.7, minerals 1.5. There are also several high active micromaterials as follows: morchella lentinan 1.45 g/L, 10 kinds of essential and semiessential amino acid, 12 kinds of mineral (Fe, Zn Se, Cr, etc.). The amount of soluble proteins are high in the liquid(one wider zone and four narrow zones on electrophoresis with molecular weights of 31.0 kd, 97.4 kd, 66.2 kd and 52.9 kd respectively). The morchella liquid can be used as a new kind of base material for health foods and a flavoring agent.

Culture Media↗
PubMed1998

Cleavage of highly structured viral RNA molecules by combinatorial libraries of hairpin ribozymes. The most effective ribozymes are not predicted by substrate selection rules.

Combinatorial libraries of hairpin ribozymes representing all possible cleavage specificities (>10(5)) were used to evaluate all ribozyme cleavage sites within a large (4.2-kilobase) and highly structured viral mRNA, the 26 S subgenomic RNA of Sindbis virus. The combinatorial approach simultaneously accounts for target site structure and dynamics, together with ribozyme folding, and the sequences that result in a ribozyme-substrate complex with maximal activity. Primer extension was used to map and rank the relative activities of the ribozyme pool against individual sites and revealed two striking findings. First, only a small fraction of potential recognition sites are effectively cleaved (activity-selected sites). Second, nearly all of the most effectively cleaved sites deviated substantially from the established consensus selection rules for the hairpin ribozyme and were not predicted by examining the sequence, or through the use of computer-assisted predictions of RNA secondary structure. In vitro selection methods were used to isolate ribozymes with increased activity against substrates that deviate from the GUC consensus sequence. trans-Acting ribozymes targeting nine of the activity-selected sites were synthesized, together with ribozymes targeting four sites with a perfect match to the cleavage site consensus (sequence-selected sites). Activity-selected ribozymes have much higher cleavage activity against the long, structured RNA molecules than do sequence-selected ribozymes, although the latter are effective in cleaving oligoribonucleotides, as predicted. These results imply that, for Sindbis virus 26 S RNA, designing ribozymes based on matches to the consensus sequence may be an ineffective strategy.

Base Sequence↗
PubMed1998

Syntheses and anticholinesterase activities of (3aS)-N1, N8-bisnorphenserine, (3aS)-N1,N8-bisnorphysostigmine, their antipodal isomers, and other potential metabolites of phenserine.

Hydrolysis of the carbamate side chains in phenserine [(-)1] and physostigmine [(-)2] yields the metabolite (-)-eseroline (3), and the red dye rubreserine (4) on air oxidation of the former compound. Both compounds lacked anticholinesterase activity in concentrations up to 30 mM, which would be unachievable in vivo. A second group of potential metabolites of 1 and 2 are the N1,N8-bisnorcarbamates (-)9 and (-)10, prepared from (3aS)-N8-benzylnoresermethole (-)12 by the carbinolamine route. These entirely novel compounds proved to be highly potent inhibitors of acetylcholinesterase [(-)9] and of acetyl- and butyrylcholinesterase (AChE and BChE) [(-)10], respectively. To elucidate further the structure/anticholinesterase activity relationship of the described compounds, the antipodal isomers (3aR)-N1,N8-bisnorcarbamates (+)9 and (+)10 were likewise synthesized from (3aR)-N8-benzylnoresermethole (+)12 and assessed. The compounds possessed moderate but less potent anticholinesterase activity, with the same selectivity as their 3aS enantiomers. Finally, the anticholinesterase activities of intermediates N1, N8-bisnorbenzylcarbamates (-)18, (-) 19, (+)18, and (+)19, also novel compounds, were additionally measured. The 3aS enantiomers proved to be potent and selective inhibitors of BChE, particularly (-)19, whereas the antipodal isomers lacked activity.

Acetylcholinesterase↗
PubMed1998

Overexpression of the transmembrane tyrosine phosphatase LAR activates the caspase pathway and induces apoptosis.

BACKGROUND: The protein tyrosine phosphatase family comprises transmembrane receptor-like and cytosolic forms. Although the exact biological functions of these enzymes are largely unknown, they are believed to counter-balance the effects of protein tyrosine kinases. We have previously identified and characterized a mammalian transmembrane protein tyrosine phosphatase, called LAR (leukocyte common antigen related gene), whose expression is often associated with proliferating epithelial cells or epithelial progenitor cells. This study investigates the potential role of LAR in the regulation of cell growth and death in mammals. RESULTS: We overexpressed in mammalian cells in culture either the full-length wild-type LAR or a truncation mutant containing only the extracellular domain of the molecule, and found that whereas the truncated LAR could be readily overexpressed in various cell lines, cells overexpressing the wild-type LAR were negatively selected. Using an inducible expression system, we demonstrated that overexpression of the wild-type LAR, but not the truncated LAR, activated the caspase pathway directly and induced p53-independent apoptosis. CONCLUSIONS: Our data suggest that LAR might regulate cellular signals essential for cell survival. Overproduction of LAR may tilt the balance between the tyrosine phosphorylation and dephosphorylation of proteins whose activities are critical for cell survival, and therefore lead to cell death. In addition, our observations that overexpression of LAR induces cell death without affecting cell adhesion suggest that LAR may activate the caspase pathway and induce cell death directly. This work is the first example of the involvement of a receptor-like protein tyrosine phosphatase in cell-death control and provides the basis for searching for molecules and mechanisms linking signal transduction by protein tyrosine phosphorylation to the caspase-mediated cell-death pathway.

Animals↗
PubMed1998

Effects of halobenzenes on growth rate of fish (Gambusia affinis).

The growth rate reduction of mosquito fish (Gambusia affinis) fry was investigated with a range of sublethal exposure levels of four halobenzenes for 42 days. These compounds were found to produce growth rate reduction in mosquito fish fry at concentrations as low as 0.30, 0.18, 0.025, and 0.010 mumol liter-1 for 1,4-dibromobenzene, 1,2,3-trichlorobenzene, 1,2,4-tribomobenzene, and pentachlorobenzene, respectively. The aqueous exposure concentrations causing growth rate reduction of 50 and 10% (EC50 and EC10, respectively) for the halobenzenes were 0.067-3.4 and 0.0042-0.32 mumol liter-1, respectively. The EC50 and EC10 values are within the ranges of 5 to 8% and 0.1 to 3.9% of the LC50 values, respectively. The percentage of growth rate reduction relative to the LC50 could possibly be used to describe chronic toxicity effects of organic compounds with the aquatic organisms. The internal concentrations obtained from the analysis for the halobenzenes were generally consistent with the calculated internal concentrations. The lipid-based internal concentrations that gave 50 and 10% growth rate reductions were 8.3-27 and 0.5-1.6 mmol kg-1, respectively. These values have a more limited range than the corresponding external aqueous concentrations. The quantitative structure-activity relationships between the internal concentrations at 50 and 10% growth rate reduction and physicochemical parameters were found to be less satisfactory than those based on external aqueous concentrations.

Animals↗
PubMed1998

The lesions of the pterygopalatine and infratemporal spaces: Computed tomography evaluation.

OBJECTIVE: The purpose of this study was to categorize the computed tomography features of lesions affecting the pterygopalatine fossa and infratemporal fossa and thus aid in the diagnosis of these lesions. DESIGN: Eighty-six patients with lesions of the pterygopalatine fossa and infratemporal fossa were examined with computed tomography; the lesions were confirmed by both surgery and biopsy. The patients were divided into three groups: group I consisted of patients in whom the lesions had originated in one or both fossae; group II, of patients in whom the lesions originated in other oral and maxillofacial regions but showed extension into the pterygopalatine and infratemporal fossae; and group III, of patients in whom the lesions had multicentric origins. RESULTS: Of the 11 cases in group I, demarcation was confined to both fossae in 4 patients, and involvement of the adjacent structures was shown on computed tomography images in 7 patients. Involved structures included the maxillary sinus (4 sides), nasal cavity (3 sides), mandibular ramus (6 sides), buccal space (2 sides), base of the skull (5 sides), palate (3 sides), and parapharyngeal space (5 sides). In the 70 cases in group II, computed tomography images showed that lesions had invaded both fossae via following routes: (1) 40 lesions in the maxillary sinus had infiltrated posterolaterally into 26 pterygopalatine and 39 infratemporal fossae; (2) two nasal cavity and three nasopharynx tumors had infiltrated laterally or lateroanteriorly into five pterygopalatine and one infratemporal fossae; (3) lesions originating in mandibular rami (9 lesions), buccal regions (4 lesions), parapharyngeal spaces (1 lesion) and parotid glands (1 lesion) had intruded medially into 15 infratemporal fossae; (4) two temporal bone tumors had encroached inferiorly on two infratemporal fossae; (5) four palate tumors had led to involvement of three pterygopalatine and four infratemporal fossae; and (6) four inflammatory diseases of the facial spaces involved two pterygopalatine and four infratemporal fossae. Group III lesions (5 cases) affecting one pterygopalatine and five infratemporal fossae were hemangiomas; one was a malignant lymphoma. CONCLUSION: Group I lesions may involve the adjacent anatomic structures of both pterygopalatine and infratemporal fossae in every direction. Group II lesions that correspond to the various origins of the maxillofacial region have different pathways of infiltration into the pterygopalatine or infratemporal fossae. Computed tomography examination is very important in the evaluation of lesions involving the pterygopalatine and infratemporal fossae.

Adolescent↗
PubMed1998

Detection of Borrelia burgdorferi from ticks (Acari) in Hebei Province, China.

From May 1992 to August 1993, 1,196 ticks were collected by flagging vegetation and from domestic animals in Chengde, Zhangjiakou, Shijiazhuang, and Handan districts of Hebei Province. Of those ticks collected, 954 were Haemaphysalis japonicum Warburton and H. longicornis Neumann, 205 were Ixodes persulcatus Schulze, and 37 were Dermacentor silvarum Olenev. Four strains of Borrelia burgdorferi were isolated from 135 I. persulcatus collected in Weichang and Zhuolu counties. Three of 574 Haemaphysalis spp. (collected in Laishui, Pingshan, and Xinglong counties) were positive for B. burgdorferi by direct immunofluorescent assay. One of 24 H. japonicum and 1 of 1 I. persulcatus (collected in Zhuolu) were positive for B. burgdorferi by polymerase chain reaction. This is the 1st report of a B. burgdorferi isolation from H. japonicum.

Animals↗
PubMed1998

Preferential completion of human immunodeficiency virus type 1 proviruses initiated with tRNA3Lys rather than tRNA1,2Lys.

All retroviral genomes contain a nucleotide sequence designated as the primer binding site (PBS) which is complementary to the tRNA used for initiation of reverse transcription. For human immunodeficiency virus type 1 (HIV-1), all naturally occurring genomes have a PBS complementary to tRNA3Lys. However, within HIV-1 virions, there are approximately equal amounts of tRNA1Lys, tRNA2Lys, and tRNA3Lys. We have used an endogenous reverse transcription-PCR technique specific for the tRNA species within isolated HIV-1 virions to demonstrate that in addition to tRNA3Lys, tRNA1Lys and tRNA2Lys could be used for initiation of HIV-1 reverse transcription. Using a single-round infection assay which employed an HIV-1 genome with a gpt gene encoding xanthine-guanine phosphoribosyl transferase in place of the env gene, we generated cell lines resistant to mycophenolic acid. Analysis of the U5-PBS from single-cell clones revealed PBS complementary to tRNA3Lys, not tRNA1Lys or tRNA2Lys. A mutant HIV-1 genome was then created which would favor the completion of reverse transcription with tRNA1,2Lys. Using this provirus in the complementation system, we again found only genomes with a PBS complementary to tRNA3Lys from proviral DNA isolated from gpt-resistant single-cell colonies. Finally, infection of cells with a mutant HIV genome with a PBS complementary to tRNA1,2Lys resulted in gpt- resistant cell colonies which contained integrated provirions with a PBS complementary to tRNA1,2Lys. The results of these studies suggest that the selection of tRNA3Lys for initiation of HIV-1 reverse transcription occurs both at the initiation and at a postinitiation step in reverse transcription prior to integration of the proviral DNA.

Base Sequence↗
PubMed1998

Mutations in the primer grip of human immunodeficiency virus type 1 reverse transcriptase impair proviral DNA synthesis and virion maturation.

This report describes the effects of mutating highly conserved residues in the primer grip domain of human immunodeficiency virus type 1 reverse transcriptase (RT) on virus formation and infectivity. Among a series of RT mutant viruses, three (M230A, L234D, and W239A) were found to be noninfectious or very poorly infectious. Our data indicate that these mutations in RT caused severe defects in proviral DNA synthesis. Interestingly, assembly and maturation of mutant virus M230A were similar to those of the wild type, while mutants L234D and W239A showed impaired maturation. The immature morphology of RT mutants L234D and W239A is due at least in part to premature cleavage of the gag-pol precursor, prior to virion budding, indicating that intracellular stability of Pr160(gag-pol) is of key importance during virus assembly.

Amino Acid Sequence↗