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Biomedical subjects

Z J Sheng

Publications and source records attributed to Z J Sheng.

15 recordsLinked to original sources
PubMed1999

[Effect of chitosan membrane on tendon adhesion and healing].

OBJECTIVE: To investigate the effects of chitosan membrane on tendon adhesion and healing and obtain experimental data for clinical use in preventing postoperative tendon adhesion. METHODS: The long flexor tendon of 55 adult legborn hens were cut and sutured encapsulated by chitosan membrane. Movement and anti-tension capability of tendon were assessed at 2, 4, 6, 8 and 10 weeks after operation by SWD-10 type tendon stretcher. Tendon healing and adhesion were observed with light microscope. RESULTS: Tendon healing could be effected by chitosan membrane within 4 weeks, and tendon anti-tension strength was increased after 4 weeks. CONCLUSION: Chitiosan membrane possesses the following characteristics: no side effects, good permeability, resolvable, absorbable and selective inhibition the growth of fibroblast. It is a desirable biological material to prevent tendon adhesion.

Animals↗
PubMed1993

On two transposable elements from Bacillus stearothermophilus.

Two transposable elements, IS5376 and IS5377, were identified in the thermophile Bacillus stearothermophilus CU21 based upon the following criteria: (1) both were found to appear on different plasmids introduced into the same host CU21; (2) signals of homology were found between the genomic DNA of CU21 and each of them; (3) different numbers of Southern hybridization bands were found for the genomic DNA of different strains of B. stearothermophilus; and (4) characteristic inverted repeats at both ends and direct repeats of the target DNA adjacent to them were found for both IS5376 and IS5377. Two open reading frames (ORFs) were detected for IS5376 and one for IS5377. The putative coding products of the ORFs are homologous to those of known ISs from mesophiles and are considered to be transposases. The results of analyses of nucleotide sequence and the deduced amino acid sequence suggest that IS5376 is a member of the IS21 family and that IS5377 is a member of the IS4 family.

Amino Acid Sequence↗
PubMed1992

Molecular cloning and mapping of phenol degradation genes from Bacillus stearothermophilus FDTP-3 and their expression in Escherichia coli.

Two genes of the meta pathway of phenol degradation were cloned from a phenol-utilizing strain of Bacillus stearothermophilus and were mapped by subcloning and by use of a Tn5 insertion mutation. They code for phenol hydroxylase and catechol 2,3-dioxygenase, respectively. The gene encoding catechol 2,3-dioxygenase, which is more thermostable than catechol 2,3-dioxygenase encoded by the other gene, shares rather limited homology with that from Pseudomonas putida.

Catechol 2,3-Dioxygenase↗
PubMed1991

recA gene dependence of replication of the Escherichia coli chromosome initiated by plasmid pUC13 integrated at predetermined sites.

Plasmid pUC13 was used to clone DNA fragments of known sites from the chromosome of Escherichia coli. Each chimeric plasmid was introduced individually into the same dnaA46 mutant strain LC381 and suppressive integration (Sin) strains were selected. By means of cotransduction the null mutation recA56 was then introduced into each Sin strain and growth of each recA56 derivative at 42 degrees C was scored. Strains that failed to grow at 42 degrees C depended upon the recA gene for replication. Three factors were shown to limit the viability of LC381 harboring different chimeric plasmids and affect the degree of recA gene dependence of chromosome replication in the Sin strains at 42 degrees C. It is suggested that these three constraints are the consequence of the organization of the E. coli chromosome, particularly the unique ability of terC to retard the progression of replication forks. Two classes of hypotheses concerning the function of the recA gene are considered.

Chromosome Mapping↗
PubMed1991

[Through homologous recombination pathway recA gene takes part in chromosome replication of E. coli initiated by integrated plasmid].

We have reported in our previous paper that replication of E. coli chromosome initiated by the integrated F' plasmid depends on the recA gene. Here we report on work dealing with the role played by recA, recB, recC, lexA alleles in chromosome replication. Our results show that the recA gene takes part in chromosome replication through homologous recombination rather than SOS pathway and that Chi hot spot is not concerned with. They also show that the ATP-dependent dsDNA exonuclease activity of the RecBC enzyme has nothing to do with the recA gene in chromosome replication.

Bacterial Proteins↗
PubMed1991

[recA gene dependence of chromosome replication of Escherichia coli initiated by mini-F plasmids integrated at predetermined sites].

mini-F plasmids carrying particular chromosomal fragments were constructed. Through homologous recombination they were expected to integrate onto predetermined sites of the chromosome of dnaA46 strain LC381. Chromosome replication of suppressive integration (Sin) strains were recA dependent or independent according to the site of integration of the plasmid: chromosome replication of those with the plasmid integrated close to oriC were found to be recA dependent at 40 degrees C; those with the plasmid integrated between oriC and terC were recA dependent on rich medium but independent on minimal medium; those with the plasmid integrated close to terC were recA dependent even on minimal medium.

Chromosomes↗
PubMed1990

[Replication characteristics of plasmids and their dependence of recA gene for the initiation of Escherichia coli chromosome replication in the integrated state].

E. coli dnaA46 fails to grow and form colonies at 40 degrees C; integrated with plasmid enables it to grow at 40 degrees C or 42 degrees C. In a previous paper we reported that the replication of chromosome initiated by the integrated F' plasmid was recA gene dependent. In this paper we report further the behavior of 5 plasmids and 2 phages as to their dependence of recA gene in the integrated state. It was demonstrated that the dependence or independence of recA gene is not related to the direction of replication of the plasmids or phages in the free state. The hypothesis that the function of recA gene is to convert the unidirectionally replicating machinery in the free state to the bidirectionally replicating one in the integrated state is refuted accordingly.

Chromosomes, Bacterial↗
PubMed1990

[A novel type of phase variation regarding integrated and free states of plasmid pFDX163 in Bacillus stearothermophilus CU21].

pFDX1 is a recombinant plasmid which carries a foreign gene xylE. By selecting for kanamycin-resistant mutants of Bacillus stearothermophilus CU21(pFDX1) at higher temperature, a variant strain CU21-163 was obtained. This strain harbors a mutant plasmid pFDX163, which was formed by insertion of a 2.0kb H-fragment from the CU21 genome onto the plasmid pFDX1. pFDX163 was supposed to be integrated into the CU21 chromosome via homologous recombination of H-fragments. The CU21-163 strain consists of two cell types, i.e. y-cell and w-cell. The expression level of xylE gene in the former is higher than that in the latter. The progeny of a y-cell always contains some w-cells, while that of a w-cell contains y-cells. This is supposed to be due to a phase variation of CU21-163. Analysis on the amount of free and integrated plasmid DNA in different DNA samples of CU21-163 cells allows us to draw the conclusion that there are both free and integrated plasmids in the y-cells, whereas only integrated ones in the w-cells.

Blotting, Southern↗
PubMed1990

[Dependence of recA gene for the replication of chromosome of Escherichia coli initiated by the integrated mini-F plasmid carrying IS1 sequence].

We have reported the dependence of recA gene for the replication of chromosome of E. coli initiated by the F' plasmid but not the F plasmid. Mini-F plasmids with ISI sequence and origin of replication from F and F' plasmid have been constructed. 20% of the integrative suppression strains of these mini-F plasmids were found to be recA dependent, irrespective of the origin of replication (F or F' plasmid) and the direction of replication (uni- or bidirectional). The reported experimental results tend to suggest that the site of integration is of primary importance in the dependence vs independence of recA gene for the replication of the chromosome initiated by the integrated plasmid.

Base Sequence↗
PubMed1990

[Expression of xylE gene in Bacillus stearothermophilus].

Using the gene expression vector pFDC11 for Bacillus stearothermophilus CU21, a recombinant plasmid pFDX1 was constructed, which carries the Pseudomonas-derived xylE gene coding for Catechol 2,3-dioxygenase (CatO2ase). CatO2ase activity can be detected from CU21 (pFDX1) cells grown at 48 degrees C. This result indicates that the promoterless xylE gene can be expressed in a thermophilic host under the direction of a promoter from a thermophilic bacterium. By selecting Kmr mutants at elevated growth temperature, a segregant CU21-161 was obtained, the xylE gene expression of which at 55 degrees C and 60 degrees C was much higher than that of the parental strain. A method for CatO2ase assay with suspension of intact cells was also reported in this paper.

Catechol 2,3-Dioxygenase↗
PubMed1989

[Dependence of the recA gene for the replication of the bacterial chromosome initiated by the integrated F' plasmid in Escherichia coli].

Mutant strain dnaA46 of Escherichia coli can be integratively suppressed by the F' plasmid. Upon introducing the recA56 mutation through transduction the suppressive integration strain (Sin) becomes unable to grow at 40 degrees C. By means of experiments of marker transfer, acridine orange sensitivity test, F' curing and mini-chromosome transformation it is concluded that the F' plasmid is always in an integrated state in the Sin strains and that the initiation of the replication of the bacterial chromosome is carried on by the integrated F' plasmid. The biosynthesis of DNA and protein of the Sin recA+ and Sin recA- strains at different temperatures were compared. It is concluded from the experimental results that the recA gene functions at the level of DNA replication. The recA gene is known to be the key gene in DNA recombination and SOS repair of DNA damage. The works reported here throw some light on the understanding of the function of the recA gene.

Chromosomes, Bacterial↗
PubMed1989

[A low copy number mutant of pUC-derived plasmid].

A low copy number mutant of ColE1-like plasmid of Escherichia coli was reported in this paper. The recombinant plasmid pPGVT3 derived from the vector pUC4 was unstable in the E. coli host strain DF2145. No transformant could be obtained at 40 degrees C when DF2145 was transformed with pPGVT3. By in vitro mutagenesis of pPGVT3 plasmid DNA with hydroxylamine which induces point mutations, a mutant plasmid pPGVT3HA was obtained, which was stable in DE2145. The mutation site was localized within the pUC moiety of pPGVT3HA. The copy number of the mutated pUC vector and its derivatives were found to be reduced. The effect of low copy number mutation on the stability of the recombinant plasmids was discussed.

Escherichia coli↗
PubMedDate not supplied

Detection of HTLV-I antibodies and DNA in blood sample of a patient with myelopathy in Nigeria.

We describe a case of human T-lymphotropic virus type I associated myelopathy in a 50-year old woman in Nigeria. The patient presented with progressive loss of tone to the two lower limbs and later inability to walk. The HTLV-I antibody presence in the plasma collected from the patient was repeatedly detected by enzyme immunoassays (Abbott HTLV-I EIA and Coulter SELECT-HTLV I/II) and confirmed by Western blot technique. In addition, HTLV-I DNA was amplified from the genomic DNA isolated from the peripheral blood mononuclear cells of the patient by the polymerase chain reaction technique. This finding is significant being the first report of association of HTLV-I with myelopathy in Nigeria.

Blotting, Western↗