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Biomedical subjects

T Zhang

Publications and source records attributed to T Zhang.

At least 361 records · Page 20Linked to original sources
PubMed1994

Persistence of type-specific human papillomavirus infection among cytologically normal women.

Determinants of genital human papillomavirus (HPV) persistence in 393 women initially cytologically normal were investigated by testing them for HPV DNA twice over a median interval of 14.9 months. At each visit, interview information was obtained and a cervicovaginal lavage sample was collected for polymerase chain reaction-based HPV testing. Twenty-six percent of the women were HPV-positive at the first sampling. Data on HPV type was available for 86 HPV-positive women (84%); 35 of these women (41%) had persistent type-specific HPV detection. Persistence decreased with time between samplings. Women aged > or = 30 years had a higher percentage of persistence (65%) than those < or = 24 years (32%, P = .02). The percentage of persistence was higher among women infected with HPV types known to be cancer-associated (45%) than among those infected with other types (24%, P = .11). These findings were independent of each other and of timing between samplings. Although based on a prevalent cohort, these results are concordant with previous suggestions that HPV infection is usually transient and that cervical cancer may arise from within the subset of women with persistent HPV infection.

Adolescent↗
PubMed1994

Antibodies to the serine rich Entamoeba histolytica protein (SREHP) prevent amoebic liver abscess in severe combined immunodeficient (SCID) mice.

Amoebic liver abscess caused by Entamoeba histolytica is a major cause of morbidity and mortality worldwide. We used mice with severe combined immunodeficiency (SCID mice) to study the role of antibody in protection from amoebic liver abscess, and to identify protective antigens of E. histolytica. Antisera to recombinant versions of two major surface antigens of E. histolytica, the serine rich E. histolytica protein (SREHP) and the 170 kDa adhesin were used in this study. We found that 100% of SCID mice passively immunized with antiserum to the recombinant SREHP molecule were protected from developing amoebic liver abscess after intrahepatic challenge with virulent E. histolytica trophozoites. In contrast, preimmune serum, antiserum to a portion of the 170 kDa adhesin, and antiserum to the trpE fusion partner of SREHP did not protect SCID mice from amoebic liver abscess. Our study demonstrates that antibodies to a recombinant version of the amoebic SREHP molecule can protect against amoebic liver abscess, and suggest the recombinant SREHP molecule should be considered as a possible vaccine candidate to prevent amoebic liver abscess.

Animals↗
PubMed1994

Protection of gerbils from amebic liver abscess by immunization with a recombinant Entamoeba histolytica antigen.

Amebiasis, infection by the intestinal protozoan parasite Entamoeba histolytica, is a leading parasitic cause of death. As a step in the development of a recombinant antigen vaccine to prevent E. histolytica infection, we looked at the ability of a recombinant version of the serine-rich E. histolytica protein (SREHP) to elicit a protective immune response against invasive amebic disease. Gerbils, a standard model for amebic liver abscess, were immunized with either a recombinant SREHP/maltose-binding protein (MBP) fusion, recombinant MBP alone, or phosphate-buffered saline (PBS), all combined with complete Freund's adjuvant. In the first trial (group 1), gerbils received a primary and two booster immunizations intraperitoneally; in the second trial (group 2), gerbils were immunized by a single intradermal injection. SREHP/MBP-immunized gerbils in both groups produced antibody to native SHEHP and developed delayed-type hypersensitivity responses to recombinant SREHP. All gerbils were challenged by an intrahepatic injection with 5 x 10(4) virulent E. histolytica HM1-IMSS trophozoites. Complete protection from amebic liver abscess was seen in 64% of the SHEHP/MBP-immunized gerbils in group 1 and in 100% of the SREHP/MBP-immunized gerbils in group 2. There was no protection observed in MBP- or PBS-immunized gerbils in either group. Our results indicate that the SREHP molecule has potential as a vaccine to prevent amebic infection and demonstrate that successful vaccination of animals with recombinant E. histolytica antigen vaccines is possible.

Animals↗
PubMed1994

Protection of gerbils from amebic liver abscess by immunization with a recombinant protein derived from the 170-kilodalton surface adhesin of Entamoeba histolytica.

The protozoan parasite Entamoeba histolytica causes extensive morbidity and mortality worldwide through intestinal infection and amebic liver abscess. Here we show that vaccination of gerbils, a standard model for amebic liver abscess, with recombinant proteins derived from the 170-kDa galactose-binding adhesin of E. histolytica and the serine-rich E. histolytica protein or a combination of the two recombinant antigens provides excellent protection against subsequent hepatic challenge with virulent E. histolytica trophozoites.

Animals↗
PubMed1994

AML-1 gene rearrangement and AML-1-ETO gene expression as molecular markers of acute myeloblastic leukemia with t(8;21).

Rearrangements of the AML-1 gene on chromosome 21 as well as transcriptional expression of AML-1-ETO fusion gene were studied in 35 leukemic patients with t(8;21)(q22;q22). A panel of probes generated from the AML-1 gene regions flanking the breakpoint on chromosome 21 allowed us to detect the rearrangement in 24 out of 29 patients. A specific nested reverse transcriptase/polymerase chain reaction (RT/PCR) was developed to detect the t(8;21), either at diagnosis or as minimal residual disease. PCR amplification products were obtained in ten out of 11 patients investigated, and the sensitivity of the reaction was estimated to be between 1 x 10(4) and 1 x 10(-5) cell. An AML-1 rearrangement was also detected in one patient with 8q- and only one chromosome 21, but without 21q+. This indicated that the molecular rearrangement of the der(8) chromosome is more important than the reciprocal one in the malignant process.

Adolescent↗
PubMed1994

[Cloning and sequencing of promoter and signal sequence coding regions from Bacillus subtilis].

Promoter and signal sequence coding regions from B. subtilis were cloned in E. coli using a bifunctional and signal sequence selection plasmid pGPB14 as a vector. The Sau3A digested chromosome DNA was ligated with BamHI digested pGPB14. The ligated mixture was used to transform E. coli C600. Ampicillin and erythromycin resistant clones were selected. Recombinant plasmids were isolated from double resistant transformants. Restriction analysis showed that inserts of various length had been cloned and these inserts rendered the E. coli cells resistant to different concentrations of ampicillin. The recombinant plasmids were transformed and showed the same secretion function in B. subtilis. The amount and localization of beta-lactamase were determined in transformed E. coli and B. subtilis. The results indicate that the beta-lactamase activities of E. coli mainly in periplasm while the enzyme produced by B. subtilis secreted extracellularly. 10 of the cloned fragments were sequenced by Sanger's dideoxy chain termination method. The sequencing data show that all fragments contain promoter, ribosome binding site and signal sequence coding region.

Amino Acid Sequence↗
PubMed1994

[Effects of moxibustion on the function of MDR gene product, P-glycoprotein (P-170)].

The experiments were performed on BABL/c mice with S-180R adriamycin resistant tumor cells. This animal model was used to analyze the drug accumulation in the S-180R cells by flow cytometer. The drug accumulation presents the pump activity of multidrug resistance (MDR) gene product P-glycoprotein (P-170) in the cell membrane, A weak inhibition was found when moxibustion at Guan-Yan point alone. And a very significant inhibition was observed in the presence of low-dosage of verapamil, but not at high dose. This study may develop a new way to research the mechanism of acupuncture and moxibustion at molecular level, and may be useful to overcome the anticancer drug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Expression and secretion of alpha-amylase and glucoamylase in Saccharomyces cerevisiae.

alpha-Amylase genes of Bacillus licheniformis and glucoamylase cDNA of Aspergillus niger were ligated to a E. coli-yeast shuttle vector. The resultant plasmid was used to transform Saccharomyces cerevisiae to construct starch-degrading yeast strain. The results of enzyme activity assay and enzyme property analysis show that alpha-amylase and glucoamylase genes have been expressed simultaneously in yeast under the control of promoters and terminators of yeast MF-alpha 1 factor and PGK genes and over 99% of enzyme activities were secreted to the medium. The engineered yeast strain hydrolyses 97% of the starch (10%) in the medium after 6 days. The recombinant plasmid exists stably in yeast.

Aspergillus niger↗
PubMed1994

[Analysis and comparison of the essential oil from Evodia rutaecarpa (Juss.) Benth. before and after processing by GC-MS].

Analysis has been carried out by GC-MS on the essential oil from the crude drug Evodia rutaecarpa and its Glycyrrihiza uralensis processed product, vinegar processed product and salt processed product. The total amount of essential oil decreases in the order of crude drug, vinegar processed, G. uralensis processed and salt processed products. The results of GC-MS analysis show that the constituents of the essential oil from the crude drug and its G. uralensis processed product are markedly different, and the contents of these constituents vary significantly.

Drugs, Chinese Herbal↗
PubMed1994

[Observation on cunkou pulse picture, sphygomogram and forearm rheohemogram of acute stroke patients].

Observation of Cunkou pulse picture, main wave of sphymogram (MW) and foreman rheohemogram and blood pressure (BP) were made on 41 acute stroke patients divide into two groups according to Syndrome Differentiation of TCM; including those involved in viscera and in meridian. The difference between these two groups were significant. The MW, the forearm blood volume (FBV) and BP were all significantly higher in those involved in viscera than that of in meridian. In the different phases of disease course, the MW, FBV and BP changed gradually. During recovery, the MW, FBV and BP were lowered gradually, and finally it remained stable.

Adult↗
PubMed1993

A switch between two-, three-, and four-stranded coiled coils in GCN4 leucine zipper mutants.

Coiled-coil sequences in proteins consist of heptad repeats containing two characteristic hydrophobic positions. The role of these buried hydrophobic residues in determining the structures of coiled coils was investigated by studying mutants of the GCN4 leucine zipper. When sets of buried residues were altered, two-, three-, and four-helix structures were formed. The x-ray crystal structure of the tetramer revealed a parallel, four-stranded coiled coil. In the tetramer conformation, the local packing geometry of the two hydrophobic positions in the heptad repeat is reversed relative to that in the dimer. These studies demonstrate that conserved, buried residues in the GCN4 leucine zipper direct dimer formation. In contrast to proposals that the pattern of hydrophobic and polar amino acids in a protein sequence is sufficient to determine three-dimensional structure, the shapes of buried side chains in coiled coils are essential determinants of the global fold.

Amino Acid Sequence↗
PubMed1993

Circular permutation of T4 lysozyme.

To examine the relationship between polypeptide chain synthesis and protein folding, we have constructed a circularly permuted variant of phage T4 lysozyme. The permuted protein begins at residue 37 of the wild-type sequence and ends at residue 36. The normal chain termini are joined by a six-residue linker, Ser-Gly4-Ala. The permuted lysozyme folds efficiently and cleaves bacterial cell walls with normal specific activity. As judged by circular dichroism, UV absorbance, fluorescence, and nuclear magnetic resonance spectroscopy, the permutation causes little change in the structure of the protein. Reversible denaturation experiments show that the permutation reduces the stability of T4 lysozyme only 0.8-1.1 kcal/mol. These results demonstrate that a protein with two domains can be permuted with little change in activity, structure, and stability. The order of chain synthesis, the sequential arrangement of secondary structures, and the position of chain termini with respect to domain boundaries do not determine the protein fold.

Amino Acid Sequence↗