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Biomedical subjects

L Shi

Publications and source records attributed to L Shi.

At least 235 records · Page 13Linked to original sources
PubMed1995

Rescue from granzyme B-induced apoptosis by Wee1 kinase.

Granzymes are a family of granule-associated serine esterases that mediate apoptosis by cytotoxic T lymphocytes and natural killer cells. We have previously shown that cdc2, the mitosis-regulating cyclin-dependent kinase, is required for granzyme B-induced apoptosis in target cells. In addition, granzyme B induces premature activation and tyrosine dephosphorylation of cdc2 during apoptosis. Throughout most of the cell cycle and until the cell is prepared to enter mitosis, cdc2 kinase activity is negatively regulated by phosphorylation of a residue within its adenosine triphosphate-binding domain by Wee1, a nuclear kinase that maintains mitotic timing in eukaryotic cells. We have transiently expressed c-myc epitope-tagged Wee1 cDNA in BHK cells. Cells that expressed Wee1 in the nucleus became resistant to apoptosis induced by granzyme B and perforin. Wee1-transfected cells also exhibited markedly increased cdc2 tyrosine phosphorylation. Thus, Wee1 can rescue cells from granzyme-induced apoptosis by preventing cdc2 dephosphorylation.

Animals↗
PubMed1995

Influenza A virus RNA polymerase subunit PB2 is the endonuclease which cleaves host cell mRNA and functions only as the trimeric enzyme.

The influenza A virus RNA-dependent RNA polymerase catalyzes several reactions in transcription and replication of the genome RNA. The first step in viral mRNA synthesis is the endonucleolytic cleavage of host cell mRNAs containing a cap structure to generate capped primers that are 10-14 nucleotides long which are then used to prime transcription of virus-specific mRNAs. To analyze the properties of the capped RNA-specific endonuclease associated with the influenza virus polymerase and the roles of each of the three subunits in transcription initiation, we established an in vitro assay to investigate this endonucleolytic cleavage reaction. This assay consists of an artificial RNA substrate containing a cap-0 structure at its 5' end and a partial alfalfa mosaic virus RNA 4 (AIMV RNA 4) sequence which had been shown to be cleaved by the influenza polymerase. Results showed that purified virion ribonucleoprotein complexes cleaved the RNA substrate specifically to generate a capped 14-nt RNA fragment for use as primer to initiate viral mRNA synthesis. Purified polyclonal anti-PB2 IgG inhibited the endonuclease activity, but anti-PB1 and anti-PA antibodies did not inhibit the cleavage. Partially purified trimeric polymerase expressed by recombinant baculovirus in insect cells cleaved the artificial substrate, but if one or two subunits were removed from the polymerase complex, the cleavage activity was totally lost. Our results suggest that viral PB2 protein is the endonuclease that cleaves host cell mRNA to produce the primer used to initiate transcription; however, association with the other two enzyme subunits seems to be required for this PB2 function.

Animals↗
PubMed1995

Rapid identification of highly active and selective substrates for stromelysin and matrilysin using bacteriophage peptide display libraries.

The discovery of useful peptide substrates for proteases that recognize many amino acids in their active sites is often a slow process due to the lack of initial substrate data and the expense of analyzing large numbers of peptide substrates. To overcome these obstacles, we have made use of bacteriophage peptide display libraries. We prepared a random hexamer library in the fd-derived vector fAFF-1 and included a "tether" sequence that could be recognized by monoclonal antibodies. We chose the matrix metalloproteinases stromelysin and matrilysin as the targets for our studies, as they are known to require at least 6 amino acids in a peptide substrate for cleavage. The phage library was treated in solution with protease and cleaved phage separated from uncleaved phage using a mixture of tether-binding monoclonal antibodies and Protein A-bearing cells followed by precipitation. Clones were screened by the use of a rapid screening assay that identified phage encoding peptide sequences susceptible to cleavage by the enzymes. The nucleotide sequence of the random hexamer region of 43 such clones was determined for stromelysin and 23 for matrilysin. Synthetic peptides were prepared whose sequences were based on some of the positive clones, as well as consensus sequences built from the positive clones. Many of the peptides have kcat/KM values as good or better than those of previously reported substrates, and in fact, we were able to produce stromelysin and matrilysin substrates that are both the most active and smallest reported to date. In addition, the phage data predicted selectivity in the P2 and P'1 positions of the two enzymes that were supported by the kinetic analysis of the peptides. This work demonstrates that the phage selection techniques enable the rapid identification of highly active and selective protease substrates without making any a priori assumptions about the specificity or the "physiological substrate" of the protease under study.

Amino Acid Sequence↗
PubMed1995

Genomic organization and evolution of the soybean SB92 satellite sequence.

Repetitive DNA sequences comprise a large percentage of plant genomes, and their characterization provides information about both species and genome evolution. We have isolated a recombinant clone containing a highly repeated DNA element (SB92) that is homologous to ca. 0.9% of the soybean genome or about 10(5) copies. This repeated sequence is tandemly arranged and is found in four or five major genomic locations. FISH analysis of metaphase chromosomes suggests that two of these locations are centromeric. We have determined the sequence of two cloned repeats and performed genomic sequencing to obtain a consensus sequence. The consensus repeat size was 92 bp and exhibited an average of 10% nucleotide substitution relative to the two cloned repeats. This high level of sequence diversity suggests an ancient origin but is inconsistent with the limited phylogenetic distribution of SB92, which is found at high copy number only in the annual soybeans. It therefore seems likely that this sequence is undergoing very rapid evolution.

Base Sequence↗
PubMed1995

Immuno-gold localization of hepatotoxins in cyanobacterial cells.

A polyclonal antibody against the potent hepatotoxic cyclic peptide microcystins and nodularins was used in conjunction with immuno-gold labelling to localize the toxins in three strains of cyanobacteria. Ultrastructurally, there were no major differences between unicellular Microcystis aeruginosa strain PCC 7820 (toxin-producing strain) and M. aeruginosa strain UTEX 2063 (non-toxin-producing strain), except that M. aeruginosa PCC 7820 cells had a sheath. The thickness of the sheath was about 12 nm and was distinguishable from the cell wall at the ultrastructural level only when the specimen was stained en bloc with uranyl acetate. Microcystins and nodularin were found in M. aeruginosa PCC 7820 and Nodularia spumigena strain L-575 respectively, but not in nontoxic M. aeroginosa UTEX 2063. In M. aeruginosa PCC 7820 cells, microcystin was found primarily in the thylakoid area and nucleoid, with smaller amounts in the cell wall and sheath. Only nonspecific labelling was found in other cellular inclusions, such as polyhedral bodies, cyanophycin granules and membrane-limited inclusions. In strain N. spumigena L-575, nodularin was found in both vegetative cells and heterocysts with a distribution similar to that in M. aeruginosa PCC 7820.

Bacterial Toxins↗
PubMed1995

A comparative study of karyotypes of muntjacs by chromosome painting.

We have used a combination of chromosome sorting, degenerate oligonucleotide-primed polymerase chain reaction (DOP-PCR), chromosome painting and digital image capturing and processing techniques for comparative chromosome analysis of members of the genus Muntiacus. Chromosome-specific "paints" from a female Indian muntjac were hybridised to the metaphase chromosomes of the Gongshan, Black, and Chinese muntjac by both single and three colour chromosome painting. Karyotypes and idiograms for the Indian, Gongshan, Black and Chinese muntjac were constructed, based on enhanced 4', 6-diamidino-2-phenylindole (DAPI) banding patterns. The hybridisation signal for each paint was assigned to specific bands or chromosomes for all of the above muntjac species. The interspecific chromosomal homology was demonstrated by the use of both enhanced DAPI banding and comparative chromosome painting. These results provide direct molecular cytogenetic evidence for the tandem fusion theory of the chromosome evolution of muntjac species.

Animals↗
PubMed1995

Phylogeny of Muntiacus (Cervidae) based on mitochondrial DNA restriction maps.

Mitochondrial DNA restriction maps for 12 restriction enzymes of four species of muntjacs--Indian muntjac (M. muntjak), Gongshan muntjac (M. gongshanensis), black muntjac (M. crinifrons), and Chinese muntjac (M. reevesi)--were compared to estimate the phylogenetic relationships among them. Phylogenetic trees were constructed by both distance and parsimony methods. The two resulting trees share a similar topology, which indicates that the black muntjac and the Gongshan muntjac are closely related, followed by the Chinese muntjac; the Indian muntjac is the sister taxon to all the other muntjacs.

Animals↗
PubMed1995

Rural physicians: a survey analysis of HIV/AIDS patient management.

Primary care physicians in South Carolina were asked about their knowledge, attitudes, beliefs, and services provided to HIV/AIDS patients. The study focused on conditions under which physicians would provide additional services in an effort to develop more effective state policies regarding HIV/AIDS. There was a 66 percent (597/900) response rate. This analysis focuses on a group of 338 physicians that identified themselves as rural (nonurban) physicians. Of the rural physicians responding, 42 percent had not treated a case of HIV/AIDS during the last year and 52 percent had seen only 1 to 9 patients. They identified lack of specialty back-up support, likelihood of losing patients, legal and ethical issues, and lack of community services as the primary barriers to service. Gaps in rural physician knowledge included when to refer HIV/AIDS cases to specialists and information on legal and ethical issues. They, like their urban colleagues, would provide additional services to HIV/AIDS patients with specialty back-up (57 percent), better community and social services support (54 percent), additional training (48 percent), and limited liability (47 percent). The authors conclude that policy changes addressing these areas in the broader contexts of rural health issues would expand access to care for persons with HIV infection in rural states.

Adult↗
PubMed1995

Public health, medical care, and mortality rates.

This study examined the association between public health spending and leading mortality rates in the United States. Results indicate that government spending on public health is significantly associated with improving the life chances of the population. Public health spending was consistently associated with reduced total mortality and with lower mortalities due to heart disease, cancer, and stroke--the leading causes of death in the United States. However, medical care expenditures on hospital care and prescription drugs were significantly associated with increased total mortality and mortalities due to heart disease, cancer, and stroke. The policy implication is to reorient the currently expensive, clinically based, treatment-focused medical care system toward a more cost-effective health care system oriented toward public health and prevention. A more balanced health care system, with concomitant emphasis on medical care and public health, should be established.

Cause of Death↗
PubMed1995

[IgG RF analysis of supernatant of cultured synovia in patients with rheumatoid arthritis].

We used Enzyme Linked Immuno-Sorbent Assay (ELISA) to measure IgG RF of supernatant of cultured knee synovia in 45 patients with various rheumatic diseases (Harvest time for the supernatant was 1,4,7,14,28 days). 25 cases of patients with osteoarthritis (OA) and non-synovitis (Non-S) were regarded as the negative control. IgG RF was positive in 4 of 12 patients with rheumatoid arthritis (RA), whose IL-1 bioactivity is also high. Meanwhile these 4 patients had not received disease-modifying anti-rheumatic drugs (DMARDs) and their clinical and laboratory parameters were active. IgG RF was negative in other groups. It is suggested that humoral factor such as IgG RF and cytokine such as IL-1 may play the synergistic role in the pathogenesis of RA and DMARDs may suppress these two kinds of pathological factors.

Adult↗
PubMed1995

[Radioimmunoimaging (RII) and radioimmunotherapy (RIT) of human primary hepatic cancer (hPHC) with anti-PHC monoclonal antibody in tumor bearing nude mice].

Tumor xenografts of human PHC were grown in nude mice subcutaneously. The studies were performed in nude mice with tumor base aear of 0.8cm-1.0cm. For the study of RII, the mice were injected intravenously with 1.11 x 10(7)Bq/mouse of 131I-hepama-1. All tumours were clearly visualied on the 4th day after injection and remained the same until the 7th day. No tumor image was found in 131I-mIgG. The tumor to liver ratio of radioactivity increased from 1.3 to 3.03 in 131I-Hepama-1 group, but decreased from 13.6 to 6.88% in 131I-mIgG group. For the study of RIT 131I-hepama-1 (1.85 x 10(10)Bq) was administered intraperitoneally. A tumor growth inhibition rate at the 4th week after the infusion of 70.5% was obtained. The median survival time of the nude mice in 131I-hepama-1 group was much longer than in control groups in mice.

Animals↗
PubMed1995

[Effect of 3,4-dihydroxyacetophenone on phospholipid components of platelet membrane in aged rats].

3,4-Dihydroxyacetophenone (DHAP) is one of the constituents of Ilex pubescence Hook. et Arn. var. glaber Chang. The effects of DHAP on the composition of blood platelet membrane in aged rats was examined. No change of total lipid and cholesterol contents was observed in aged rats. While a slight but significant decrease of phospholipid in platelet membrane was found, which lead to diminution of the ratio of phospholipid to cholesterol. The contents of phosphatidylethanolamine and phosphatidylcholine decreased markedly by as less as 23.0% and 19%, respectively, compared with the young group. Whereas the degree of reduction of phospholipid, the ratio of phospholipid to cholesterol, phosphatidylethanolamine and phosphatidylcholine were significantly lightened after irrigation with DHAP 100 mg.kg-1 for 10 weeks. In the treatment group, the values of phosphatidylethanolamine and phosphatidylcholine of platelet membrane were reduced by 8.0% and 10.5%, respectively, vs the group of aged rats. It is concluded that reduced phospholipid hydrolysis is involved in mediating DHAP inhibition of platelet function.

Acetophenones↗
PubMed1995

The measurement and application of TSH-IRMA levels among different age groups in areas with iodine deficiency disorders.

Using immunoradiometric TSH assay (TSH-IRMA) to measure whole blood TSH levels spotted onto filter paper, we compared TSH levels among different age groups (neonates, < 1 yr infants, schoolchildren aged 7 to 14 yrs, adults, pregnant women and reproductive-age women) in Guiyang, where iodine deficiency has long been a problem. The results showed: 1) The percentage of subjects with TSH levels equal to or greater than 5 mIU/L in the neonate group was 38.9% while the percentages in the other groups were 0-3.3% (P < 0.01); 2) The TSH levels of the neonates were inversely related to the urinary iodine values of their mothers (pregnant women). (r = -0.5, P < 0.01); 3) 97.6% of the inhabitants in Guiyang ingested salt with less than 20 mg/kg iodine. The results indicate that iodine deficiency remains a problem in Guiyang. Neonates are the only ideal population for monitoring iodine deficiency.

Adolescent↗
PubMed1995

Establishment of a human T-lymphoma cell line (H-TL90) and analysis of its biological characteristics.

We established a human T-lymphoma cell line from the cancerous ascites of a male patient with prostate cancer which was named H-TL90. This cell line was characterized by its histological features, and by chromosomal and immunological analysis. Immunophenotypic analysis revealed that the cells expressed surface antigen CD-3CD-4CD+7CD-8. Biological analysis revealed that the cell can promote lymphocyte proliferation. This suggested that the cell line has an autosecretion function. Cytogenetic analysis revealed that H-TL90 was a hyperdiploid with 47 chromosomes and had characteristic translocation between chromosome 3 and 11, and the deletion of the long arm of chromosome 6. These results demonstrated the H-TL90 cell line can be a useful model for the study of human T-lymphoma.

Adult↗
PubMed1995

[Mitochondrial DNA polymorphism in the Han, Miao, Buyi, and Shui ethnic groups from Guizhou province].

Sixteen restriction endonucleases were used to assay the mtDNA polymorphism in the Han, Miao, Buyi and Shui ethnic groups from Guizhou province. Thirty-one restriction patterns were observed in a total of 150 subjects studied, out of which HacII-13, EcoRV-3 and PstI-4 are first reported by this paper. From all restriction patterns disclosed by 16 enzymes, twenty-eight mtDNA types were obtained. UPG method and parsimony networks were employed to analyze the clustering relationships between types or populations. Following conclusions are obtained: the mt-DNA from the Shui nationality possesses the highest polymorphism; the Han and the Miao are most closely related; and the genetic relation between the Buyi and the Shui is somewhat distant.

China↗