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Biomedical subjects

L Yin

Publications and source records attributed to L Yin.

At least 127 records · Page 7Linked to original sources
PubMed1995

[The regulation of calmodulin in the cell cycle].

In order to study the role of calmodulin (CaM) in the cell cycle, RC 3 cells carring the CaM expression vectors which was constructed by joining the CaM cDNA with a plasmid of mouse mammary tumor virus (MMTV), were used in this experiment. The CaM expression vectors transcription is regulated by a dexamethasone (DXM) inducible MMTV LTR promoter. Upon addition of DXM, cells have transiently increased CaM mRNA and protein levels. Increased CaM caused a acceleration of proliferation. Flow cytometric analysis showed that progression though G1, G2 and metaphase was accelerated by increase in CaM levels, while treatment with the CaM antagonist trifluoperazine (TFP) blocked cell cycle progression at G1/S boundary and during G2/M and metaphase. The studies have shown that CaM is important in controlling progression at three points in the cell cycle: (1) The G1/S boundary to permit the initiation of DNA synthesis; (2) The G2/M boundary to permit the initiation of mitosis; (3) At the metaphase/anaphase transition of mitosis to permit chromosome segration and the completion of mitosis. This study indicates that the RC 3 cell is a useful experimental cell model for studing the effect of a transient increase of intracellular CaM levels on control of cell cycle.

3T3 Cells↗
PubMed1994

Unconventional cytotoxic T lymphocyte recognition of synthetic peptides corresponding to residues 1-23 of Ras protein.

A peptide corresponding to amino acids 1 through 23 of Ras protein containing a mutation at position 12 was used to induce cytotoxic T lymphocytes (CTL) in mice. Although the CTL were CD8+ and expressed alpha, beta T cell antigen receptors (TCR), their major histocompatibility complex (MHC)-restriction was unconventional. They recognized peptide-treated murine cells of different H-2 haplotypes, but not MHC class I-negative cells. Human HLA class I molecules did not present Ras peptides and hybrid human/mouse MHC molecules revealed that all three extracellular domains alpha 1, alpha 2 and alpha 3 were required for recognition by peptide-specific CTL. Shortening the 23-mer peptide by 5 residues at either the amino or carboxy terminus resulted in loss of CTL recognition. This demonstrates an unusual form of antigen recognition by mouse CTL in which peptide presentation requires murine H-2 class I molecules but is not class I allele restricted, and the peptides recognized are much larger than peptides in conventional class I-restricted responses.

Amino Acid Sequence↗
PubMed1994

Heterogeneity and low detection rate of RET mutations in Hirschsprung disease.

Mutations in some exons of the RET proto-oncogene were recently observed in Hirschsprung patients. Using DNA polymorphisms and single-strand conformation polymorphism analysis for the whole coding sequence of the RET proto-oncogene, 82 unrelated Hirschsprung patients were screened systematically. A total of 4 complete deletions of RET and 12 point mutations were identified, each present in no more than one patient and distributed along the whole gene. De novo mutations could be documented in 4 patients. Southern blot and fluorescence in situ hybridization analysis carried out in a restricted number of patients did not reveal any deletion of RET. The low efficiency in detecting mutations of RET in Hirschsprung patients (20%) may originate mainly from genetic heterogeneity.

Blotting, Southern↗
PubMed1994

Influence of in vitro methods, receptor fluids on percutaneous absorption and validation of a novel in vitro method.

In vitro experiment using excised skin has been valuable for studying the mechanism of percutaneous absorption. Based on previously established static diffusion cell system in this laboratory, a novel model-perfused glass diffusion cell system is designed. The results of initial comparative study on percutaneous absorption between glass perfused diffusion cell and static diffusion cell, in vitro and in vivo permeation as well as factors affecting permeation with seven radiolabelled chemicals are presented. The results demonstrate that the perfused diffusion cell system, which used a perfusion fluid below the surface of skin to take up the materials which penetrated the skin, is more similar to physiologic condition, convenient and automatic than that of the static cell. It well predicts the in vivo percutaneous absorption if appropriate receptor fluid is chosen. The results also show that the selection of receptor fluid is critical for in vitro permeation of chemicals with different solubility.

Animals↗
PubMed1993

Few peptides dominate cytotoxic T lymphocyte responses to single and multiple minor histocompatibility antigens.

Minor histocompatibility (H) antigens are T cell recognized self proteins which can cause graft versus host disease or organ transplant rejection. We have analysed the number of peptide epitopes involved in cytotoxic T lymphocyte (CTL) responses to single or multiple minor H antigens. Bulk CTL responses were generated in H-2b mice differing in one (H-1), two (H-1 and H-25), or multiple (> 29) minor H loci, and HPLC separation was used to analyse the complexity of CTL recognized peptides. Anti-H-1 CTL recognize one out of 50 HPLC peptide fractions and recognition is H-2Kb restricted. The same peptide fraction is also recognized by anti-H-1/H-25 CTL and no additional epitopes are detected, indicating that the H-25 locus does not stimulate CTL when combined with H-1. CTL generated to multiple minor H loci (including H-1 and H-25) recognize two HPLC peptide fractions which are presented by H-2Db and H-2Kb class I molecules, respectively. The H-2Kb presented fraction is the same as that recognized by anti-H-1 and anti-H-1/H-25 CTL, and it is shown to contain a H-1-derived peptide. Subfractionation of the CTL recognized HPLC fractions is consistent with the presence of only one peptide epitope. Thus, in the responses analysed here one minor H locus encodes probably only one CTL epitope. The study provides a molecular explanation for immunodominance among minor H antigens, suggesting that dominant loci encode single peptide epitopes which are presented efficiently by MHC class I molecules enabling them to readily stimulate CTL responses.

Animals↗
PubMed1993

T cell recognition of a point mutation in the P21 Ras protein.

Point mutations of p21 Ras proteins correlate with many human malignancies. To determine whether the mutations of Ras proteins generate immunogenic determinants which can be recognized by T cells and possibly serve as targets for immunotherapy, we studied the murine T helper responses to synthetic Ras peptides corresponding to amino acids 1-23 of normal or mutant Ras protein. Immunization of C3H/He and B10.BR mice with Ras peptides containing a valine mutation at position 12 stimulated MHC class II-restricted T helper cells which recognised specifically the Ras mutation. Surprisingly C57BL/10 mice generated T helper responses not only against mutant but also against normal Ras peptides. Importantly, natural processing of Ras protein was found to generate the epitopes recognized by the peptide-induced T cells.

Amino Acid Sequence↗
PubMed1992

Radiation hybrids for mapping and cloning DNA sequences of distal 16p.

Three hundred fifteen radiation hybrids (RH) were isolated using a monochromosomal cell hybrid containing chromosome 16 only. A panel of 18 RH, which showed breakpoints among four markers (3.15, 26.6, 3'HVR, and 5'HVR) mapping in the distal portion of 16p, were selected and characterized for the retention of nine additional DNA sequences already localized in this region, and for one centromeric sequence. One or more breakpoints were identified in nine of the 12 intervals defined by the 13 single-copy sequences used. This panel of RH represents a tool for the construction of a detailed physical map of the distal part of 16p and for cloning sequences located in the proximity of disease genes. Three inter-Alu DNA sequences, amplified from one of these RH containing the autosomal dominant polycystic kidney disease (PKD1) gene, were cloned and mapped in the panel. Sequencing of the ends of one of three clones showed a (CAAA)n repeat, which revealed a two-allele polymorphism.

Base Sequence↗
PubMed1992

[Effects on the normalization of amino acids in metabolic support for trauma surgical patients].

Both serum and muscle intracellular amino acids pattern are changed after trauma. The formulation of amino acid solutions is important for the balance of the patient's serum or intracellular amino acids. In 45 gastric cancer patients after total gastrectomy, the efficacy of individualizal amino acid solution (IDAA) was compared with that of other two balance amino acid solutions. The result showed that metabolic support with IDAA could decrease the muscle intracellular phenylalanine level and increase the levels of free neoglycogenic amino acids, arginine and ornithine both in serum and muscle cells. It is beneficial to the early recovery from trauma and normalization of serum or muscle amino acids pattern.

Amino Acids↗
PubMed1992

[Mechanisms of protective action of radix Salviae miltiorrhizae (RSM) against experimental hepatic injury in rats].

The results indicated that RSM could significantly inhibit the lipid peroxidation of normal livers and cultured hepatocytes of rats, induce liver microsomal cytochrome P450 in normal rats, increase nucleic acids, proteins, urea and cerolloplasmin of damaged cultured hepatocytes of rats, relieve ultrastructural damage of cultured hepatocytes induced by CCl4. The pharmacological actions mentioned above should be considered as important mechanisms of RSM against liver injury.

Animals↗
PubMed1991

Suppression of lymphokine production in anti-minor histocompatibility antigen responses.

Allogeneic immunizations between mice strains that differ at multiple loci coding for minor histocompatibility antigens (mha) result in a variety of immune responses, including the induction of cytotoxic T cells, helper T cells, and delayed hypersensitivity reactions. However, high-dose intravenous immunization induces a population of cells that can suppress these responses. In this paper, we show that the transfer of this suppressor population in vivo is accompanied by a reduced ability of immune cells to produce the two lymphokines interleukin-2 (IL-2) and interleukin-3 (IL-3). In a different assay of suppressor function, suppressor cells were co-cultured with responder cells in vitro. Under these conditions, the presence of suppressor cells resulted in a lowered net production of IL-2, but not IL-3. Possible mechanisms for this phenomenon are discussed.

Animals↗
PubMed1990

[Effect of monocrotaline on human kidney cells].

The effect of monocrotaline on human kidney cells has been studied by means of monolayer cell culture, cytochemistry and 3H-thymidine incorporation. The result shows that this drug can inhibit cell DNA synthesis, featuring an irreversible damaging action to DNA templet. Also, when the process of glycolysis and saccharide utilization in the cells is inhibited, the amount of lactic acid produced decreases and the pH value becomes higher.

DNA↗