Biomedical subjects

Xin Du

Publications and source records attributed to Xin Du.

43 records · Page 3Linked to original sources

PubMed2003

From phenomenon to phenotype and from phenotype to gene: forward genetics and the problem of sepsis.

Genetic tools (especially classical tools) have enlightened our understanding of biology as no other approach could. Mendel, Morgan, Bridges, and their heirs began with phenotypic traits and ended with genes. At first, the chemical identity of genes was not known, and even after years of methodologic refinement, more years of effort were needed to find the gene and the mutational difference that caused a particular phenotype. Chemistry has now outraced phenotypic analysis; all the genes are suddenly known, but most of their functions are not. The greatest challenge confronting all fields in biology is to establish correspondence between genes and discrete biologic functions. Sepsis is a devastating problem that has eluded a solution, despite the introduction of highly effective antimicrobial agents. Sepsis is an orchestrated process, understood in broad outline, but not in all details. Which genes are involved in the pathogenesis of sepsis? As in the golden age of genetics, the answer requires the solution of phenotypic puzzles, which, in turn, requires the creation of phenotypes.

Animals↗

PubMed2003

Human tissue factor pathway inhibitor-2 does not bind or inhibit activated matrix metalloproteinase-1.

Tissue factor pathway inhibitor-2 (TFPI-2) is a Kunitz-type serine proteinase inhibitor associated with the extracellular matrices of vascular cells. A recent report provided in vitro evidence that TFPI-2 may be a novel inhibitor of the matrix metalloproteinases MMP-1, MMP-13, MMP-2 and MMP-9. In studies aimed at identifying the structural elements of TFPI-2 mediating the putative inhibition of the above MMPs, we re-examined the ability of native TFPI-2 to form complexes with MMP-2, MMP-9 and MMP-1, as well as assess its ability to inhibit the proteolytic activity of the interstitial collagenase, activated MMP-1. We report here that TFPI-2 failed to form complexes with MMP-2, MMP-9 and MMP-1 as revealed in immunoprecipitation and ligand blotting studies. In addition, TFPI-2 had no influence on the proteolytic activity of activated MMP-1 towards triple-helical collagen. These data provide presumptive evidence that TFPI-2 does not bind to MMP-2, MMP-9 and MMP-1, or regulate MMP-1, in the extracellular matrix.

Animals↗

PubMed2003

Germacrane sesquiterpene esters from Salvia roborowskii.

From the whole plant of Salvia roborowskii, four new germacrane sesquiterpene esters, 3beta,6beta,8alpha-triacetoxy-4beta,5alpha-epoxy-1-oxogermacr-10(14)-ene, 3beta,6beta,8alpha-triacetoxy-4beta,5alpha-epoxygermacr-1 (10) E-ene, 3beta,6beta,8alpha-triacetoxy-4beta,5alpha:1alpha,10beta-diepoxygermacrane and 6beta-acetoxyglechomafuran were isolated, and their structures were elucidated by spectroscopic methods including 2D NMR techniques (1H-1H COSY and 1H-1H NOESY for 1).

Esters↗

PubMed2003

Lps2 and signal transduction in sepsis: at the intersection of host responses to bacteria and viruses.

A phenotype-driven approach led to the first understanding of precisely what the Toll-like receptors (TLR) did, when it was determined that the mammalian endotoxin (lipopolysaccharide; LPS) receptor is encoded by TLR4. The TLRs are the primary sensors of the innate immune system, and without them, small inocula of microorganisms pose a major threat to the host, growing unchecked for a long period before they are recognized. Mutations that affect innate immune sensing may account for a substantial fraction of sepsis, and a highly significant excess of mutations in TLR4 has been identified in patients with systemic meningococcal disease. As such, it is important to understand the pathways that are responsible for innate immune sensing, including the signaling intermediates utilized by the TLRs. Random germline mutagenesis identified a locus, Lps2, which is required for normal responses to double-stranded RNA and LPS. Hence, a single transducer was found to serve both the TLR3 and TLR4 response pathways. The Lps2 mutation was found to ablate entirely the MyD88-independent pathway for LPS sensing, indicating that two and only two branches of the LPS sensing pathway exist in macrophages, and homozygotes for the mutation were resistant to LPS, but markedly susceptible to infection with mouse cytomegalovirus. Remarkably, Lps2 mutant mice entirely failed to produce type I interferons in response to a viral infection. It would appear that Lps2 is the most proximal component of a signal integration system required for innate immune responses to both viral and bacterial diseases. Positional cloning revealed that the TIR adapter protein Trif/Ticam-1 is structurally altered by the Lps2 mutation. This adapter is responsible for shared effects of responses to viral and bacterial pathogens.

Animals↗

PubMed2003

Lps2: a new locus required for responses to lipopolysaccharide, revealed by germline mutagenesis and phenotypic screening.

Both forward and reverse genetic techniques have been used to define components of the mammalian lipopolysaccharide (LPS) receptor. TLR4, identified by a forward genetic approach as the product of the classical Lps locus, is the only known transmembrane component of the mammalian LPS receptor. Gene knockout work has also established that LPS signal transduction requires the integrity of CD14, MD-2, and, in part, MyD88, IRAK4, and TRAF-6. However, there is no reason to believe that these are the only proteins that make up the receptor/transducer apparatus. To examine the possibility that other proteins may be involved, we initiated a mutagenesis program, in which germline mutations are induced in mice using N-ethyl-N-nitrosourea (ENU), and macrophages from individual animals are screened for their competence to respond to LPS. We now report the existence of a new locus, Lps2, which is required for TNF production in response to LPS. The Lps2 mutation that we have identified is co-dominant, is similar in phenotypic effect to Lpsd, and does not represent a novel allele of any of the genes that are known to encode the 'core' LPS signaling apparatus. The Lps2 mutation does not preclude signaling initiated by peptidoglycan or unmethylated DNA. Hence, genetic data suggest that there is at least one 'missing' component of the LPS receptor complex that has yet to be found.

Animals↗

PubMed2003

[Relationship between cyclins and prognosis of acute leukemia].

BACKGROUND & OBJECTIVE: Cell proliferation and differentiation are directed by cell cycle mechanism. When tumor cells proliferate abnormally, cyclins, which are positive agents of cell cycle, may be expressed abnormally at the same time. Now many references proved that cyclins are highly expressed in solid tumors. This study was designed to investigate the relationship between expression of cyclins and prognosis of acute leukemia. METHODS: Sixty-eight cases of acute leukemia were enrolled. Reverse transcription polymerase chain reaction (RT-PCR) was performed on tumor samples to examine the expression of cyclin A, cyclin D, cyclin E. All samples were divided into three groups: acute leukemia in complete remission (12 cases), newly diagnosed acute leukemia (16 cases) and refractory leukemia (40 case). Samples of benign hemopoietic patients were used as normal control (15 cases). RESULTS: All the 15 cases in the control group were negative of cyclin mRNA. No difference of cyclin A mRNA expression was shown between control group and the three experiment groups (P >0.05). But expression of cyclin D and cyclin E mRNA was significantly different between them (P< 0.01). There was no difference of expression of cyclin D and cyclin E mRNA among CR patients with acute leukemia(P >0.05), while the expression of cyclin D mRNA is significantly higher than that of cyclin E in refractory leukemia group. Furthermore the expression of cyclin D mRNA in recurrent refractory leukemia patients is significantly higher than that newly diagnosed cases (P< 0.05). All cyclins mRNA positive cases were divided into single cyclin gene expressed group and multiple cyclins gene expressed group. The positive rates of them were counted. No difference was found between complete remission group and refractory leukemia group (P >0.05). CONCLUSION: Cyclin D may act as a prognostic marker for acute leukemia. The amount of cyclins expressed cannot be used as a prognostic factor for acute leukemia.

Acute Disease↗

PubMed2003

[Dry eye in graft-versus-host disease].

OBJECTIVE: To investigate patients who had ocular presentations after allogeneic hematopoietic stem cell transplantation. METHODS: The eyes of 20 patients of leukemia who had undergone allogeneic hematopoietic stem cell transplantation were examined. The ocular surface of these patients was examined by slit-lamp. The eye examination also included evaluation of tear break-up time, Schirmer tests with and without nasal stimulation, and fluorescein staining, rose bengal staining, etc. Conjunctival impression cytology and pathological examination of surgical specimens from 3 patients were performed. RESULTS: Fourteen of 20 patients developed chronic graft-versus-host disease (cGVHD). Eight patients suffered from dry eye accompanied by GVHD simultaneously. The incidence of dry eye in GVHD was 57%. Among them, 4 cases were severe dry eye associated with significant decrease of visual acuity and even development of corneal ulcer. Ophthalmic pathology findings were as follows: loss of conjunctival goblet cells or significant reduction in amount; conjunctival and corneal epithelial keratinization and squamous metaplasia; and dominance of T cell in conjunctival inflammatory infiltration cells. CONCLUSION: Dry eye is the major ocular complication after allogeneic hematopoietic stem cell transplantation. It affected the patients' life quality severely. The high incidence and potentially severe ocular problems in these patients suggest that close ophthalmic monitoring is important in allogeneic hematopoietic stem cell transplantation.

Adult↗