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Biomedical subjects

S Qian

Publications and source records attributed to S Qian.

At least 109 records · Page 6Linked to original sources
PubMed1994

Split tolerance induced by orthotopic liver transplantation in mice.

Spontaneous orthotopic liver allograft acceptance associated with microchimerism in mice induces tolerance to subsequent skin or heart transplants from the donor but not third-party animals. Despite in vivo hyporesponsiveness, in vitro MLC and CTL assays showed continuing antidonor reactivity. Cells isolated from recipients' spleens and grafted livers, when tested in MLC and CTL assays, were antidonor reactive out to 3 months to the same degree as splenocytes obtained from either naive or presensitized (with skin or heart) mice. Nevertheless, passive transfer of splenocytes or liver lymphocytes from liver tolerant mice, but not naive or sensitized donor strain mice, were able to prolong skin graft survival significantly in naive irradiated recipients. By using a strain combination in which the donor but not the recipient expressed the stimulatory endogenous super-Ag (Mlsf), it was possible to determine whether super-Ag-reactive T cells bearing V beta 5 and V beta 11 were deleted or anergic. Phenotypic analysis of cells isolated from recipients' spleens and grafted livers (up to 90 days after transplant), when compared with naive animals, showed no significant difference in V beta 5 and V beta 11 TCR expression. Additionally, when these isolated spleen cells were tested for antibody-mediated stimulation, both anti-V beta 5 and V beta 11 TCR mAb led to marked proliferation of cells obtained from naive and liver-transplanted recipients, but as expected, proliferation was very low in cells from naive donors. These results suggest that liver transplantation induces donor-specific tolerance in vivo, which may not be reflected in in vitro proliferative and cytotoxicity assays (split tolerance). Furthermore, this tolerance does not seem to be induced by clonal deletion or anergy of minor-lymphocyte-stimulating-antigen-reactive T cells in the recipients.

Animals↗
PubMed1994

Propagation of dendritic cell progenitors from normal mouse liver using granulocyte/macrophage colony-stimulating factor and their maturational development in the presence of type-1 collagen.

Within 1 wk of liquid culture in granulocyte/macrophage colony-stimulating factor (GM-CSF), normal B10 BR (H-2k I-E+) mouse liver nonparenchymal cells (NPC) formed loosely adherent myeloid cell clusters that have been shown to contain dendritic cell (DC) progenitors in similar studies of mouse blood or bone marrow. Mononuclear cell progeny released from these clusters at and beyond 4 d exhibited distinct dendritic morphology and were actively phagocytic. After 6-10 d of culture, these cells strongly expressed CD45, CD11b, heat stable antigen, and CD44. However, the intensity of expression of the DC-restricted markers NLDC 145, 33D1, and N418, and the macrophage marker F4/80, intercellular adhesion molecule 1, and Fc gamma RII was low to moderate, whereas the cells were negative for CD3, CD45RA, and NK1.1. Splenocytes prepared in the same way also had a similar range and intensity of expression of these immunophenotypic markers. Unlike the splenic DC, however, most of the GM-CSF-propagated putative liver DC harvested at 6-10 d expressed only a low level of major histocompatibility complex (MHC) class II (I-Ek), and they failed to induce primary allogeneic responses in naive T cells, even when propagated additionally in GM-CSF and tumor necrosis alpha and/or interferon gamma-supplemented medium. However, when 7-d cultured GM-CSF-stimulated liver cells were maintained additionally for three or more days on type-1 collagen-coated plates in the continued presence of GM-CSF, they exhibited characteristics of mature DC: MHC class II expression was markedly upregulated, mixed leukocyte reaction stimulatory activity was increased, and phagocytic function was decreased. Similar observations were made when Ia+ cells were depleted from the GM-CSF-propagated cells before exposure to collagen. Further evidence that the GM-CSF-stimulated class IIdim or class II-depleted hepatic NPC were immature DC was obtained by injecting them into allogeneic B10 (H-2b I-E-) recipients. They "homed" to T cell-dependent areas of lymph nodes and spleen where they strongly expressed donor MHC class II antigen 1-5 d later. These observations provide insight into the regulation of DC maturation, and are congruent with the possibility that the migration of immature DC from normal liver and perhaps other organ allografts may help explain their inherent tolerogenicity.

Animals↗
PubMed1994

Murine liver allograft transplantation: tolerance and donor cell chimerism.

Nonarterialized orthotopic liver transplantation with no immunosuppression was performed in 13 mouse-strain combinations. Two strain combinations with major histocompatibility complex class I and class II and minor histocompatibility complex disparity had 20% and 33% survival of more than 100 days, but the other 11 combinations, including four that were fully allogeneic and all with only class I, class II or minor disparities, yielded 45% to 100% survival of more than 100 days. Long-living recipients permanently accepted donor-strain heterotopic hearts transplanted on the same day or donor-strain skin 3 mo after liver transplantation, in spite of detectable antidonor in vitro activity with mixed lymphocyte reaction and cell-mediated lymphocytotoxicity testing (split tolerance). In further donor-specific experiments, liver grafts were not rejected by presensitized major histocompatibility complex class I-disparate recipients and they protected donor-strain skin grafts from second set (or any) rejection. Less frequently, liver transplantation rescued rejecting skin grafts placed 1 wk earlier in major histocompatibility complex class I, class II and minor histocompatibility complex, class II or minor histocompatibility complex-disparate strain combinations. Donor-derived leukocyte migration to the central lymphoid organs occurred within 1 to 2 hr after liver transplantation in all animals examined, persisted in the surviving animals until they were killed (> 375 days), and was demonstrated with double-immunolabeling to be multilineage. The relation of these findings to so-called hepatic tolerogenicity and to tolerance in general is discussed.

Animals↗
PubMed1994

Synthesis and cloning of the human lysozyme gene.

The human lysozyme is an enzyme with potential importance in clinical and industrial application. Owing to the limitation of its natural resource, we are making an attempt to produce the enzyme with the aid of recombinant DNA technology. Twenty-four segments with length ranging from 26 to 38 nucleotides were chemically synthesized by solid phase. The oligonucleotides were joined to form DNA duplexes by two different ligation methods. The entire gene covers a start signal ATG and a BamHI restriction site at its 5' end, and two stop signals TAA TGA and a SphI restriction site at its 3' end, besides the structural gene of human lysozyme. The synthetic gene was cloned into vector M13. The positive colonies were confirmed by dot-blot hybridization and analysis by restriction enzymes. The DNA sequence of the cloned enzyme gene was proved to be correct by M13 dideoxynucleotide chain termination method. The study on gene expression is under way.

Base Sequence↗
PubMed1993

Molecular mechanisms of pattern formation by the BRE enhancer of the Ubx gene.

The core activity of the Ubx gene enhancer BRE (bx region enhancer) is encoded within a 500 bp module. bx DNA outside this active module increases the level of expression, expands the expression into ventro-lateral ectoderm and partially stabilizes the late expression pattern. The products of the gap genes hb and tll and of the pair-rule gene ftz bind to the 500 bp BRE module and control directly its initial pattern of expression. ftz enhances expression in even-numbered parasegments within the correct spatial domain whose boundaries are set by hb and tll. In addition, en and twi products activate the enhancer, probably directly. en broadens the parasegmental stripe while twi cooperates with ftz to enhance expression in the mesoderm. Binding sites for the five regulators are closely clustered, often overlapping extensively with one another. In vitro, hb blocks the binding of ftz and can also displace ftz protein pre-bound to an overlapping site, suggesting that competitive binding and/or interference by hb sets the initial boundaries of the domain of expression. Our results also suggest that this interaction is short-range and the long distance interactions among different enhancers may depend on each enhancer's ability to complex with the promoter.

Animals↗
PubMed1993

Effect of ticlopidine on the cutaneous circulation in peripheral vascular disease.

To assess the effect of ticlopidine on the cutaneous circulation, 25 patients with lower limb ischemia were investigated just before and at two hours after being given a 200 mg oral dose of ticlopidine. The transcutaneous partial pressure of oxygen (PtcO2) and the skin temperature were determined at 35 limb sites and 9 chest walls sites. Both the PtcO2 and the skin temperature were significantly increased at two hours after the administration of ticlopidine (p < 0.01). The findings suggest that ticlopidine can improve the cutaneous microcirculation in patients with peripheral vascular disease.

Aged↗
PubMed1992

Fluorescence studies of rat cellular retinol binding protein II produced in Escherichia coli: an analysis of four tryptophan substitution mutants.

Rat intestinal cellular retinol binding protein II (CRBP II) is an abundant 134-residue protein that binds all-trans-retinol which contains 4 tryptophans in positions 9, 89, 107, and 110. Our ability to express CRBP II in Escherichia coli and to construct individual tryptophan substitution mutants by site-directed mutagenesis has provided a useful model system for studying the fluorescence of a multi-tryptophan protein. Each of the four mutant proteins binds all-trans-retinol with high affinity, although their affinities are less than that of the wild-type protein. Steady-state and time-resolved fluorescence analyses of these proteins indicate that W107 is at the hydrophobic binding site, W110 is in a polar environment, and the remaining two tryptophans are in a hydrophobic environment. Time-resolved fluorescence study indicates that excited-state energy transfer occurs from the hydrophobic tryptophans to W110. The Stern-Volmer analysis with acrylamide of these proteins reveals that static quenching occurs in the W9F mutant protein while others do not. The fluorescence of rat intestinal fatty acid binding protein (I-FABP), a related protein of known X-ray structure, was also studied for comparison. The results of these findings, coupled with those derived from NMR studies and molecular graphics, suggest that CRBP II undergoes minor structural changes in all of the mutant proteins. Since these effects may be cumulative on the protein structure and function, any conclusions derived from higher mutants in this family of proteins must be treated with caution.

Amino Acid Sequence↗
PubMed1992

Evaluation of the measurement of the intraoperative transcutaneous partial pressure of oxygen (PtcO2) as a prognostic indicator in vascular reconstruction.

The intraoperative transcutaneous partial pressure of oxygen (PtcO2) was used to monitor 58 vascular reconstructive surgery procedures in 54 patients. The study comprised three groups: Group A (24 limbs without any ischemic symptoms or signs), Group B (45 limbs with intermittent claudication), and Group C (12 limbs with ischemic rest pain, ulceration, and gangrene). In addition in 31 patients the chest wall was monitored simultaneously as a control. The results showed that the PtcO2 values increased immediately and significantly to varying degrees and at varying speeds after unclamping. The controls had higher values than Group A (P > 0.05), Group B (P < 0.05), and Group C (P < 0.05) patients. Further study showed that there were no significant differences between the maximal values in the limbs with good distal vessel run-off in Groups A, B, and C, and in the controls (P > 0.05). It is thus concluded that effective vascular reconstruction in the limbs is indicated by a rapid and marked increase of both the PtcO2 value and the response value, while with a slow and low increase of the value, early graft failure and poor distal vessel run-off should be suspected. We believe that this monitoring method dynamically reflects the functional state during vascular reconstruction and is clinically valid.

Adult↗
PubMed1992

Molecular analysis of the zeste-white interaction reveals a promoter-proximal element essential for distant enhancer-promoter communication.

We have analyzed the eye and testis enhancers located 1 kb upstream of the transcription start site of the white gene. Both enhancers confer the corresponding tissue-specific expression on a heterologous promoter as well as on the white promoter. The eye determinant consists of multiple elements, each able to stimulate eye-specific expression. It also contains five binding sites for the zeste protein while the immediately adjacent testis element contains none. Site-directed mutation of these zeste binding sites abolishes the zeste-white interaction but does not significantly affect the eye enhancer activity, indicating that they are not important for the eye enhancer activity per se. Other zeste binding sites just upstream of the promoter are not necessary for the zeste-white interaction. We conclude that the overlap of the eye enhancer with the zeste binding sites is responsible for the zeste-white interaction and explains why this interaction affects eye but not testis expression. Sequence deletion or substitution experiments suggested that the white promoter is internal to the transcription start site; the zeste protein is not required for distant enhancer action but a 95-bp promoter-proximal sequence is essential for distant enhancer-promoter interaction. This element may serve as an anchor to stabilize formation of a loop that brings the enhancer to the vicinity of the promoter.

Animals↗
PubMed1992

Pulmonary vascular reactivity and hemodynamic changes in elastase-induced emphysema in hamsters.

Changes in pulmonary hemodynamics and vascular reactivity in emphysematous hamsters were studied in an isolated lung preparation perfused at constant flow with blood and 3% dextran. Hamsters were treated with intratracheal porcine pancreatic elastase at 70 days of age, and experimental studies were conducted at 1, 3, and 8 mo after treatment. Baseline pulmonary arterial pressure in elastase-treated lungs was increased compared with saline-treated control lungs 1 mo after treatment, but this increase did not progress at 3 and 8 mo. Increases in pulmonary arterial pressure in elastase-treated lungs were temporally correlated with the morphological development of emphysema and right ventricular hypertrophy; both of these were evident at 1 mo after treatment and showed little change thereafter. Pressor responses to hypoxia and angiotensin II were not different between elastase-treated and control lungs at 1 and 3 mo. At 8 mo, however, pressor responses in emphysematous lungs to 0% O2 (but not to angiotensin II) were significantly increased. This was the result of a lack of the normal age-related fall in the hypoxic pressor response. Our results suggest that the right ventricular hypertrophy found in these emphysematous animals results from a chronically increased pulmonary vascular resistance. Furthermore, increases in pulmonary vascular resistance in the early development of emphysema are likely a result of the loss of vascular beds and supporting connective tissue.

Angiotensin II↗
PubMed1991

The bx region enhancer, a distant cis-control element of the Drosophila Ubx gene and its regulation by hunchback and other segmentation genes.

The Drosophila homeotic gene Ultrabithorax (Ubx) is regulated by complex mechanisms that specify the spatial domain, the timing and the activity of the gene in individual tissues and in individual cells. In early embryonic development, Ubx expression is controlled by segmentation genes turned on earlier in the developmental hierarchy. Correct Ubx expression depends on multiple regulatory sequences located outside the basal promoter. Here we report that a 500 bp DNA fragment from the bx region of the Ubx unit, approximately 30 kb away from the promoter, contains one of the distant regulatory elements (bx region enhancer, BRE). During early embryogenesis, this enhancer element activates the Ubx promoter in parasegments (PS) 6, 8, 10, and 12 and represses it in the anterior half of the embryo. The repressor of the anterior Ubx expression is the gap gene hunchback (hb). We show that the hb protein binds to the BRE element and that such binding is essential for hb repression in vivo, hb protein also binds to DNA fragments from abx and bxd, two other regulatory regions of the Ubx gene. We conclude that hb represses Ubx expression directly by binding to BRE and probably other Ubx regulatory elements. In addition, the BRE pattern requires input from other segmentation genes, among them tailless and fushi tarazu but not Krüppel and knirps.

Animals↗