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Biomedical subjects

S Chi

Publications and source records attributed to S Chi.

36 records · Page 2Linked to original sources
PubMed1994

Fischer and Lewis rat strains show differential cocaine effects in conditioned place preference and behavioral sensitization but not in locomotor activity or conditioned taste aversion.

Current research suggests there are genetic differences in susceptibility to drug abuse. One way to examine this relationship is to study inbred strains, such as Lewis (LEW) and Fischer 344 (F344) rats, that show differential biochemical and behavioral effects in response to psychoactive drugs. In the present study several behavioral effects of cocaine were compared in these strains, including conditioned place preference (CPP), conditioned taste aversion and locomotor activity. Cocaine CPP was greater in LEW rats than in F344 rats. In contrast, cocaine conditioned taste aversion did not differ between LEW and F344 rats, or did the locomotor activity levels seen after the first cocaine administration. LEW rats, however, showed enhanced locomotor activity to repeated cocaine administrations at all doses tested, an effect not seen in F344 rats. These data suggest that differences in the development of cocaine CPP in LEW and F344 rats are not due to differences in detection of or in inability to condition to cocaine. Rather, these differences in CPP may reflect strain differences in the response to repeated cocaine administrations and may be related to previously observed biochemical differences between the two rat strains.

Animals↗
PubMed1993

[Effect of 764-3 on ConA receptors on rat alveolar macrophages].

The changes of concanavalin A (ConA) receptors on alveolar macrophage (AM) surfaces were observed by means of ConA-horseradish peroxidase gold labelling techniques. The results were as follows: 1) The average gold particle number on normal AM surfaces was 1.985 +/- 0.097/microns, distributed uniformly; 2) On AM activated by BLMA6, in vitro, this number had increased to 3.909 +/- 0.314/microns, P < 0.001 compared with the normal group; 3) On AM preincubated with 764-3, the average gold particle number was 1.577 +/- 0.090/microns, significantly lower than that in the BLMA6 group. All results suggest that 764-3 might partially inhibit the expression of ConA-R on AM activated by BL-MA6.

Animals↗
PubMed1993

[The effect of 764-3 on alveolar macrophage morphologic changes induced by BLM-A6].

The morphologic changes of alveolar macrophages (AM) were observed by electron microscopy, computer controlled image analysis and stereoscopy. The results showed that 764-3 had no effect on normal AM morphology and structure, but inhibited the BLM-A6 induced increase of volume, specific surface, and lysosome volume density of AM. At the same time, the spreading ability of AM on the slide was markedly reduced by 764-3, indicating that 764-3 can partially prevent the AM activation caused by BLM-A6 in vitro.

Animals↗
PubMed1992

Interaction of human bone marrow fibroblasts with megakaryocytes: role of the c-kit ligand.

Human kit ligand (KL), also known as stem cell factor (SCF), steel factor, or mast cell growth factor, is a recently identified hematopoietic growth factor whose receptor is the product of the c-kit proto-oncogene. Alternative splicing of the pre-mRNA of KL/SCF results in secreted and membrane-bound forms of the protein. We and others have recently shown that the c-kit gene product is expressed on human megakaryocytes and that soluble KL/SCF in combination with granulocyte-macrophage colony-stimulating factor, interleukin-3 (IL-3), or IL-6 increased megakaryocyte progenitor colony formation (CFU-MEG) and stimulated mature megakaryocytes. Here we show that adhesion of human megakaryocytes to bone marrow stromal fibroblasts, which express the membrane-bound form of KL/SCF (mKL/SCF), is mediated in part by the interaction between mKL/SCF and the c-kit protein. This interaction also results in marrow fibroblast-stimulated proliferation but not an increase in ploidy of megakaryocytes; when the two cell types were separated by a transoluble membrane, proliferation did not occur. Adhesion and proliferation of human megakaryocytes to an immortalized murine stromal cell line SI/SI lacking the KL/SCF gene was impaired, whereas transfection of SI/SI cells with human mKL/SCF significantly increased both adhesion and proliferation. Marrow stromal fibroblast mKL/SCF may serve both as an adhesion structure and as a growth-potentiating factor for megakaryocytes in the bone marrow.

Animals↗
PubMed1992

Effects of the stem cell factor, c-kit ligand, on human megakaryocytic cells.

The kit ligand (KL), also termed stem cell factor (SCF), is a recently discovered hematopoietic growth factor that augments response of early progenitor cells to other growth factors and supports proliferation of continuous mast cell lines. Histological studies suggest that the receptor for SCF/KL, the c-kit proto-oncogene product, is present in bone marrow megakaryocytes. We studied the effects of SCF/KL on immortalized human megakaryocytic cell lines (CMK, CMK6, and CMK11-5) and on isolated human marrow megakaryocytes. Human SCF/KL alone or in combination with the hematopoietic growth factors, interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-6, stimulated proliferation of these megakaryocytic cell lines. SCF/KL treatment did not alter expression of gpIb, gpIIb/IIIa, LFA-1, ICAM-1, or GMP-140 in CMK cells. No effect on ploidy was observed. Furthermore, human SCF/KL induced expression of IL-1 alpha, IL-1 beta, IL-2, and IL-6 in CMK cells. In a fibrin clot system, SCF/KL modestly potentiated megakaryocyte colony formation when added alone to cultures containing CD34+, DR+ bone marrow cells. Addition of SCF/KL with IL-3 or GM-CSF to these cultures resulted in a more marked marrow megakaryocytic cells. SCF/KL may directly affect megakaryocytopoiesis, as well as secondarily modulate hematopoiesis through induction of cytokines in target cells.

Antigens, Surface↗
PubMed1991

The pericardial valve in the aortic position ten years later.

To assess the behavior of the pericardial valve at 10 years after implantation, the cases of 240 patients who had undergone aortic valve replacement with the standard Ionescu-Shiley (Shiley, Inc., Irvine, Calif.) bovine pericardial valve between February 1977 and December 1983 were reassessed. Follow-up of the 224 hospital survivors was 99.6% complete. Fifty-seven valve-related events occurred. Fourteen were thrombotic events (1.2%/patient-year), 28 were intrinsic tissue failures (2.4%/patient-year), 13 were cases of prosthetic valve endocarditis (1.1%/patient-year), and 2 were paravalvular leaks (0.17%/patient-year). The linearized rate for death, reoperation, or both resulting from valve-related events was 3.6%/patient-year. Time-related hazard function for the instantaneous risk of death and/or reoperation resulting from valve-related events demonstrated an exponential increase after 80 months. These data, in conjunction with our previous reports on the histologic changes in pericardial collagen and the incidence of calcification (26/28), should be considered regarding new and future generations of pericardial bioprostheses. Although this device provides good hemodynamics and carries a low incidence of thromboembolism, it has a limited durability. New generations of pericardial valves may have improved structural features, but the behavior of glutaraldehyde-fixed, formaldehyde-stored bovine pericardium as currently selected and prepared is unlikely to change.

Adolescent↗
PubMed1986

Clinical results after bioprosthetic aortic valve replacement in patients with and without coronary artery disease: value of concomitant myocardial revascularization.

The present study analyzes a 7-year experience of two concurrent groups of patients, one with and one without coronary artery disease. These groups underwent aortic valve replacement within the same time frame. They had the same method of myocardial protection and type of valve substitute, and there was no postoperative anticoagulant therapy. There was no statistically significant difference in hospital and late mortality, or in actuarial survival of the two groups after 4 years. Bypass grafting in patients with coronary artery disease undergoing aortic valve replacement reverts these groups of patients to the longterm prognostic level of patients with isolated aortic valve disease undergoing aortic valve replacement.

Journal Article↗
PubMed1984

Thromboembolism and bleeding after mitral valve replacement with porcine valves: influence of thromboembolic risk factors.

The risk of postoperative thromboembolism (PTE), anticoagulant related hemorrhage (ARH), and the influence of thromboembolic risk factors ( TERF ) were assessed retrospectively in 206 unselected patients undergoing mitral valve replacement (MVR) with porcine xenobioprotheses ( PXBP ). Other aims were to identify the "high-risk" group with respect to PTE and to assess the effectiveness of long-term anticoagulant therapy (AT) in this subset, as well as to elucidate the most adequate method of AT and ascertain if AT is strictly necessary in patients undergoing MVR with PXBP . Patients were divided in two groups: Group I (N = 115) received long-term AT; there were 22 PTE. Group II (N = 91) with only 8 weeks of AT had 2 PTE (P less than 0.01). ARH was the same in both groups. Actuarially , 71.7% of the patients in group I and 96.3% of the patients in group II were free of PTE at 6 years. Long-term AT proved ineffective in preventing PTE and carried a significant incidence of ARH. ARH surpassed PTE (3.5:1) in patients on short-term AT. Patients without TERF have a low incidence of PTE, and AT is not indicated. The "high-risk" group were patients in postoperative atrial fibrillation and left atrial enlargement. One week heparin therapy and 3 months oral AT is suggested for patients with TERF . PXBP for MVR in patients with TERF is significantly thrombogenic. Early operation is advocated to avoid development of TERF that will affect patient outlook after MVR with PXBP due to the significantly increased risks of PTE and (if placed on AT) ARH.

Adult↗
PubMed1984

The risk of thromboembolism and hemorrhage following mitral valve replacement. A comparative analysis between the porcine xenograft valve and Ionescu-Shiley bovine pericardial valve.

To ascertain the risk of thromboembolism and anticoagulant-related hemorrhage following mitral valve replacement with bioprostheses, an 8 year retrospective study between two groups of patients was analyzed. Group I included 206 patients undergoing mitral valve replacement with porcine xenograft valves. They were placed on a regimen of long-term oral anticoagulation (greater than 8 weeks, mean 6 months). Follow-up was 524.3 patient-years, mean 30.5 months. There were 24 thromboembolic events (4.6% per patient-year), four of which were fatal. Actuarially, 80.7% +/- 4.3% are free of thromboembolism at 8 years. There were 12 instances of major bleeding episodes, for a linearized incidence of 2.5% per patient-year; two were fatal. Group II included 322 patients undergoing mitral valve replacement with a bovine pericardial valve. They were placed on a program of short-term anticoagulation (6 weeks only). Follow-up was 1,106 patient-years, mean 46.4 months. There were four thromboembolic episodes (none fatal), an incidence of 0.36% per patient-year. Seven bleeding episodes occurred, 0.63% per patient-year; none was fatal. The difference between the groups reached statistical significance (p less than 0.001). The low risk of thromboembolism with the bovine pericardial valve appears to be due to its superior hydraulic characteristics. Use of this valve allows mitral valve replacement without long-term oral anticoagulation and the associated risk of anticoagulant-related hemorrhage.

Adolescent↗
PubMed1983

Five-year experience with the Ionescu-Shiley bovine pericardial valve in the aortic position.

Between February, 1977, and April, 1982, 168 patients underwent aortic valve replacement (AVR) with an Ionescu-Shiley bovine pericardial valve. Concomitant procedures were performed in 71 patients. There were 12 hospital deaths (7.1%). Among patients having AVR only, there were 5 deaths (5.2%). Assessment included valve durability, incidence of thromboembolism, clinical improvement, and patient survival. There was 100% follow-up. Actuarial freedom from intrinsic valve failure at 5 years was 96.3 +/- 3.6%. Intrinsic valve failure occurred only once, 0.3 episodes per 100 patient-years. Four patients had thromboembolic complications. As for clinical status, 99.3% of surviving patients are in New York Heart Association Functional Class I or II, including 79 patients with valve sizes 17, 19, or 21 mm (56%). Among 13 late deaths, 9 were related to the cardiovascular system. Overall patient survival is 84.9 +/- 4.7%. Among the 92 patients with isolated AVR, 87.8 +/- 5.9% are alive at the 5-year follow-up. If the incidence of valve failure is not altered in years to come, the durability of the Ionescu-Shiley bovine pericardial valve will surpass that of previous bioprostheses.

Actuarial Analysis↗
PubMed1978

Aortic valve replacement during acute rheumatic fever.

Emergency aortic valve replacement was performed during an attack of acute rheumatic fever in a 12-year-old black boy. He had an uneventful recovery and has remained asymptomatic 27 months after operation. In the light of this experience and that of others, one might conclude that the decision to operate on these patients should be based on the severity of the haemodynamic derangement rather than on the state of activity in the rheumatic process.

Acute Disease↗
PubMed1977

Rupture of the normal aortic valve after blunt chest trauma.

Rupture of the normal aortic valve after blunt trauma to the chest is seen infrequently. With the ever-increasing incidence of car and motorcycle accidents, this injury should be considered during the initial examination of an accident victim. Any patient without a history of heart disease presenting with heart murmurs after severe blunt trauma to the chest should give rise to the suspicion of aortic valve damage. When the diagnosis is proved, aortic valve expoloration is necessary. Review of the published cases establishes that valve replacement is the treatment of choice.

Accidents, Traffic↗
PubMed1977

Orthoterminal correction of coexisting d-transposition of the great arteries, subpulmonary stenosis, and a complete form of atrioventricular canal.

This report outlines orthoterminal correction in an 8-year-old boy with coexisting d-transposition of the great arteries (d-TGA), subpulmonary stenosis, and a complete form of atrioventricular canal (CAVC). The repair consisted of covering the tricuspid valve and atrial part of the atrioventricular canal with a Dacron patch and inserting a valve-containing conduit between the then isolated right atrium and the pulmonary artery to create a venous outlet. The patient's exercise tolerance has improved remarkably. The arterial oxygen saturation has risen from 86 to 90 per cent. A plea is made to expand the indications for orthoterminal correction to patients in whom the severity of the heart malformation precludes application of well-established methods of surgical repair.

Child↗