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S M Yuan

Publications and source records attributed to S M Yuan.

15 recordsLinked to original sources
PubMed1999

Cytochemistry and ultrastructure of canine myocardium undergoing global ischemia and reperfusion injury.

In order to highlight severity of myocardial injury during the course of global ischemia and reperfusion, cytochemistry of glycogen and succinate dehydrogenase (SDH) as well as hematoxylin and eosin staining (H & E) and electron microscopy were observed in canine myocardium. Seven mongrel dogs were selected for reperfusion injury after global ischemia in this study. Myocardial biopsies were taken from the anterior wall of the left ventricle (a) after cardiopulmonary bypass (the first biopsy); (b) at the end of the aortic crossclamp (the second biopsy); and (c) 30 minutes after crossclamp removal (the third biopsy). All biopsies were cytochemically assessed, and the latter two, for electron microscopic studies. The averages of myocardial necrotic rate and surface to volume ratio of myocardial mitochondria were calculated under electron microscopy and in electron microscopic slices, respectively. Myofibrillae were of normal morphology in the first biopsy; in wave-shape and partly vacuolated, with large and deformed nuclei in the second one; and in wave-shape and severely vacuolated in the third one, in H & E. Glycogen granules were variously stained in moderate, weak and intensive positive reactions in the three biopsies respectively in glycogen staining. SDH was stained in intensive, weak, and moderate positive reactions in three, respectively. By electron microscopy, Z bands twisted severely, and local dissolution of cristae and matrix occurred in a minority of the mitochondria in the second biopsy; and majority of the Z bands in necrotic region had disappeared, the myofibrillae were obscure and patchily dissolved. Clustered and deformed mitochondria could be found in the third biopsy. Significant difference could be noted between the averages of the second and third biopsies (14.88 +/- 3.09% vs. 60.25 +/- 8.55%, p < 0.001). The surface to volume ratio of the ischemic mitochondria was much bigger than that of the reperfused (3.95 +/- 1.09 micron-1 vs. 2.77 +/- 0.93 micron-1, p = 0.041). Myocardial injury was more severe in reperfusion than in ischemia myocardium. There were correlations between histobiochemical and ultrastructural alterations in damaged canine myocardium.

Animals↗
PubMed1999

A delivery circuit for normothermic reperfusion model.

In order to facilitate the introduction and assessment of Injectio Radix Ginseng Compositae in normothermic reperfusion model, a simplified delivery circuit is described herein. The circuit added mainly a venous reservoir collecting Injectio Radix Ginseng Compositae with cardiopulmonary bypass. Injectio Radix Ginseng Compositae was pumped into the ascending aorta of the animal after mixing with cardioplegia in the venous reservoir. The circuit was acceptable in terms of price by most inland medical laboratories. Perfusion as well as biochemical results monitored were satisfactory. Significant difference was noted between the average damage rates of the reperfused myocardial mitochondria in groups by ultrastructural analysis (70.12 +/- 2.56% vs. 25.33 +/- 17.62%, p = 0.023). No complications associated with perfusion technique occurred in either group. The circuit could offer a constant arterial perfusion, and was proved to be simple, safe and effective in cohort.

Animals↗
PubMed1998

A hybrid sequence approach to the paracelsus challenge.

Inspired by the Paracelsus Challenge of Rose and Creamer (Proteins 19: 1-3, 1994), we have designed a protein sequence that is 50% identical to an all-helical protein but is intended to fold into a largely beta-sheet structure. Rather than attempt a de novo design, our strategy was to construct a hybrid sequence based on a helical "parent" protein (434 Cro) and a "target" protein with the desired fold (the B1 domain of protein G). The hybrid sequence (Crotein-G) is 50% identical to 434 Cro but is also 62% identical to the B1 domain of protein G. We also created a variant of Crotein-G (ZCrotein-G) that contains a potential His3Cys1 zinc binding site. At low protein concentrations and in the presence of 20% 2,2,2-trifluoroethanol (TFE) (v/v), the circular dichroism spectra of the designed proteins are distinct from that of 434 Cro and similar to that of the B1 domain of protein G. However, the proteins fail to denature in a cooperative manner. Furthermore, aggregation occurs at moderate protein concentrations or in the absence of TFE. Addition of zinc to ZCrotein-G does not promote structure formation. In summary, 434 Cro has been altered to something that may resemble the B1 domain of protein G, but the protein does not adopt a native structure.

Amino Acid Sequence↗
PubMed1998

In vitro pulsatile flow visualization on extracardiac conduits for the right ventricular outflow tract reconstruction: qualitative considerations.

Valved homograft conduits play an important role in the right ventricular outflow tract (RVOT) reconstruction for the surgical treatment of complex congenital heart disease. An excellent immediate rather than long-term outcome could be obtained. The hemodynamics for late failure, however, remained unclear. In vitro pulsatile flow visualization was not conducted before. A simplified right heart duplicator system was set up and driven under physiologic conditions. Polystyrene of 0.18 mm in diameter was applied as the tracing particle. Flow characteristics of models of normal pulmonary circulation as well as pulmonary artery atresia with the RVOT reconstructed utilizing valved and non-valved extracardiac conduits were observed. Flow patterns in the normal pulmonary circulatory model were mainly of axial flow associated with small scope of flow disturbances. A single vortex in the right ventricle was noted in diastole. In the pulmonary artery atresia model, a couple of vortexes were found in the right ventricle, a secondary flow in the main pulmonary artery, and a stronger secondary flow than in the normal pulmonary circulatory model in the two branches in both systole and diastole. A secondary flow was found in the proximal, an axial flow was observed in the distal portion of the extracardiac conduit with normal bioprosthetic valves and a secondary flow was observed in the entire conduit with stenotic bioprosthetic valves. The secondary flow intensity became stronger with the development of the stenosis. Severe insufficiency occurred in the bileaflet ceramic tilting-disc prosthesis during the entire cardiac circle, i.e., the prosthesis was in a maximum open position. Severe reverse flow could be found in the extracardiac conduit in the deceleration phase. Concavity of the crank shaft was found by examination to be filled with tracing particles and the prosthesis became stuck. Model of RVOT reconstruction with non-valved conduit yielded reverse flow inside the extracardiac conduit as well. Secondary flow may occur in normal or diseased extracardiac conduit for RVOT reconstruction. If micro-thrombus of over 0.18 mm in diameter attached in the concave of the crank shaft of a bileaflet tilting-disc prosthesis under a condition of resistance as occurred in the present study, the prosthesis may become stuck. Model of RVOT reconstruction with non-valved extracardiac conduit yielded reverse flow inside the conduit, of which the flow pattern was of greater energy consumption. Thus, a non-valved conduit should be avoided in clinical practice as far as possible.

Heart Defects, Congenital↗
PubMed1998

A generalized consideration of myocardial preservation with cold crystalloid versus warm blood cardioplegia in heart valve replacement.

Continuous warm blood cardioplegia was widely used, as an effective means of myocardial preservation, in open heart surgery. The comparisons of myocardial protective effects between traditional cold crystalloid and warm blood cardioplegia, however, have been based mainly on hemodynamics, cardiac function and myocardial metabolism, other than clinical outcome. The present study was designed to examine myocardial protective effects by assessing clinical outcome, enzyme levels and myocardial cytochemistry. Twenty patients undergoing heart valve replacement were divided randomly into two groups: Group I was given intermittent perfusion of cold crystalloid (St. Thomas Hospital solution) with hypothermic cardiopulmonary bypass (CPB) and Group II was given continuous administration of warm blood cardioplegia with normothermic CPB. The groups were similar with respect to sex, age, body surface area and preoperative ventricular function. Blood samples were obtained from an indwelling radial arterial catheter or from the arterial end of the oxygenator. Biopsy specimens from the right atrium were obtained immediately before aortic declamping (ischemic period) and 30 minutes after crossclamp removal (reperfusion period). Serum enzymes, including alanine transaminase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and its isoenzymes and creatine phosphokinase (CK) and its isoenzyme, were determined. Myocardial cytochemistry were chiefly assessed by grey-scale image processing of adenosine triphosphatase (ATPase), succinate dehydrogenase (SDH) and cytochrome oxidase (CCO) examinations. Relations among the results were discussed. Reperfusion time was reduced and ventilation support time decreased in Group II (33.50 +/- 3.78 min vs. 25.00 +/- 4.46 min, p < 0.05; 38.98 +/- 16.55 h vs. 19.84 +/- 1.11 h, p < 0.05). Rates of atrial beating during aortic crossclamp and spontaneous recovery to normal sinus rhythm were much higher in Group II than in Group I (80% vs. 20%, p < 0.05; 70% vs. 10%, p < 0.05). Differences in hospital morbidity and mortality between groups were nonsignificant. Serum AST, ALT, LDH and LDH1 + LDH2 all showed no significant intergroup differences. There was a higher serum CK-MB level with a delayed peak in Group II. The cytochemistry activities of ATPase was not different between groups and periods and SDH was the highest during reperfusion period in Group I and of CCO significantly much promoted in Group II in both periods. Continuous warm blood cardioplegia resulted in higher spontaneous recovery to sinus rhythm, shorter reperfusion and ventilation support time. Damage to the myocardium, skeletal muscle and liver always occur in warm blood cardioplegic patients. However, warm blood cardioplegia is still a practical method for myocardial preservation in open heart surgery.

Adenosine Triphosphatases↗
PubMed1998

Benefits and pitfalls of warm blood cardioplegia in heart valve replacement: systemic protective effects.

The purpose of this paper was to assess the role of continuous warm blood cardioplegia in heart valve replacement in comparison with standard intermittent cold crystalloid cardioplegia. Twenty patients undergoing open heart valve replacement were divided arbitrarily into two groups in this study; Group I was given intermittent perfusion of cold crystalloid (St. Thomas Hospital solution) with hypothermic cardiopulmonary bypass (CPB) (10 patients) and Group II was given continuous administration of warm blood cardioplegia with normothermic CPB (10 patients). The groups were similar with respect to sex, age, body surface area and preoperative ventricular function. Bypass conditions as well as perioperative complications were evaluated in the respective groups. Peak values of the serum enzyme levels within 120 hours of postoperation including alanine transaminase, aspartate aminotransferase, lactate dehydrogenase (LDH) and its isoenzymes LDH1 + LDH2, phosphokinase (CK) and its isoenzyme CK-MB, superoxide dismutase, and malondialdehyde in the two groups were also assessed. Biopsies from the right atrium were obtained immediately before aortic cross clamp removal (ischemic period), and 30 minutes after cross clamp removal (reperfusion period). Myocardial structures were observed and scored. No significant intergroup differences were found in the bypass conditions except for the perfusion flow, systemic temperature and central venous pressure. There were no significant differences in the intergroup perioperative complications, either. Serum enzymes except CK which reached peak values in Group I appeared prior to or consistent with Group II. There were no significant intergroup differences in peak levels of the serum enzymes except CK (307.44 +/- 38.56 U/L vs. 466.29 +/- 52.03 U/L, p = 0.039 for CK). From the pathological assessment, the structural alterations were the most severe during the reperfusion period in group I. Myocardial damage showed more severely in reperfusion than in ischemia in both. Warm blood cardioplegic technique, raising potential hazards, is still a practical method for myocardial protection in open heart surgery, but might be less effective in protecting the tissues beyond myocardium.

Creatine Kinase↗
PubMed1998

In vitro flow visualization on the right ventricular outflow reconstruction utilizing extracardiac conduits: set-up of duplicator system and its clinical significance.

The right ventricular outflow tract (RVOT) reconstruction with cryopreserved valved homograft conduits was one of the most important methods in the surgical management of congenital heart defects. However, the hemodynamics for long-term conduit failure remain uncertain, and in vitro studies have not been conducted. Based on the surgical patterns of RVOT reconstruction in clinical practice, the compliant silicon elastomers were cast, and the simplified duplicator system was set up. When the system connected with an eight-channel recorder, and driven by a specified software, flow patterns were able to be visualized, and data to be collected. The simplified right heart system was stable and duplicated well as to the characteristics according with laws of similitude in geometry and physiology, although the conduit model is not in accordance with the clinical extracardiac conduit in angulation, length, diameter, curvature and anastomsis fashion. The right heart duplicator system was a prerequisite condition for the successful research of flow fields of the right heart conduits.

Blood Pressure↗
PubMed1997

Effects of myocardial preservation on enzyme levels in serum and myocardium: a clinical study comparing cold crystalloid versus warm blood cardioplegia.

BACKGROUND: Enzyme activities have been recognized as one of the parameters in the assessment of the effects of various forms of myocardial preservation. However, comparisons between different methods of myocardial protection by the use of enzyme assay in clinical settings in uncommon. METHODS: Twenty patients who underwent open-heart valve replacement were divided equally into two groups: intermittent perfusion of cold crystalloid (St. Thomas Hospital solution) with hypothermic cardiopulmonary bypass (CPB) (Group I) and continuous administration of warm blood cardioplegia with normothermic CPB (Group II). The groups were similar with respect to sex, age, body surface area and preoperative ventricular function. Blood samples were obtained from an indwelling radial arterial catheter or from the arterial end of the oxygenator. Biopsy specimens from the right atrium were obtained immediately before aortic declamping (ischemic period), and 30 minutes after crossclamp removal (reperfusion period). The cumulative release of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and its isoenzymes; linear correlation between (iso)-enzymes of each group and multivariate regression between blood potassium and serum enzymes were determined. The enzyme levels of myocardial specimens including ALT, AST, LDH, creatine phosphokinase (CK), superoxide dismutase (SOD), and malondialdehyde (MDA) were recorded and compared both between the two groups and within each group. RESULTS: No significant intergroup difference was found in the cumulative release of the serum (iso)-enzymes. Close relationships were found in all the correlation coefficients except for the CK-ALT couple in Group I. Neither were intergroup differences found in each parameter of the linear correlations between the (iso)-enzymes. A close correlation between blood potassium and serum enzymes was found in Group I rather than in Group II. Differences of enzyme levels of myocardial specimens between ischemic periods and reperfusion periods were also not statistically significant either within the group or between the groups. CONCLUSIONS: Judging from the results of enzyme assay, similar myocardial preservation effects against ischemia-reperfusion injuries could be obtained by either of the techniques of myocardial preservation.

Alanine Transaminase↗
PubMed1997

Association of secundum atrial septal defect and mitral lesion in childhood: a case report.

The association of secundum atrial septal defect (ASD) and congenital or acquired mitral lesions is rare. Only one case of secundum ASD and mitral lesion, in a three-year-old girl, has been encountered over a three-year period in this hospital. Diagnosis was not difficult with echocardiography, and was confirmed by operation. Surgical procedures including repair of ASD and annuloplasty of the mitral valve were performed under cardiopulmonary bypass. The mitral valve lesion was found during the operation to be of a congenital origin. Mitral lesions should not be neglected, and repair should be attempted even in a pediatric patient. Otherwise, anatomical and functional disorders of the mitral valve may develop at the early postoperative stage.

Child, Preschool↗
PubMed1995

Metal search: a computer program that helps design tetrahedral metal-binding sites.

We describe a computer program (Metal Search) that helps design tetrahedrally coordinated metal binding sites in proteins of known structure. The program takes as input the backbone coordinates of a protein and outputs lists of four residues that might form tetrahedral sites if wild-type amino acids were replaced by cysteine or histidine. The program also outputs the side chain dihedral angles of the amino acids and the coordinates of the predicted metal ion. The only function evaluated by Metal Search is the ability of side chains to meet simple geometric criteria for formation of a tetrahedral site, but these criteria are sufficient to produce a manageably small list that can then be evaluated by other means. The program has been used in the introduction of zinc binding sites in the designed four-helix bundle protein alpha 4 and in the B1 domain of streptococcal protein G, and in both cases the tetrahedral coordination of a bound metal ion has been confirmed (Klemba, M., Gardner, K. H., Marino, S., Clarke, N.D., and Regan, L., Nature: Structural Biology 2:368-373, 1995).

Amino Acids↗
PubMed1994

Myocardial protection of cold crystalloid and warm blood cardioplegia. A comparative study.

Twenty patients undergoing open-heart valvular operations were divided randomly into two groups. Intermittent perfusion of cold crystalloid (St. Thomas Hospital solution) with hypothermic cardiopulmonary bypass (CPB) in the hypothermic group and continuous administration of warm blood cardioplegia with normothermic CPB in the normothermic group were used respectively. The results of warm blood cardioplegia were superior to those of cold crystalloid. 70% of patients treated with the warm technique had spontaneous return of normal sinus rhythm shortly after removal of the aortic cross-clamp, compared with only 10% of the hypothermic group (P < 0.05). The extracorporeal support time from releasing of aortic clamp to the weaning of CPB was significantly shorter in the normothermic group (33.50 +/- 3.78 min vs. 25.00 +/- 4.64 min, P < 0.05). The postoperative ventilation support time was also much shorter than that of the hypothermic group (19.84 +/- 1.11 h vs. 38.98 +/- 16.55 h, P < 0.05). More atrial beating occurred in the normothermic group (80% vs. 20%, P < 0.05) during aortic clamping, and it is showed that continuous warm blood cardioplegia might not efficiently prevent the atrium from damage.

Adult↗