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Biomedical subjects

S Y Ho

Publications and source records attributed to S Y Ho.

At least 19 recordsLinked to original sources
PubMed1992

Right ventricular outflow obstruction by anomalies of the tricuspid valve: report of a windsock diverticulum.

A 9-month-old infant with a clinical diagnosis of double outlet from the right ventricle, subaortic ventricular septal defect, and muscular subpulmonary obstruction underwent surgical repair. The defect was corrected and the right ventricular infundibulum enlarged with a patch. Eight hours after the operation there was a sudden collapse which rapidly progressed to cardiac arrest and death. Postmortem examination of the heart confirmed the clinical diagnosis but noted that the subpulmonary obstruction was caused by a "windsock" deformity of the tricuspid valve which was not identified at operation. The variants of malformations of the tricuspid valve causing subpulmonary obstruction are reviewed.

Heart Septal Defects, Ventricular↗
PubMed1992

Morphology of the posterior junctional area in atrioventricular septal defects.

The location and size of the coronary sinus in hearts with atrioventricular septal defect were investigated in relation to the known disposition of the atrioventricular conduction axis. We examined the morphology in 40 hearts and supplemented this series with two other hearts that had been serially sectioned previously. The coronary sinus received drainage from a persistent left superior caval vein in 5 hearts. Six cases of 40 had malalignment of the septal structures relative to the crux of the heart. In these, the conduction axis was anticipated to course in the position where the inlet ventricular septum met the atrioventricular junction. The coronary sinus terminated in the left atrium in 4 hearts: 2 in the morphological series and 2 that were sectioned for histological studies. The sectioned hearts showed the atrioventricular conduction axis in the usual position for the defect, unrelated to the coronary sinus. The principle that the node and penetrating bundle are located at the intersection of the ventricular septum with the atrioventricular junction holds good despite the variability of the coronary sinus.

Adolescent↗
PubMed1992

Disposition of the atrioventricular conduction tissues in the heart with isomerism of the atrial appendages: its relation to congenital complete heart block.

OBJECTIVES: Our goal was to compare histologically the mechanisms producing congenital complete heart block in normally structured hearts and in hearts with isomerism of the atrial appendages. BACKGROUND: It is known that several different histologic patterns can underscore the existence of congenital complete heart block in the normally structured heart, and that block is particularly frequent in the setting of isomerism of the atrial appendages. The histologic findings in the latter setting were compared and contrasted with those found in the normally structured heart. METHODS: Serial section techniques were used to study 14 hearts with isomerism of the atrial appendage (12 with left isomerism and 2 with right isomerism) and 7 normally structured hearts. RESULTS: Discontinuity between the atrioventricular (AV) node and the ventricular conduction tissues was found in 10 of the 12 hearts with left isomerism; the other 2 hearts had a normally formed conduction axis and heart block was not present in these cases. In both hearts with right isomerism, "slings" of ventricular conduction tissue connected dual AV nodes; congenital complete heart block was not present in either case. In six of the seven cases with a normally structured heart, anti-Ro antibodies had been found in the maternal serum. All six of these hearts had discontinuity between the atrial tissues and the ventricular conduction axis. Intraventricular discontinuity was found in the seventh case, in which anti-Ro antibodies were not found in the mother. CONCLUSIONS: The pattern of congenital complete heart block in cases with left isomerism is discontinuity between the AV node and the conduction axis, in contrast to the pattern of atrial-axis discontinuity produced in the normally structured heart when anti-Ro antibodies are found in the maternal serum.

Abnormalities, Multiple↗
PubMed1992

Histopathological findings in three children with His bundle tachycardia occurring subsequent to cardiac surgery.

This report concerns three children with His bundle tachycardia who died following cardiac surgery. At autopsy the conduction system was examined in detail. In all three, the sinus node was intact and supplied by a well-formed artery. Haemorrhagic tracks were identified invading the penetrating atrioventricular bundle. The tracks originated from stitches placed close to the conduction tissue. The hypothesis that disruption of the conduction tissue results in an arrhythmogenic focus is discussed.

Bundle of His↗
PubMed1992

Radioactive contamination in hospitals from nuclear medicine patients.

Comparatively little research has been published on radioactive contamination from nuclear medicine patients using hospital toilet facilities. The present study was undertaken to obtain an estimate of the amount of restroom contamination found in a typical 700-bed community hospital as a result of nuclear medicine procedures. Wipe tests were performed on designated areas for two 1-wk periods approximately 6 mo apart. For a typical workload of approximately 25-30 procedures per day, it was found that radioactive contamination ranged from approximately 10(3) Bq 100 cm-2 99mTc for the nuclear medicine restrooms to approximately 10(4) Bq 100 cm-2 for men's toilet facilities. The major component of the activity was found in the vicinity of the toilet. Although this contamination is minimal, it is recommended that nuclear medicine patients be directed to designated restroom facilities while awaiting examinations.

Female↗
PubMed1992

Quantitative assessment of tumor enhancement by ultrastable lipid-coated microbubbles as a sonographic contrast agent.

We have previously reported that ultrastable lipid-coated microbubbles make a suitable ultrasonic contrast agent in the brain, causing increased intensity of echoes that persists for many hours. We showed that intravenously administered lipid-coated microbubbles accumulate selectively in rat brain gliomas with echogenicity enhancement for up to 1 hour, allowing visualization of the growing lesions 40% (2 days) earlier than can be seen without contrast. This work is a detailed evaluation of the accumulation of the lipid-coated microbubbles in tumor and the effect of the bubbles on the echogenicity of insonified tumors. Using a lipid-specific stain, we measured and characterized the distribution of the bubbles in the brain and tumor. We showed that on the scan, the enhancement of the tumor is accompanied by a change in the signal-to-noise ratio of the echoes from the tumor. We identified characteristic textural changes associated with contrast-enhanced tumor using spectral analysis.

Animals↗
PubMed1992

Surgical significance of morphological variations in the atrial septum in atrioventricular septal defect for determination of the site of penetration of the atrioventricular conduction axis.

The morphological variation in the recognized landmarks for the atrioventricular conduction system was studied grossly in 94 hearts with atrioventricular septal defect, assessing 20 hearts with normal atrioventricular septation as a control. In all the hearts with intact atrioventricular septal structures, the tendon of Todaro demarcated the superior boundary of the triangle of Koch. In hearts with atrioventricular septal defect, however, the landmarks for the conduction axis made up a separate nodal triangle. The tendon of Todaro, along with a bridging tendon not found in the normal heart, were variably developed in hearts with atrioventricular septal defect and formed a further triangle unrelated to the axis for atrioventricular conduction. The opening of the coronary sinus was also variable in its location and size. It was the location of the inferior bridging leaflet as it crossed the ventricular septum that was the best surgical landmark to the site of penetration of the atrioventricular conduction axis.

Atrioventricular Node↗
PubMed1992

Morphological study of defects of the atrial septum within the oval fossa: implications for transcatheter closure of left-to-right shunt.

OBJECTIVE: To determine the anatomical variability of the oval fossa in cases of atrial septal defect and to find out which factors might make such defects suitable or unsuitable for closure by umbrella or clamshell devices. DESIGN: 100 specimens with defects of the atrial septum within the oval fossa were studied, especially the position of the defects within the fossa; the area of the defect in relation to the total area of the oval fossa; the shape of the rims and flap valve of the oval fossa; and the anatomical variability in the eustachian and thebesian valves. RESULTS: The oval fossa was displaced to the mouth of the inferior caval vein in four cases; displaced to the mouth of superior caval vein in two cases; placed on the middle of the interatrial wall in 43; or placed slightly towards the inferior caval vein in 51. Because of their shape 29 of the hearts were considered to be unsuitable for transcatheter closure of the defect. This was because the defect was too large (16 hearts); the oval fossa was displaced to the mouth of the inferior caval vein (four hearts) or to the superior caval vein (two hearts); lacked its anterior rim (two hearts); lacked the posteroinferior rim (one heart); because a thick eustachian valve was displaced posteriorly forming a false posteroinferior rim (one heart); or because the strand of insertion of the floor of the oval fossa was too distant from the left atrial aspect (three hearts). CONCLUSION: 68 hearts appeared to be ideal candidates for transcatheter closure; 3 would probably have been suitable; but 29 were unsuitable. These morphological variations might explain why the procedure has been unsuccessful in so many cases. Patients should be screened before any attempt is made at transcatheter closure.

Adolescent↗
PubMed1992

Abnormal laterality and congenital cardiac anomalies. Relations of visceral and cardiac morphologies in the iv/iv mouse.

BACKGROUND: In the management of hearts with deranged laterality, it is essential that the left and right atrial chambers are correctly identified. There are two major approaches, which are based on venous connections or on the morphology of the atrial appendages, and there is no consensus as to which is the most useful. We used the iv/iv mouse mutant, which is known to be pertinent to this problem, to evaluate the relations of cardiac defects with atrial, venous, and other visceral morphologies. METHODS AND RESULTS: The morphology of the heart and other organs was examined in 275 iv/iv mice using criteria based on abnormal laterality in humans. The arrangement of the atrial appendages was determined by morphological examination of the junction between the appendage and the venous component of the atrium. On this basis, 45.1% of cases were shown to have usual atrial arrangement, 50.2% had mirror imagery, 1.5% had right isomerism, and 3.3% had left isomerism. Every case of atrial isomerism had a cardiac lesion; the morphological types were similar to those seen in human cases. Of cases with either usual or mirror-image arrangement of the appendages, 33.2% had abnormal spleens, but only 3.1% had cardiac defects. Similarly, venous abnormalities were much more common (30.1%) than cardiac defects. CONCLUSIONS: Study results endorse the importance of the morphology of atrial appendages in predicting cardiac abnormalities and point to the marked inconsistency of the arrangement of other organs, including the spleen and the connections of the systemic veins.

Animals↗
PubMed1992

Use of helper-free retroviral vector to direct a high expression of porcine growth hormone in mouse fibroblast cells.

A retroviral vector has been employed to express the cDNA coding for porcine growth hormone (pGH) in the mouse fibroblast cell NIH 3T3 in large quantity. In this study, a single gene vector which contained no selectable marker was used. We have coinfected NIH 3T3 cells with pGH retrovirus and Neo(r) retrovirus to obtain a stable, high-expression clone. Using a superinfection strategy, we further increased the copy number of proviral DNA in the host chromosome, thus increasing the pGH secretion from 22 to 55 micrograms/10(6) cells/24 h. The recombinant pGH produced from mouse fibroblast cells was heterogeneous at the N-terminus, which mimicked the situation with bovine growth hormone either from natural sources or from recombinant products derived from mouse fibroblasts. This technology is useful for many biologically important genes to be stably transduced by retroviral vector into mammalian cells and highly expressed.

3T3 Cells↗
PubMed1991

Aortic atresia with aortopulmonary window and interruption of the aortic arch.

The cross-sectional echocardiographic and postmortem appearances of the heart from a patient with the rare association of aortic valve atresia, aortopulmonary window, and interrupted aortic arch are described. Differentiation of this anomaly from truncus arteriosus with interrupted aortic arch is important.

Aorta, Thoracic↗
PubMed1991

Fibrous skeleton and ventricular outflow tracts in double-outlet right ventricle.

Twenty-four hearts in which both great arteries arose from the right ventricle were studied to establish variations present within the fibrous skeleton and infundibular morphologies. Variations were also noted in the location of the ventricular septal defect and measurements were obtained of the outlet septum and the circumferences of the arterial valves. Completely muscular subarterial infundibulums were present in only 9 (37.5%) of the hearts, with varying degrees of fibrous continuity between the leaflets of the arterial and atrioventricular valves in the remainder. The aorta was rightward and posterior in 12 (50%) of the hearts, and subaortic and subpulmonary ventricular septal defects were present in equal numbers in this group. No subaortic defects were present when the aorta was side-by-side and right-sided. No subpulmonary defects were present in hearts with a posterior aorta. The mean ratio of 0.91 +/- 0.36 for the subpulmonary to subaortic length of the outlet septum was significantly less than the value of 1.54 +/- 0.41 noted previously in hearts with tetralogy of Fallot (p less than 0.001).

Aortic Valve↗
PubMed1991

The myth of the aortic annulus: the anatomy of the subaortic outflow tract.

Surgical repair of the small aortic root is limited in part by the very structure of the outflow tract from the left ventricle. The root is not constructed on the basis of a ringlike annulus supporting the leaflets of the aortic valve. The only truly circular structure within the outflow tract is the junction of the aortic wall with the underlying ventricular structures, themselves partly muscular and partly fibrous. This circular ventriculoarterial junction is crossed by the semilunar attachments of the leaflets of the aortic valve, producing an interlinking arrangement between the expanded aortic sinuses and three triangles of fibrous tissue placed beneath the apexes of the commissures between the valve leaflets. The triangles form extensions of the left ventricle that are related, in part, to the pericardial cavity surrounding the heart. The arrangements of the attachment of the leaflets in malformed valves with two (or only one) effective leaflets are highly abnormal, although these valves are usually produced on the template of three aortic sinuses. The valve with two leaflets rarely gives problems during childhood. In valves producing "critical stenosis", there is usually only one effective leaflet, a condition due to incomplete liberation of two of the anticipated three commissures. Detailed study shows that, in these malformed hearts, the attachment of the leaflets is much more annular than in normal valves, with inadequate formation of the fibrous triangles.

Aortic Valve↗
PubMed1991

Ventricular septal defects in a family of Yucatan miniature pigs.

We have studied the hearts from a colony of Yucatan miniature pigs with spontaneously occurring congenital defects. Ventricular septal defect was encountered in 57 of 81 neonates from 15 consecutive litters. Of 73 hearts preserved for morphological assessment, 52 were found to have defects within the ventricular septum remarkably similar to those observed in humans with deficient ventricular septum. The defects, including 3 which had closed spontaneously, were perimembranous in 34, muscular in 12 and doubly committed and juxtaarterial in 6 hearts. Atrial septal defects were found in 12 of the 52 hearts with deficient ventricular septation; only 1 atrial septal defect was seen among 21 hearts with an intact ventricular septum. Anomalies of the aortic arch were associated with ventricular septal defect in 2 cases; 1 with a solitary arterial trunk and one with hypoplasia of the aorta and patent arterial duct. All these findings are replicated in human hearts. This strain of pig provides an ideal large animal model for morphologic and genetic investigations concerning the details of ventricular septation, including potential mechanisms of late spontaneous closure.

Animals↗
PubMed1991

Cerebrospinal fluid eicosanoid levels: endogenous PGD2 and LTC4 synthesis by antigen-presenting cells that migrate to the central nervous system.

We analyzed CSF from patients with multiple sclerosis, patients with other neurologic diseases, and healthy controls for the presence of prostaglandin (PG) E2, F2 alpha, D2, I, A, and leukotriene (LT) C4. Control CSF had little measurable PGs or LTs. CSF eicosanoids from patients with progressive MS were increased. We found PGD2 only in MS CSF. CSF monocytes from patients in active disease produced significantly increased PGD, PGE, and LTC4 than paired peripheral blood monocytes and monocytes from healthy controls. We saw no significant difference in LTC4 production between MS and control peripheral blood monocytes.

Antigen-Presenting Cells↗