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S Y Ho

Publications and source records attributed to S Y Ho.

At least 181 records · Page 10Linked to original sources
PubMed1993

Applications of lipid-coated microbubble ultrasonic contrast to tumor therapy.

Lipid-coated microbubbles (LCM) make an excellent diagnostic ultrasonic contrast agent in experimental tumor systems. LCM have been shown to aggregate in brain tumors and subcutaneous tumors after intravenous administration, and to provide persistent image enhancement for many minutes. In this work, experimental subcutaneous Walker Carcinosarcoma is insonated after the bubbles are given intravenously. Selective necrosis, lymphocyte proliferation and hemorrhage within the tumor can be demonstrated. Preliminary data are given to demonstrate this phenomenon. The mechanism of the effect is discussed in the context of both heating and cavitation.

Animals↗
PubMed1993

Detection of experimental rat liver tumors by contrast-assisted ultrasonography.

RATIONALE AND OBJECTIVES: The authors characterized the effect of intravenous lipid-coated microbubbles (LCMs) on the echogenicity of malignant liver tumors. METHODS: Novikoff hepatoma cells were inoculated into the livers of 16 anesthetized Sprague-Dawley rats. Sonograms were obtained weekly after tail-vein injection with either 0.2 mL/kg LCMs or saline control. RESULTS: A statistically significant difference in the signal-to-noise ratio (SNR) was observed between the group that received LCMs (10 rats) and the group that received saline (6 rats) (P < .01). The effect persisted for 30 minutes after contrast injection. Selective leakage and accumulation of LCMs into the tumor tissue itself was confirmed histologically using lipid-specific counterstains. CONCLUSIONS: Intravenous injection of the LCM contrast agent produces a rapid increase in the echogenicity of the experimental Novikoff tumor in the rat liver.

Animals↗
PubMed1993

Morphology of the cardiac conduction system in patients with electrophysiologically proven dual atrioventricular nodal pathways.

INTRODUCTION: Although the electrophysiologic criteria for dual atrioventricular nodal pathways are well established, the anatomical substrate is still unclear. METHODS AND RESULTS: We examined the hearts from 10 patients who had been studied electrophysiologically prior to cardiac transplantation. All 10 patients were male, aged 22 to 60 years. Nine of the 10 patients had dual atrioventricular nodal pathways according to accepted criteria. Histologic studies of the atrioventricular conduction system showed normal structure of the atrioventricular node in all 10 hearts, with minor variations within the node in 3 cases, within the penetrating bundle in 3 cases, and within the nonbranching bundle in 3 cases. The atrial approaches to the atrioventricular node were generally scanty in 6 hearts. The solitary case that was shown electrophysiologically to lack dual pathways had no obvious difference in the structure of the nodal area other than sparsity of transitional cells. We were unable to locate any extranodal atrial tracts as described by other investigators. CONCLUSION: The anatomical substrate for conduction over dual pathways may be too subtle to be detected by gross morphologic studies. Since dual pathways were unmasked in all patients but one during electrophysiologic studies, it may be that the potential for these pathways is ubiquitous.

Adult↗
PubMed1993

"AV nodal" reentry: Part I: "AV nodal" reentry revisited.

This review is the first of a two-part series of articles on "atrioventricular [AV] nodal reentry." The early clinical literature as well as the experimental studies are reviewed, and more recent morphologic data are presented, with the aim of clarifying whether the reentrant circuit is confined to the AV node, or consists in part of extranodal components. Most of the evidence supports the concept that atrial tissue is an essential link in the reentrant pathway. Arguments will be presented to indicate that within the AV node, the separation between antegrade and retrograde pathways is functional, not anatomical, and that both pathways are in electrotonic contact.

Animals↗
PubMed1993

Transcatheter stent implantation to treat aortic coarctation in infancy.

A ten week old girl who had previously undergone a palliative procedure for the hypoplastic left heart syndrome had unrelieved aortic coarctation that did not respond to standard balloon dilatation. Complete relief of coarctation with prompt clinical improvement was achieved with placement of an 8 mm self-expanding stent. Transcatheter stent implantation may have a role in selected patients with aortic coarctation.

Aortic Coarctation↗
PubMed1993

Dysplastic conditions of the right ventricular myocardium: Uhl's anomaly vs arrhythmogenic right ventricular dysplasia.

OBJECTIVE: Since 1905 there have been many reports of cases in which the right ventricle was deficient in myocardium. Several terms have been used to describe this condition. Of these, "Uhl's anomaly" and "arrhythmogenic right ventricular dysplasia" are most often used. Our study investigates the relation between these entities. METHOD: Five cases with a primary deficiency of the right ventricular musculature were examined. The findings were compared with those published reports to evaluate the similarities and differences between Uhl's anomaly and arrhythmogenic dysplasia. RESULTS: The five cases showed two patterns of myocardial deficiency in the right ventricle. On the one hand, the parietal wall was paper thin with complete absence of musculature and apposition of the endocardial and epicardial layers. On the other hand, patchy, localised fibrofatty tissue replacement was found within the parietal musculature. Evidence from our cases, combined with analysis of other publications, showed different modes and timing of clinical presentation of the patients with these two anatomical conditions, congestive heart failure or arrhythmia. CONCLUSIONS: The conditions variously described as Uhl's anomaly and arrhythmogenic dysplasia are separate and distinct morphological entities.

Adolescent↗
PubMed1993

[Hemodynamic actions of N-nitro-L-arginine and its effect on renal sympathetic nerve activity in anesthetized rats].

The hemodynamic actions of N-nitro-L-arginine (L-NNA), a novel NO synthesis inhibitor, and its effect on renal sympathetic nerve activity (RSNA) were examined in anesthetized rats to define the possible role of L-NNA in the regulation of blood pressure and the underlying mechanism(s). The results obtained were as follows. (1) Following intravenous bolus injection of L-NNA (15 mg/kg), MAP was changed from 9.87 +/- 0.80 to 14.67 +/- 0.53 kPa (P < 0.001), HR from 317 +/- 13 to 303 +/- 14 bpm, CI from 9.79 +/- 0.83 to 7.04 +/- 0.41 ml/min.100 g-1 (P < 0.05), and TPRI from 1.04 +/- 0.10 to 2.15 +/- 0.18 u/100 g (P < 0.001), all lasting for more than 30 min. The above-mentioned actions of L-NNA could be inhibited by prior administration of L-arginine (200 mg/kg). (2) In rats with sinoaortic denervation (SAD), i.v. L-NNA might induce an increase in HR, indicating that L-NNA-induced bradycardia was resulted from a baroreceptive activation. (3) In rats with buffer nerves intact, i.v. L-NNA failed to induce a significant change in RSNA, though an increase in MAP accompanied by bradycardia was observed. (4) With i.v. L-NNA for SAD rats, MAP, HR and RSNA were markedly increased by 55.6%, 5.1% and 34.3%, respectively. The results implied that L-NNA was able to activate sympathetic center, and L-NNA-induced change of RSNA could be masked by baroreflex. Prior administration of L-arg was capable of inhibiting the effect of L-NNA on RSNA in SAD rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

[Effects of angiotensin II, atrial natriuretic peptide and arginine vasopressin on activity of subfornical organ neurons in rat brain slices].

The effects of angiotensin II (AG II), atrial natriuretic peptide (ANP) and arginine vasopressin (AVP) on 87 subfornical organ (SFO) neurons from 31 brain slices of rats were observed. After perfusing the brain slices with AG II (10(-7) mol/L, 3 min), spontaneous discharge rate of 40/55 (72.73%) neurons was significantly increased, while that of 3/55 (5.45%) was decreased and 12/55 (21.82%) neurons were non-responsive. The excitatory effects of AG II on neurons in SFO were completely blocked by AG II receptor blocker saralasin (10(-6) mol/L). As the brain slices were perfused with atrial peptide III (AP III) (10(-7) mol/L, 3 min), the firing rate of 7/17 (41.18%) neurons was significantly decreased, while that of 2/17 (11.76%) neurons was increased and 8/17 (47.06%) neurons were non-responsive. By perfusing brain slices with AVP (10(-7) mol/L, 3 min), the firing rate of 8/15 (53.33%) neurons was significantly increased, while that of 3/15 (20.00%) neurons was decreased and 4/15 (26.67%) neurons were non-responsive. Twelve SFO neurons were successively perfused with three peptides. Among them, one was excited by both AG II and AVP, 3 were excited by AG II and inhibited by AP III, and the other one was excited by AVP and inhibited by AP III. The results suggest that the discharge rate of SFO neurons is affected by AG II, ANP and AVP. SFO may be one of the central regions in regulation of water balance and blood pressure.

Angiotensin II↗
PubMed1993

Obstruction of the left ventricular outflow tract: anatomical observations and surgical implications.

Obstruction within the outflow tract from the left ventricle can take several anatomic forms. To understand better these substrates, we reviewed the anatomy in the normal heart and, with this background, focused on the malformations observed at each level of the outflow tract which produce stenosis. We examined 75 malformed hearts and reviewed the literature pertinent to surgical aspects of obstruction. Close study of the normal aortic valve shows the lack of any discrete fibrous structure which can be described in terms of a ring-like annulus. The semilunar attachment of the leaflets makes a crown-shaped arrangement at the ventriculo-arterial junction rather than a strict ring. In the pathological study, valvar abnormalities were found in 45 cases. The valve had three leaflets in 20 cases, two leaflets in 24 cases and one leaflet in to the other. In two cases, additional obstruction was found at the sinutubular junction. Subvalvar stenosis was found in 30 hearts, the aortic valve being trifoliate in 28 and bifoliate in 2. The main substrate of subvalvar obstruction was posterior malalignament of the outlet septum (40%), followed by muscular septal hypertrophy (23%); obstruction was also an intrinsic feature in association with atrioventricular septal defects (14%). Although rare in our material, it can also be due to a fibrous or fibromuscular shelf. In our review of the literature, we have highlighted the various forms of valvar malformation and commented on the surgical options. Clear analysis of both the level of obstruction, and its precise anatomic substrate are essential for optimal surgical intervention.

Adolescent↗
PubMed1993

[Effects of angiotensin II, atrial natriuretic peptide III and arginine vasopressin on activity of paraventricular neurons of rat hypothalamic slices].

The effects of angiotensin II (AG II), atrial natriuretic peptide III (ANP III) and arginine vasopressin on 101 paraventricular nucleus (PVN) neurons from 28 brain slices of rats were observed. After perfusing the brain slices with AG II (10(-7) mol/L, 3 min), spontaneous discharge rate of 28/50 (56.0%) neurons was significantly increased, while that of 5/50 (10.0%) was significantly decreased and 17/50 (34.0%) neurons were non-responsive. Both of excitatory and inhibitory effects of AG II on neurons in PVN were completely blocked by AG II receptor blocker saralasin (10(-6) mol/L). As the brain slices were perfused with ANP III (10(-7) mol/L, 3 min), the firing rate of 16/26 (61.54%) neurons was decreased, while that of 1/26 (3.85%) neurons was increased and 9/26 (34.61%) neurons were non-responsive. During perfusing brain slices with AVP (10(-7) mol/L, 3 min), the firing rate of 19/25 (76.0%) neurons was significantly increased, while that of 1/25 (4.0%) neurons was decreased and 5/25 (20.0%) neurons were non-responsive. Twenty-five PVN neurons were successively perfused with three peptides. Among them, 4 were excited by both AG II and AVP, 2 were excited by AG II and inhibited by ANP III, and 7 were excited by AVP and inhibited by ANP III. The results show that the discharge rate of PVN neurons may be affected by AG II, ANP III and AVP. It is likely that PVN acts as an integrative site for neuroendocrine and autonomic functions.

Angiotensin II↗
PubMed1993

Mitral valve anomalies associated with Ebstein's malformation of the tricuspid valve.

The original description of Ebstein's anomaly mentioned a mild deformity of the mitral valve. Reviews of large series of cases with Ebstein's malformation have, however, tended to omit reference to accompanying mitral valve malformations. We have compared the mitral valves in 19 specimens with Ebstein's malformation with those in 30 age-matched controls in order to determine the prevalence and nature of these anomalies. In the Ebstein's group the mitral valve was abnormal in 14 hearts with orificial anomalies in four, leaflet anomalies in 11, cord anomalies in 11 and papillary muscle anomalies in 13. In the control group, five cases showed mild shortening of the tendinous cords. Half of the changes found in the Ebstein's group were of moderate or significant degree suggesting a primary involvement of the mitral valve. In time, dynamic alterations within the left ventricle might become superimposed and contribute to the development of clinically significant lesions.

Adult↗
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↗