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Biomedical subjects

S Y Ho

Publications and source records attributed to S Y Ho.

At least 109 records · Page 6Linked to original sources
PubMed1998

Suramin disrupts the gliotic response following a stab wound injury to the adult rat brain.

Reactive gliosis, observed in numerous pathological states, leads to the formation of a glial scar that is believed to impede axonal regeneration. Astrocyte reactivity can be initiated both in vitro and in vivo by various cytokines. Thus, the aim of this study was to investigate if suramin, a polysulfonated napthylurea that has been shown to inhibit the binding of many different cytokines to their cell surface receptors, could attenuate the glial response after brain injury. A single dose of suramin (5 microl, 75 microM) or saline vehicle was injected intracerebrally through the same needle used to make the stab wound at the time of lesioning. Suramin-treated animals showed an obvious reduction in several parameters of CNS inflammation: cellular proliferation, GFAP levels, and tenascin-C immunoreactivity were reduced in suramin-treated as compared to control animals at early time points. GFAP immunoreactivity was strikingly reduced at 3 days after injury, as confirmed by Western blot analysis. This reduction was transient, however, in that the difference in GFAP expression between suramin-treated and control animals was less apparent at 7 days and had disappeared by 30 days after injury. Likewise, fewer BrdU-positive cells were noted in treated versus control tissue at 1 and 3 days, but this difference was not significant by 7 days. Moreover, tenascin immunoreactivity was significantly diminished at 24 h as confirmed by Western blot analysis in suramin-treated lesion areas, which is analogous to our observations that suramin can antagonize tenascin expression by cultured astrocytes treated with bFGF. In addition, examination of the corpus callosum of saline-treated animals 30 days post-trauma revealed a disruption of the fiber tract within the lesion site, while suramin-treated animals displayed numerous fibers spanning the lesion. These results demonstrate that a single injection of suramin transiently inhibits the gliotic response, which may be sufficient to ameliorate subsequent tissue damage.

Animals↗
PubMed1998

Anatomy of the pig heart: comparisons with normal human cardiac structure.

Transgenic technology has potentially solved many of the immunological difficulties of using pig organs to support life in the human recipient. Nevertheless, other problems still remain. Knowledge of cardiac anatomy of the pig (Sus scrofa) is limited despite the general acceptance in the literature that it is similar to that of man. A qualitative analysis of porcine and human cardiac anatomy was achieved by gross examination and dissection of hearts with macrophotography. The porcine organ had a classic 'Valentine heart' shape, reflecting its location within the thorax and to the orientation of the pig's body (unguligrade stance). The human heart, in contrast, was trapezoidal in silhouette, reflecting man's orthograde posture. The morphologically right atrium of the pig was characterised by the tubular shape of its appendage (a feature observed on the left in the human heart). The porcine superior and inferior caval veins opened into the atrium at right angles to one another, whereas in man the orifices were directly in line. A prominent left azygous vein (comparable to the much reduced left superior caval or oblique vein in man) entered on the left side of the pig heart and drained via the coronary sinus. The porcine left atrium received only 2 pulmonary veins, whereas 4 orifices were generally observed in man. The sweep between the inlet and outlet components of the porcine right ventricle was less marked than in man, and a prominent muscular moderator band was situated in a much higher position within the porcine right ventricle compared with that of man. The apical components of both porcine ventricles possessed very coarse trabeculations, much broader than those observed in the human ventricles. In general, aortic-mitral fibrous continuity was reduced in the outlet component of the porcine left ventricle, with approximately two-thirds of the aortic valve being supported by left ventricular musculature. Several potentially significant differences exist between porcine and human hearts. It is important that these differences are considered as the arguments continue concerning the use of transgenic pig hearts for xenotransplantation.

Adult↗
PubMed1998

The use of lipid-coated microbubbles as a delivery agent of 7beta-hydroxycholesterol in a radiofrequency lesion in the rat brain.

OBJECTIVE: This laboratory has previously described the aggregation of intravenously administered lipid-coated microbubbles (LCM) around tumors and areas of injury. 7Beta-hydroxycholesterol has been used to inhibit astrocytic proliferation in nervous system injury models. The compound has been given by direct infusion, by epidural catheter, or in liposomes (delivered stereotactically to the injury site). In this article, we report the use of LCM to deliver 7beta-hydroxycholesterol to a radiofrequency injury site in the rat cerebrum. METHODS: First, the ability of LCM to target the thermal lesion in the rat brain was characterized using a lipid-soluble fluorescent dye 3,3-dioctadecyloxacarbocyanine perchlorate. Then, the effectiveness of this delivery system in suppression of glial proliferation was measured by glial fibrillary acidic protein immunoreactivity. RESULTS: Glial fibrillary acidic protein immunoreactivity was significantly reduced when 7beta-hydroxycholesterol was administered via LCM but not alone, suggesting that astrocytic proliferation would correspondingly be diminished. CONCLUSION: LCM were assessed as a delivery vehicle for 7beta-hydroxycholesterol in a rat brain radiofrequency lesion and found to be efficient in reducing astrogliosis, as measured by glial fibrillary acidic protein immunoreactivity.

Animals↗
PubMed1998

The architecture of the atrial musculature between the orifice of the inferior caval vein and the tricuspid valve: the anatomy of the isthmus.

INTRODUCTION: Electrophysiologists recognize a so-called "isthmus" in the right atrium through which passes the reentrant circuit of common atrial flutter. Ablative lesions placed in this narrow channel have proved effective in breaking the circuit. To the best of our knowledge, however, no study has been performed to establish the arrangement and orientation of the atrial myocardial fibers in this crucial area. METHODS AND RESULTS: We examined 28 normal heart specimens, identifying a quadrilateral area composed of three morphologic sectors between the inferior caval vein and the tricuspid valve confluent superiorly with the triangle of Koch. Within this quadrilateral, there are constant recesses, or sinuses, inferior and lateral to the orifice of the coronary sinus. The inferior isthmus measured an average of 31+/-4 mm (range 19 to 40). Gross examination identified marked differences in the atrial wall forming the quadrilateral. A smooth anterior component forming the vestibule of the tricuspid valve was found in all the hearts, but variations in the remaining sectors were seen in ten specimens. The usually membranous posterior sector was noticeably muscular in three specimens, while the middle, trabecular sector was more membranous in five specimens. We demonstrated the orientation of the subendocardial atrial fibers by dissection in 14 specimens, revealing a relatively constant overall pattern in eight specimens and variations in fiber orientation in the remaining specimens. CONCLUSION: There are considerable anatomic variations in the atrial wall that comprises the so-called isthmus. The presence of recesses and membranous areas in some hearts and the variations in arrangement of the subendocardial fibers are relevant in improving understanding of conduction in this area.

Data Interpretation, Statistical↗
PubMed1998

The architecture of the sinus node, the atrioventricular conduction axis, and the internodal atrial myocardium.

Concomitant with the development of catheter ablation techniques for the treatment of atrial arrhythmias, there is renewed interest in the morphologic arrangement of the cardiac conduction system. In this article, we revisit the anatomy of the specialized tissues, making special reference to the descriptions given at the time of their discovery. According to criteria for histologic distinction of morphologically specialized tracts set nearly 100 years ago, the penetrating bundle (of His) and the ventricular bundle branches are tracts of specialized cells encased by insulating sheaths of fibrous tissue. In contrast, the sinus and AV nodes are recognized histologically but are not insulated from the working atrial myocardium. At its distal extent, the AV node is distinguished from the penetrating bundle not so much by cellular characteristics, but by the presence of a fibrous collar that surrounds the specialized cells. At the atrial part, a zone of histologically transitional cells interposes between the compact node and the working atrial myocardium. Transitional cells enter the triangle of Koch to join the compact node from superiorly, inferiorly, posteriorly, and from the left. Transitional cells of the sinus node, in contrast, are limited to short tongues that interdigitate with musculature of the terminal crest. Apart from a variable extension of its tail, there are no prominent histologically discrete extensions from the sinus node into the working atrial musculature. The internodal myocardium does not contain discrete conducting tracts comparable with the ventricular bundle branches. Preferential conduction more likely reflects the arrangement of the working internodal cells and their related cellular properties.

Atrioventricular Node↗
PubMed1998

Coronary arterial anatomy in tetralogy of Fallot: morphological and clinical correlations.

OBJECTIVE: To clarify the problems in angiographic diagnosis of major coronary arteries crossing the right ventricular outflow tract. DESIGN: A retrospective study with clinicomorphological correlations to ascertain any aberrant coronary arteries and variations in distribution of the normal right coronary arterial branches. SETTING: Tertiary referral centre. SUBJECTS: 36 necropsy specimens together with the aortograms and surgical reports from 130 patients with tetralogy of Fallot. RESULTS: A preventricular branch was found in 19% of cases with tetralogy of Fallot, but in none of 13 normal hearts. Aberrant origin of the anterior interventricular coronary artery was found in 14% of the specimens. The combination of "laid back" and straight lateral views, when reviewed retrospectively, identified this anomaly correctly in nine of 16 patients, with these findings confirmed at surgery in seven patients. A major branch initially thought to cross the outflow tract was shown retrospectively to be an infundibular artery in six, with surgical confirmation in four. It was a preventricular branch in another patient. CONCLUSIONS: Using the laid back view alone, infundibular and preventricular branches may be mistaken for a major aberrant artery. A combination of laid back and straight lateral views is needed to avoid false positive diagnosis.

Child↗
PubMed1998

[Inhibitory effects of nitric oxide on glutamate-induced neuronal activity of CA1 area in rat hippocampal slices].

Using extracellular recording technique, the effects of L-arginine (L-arg), SIN-1 and N-nitro-L-arginine (L-NNA) on glutamate-induced discharge of neurons in CA1 area of hippocampal slices were examined to define the role of L-arg:NO pathway in glutamate-induced discharge of hippocampal neurons and its possible underlying mechanism. The results obtained are as follows. (1) In response to the application of glutamate (0.5 mmol/L) into the superfusate for 1 min, the discharge rate of 12 neurons was increased markedly in an epileptiform pattern. (2) The increased discharge induced by glutamate (0.5 mmol/L) in 10 neurons was suppressed significantly by application of L-arg (10 mmol/L) into the superfusate for 2 min. (3) The glutamate-induced increase of discharge in 12 neurons was decreased markedly by superfusing the brain slice with NO donor SIN-1 (5 mmol/L) for 1 min. (4) As the discharge rate of 12 neurons was increased by pretreatment with glutamate (0.5 mmol/L), application of L-NNA (0.15 mmol/L) into superfusate for 2 min might further augment the discharge intensively and in some case eventually led to abrupt suppression of the discharge. Taken together, it is likely that glutamate binding with NMDA receptors in hippocampal neurons not only induces an increase in discharge, but also activates the L-arg: NO pathway to generate NO responsible for neuroprotection via negative feedback mechanisms.

Action Potentials↗
PubMed1998

The structure of the common atrioventricular valve in hearts having isomeric atrial appendages and double inlet ventricle.

BACKGROUND AND AIMS OF THE STUDY: It is now well recognized that regurgitation through a common atrioventricular valve can compromise the clinical course both before and after surgical interventions in patients with visceral heterotaxy. This may reflect the anatomic structure of the valve. This study aimed to determine whether the structure of the common atrioventricular valve found in the setting of hearts with isomeric atrial appendages and double inlet ventricle differs from that of the valve guarding a common junction in hearts with biventricular atrioventricular connections. METHODS: Sixty-three autopsied hearts with double inlet ventricle and isomeric atrial appendages were studied, in addition to 79 with isomerism and biventricular atrioventricular connections, all having a common valve guarding the atrioventricular junctions. RESULTS: A valve with three or four leaflets was seen more frequently in hearts with double inlet ventricle than in those with biventricular atrioventricular connections (p = 0.016, chi-squared test). Complicated multiple orifices within the valvular curtain, including abnormal accessory orifices within a leaflet, were found in seven cases with double inlet to a dominant morphologically left or right ventricle. The presence of four papillary muscles was the most common pattern in hearts with double inlet ventricle. Straddling of the papillary muscles to a rudimentary and incomplete ventricle was seen in 23% of cases. Direct attachment of tendinous cords to the ventricular septum or parietal wall was seen 81% of hearts with double inlet. CONCLUSIONS: These features of the common valve found with double inlet atrioventricular connection seem less suited to function as the inlet valve supporting the systemic circulation. The recognized abnormal features should be identified preoperatively so as to plan more effective valvular plasty, or alternatively to establish different surgical strategies.

Abnormalities, Multiple↗
PubMed1997

Angiographic and morphologic features of the left ventricle in Ebstein's malformation.

Quantitative and qualitative cineangiographic analysis of the left ventricle (LV) was performed in 26 patients with isolated Ebstein's malformation, having a mean age of 23 +/- 17 years. Nine autopsied hearts with isolated Ebstein's malformation were submitted to morphologic and morphometric analysis. In 4 of the cases, it was possible to make a direct correlation between the angiographic data obtained during life and the autopsy findings. On the basis of the LV end-diastolic volume we identified 3 groups of patients: 7 with volume <60 ml/m2, another 7 with volume between 60 and 80 ml/m2, and 12 with volume >80 ml/m2. The LV ejection fraction was reduced in 2 patients with normal LV end-diastolic volume and in 6 with increased LV end-diastolic volume. The ratio of ventricular mass to LV end-diastolic volume was always adequate, but a reduction of the ventricular contractive performance (end-systolic pressure to end-systolic volume ratio <3 mm Hg/ml/m2) was found only in patients with a dilated left ventricle. No correlation was demonstrated between the extent of the atrialized component of the right ventricle (mean value 67 +/- 31 cm2, range 13 to 133) and the LV dimensions. All but 2 patients showed a leftward diastolic displacement of the ventricular septum, but in only 1 did this produce an elongated shape of the left ventricle. Sixteen had anomalies of LV dynamics: 10 with hypokinesia (3 of the posterior wall, 4 of the apex, 1 of the inferior wall, 1 of the septum, and 1 global), 6 with dyskinesia (1 of the posterior wall, 2 of the apex, 1 of the posterior wall and apex, 1 of the superior part of the septum, and 1 of the anterior wall), and 8 with premature diastolic distension of the anterobasal wall. Morphometric analysis produced mean values for myocytes of 59 +/- 10%, for the interstitium of 21 +/- 4%, and for fibrous tissue of 20 +/- 9% (normal 4 +/- 1%). Five autopsied hearts had a prolapsing and/or dysplastic mitral valve.

Adolescent↗
PubMed1997

Location of the coronary arterial orifices in the normal heart.

We examined the coronary arterial orifices in relation to the aortic valve to determine the range of normality in 23 normal hearts from autopsied adults. We determined the position of the zones of apposition between leaflets, the size of the leaflets, the number, position, and shape of the coronary arterial orifices, and their relation to the sinutubular junction. The aortic valve had three leaflets in all specimens, nearly equally spaced around the aorta. The left coronary artery arose within the left posterior aortic sinus (of Valsalva) in 16 (69%) specimens, above the sinutubular junction in five (22%), and at the level of the junction in two (9%). The distance of the left orifice from the zone of apposition between the left posterior and anterior aortic leaflets was between 13% and 61% of the width of the aortic sinus at the sinutubular junction. The right coronary artery arose within the anterior aortic sinus in 18 (78%) specimens, above the junction in three (13%), and at the level of the junction in two (9%). The distance of the orifice from the zone of apposition between the leaflets hinged from the anterior and right posterior aortic sinuses was between 5% and 62% of the width of the aortic sinus at the sinutubular junction. An accessory coronary orifice was found in the anterior aortic sinus in 17 (74%) specimens, whereas a third orifice in this sinus was found in five hearts. The coronary arterial orifices are usually located within the aortic sinuses below the sinutubular junction, but are rarely centrally located. Accessory coronary arterial orifices are found in the majority of the anterior aortic sinuses.

Adult↗
PubMed1997

Is there such a thing as the "tendon of the infundibulum" in the heart?

The fibrous skeleton of the heart has featured prominently in anatomical and surgical descriptions, although all its purported components are difficult to demonstrate. In descriptions of the skeleton, there have been repeated references to the presence of a tendon (or ligament) between the aortic and pulmonary roots. Such a tendon is rarely, if ever, discussed in the context of surgical procedures being carried out on the ventricular outflow tracts. Our study was undertaken, therefore, to investigate the existence and nature of such a tendon or ligament. Serial transverse sections were made through roots of aorta and pulmonary trunk in an intact fetal heart. In addition, ten normal adult hearts were dissected to display the components of the fibrous skeleton of the heart. No discrete fibrous or elastic structure could be detected in the tissue plane between the aortic sinuses and the subpulmonary muscular infundibulum, although a fascial strand was observed in one heart. Apart from this specimen, the space between the free-standing muscular subpulmonary infundibulum and the sinuses of aorta hearing the coronary arteries was occupied only by loose fibroareolar tissue. The initial presence of the ligament was described following studies of animal and macerated human hearts. Subsequently, it would seem its existence has been passed down through generations of morphologists and surgeons without its presence being reconfirmed. We have been unable to demonstrate any structure approximating to the initial illustrations.

Aortic Valve↗
PubMed1997

Anomalous papillary muscle as a cause of left ventricular outflow tract obstruction in an adult.

Left ventricular outflow tract obstruction may be caused by abnormalities of the various structures comprised by the outflow tract. Hypertrophic cardiomyopathy is one of the more common causes, but many are rare anomalies, a collection of which we have compiled. We present a case of left ventricular outflow tract obstruction mimicking aortic stenosis in an adult. This was found to be due to abnormal insertion of a hypertrophied papillary muscle, successfully corrected by mitral valve replacement.

Aged↗
PubMed1997

The aortic root in supravalvular aortic stenosis: the potential surgical relevance of morphologic findings.

OBJECTIVE: We aimed to elucidate the structural basis of supravalvular aortic stenosis in the context of its surgical repair. METHODS: We examined retrospectively the angiograms and echocardiograms of 37 patients and compared them with those of control groups. Additionally, we studied 8 pathologic specimens. RESULTS: Partial adhesion of the leaflets to the stenosing ridge was observed in 54% of the cases and the leaflets were thickened and less mobile in 30%. Forty-five percent of the angiograms showed evidence of coronary orificial stenosis. The sinuses of Valsalva were significantly enlarged in 75% of the cases. Changes in dimensions of the aortic root were demonstrated more clearly by angiography than by echocardiography. In all anatomic specimens, a marked redundancy of the leaflets was observed and quantified. CONCLUSIONS: Our data demonstrate that the entire valvular apparatus is always affected by the so-called supravalvular stenosis. Anatomic restoration of the aortic root should ideally take into account all of the deformed components by enlarging all three sinuses of Valsalva at the sinotubular junction.

Adolescent↗
PubMed1997

The affinity of lipid-coated microbubbles for maturing brain injury sites.

The availability of a vehicle to deliver lipid soluble agents to a brain injury site may be of potential value in management of brain injury. This work describes the aggregation of intravenously administered Lipid-Coated Microbubbles (LCM) in the injury site following an experimental radiofrequency rat brain lesion. The bubbles can be identified around the region of the injury after the lesion has matured at least 48 h. The greatest bubbles density is evident after the lesion has matured for 10 days. This bubble density, reflecting "affinity," decreases to a plateau level from the second to the third week after injury. In order to investigate the potential relationship of bubble influx to posttraumatic astrocytosis and to cell turnover in the region, we utilized dual-channel laser-scanning confocal microscopy to track both bubble influx into the region and concomitant Glial Fibrillary Acidic Protein (GFAP) expressing astroctyte cell distribution. Cell turnover was assayed in separate sections using immunohistochemical staining of Proliferating Cell Nuclear Antigen (PCNA). We suggest a relationship between the LCM affinity and reactive astrocytes, but found no affinity of LCM for cells which stained positive with PCNA.

Animals↗