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Biomedical subjects

R Chang

Publications and source records attributed to R Chang.

At least 163 records · Page 9Linked to original sources
PubMed1985

Percutaneous displacement of calyceal calculi. Adjunct to percutaneous nephrolithotripsy.

Two cases are presented of successful percutaneous removal of adherent calyceal calculi which were initially inaccessible for removal with the rigid nephroscope. In each case, the calculus was dislodged from the calyceal wall by the direct force of a needle introduced percutaneously against the stone. In the first patient, a wedged calyceal calculus was dislodged percutaneously and manipulated into the renal pelvis the day before extraction using the rigid nephroscope. In the second patient, the adherent calculus was dislodged percutaneously at the same time of endoscopic removal. In both patients, prior carbon dioxide pyelography was helpful in determining the optimum direction for advancing the needle against the calculus. Percutaneous stone dislodgement technique is a useful adjunct to percutaneous nephroscopic removal of the difficult calyceal calculus.

Endoscopy↗
PubMed1985

Nonoperative management of benign postoperative biliary strictures.

Selected benign biliary strictures can be treated safely and successfully by percutaneous balloon dilatation. Primary biliary strictures appear to be less responsive to balloon dilatation alone and require stenting with large catheters (16-20 F) for several months to permit scarring around the catheter. A long period of healing around such a large-bore stent is crucial to the success of such treatment. The most important physiologic indicators for successful dilatation are a long period of stricture challenge with a catheter placed proximal to the dilated segment to allow bile to drain internally across the previously strictured segment, and a near anatomic result as demonstrated by cholangiogram.

Adolescent↗
PubMed1985

Biliary catheter drainage complicated by hemobilia: treatment by balloon embolotherapy.

Seventeen patients experienced severe hemobilia following percutaneous (nine patients) or surgical (eight patients) placement of biliary drainage catheters. Fourteen patients bled early after catheter placement (0.5-32 weeks; mean, 5.4 weeks) and three bled late during long-term biliary drainage (1.1-3.6 years; mean, 2 years). Hepatic angiography demonstrated the source of bleeding in 15 (88%) patients (hepatic artery pseudoaneurysm in ten, hepatic artery-portal vein fistula in four, varix along the tube tract in one) but showed no source of bleeding in two. Thirteen patients with hemobilia were treated with embolotherapy, using detachable balloons in 12. The advantages of this technique included the ability to flow-direct the balloon without selective catheterization; the ability to test-inflate the balloon at the site of the aneurysm or fistula during angiographic study and adjust its position before detachment; and preservation of the hepatic artery proximal and distal to the inflated balloon, thus preserving hepatic function following embolization.

Adult↗
PubMed1985

Hemodynamic consequences of inotropic support with digoxin or amrinone in lambs with ventricular septal defect.

Inotropic support with digoxin is commonly used in patients with left ventricular volume overload due to ventricular septal defect (VSD). However, the hemodynamic consequences of inotropic agents with VSD have not been experimentally explored. We studied two inotropic agents, digoxin and amrinone, in chronically instrumented lambs with left ventricular volume overload due to a surgically created VSD. Intravenous digoxin (40 micrograms/kg) produced serum levels of 3.5 +/- 0.9 ng/ml (mean +/- SD) in seven lambs 60 min after administration, reduced the heart rate by 16% (172 to 149 beats/min, p less than 0.05), increased the stroke volume 16% (29.8 to 34.5 ml/beat, p less than 0.05) but did not significantly alter the systemic flow index (Qs), the pulmonary flow index (Qp), or the volume of left to right shunt (QL-R, 6.74 to 6.77 liter/min/m2). The mean left atrial pressure (LA) was unchanged (17.6 versus 17.1 mm Hg) following digoxin. Chronic digoxin use in four lambs for 4 days (25 +/- 8 micrograms/kg/8 h) produced trough serum levels of 1.2 +/- 0.2 ng/ml. There was no additional hemodynamic effect compared to acute digoxin, the Qp/Qs ratio was unchanged (3.10 versus 3.08) and evidence of left ventricular volume overload (LA - 14.0 versus 13.4) was unchanged. Amrinone lowered the systemic resistance index in a dose dependent fashion. The peak reduction of 20% (25.3 to 20.3 U/m2, p less than 0.01) occurred at 20 min after an intravenous (3 mg/kg) bolus in seven lambs. The Qs increased from 2.58 to 3.10 liter/min/m2 (p less than 0.01). The Qp was unchanged, thus the Qp/Qs ratio was lowered by 16% (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aminopyridines↗
PubMed1985

Percutaneous transhepatic biliary drainage for bile leaks and fistulas.

Percutaneous transhepatic cholangiography and biliary drainage were performed in 12 patients with major injuries to the bile ducts manifested by biliary leaks and fistulas. Eleven of the 12 patients had had inadvertent biliary trauma during surgery. In six patients, the biliary leaks sealed with percutaneous drainage. In other patients requiring definitive surgical procedures on the biliary tract, initial percutaneous drainage allowed these procedures to be delayed until the patients' clinical condition improved. Percutaneous biliary drainage is an important adjunct to the management of patients with traumatic extravasation of bile into the peritoneal cavity or biliary-cutaneous fistula.

Abscess↗
PubMed1984

Intraarterial digital subtraction angiography in diagnostic arteriography.

Intraarterial digital subtraction angiography (DSA) was performed in 133 diagnostic arteriographic procedures during a 10-month period. The increased contrast resolution of DSA permitted the use of a dilute (15%) contrast material. A significant reduction in contrast material dose compared with conventional film-screen arteriography and intravenous DSA was thus achieved. This was especially advantageous in patients with diminished renal function. The dilute contrast material also resulted in less patient discomfort. Subtracted images were available immediately on cathode ray tube display, resulting in faster procedures, and a considerable saving in film cost compared with conventional arteriography. It is concluded that intraarterial DSA is a useful technique that may replace conventional film-screen arteriography in many applications.

Angiography↗
PubMed1984

Iliac artery occlusion: management with intrathrombus streptokinase infusion and angioplasty.

Chronic and acute unilateral iliac artery occlusions were successfully treated in 7 of 8 patients using low-dose intrathrombus streptokinase infusions ranging from 6 to 43 hours in combination with percutaneous transluminal angioplasty. Angioplasty of an underlying stenosis was performed as soon as clot lysis was maximal and an underlying stenosis was demonstrated. Long-term follow-up to date has been excellent. This approach to unilateral iliac occlusion appears to be safer than previously reported angioplasty of iliac artery occlusion.

Adult↗
PubMed1984

Vasodilators and ventricular septal defect: comparison of prazosin, minoxidil, and hydralazine in a chronic lamb model.

The volume overloading of the left ventricle which results from left to right (L-R) shunting through a ventricular septal defect (VSD) may be reduced by pharmacologic agents which lower systemic vascular resistance (Rs) in excess of pulmonary arteriolar vascular resistance (Rpa). To study agents capable of decreasing the L-R shunt through systemic vasodilatation, we created a chronic lamb model with VSD and administered three vasodilators, prazosin (0.05 mg/kg), hydralazine (0.75 mg/kg), and minoxidil (0.25 mg/kg). Prazosin increased the Rpa while lowering Rs, resulting in an increase in Rpa/Rs by 43% (p less than or equal to 0.005). Prazosin decreased the pulmonary flow (Qp) slightly, decreased L-R shunt by 16%, reduced the pulmonary to systemic flow ratio (Qp/Qs) by 22% (p less than or equal to 0.005), and lowered the left atrial mean pressure (LA) by 16% (p less than or equal to 0.005) with no effect on heart rate. Hydralazine lowered the Rpa and Rs equally and thus did not change the Rpa/Rs or the volume of L-R shunt (7.6 versus 8.1 liters/min/m2). No change in LA was seen with hydralazine but heart rate increased from 162 to 200/min (p less than or equal to 0.01). Minoxidil did not change the L-R shunt (6.9 versus 6.8 liters/min/m2) and, in general, produced effects intermediate between prazosin and hydralazine. The data support a selective systemic vasodilation with prazosin, a property not shared by either minoxidil or hydralazine, which results in a reduction of shunting and left ventricular volume overloading in lambs with VSD.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Digital subtraction angiography in interventional radiology.

Intraarterial digital subtraction angiography (DSA) was used an an adjunct to interventional vascular procedures (embolotherapy and transluminal angioplasty) in 56 patients. The advantages of intraarterial DSA include improved contrast resolution, instantaneous subtraction capability, and immediate image availability. A considerable reduction in contrast dose and concentration, procedure time, and patient discomfort can be expected when interventional vascular procedures are performed with the assistance of intraarterial DSA.

Angiography↗
PubMed1984

Tailored approach for evaluation of peripheral vascular disease: intravenous digital subtraction angiography.

A tailored approach for evaluating patients with peripheral vascular disease has been developed using intravenous digital subtraction angiography (IV DSA). This approach includes a history, physical examination, and correlation with Doppler pressure measurements to predict the location of the dominant lesion. In 60 patients, two views of the aortoiliac segment plus three or four views of the femoral and runoff circulation in the most symptomatic leg were obtained. Of the 60 patients, 36% had percutaneous transluminal angioplasty as a primary form of therapy, 32% were treated surgically, and 32% were followed clinically. Only 10% of these patients required further evaluation by conventional angiography. By omitting inpatient arteriography, considerable financial savings and increased patient comfort result.

Aortic Diseases↗
PubMed1983

Selective effects on catalysis by the multiple forms of monoamine oxidase produced by interactions of acidic phospholipids with mitochondrial membranes.

The effect of acidic phospholipids on the A and B multiple forms of membrane-bound mitochondrial monoamine oxidase has been investigated by incubating liposomes with isolated rat liver mitochondrial outer membrane preparations at lipid:protein ratios of 0.01 to 1. A strong inhibition of monoamine oxidase B was observed with phosphatidylserine and a moderate activation of monoamine oxidase A with phosphatidylinositol, while cardiolipin had no significant effect on either form. The specificity of phosphatidylserine inhibition for monoamine oxidase B was also confirmed in mitochondrial outer membrane isolated from tissues containing exclusively the A or B form of the enzyme (human placenta and bovine liver). Levels of incorporation were comparable for all the phospholipids and tissues studied and could not account for the different effects observed. Inhibition of monoamine oxidase B was found to be similar in an intact mitochondria preparation to that observed in the isolated outer membrane. A recent report of activation of both monoamine oxidase forms in delipidated whole mitochondria by the acidic phospholipids was re-examined and found to involve release of monoamine oxidase from the mitochondria. The details of the effects of phosphatidylserine and phosphatidylinositol on membrane-bound monoamine oxidase are consistent with the concept of the multiple forms as two distinct peptides, and suggest a second possible mode of in vivo regulation of substrate specificity.

Animals↗
PubMed1983

Intraarterial digital subtraction angiography: a comparative view.

Intraarterial digital subtraction angiography (IA DSA) was performed in 122 patients undergoing a variety of diagnostic and interventional angiographic procedures. Owing to the increased contrast resolution of DSA, diluted contrast material in concentrations of from 12-19% could be employed, thereby significantly reducing contrast material doses compared to doses used with conventional film-screen angiography or intravenous DSA. Patient discomfort was convincingly reduced due to the injection of dilute contrast material. Subtracted digital images could be viewed immediately on a cathode ray tube (CRT) resulting in faster procedures with less catheter time. Savings in film costs relative to conventional angiography were also achieved.

Angiography↗
PubMed1983

Percutaneous transluminal angioplasty of aortic graft stenoses.

Postoperative aortic graft anastomotic stenoses at nine sites in eight patients were successfully treated with percutaneous transluminal angioplasty. There was a decrease in peak systolic pressure gradient in all eight patients, and in seven of the eight patients symptoms of claudication disappeared immediately after angioplasty. Four of the eight patients remained asymptomatic at follow-up. Ankle/arm indices were obtained before and after angioplasty in five patients, with postangioplasty improvement in all five.

Aged↗
PubMed1983

Angioarchitecture of pulmonary arteriovenous malformations: an important consideration before embolotherapy.

Seventeen patients with 91 pulmonary arteriovenous malformations were evaluated by superselective angiography. Seventy-two (79%) of the malformations consisted of a simple type characterized by a single feeding artery draining into a bulbous, nonseptated aneurysmal communication with a single draining vein. The other 19 (21%) were complex, consisting of two or more pulmonary artery branches communicating with a bulbous septated aneurysmal part with two or more draining veins. Two patients had diffuse pulmonary arteriovenous malformations confined to multiple lobes of the lung. Balloon embolotherapy was effective in permanently obliterating the malformations in 14 patients treated. Therapy provided a sustained rise in arterial PO2 in the sitting position from a mean value of 44 mm Hg before occlusion to 65 mm Hg after occlusion. In three patients the process was too diffuse and/or the malformations too large for therapy to be effective. Complex pulmonary arteriovenous malformations required occlusion of all feeding arteries. Balloon embolotherapy provided an effective treatment for pulmonary arteriovenous malformations regardless of anatomic type.

Adolescent↗
PubMed1982

Studies on the disulfide region of alpha 1-protease inhibitor.

The single disulfide bond of purified human alpha 1-protease inhibitor was reduced with dithiothreitol in the absence of denaturant and the resultant sulfhydryl groups were alkylated with iodoacetamide-1-C14. The product was found to be fully functional as an inhibitor of trypsin and elastase in esterolytic and proteolytic assays. The modified protein was also found to be nearly identical to native alpha 1-protease inhibitor when analyzed by immunological, electrophoretic, and spectral methods. The performic acid oxidized inhibitor, on the other hand, was devoid of any enzyme inhibitory activity. Analysis of the derivatized protein by amino acid analysis and by radioactive counting revealed only a single cysteine-containing peptide. The alkylated inhibitor was digested with cyanogen bromide and then trypsin, and subjected to two-dimensional peptide mapping. A single cysteine-containing peptide was recovered and shown to have the sequence Phe-Asn-Ile-Gln-His-Cys-Lys. A variety of experiments involving gel filtration or dialysis of reduced or oxidized alpha 1-protease inhibitor indicate that this Cys-peptide is covalently bound to either free cysteine or to glutathione via a disulfide bridge.

Amino Acid Sequence↗
PubMed1982

The teardrop shadow of the pelvis; anatomy and clinical significance.

The teardrop shadow of the pelvis is poorly understood and as a result its clinical significance is not appreciated. The structure responsible for this shadow was pinpointed by removing sections from the hemipelvis of an anatomic specimen with an electric saw. This structure is located in the anteroinferior portion of the acetabular fossa at the acetabular notch and consists of cortical and medullary bone contributed primarily from the ischium with a much smaller contribution from the superior pubic ramus. The normal and abnormal appearances of the teardrop shadow of the acetabulum of three patients were demonstrated on both plain radiographs and computed tomographic (CT) scans.

Acetabulum↗