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Biomedical subjects

R Chang

Publications and source records attributed to R Chang.

At least 127 records · Page 7Linked to original sources
PubMed1991

Intravascular streaming during carotid artery infusions. Demonstration in humans and reduction using diastole-phased pulsatile administration.

Intra-arterial carotid artery chemotherapy for malignant gliomas is limited by focal injuries to the eye and brain which may be caused by poor mixing of the drug with blood at the infusion site. This inadequate mixing can be eliminated in animal models with diastole-phased pulsatile infusion (DPPI) which creates 1-ml/sec spurts during the slow blood flow phase of diastole. Before treatment with intracarotid cisplatin, 10 patients with malignant gliomas were studied to determine whether intravascular streaming occurs after intracarotid infusion in humans, and if so, if it is reduced with DPPI. Regional cerebral blood flow (rCBF) studies were performed by intravenous injection of H2(15)O and positron emission tomography. This was followed by supra- or infraophthalmic internal carotid artery (ICA) injections of H2(15)O with either continuous infusion or DPPI. Local H2(15)O concentration in the brain was determined and the images of radiotracer distribution in the continuous infusion and DPPI studies were compared to the rCBF images. Intravascular streaming of the infusate was identified by a heterogeneous distribution of the infused H2(15)O in brain compared to rCBF. Extensive and variable intravascular streaming occurred in three patients who received infusions into the supraophthalmic segment of the ICA. Some brain areas received up to 11 times the expected radiotracer delivery, while other regions received as little as one-tenth. This streaming pattern was markedly reduced or eliminated by DPPI. In the five patients who received infraophthalmic infusions, a minimally heterogeneous distribution of the infusate was detected. The authors conclude that extensive intravascular streaming accompanies supraophthalmic ICA infusions in patients. The magnitude of streaming can be substantially reduced or eliminated with DPPI. Those who perform intra-arterial infusion should consider using DPPI to assure uniform drug delivery to brain.

Analysis of Variance↗
PubMed1991

[Preliminary studies on subtypes of respiratory syncytial virus in China].

An analysis of subtypes of 9 respiratory syncytial (RS) viruses isolated from Guangzhou and Nanjing areas of china was carried out with eight Sweden RS-subtype specific monoclonal antibodies (MAbs) and 7 internal anti-RS MAbs. All these MAbs directed against respectively the large Glycoprotein (G), fusion protein (F), nucleoprotein (NP), and phosphoprotein (P) components of the prototype Long strain of RS virus. The patterns of the reactions of these MAbs to the nine isolated strains of RS virus were compared with indirect immunofluorescence assay (IFA), alkaline phosphoesterase-anti alkaline phosphoesterase (APAAP) enzyme-linked assay and Western blotting. The antigenic variations were founded among the strains of RS virus, and two subtypes allocated to the subtype A and B of RS virus by using the eight RS-subtype specific MAbs. Seven out of the 9 isolated strains of RS virus belonged to the subtype A, and two were being to the subtype B. The antigenic diversities were also founded within the same subtype, and the main pronounced difference were observed on the G glycoprotein by using the internal anti-RS MAbs. These findings are potentially important both for vaccine development and for the understanding of clinical and epidemiological characteristics of RS virus.

Antigenic Variation↗
PubMed1990

Gastrinomas: localization by means of selective intraarterial injection of secretin.

Small doses (30 U) of secretin were injected directly into the splenic, gastroduodenal, hepatic, and superior mesenteric arteries of 13 patients with Zollinger-Ellison syndrome who were undergoing angiography to localize gastrin-secreting tumors of the islet cells. Blood samples from the right hepatic vein and a peripheral vein were drawn before and 30, 60, 120, and 210 seconds after each intraarterial secretin (IAS) injection. A 50% rise in gastrin level in the 30-second sample from the hepatic vein localized the gastrinoma to the head, body, or tail of the pancreas, depending on the artery into which secretion was injected. IAS results were positive in seven of 13 patients (54%); selective angiography was positive in five of 13 (38%); and the combined study, selective angiography with IAS injection, was positive in 10 of 13 (77%). Portal venous sampling was positive in six of 13 (46%). Selective IAS injection, combined with angiography, is the most sensitive study for localizing gastrinomas and avoids percutaneous transhepatic catheterization for portal venous sampling.

Adult↗
PubMed1990

von Hippel-Lindau disease: radiologic screening for visceral manifestations.

The visceral manifestations of von Hippel-Lindau (VHL) disease can cause significant morbidity and mortality. The authors prospectively screened 37 persons from a single kindred. Twenty-five subjects underwent abdominal ultrasound (US), contrast material-enhanced abdominal computed tomography (CT), and nonenhanced abdominal magnetic resonance (MR) imaging. Eight subjects younger than 16 years of age underwent abdominal US and MR imaging only. Scrotal US was employed in 25 male patients. Eleven subjects had renal cysts or tumors. Contrast-enhanced CT depicted renal abnormalities in 10 of these subjects, US in seven, and MR imaging in nine. Among 12 subjects with pancreatic cysts or tumors, CT showed pancreatic abnormalities in all 12, US in nine, and MR imaging in nine. Three subjects (mean age, 34.5 years) had renal tumors, and three had pancreatic masses. Scrotal US revealed epididymal cystadenomas in seven subjects; two of these tumors were surgically verified. A combination of contrast-enhanced CT and scrotal US in male patients appears to be the best way to screen for visceral manifestations of VHL disease.

Adolescent↗
PubMed1990

Fluorescence-guided laser-assisted balloon angioplasty in patients with femoropopliteal occlusions.

In 12 patients (aged 64 +/- 10 years) with femoropopliteal occlusions (1-27 cm; average, 8.4 cm length) that could not be recanalized by standard guidewire-balloon angioplasty techniques, percutaneous laser-assisted balloon angioplasty was performed by use of a new fluorescence-guided dual-laser system. Plaque detection by 325-nm laser-excited fluorescence spectroscopy provided real-time feedback control to a 480-nm pulsed dye laser (2-microseconds pulses) for atheroma ablation. By means of a common 200-microns optical fiber, after diagnostic fluorescence sensing, computer algorithms directed a fire or no-fire signal (5 Hz) to the treatment laser for selective plaque removal. Laser recanalization (15-50 mJ/pulse) was successful in 10 of 12 patients; this procedure was followed by definitive balloon angioplasty in seven of 12 patients with increased ankle/arm indexes (from 0.60 +/- 0.12 at baseline to 0.84 +/- 0.11 after treatment, p = 0.0043). In laser and balloon angioplasty failures, all femoropopliteal occlusions were heavily calcified, and there were two mechanical guidewire perforations without clinical sequelae. Ablation of calcified lesions required higher pulse energies and greater total energy per centimeter of recanalized tissue (1,837 +/- 1,251 mJ/cm vs. 90 +/- 39 mJ/cm, p = 0.0036). Fluorescence spectroscopy (n = 219 sites) was helpful in flush occlusions and correctly identified plaque, underlying media, and thrombus by changes in fluorescence intensity, shape, and peak position. Thus, when fluorescence-guided laser angioplasty was used in a subgroup of patients refractory to standard angioplasty techniques, primary recanalization and subsequent balloon angioplasty of femoropopliteal occlusions was successful in 83% and 58% of the patients, respectively. Importantly, treatment of heavily calcified lesions accounted for all of the failures and will require modified delivery systems to create larger primary channels and to increase catheter-tip control, which should improve clinical results in the future.

Adult↗
PubMed1990

Hepatoprotective compounds from Canarium album and Euphorbia nematocypha.

Successive purification of the extract from Canarium album and Euphorbia nematocypha, guided by antihepatotoxic activity in primary cultured rat hepatocytes, led to the isolation of brevifolin (1), hyperin (2), ellagic acid (3) and 3,3'-di-O-methylellagic acid (4) as hepatoprotective compounds. Compounds 1,3 and 4 also reduced carbon tetrachloride (CCl4)-induced liver damage in mice. The hepatoprotective activities of 1, 2, 3 and 4 in vitro and in vivo are apparently due to their antioxidative effects, which were exhibited by further studies using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and CCl4-induced lipid peroxidation systems.

Animals↗
PubMed1989

New hepatoprotective triterpenes from Canarium album.

Canarium album has yielded seven triterpenes of which two appear to be novel. The new triterpenes, which were identified on the basis of spectral characteristics, are urs-12-ene-3 alpha, 16 beta-diol and olean-12-ene-3 alpha, 16 beta-diol. Both compounds exhibited hepatoprotective activity in primary cultured rat hepatocytes intoxicated with D-galactosamine.

Animals↗
PubMed1989

Left lobe of the liver: percutaneous biliary drainage.

Left-sided biliary drainage was performed in 89 of 678 (13%) patients undergoing percutaneous biliary drainage procedures during a 9-year period. The most common indication was Klatskin tumor, followed by sclerosing cholangitis, carcinoma of the gallbladder, postoperative benign stricture, and metastasis to the porta hepatis. Left-duct drainage was successful in 82 of the 89 patients (92%) in whom it was attempted. One patient sustained a major hemorrhage from a hepatic artery aneurysm, which was managed with transcatheter embolization.

Bile Ducts↗
PubMed1989

Localization of parathyroid adenomas: superselective arterial DSA versus superselective conventional angiography.

A prospective comparison of superselective arterial digital subtraction angiography (DSA) and superselective conventional angiography (CA) was performed in a consecutive series of 26 patients with hyperparathyroidism, previous unsuccessful surgery, and single gland involvement. All patients had negative or inconclusive findings from noninvasive localization studies. Superselective studies included injection of both thyrocervical trunks, both internal mammary arteries, and both common carotid arteries in all patients in whom this was technically possible. DSA findings were true positive in 16 patients (62%); CA findings were true positive in ten patients (38%) and equivocal in four (15%) (P less than .046). There were no false-positive angiograms. DSA findings were positive in all patients in whom CA findings were positive or equivocal. Superselective DSA appears to be as sensitive as CA for preoperative parathyroid localization and may be more sensitive for the localization of mediastinal glands.

Adenoma↗
PubMed1989

Ectopic adrenocorticotropic hormone syndrome: localization studies in 28 patients.

A variety of imaging procedures were performed in 28 patients with ectopic adrenocorticotropic hormone (ACTH) syndrome in an attempt to localize the ACTH-producing tumor. Diagnosis was made on the basis of removal of an ACTH-producing tumor or biopsy of metastases in the 19 patients with a proved source and the absence of ACTH gradients in bilateral samples of the inferior petrosal sinuses in the nine patients in whom an ACTH-secreting tumor had not been localized. Eleven bronchial carcinoids, two thymic carcinoids, three pheochromocytomas, and three islet-cell tumors constituted the proved sources. The condition has been cured in eight patients, six are alive with residual tumor, and five have died. Of the nine patients with undetected sites of ACTH production, one has died of pneumocystis pneumonia and eight are being treated medically or with bilateral adrenalectomy. Computed tomography (CT) of the chest and abdomen was the most helpful study in the detection of these tumors. Selective arteriography (bronchial and visceral), systemic and portal venous sampling, and iodine-131 meta-iodobenzylguanidine scintigraphy failed to demonstrate tumors when findings at CT were negative. Bronchial carcinoids constituted most of the ACTH-secreting tumors in this study (58%) and in a review of four large series (47%). To assure early detection of these potentially malignant tumors, pulmonary CT should be performed every 6 months, even after hypercortisolism has been medically or surgically controlled.

ACTH Syndrome, Ectopic↗
PubMed1989

Renin-angiotensin II response to the hemodynamic pathology of ovines with ventricular septal defect.

We studied the response of the renin-angiotensin system (RAS) to a surgically created ventricular septal defect (VSD) in immature ovines and also the role of angiotensin II in the pathophysiology of VSD in the chronically instrumented ovine. Plasma renin activity (PRA) was increased from 2.39 +/- 1.1 to 3.78 +/- 1.4 ng/ml/hr (p less than 0.05, n = 17) after VSD but not after sham procedure. The change in PRA was positively correlated with the amount of left-to-right shunt through the VSD (r = 0.74, p less than 0.05). Inhibition of angiotensin II effect with saralasin (10 micrograms/kg/min) or angiotensin II production with captopril (2 mg/kg) lowered systemic resistance (Rs) by 14% and 34%, respectively (p less than 0.05), and raised pulmonary resistance (Rp) by 35% and 77%, respectively (p less than 0.05). Thirty minutes following captopril, the ratio of pulmonary to systemic flow (Qp/Qs) decreased from 3.31 +/- 0.18 to 2.15 +/- 0.18 (p less than 0.05) while total pulmonary flow fell from 7.15 +/- 0.38 to 5.92 +/- 0.34 l/min/M2 (p less than 0.05, n = 11). Systemic flow increased from 2.17 +/- 0.14 to 2.86 +/- 0.33 l/min/M2 (p less than 0.05) despite a reduction in left atrial pressure (17.3 +/- 1.0 vs. 13.0 +/- 1.7, p less than 0.01). Reinfusion of angiotensin II (0.02 micrograms/kg/min) into the central aorta after captopril returned the hemodynamics to baseline including a rise in Rs and fall in Rp. Exogenous angiotensin II alone (0.08 micrograms/kg/min) or a threefold stimulation in PRA with furosemide (2 mg/kg) caused little hemodynamic effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1989

Transgenic mice as a model to test the immunogenicity of proteins altered by site-specific mutagenesis.

Second generation therapeutic proteins are now being produced by in vitro mutagenesis of the relevant genes. Of some concern, however, is the possibility that these altered proteins will be immunogenic and the antibodies raised will also recognize the endogenous protein with undesirable consequences. We have designed a biological system to test these possibilities. In this model, transgenic mice produce and secrete human tissue plasminogen activator (h.tPA) to which these mice are immunologically tolerant. However, when challenged with a form in which a single amino acid has been substituted these mice will produce antibodies capable of recognizing h.tPA. These results indicate that there are immunological consequences connected with the design and administration of second generation therapeutic proteins.

Animals↗
PubMed1989

Prospective evaluation of hepatic imaging studies in the detection of colorectal metastases: correlation with surgical findings.

Nineteen patients with isolated colorectal liver metastases were preoperatively evaluated with five hepatic imaging studies. The results of these studies were correlated with operative findings. One study involved the use of EOE-13, an intravenously administered lipid contrast agent that enhances liver parenchyma on computed tomography (CT) scans (EOE-CT). Another study, arterial portography (AP-CT), was performed with injection of a water-soluble contrast agent into the superior mesenteric artery during CT scanning. Delayed CT scanning (DS-CT) was completed 4 hours after AP-CT. In addition, T1- and T2-weighted magnetic resonance imaging (MRI) (T1-MRI, T2-MRI) scans were done. All patients subsequently underwent laparotomy with identification of 78 lesions. A lesion-by-lesion analysis revealed that the sensitivity of EOE-CT (83%), AP-CT (78%), DS-CT (82%), and T1-MRI (84%) was comparable. T2-MRI had a significantly lower sensitivity (64%) compared with EOE-CT, DS-CT, and T1-MRI. The false-positive rate for AP-CT was 31%, which was significantly higher than that of all other studies. The T1-MRI examination had the lowest false-positive rate and proved to be the best hepatic imaging study in the detection of colorectal metastases. EOE-CT and DS-CT were comparable, whereas AP-CT and T2-MRI proved to be inferior tests.

Colorectal Neoplasms↗
PubMed1988

Interaction of 1-methyl-4-phenylpyridinium ion with human platelets.

When uptake of the Parkinson's syndrome inducing neurotoxin MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and its major brain metabolite MPP+ (1-methyl-4-phenylpyridinium ion) by human platelets were compared in platelet rich plasma, a much higher rate was observed for the metabolite. The uptake process was saturable (Km = 6.8 microM; Vmax = 0.064 nmole/min/mg protein) and could be blocked by inhibitors of serotonin uptake. The accumulation of MPP+ by the platelets was accompanied by a decrease in intracellular ATP and an inhibition of mitochondrial state 3 respiration. These findings are consistent with earlier reports of the effect of MPP+ on isolated mitochondria as a potential cytotoxic mechanism, but also demonstrate that the dopamine uptake system is not the only means by which this metabolite can be efficiently transported into cells.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1988

Cystine calculi: clinical management and in vitro observations.

Although cystine stones account for 1 to 3 per cent of renal calculi, many of these patients are difficult to manage because of recurrent urolithiasis. Seven cases of homozygous cystinuria are summarized. The evolution to the present treatment of percutaneous extraction and chemolysis appears to be the preferred form of treatment although extracorporeal shock wave lithotripsy (ESWL) may also be utilized. In addition, in vitro experiments were conducted to study the effectiveness of different chelating agents and buffers at different urinary pHs. The effect of cystinuric and noncystinuric urines was also evaluated.

Acetylcysteine↗
PubMed1988

Intravascular contrast media: effect of dose on renal function.

Effect of contrast material dose on clinically evident change in renal function was studied prospectively in 200 examinations requiring intravenous or intraarterial administration of contrast material. All patients were adequately hydrated. Blood urea nitrogen and serum creatinine were measured before and after the procedure. Ionic and nonionic contrast agents were used. Total dose of contrast material ranged from 30 to 530 mL (mean, 237 mL). There was no tendency to give smaller doses to patients with preexisting renal impairment and no relationship between total dose and patient age. No consistent clinical effect on renal function was demonstrated with increasing dose, regardless of whether ionic or nonionic agents were used. In adequately hydrated low-risk patients with predominantly normal initial renal function and within the dose range studied, there does not appear to be any consistent clinical change in renal function with increasing contrast material dose.

Adolescent↗
PubMed1988

The ultrasound appearance of radiation-induced hepatic injury. Correlation with computed tomography and magnetic resonance imaging.

The ultrasound findings in three cases of radiation-induced hepatic injury are described and compared with computed tomography and magnetic resonance imaging findings. Fatty infiltration of the liver was present in two of the cases in which concurrent chemotherapy was being administered. On ultrasound B-scans, the regions of radiation injury were hypoechoic relative to the remainder of the liver. This finding was more obvious in the patients with fatty livers. CT scans on the patients with fatty infiltrated livers showed higher attenuation in the irradiated region than in unexposed liver. In the patient where no fatty infiltration was present, the radiated section of liver had lower attenuation consistent with previous reports. Magnetic resonance imaging showed decreased signal in the exposed areas on T1 weighted images.

Child, Preschool↗