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Biomedical subjects

D C Chen

Publications and source records attributed to D C Chen.

At least 55 records · Page 3Linked to original sources
PubMed1992

[The structure identification of pyridinemono terpene isocantleyine].

Siphonostegia chinensis Benth. as a traditional Chinese medicine "liujinu" has been used for centuries in China, but up to date little has been reported about its chemistry. Now, four compounds have been isolated from the aerial parts of this genus. On the basis of spectroscopic analysis (UV, IR, MS, 1HNMR, 13CNMR and 2D-NMR) and chemical evidences, compound I was shown to be a new pyridinemonoterpene alkaloid which is a stereoisomer of the known compound cantleyine, and named isocantleyine. Its structure was determined as 5H-2-pyridine-4-carboxylic acid, 6,7-dihydro-6-hydroxy-7-methyl-methyl ester. Compound III was identified as the known compound loliolide. The other two (II and IV) are still under investigation. This paper deals mainly with the structure identification of compound I.

Drugs, Chinese Herbal↗
PubMed1991

Analysis of the quantitative structure activity relationship of technetium-99m-labeled diaminedithiol (DADT) and propylene-amine-oxime (PAO) brain blood flow analogues.

In the search for new brain imaging agents for the use with single photon emission computed tomography (SPECT), quantitative structure activity relationship (QSAR) analysis of the correlations between initial brain uptake and physicochemical parameters like lipophilicity, log P, molecular weight, log MW and log U/D (undissociated/dissociated), of the 99mTc-DADT (diaminedithiol) complexes and 99mTc-PAO (propyleneamineoxime) complexes have been analyzed. High correlations are found for both the 99mTc-DADT complexes (r = 0.94) and for the 99mTc-PAO complexes (r = 0.83) which are significant at 99.9 and 99.5 percentile level, respectively. These results will help the further design of better ligands for 99mTc in brain imaging.

Brain↗
PubMed1990

Mediation of nitrous oxide analgesia in mice by spinal and supraspinal kappa-opioid receptors.

Exposure to nitrous oxide produced concentration-dependent analgesia in the mouse abdominal constriction test. Intracerebroventricular or intrathecal pretreatment with naltrexone or nor-binaltorphimine significantly reduced nitrous oxide analgesia. However, similar pretreatment with beta-funaltrexamine had no appreciable effect. These findings suggest that nitrous oxide analgesia involves spinal and supraspinal kappa-opioid receptors.

Analgesics↗
PubMed1990

Optimization of immobilized enzyme hydrolysis combined with high-performance liquid chromatography/thermospray mass spectrometry for the determination of neuropeptides.

Peptidases, including chymotrypsin, thermolysin, trypsin, V8 protease, and carboxypeptidases A, B, and Y, were immobilized for use in conjunction with HPLC/thermospray MS for the analysis of neuropeptides. The optimal operating conditions for each immobilized enzyme bioreactor were determined. Optimal hydrolysis usually occurred at the highest percentage of aqueous solution in the mobile phase at pH 7-8 and 40-50 degrees C. Often post-HPLC column addition of aqueous solutions before the bioreactor could improve activity and thermospray sensitivity without changing the HPLC separation. Enzymatic hydrolysis requirements were compatible under conditions for HPLC separation and thermospray MS detection of the selected neuropeptides. Synthetic alpha-, beta-, and gamma-endorphins were the primary neuropeptides used to evaluate on-line immobilized enzyme bioreactor/MS. HPLC followed by peptidase hydrolysis produced characteristic hydrolysis products for confirming the peptides' identity using thermospray MS detection. Furthermore, the peptide formed from enzymatic hydrolysis resulted in a MS ion current 10-40 times higher than that of the [M + 2H]2+ ion for unhydrolyzed beta-endorphin. The increased sensitivity achieved for detecting the hydrolysis products permits detection and quantitation of synthetic peptides down to 800 fmol.

Chromatography, High Pressure Liquid↗
PubMed1990

Interpretation of bone scans using a video display. A necessary step toward a filmless nuclear medicine department.

Digital processing, storing, and interpretation of scintigraphic images from a PACS system has been postulated as an efficient, cost-saving measure that may obviate the need for analog film. In order to replace analog film, documentation that images can be interpreted from a digital video display with accuracy at least equal to film must be obtained. Analog film was compared with video images in 28 patients with cancer suspected to be metastatic to bone. Images were acquired with a gamma camera and processed in 256 x 256 word mode by the use of the Medical Data Systems A3 computer. Adjustment of gray scales provided operator-controlled digital contrast enhancement. Video and film images were independently interpreted by two experienced nuclear medicine physicians, each blinded to the other modality. A linear four-color scale was then substituted for the gray scale, and images again interpreted. Lesions were interpreted as positive or equivocal and verified through follow-up scans over a minimum of six months. Of the 28 patients, 22 proved to have metastases, in whom 129 lesions were confirmed by follow-up scintigrams. 124 of these lesions (96.1%) were detectable on both analog film and video images. An additional three proven metastatic lesions on video images were absent or equivocal on analog studies, increasing sensitivity for video images to 98.4%. Five further lesions seen on the video screen represented rib fractures and regressed on follow-up examination. All lesions seen on black-and-white video were also seen when the color scale was applied.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Autoanti-Ge associated with severe autoimmune hemolytic anemia.

Severe autoimmune hemolytic anemia due to anti-Ge is described. The patient's red cells had a positive direct antiglobulin test, and they typed as Ge+ using saline reactive reagents. Anti-Ge was eluted from her RBCs, and her serum had an IgG and IgM anti-Ge2,3.

Adult↗
PubMed1990

Effects of ileal transposition on food intake, dietary preference, and weight gain in Zucker obese rats.

This study evaluated the effects of ileal transposition (IT) surgery on food intake, body weight, and dietary preferences in Zucker obese rats. Eight rats had a 10-cm segment of terminal ileum transposed to the upper jejunum. Eight rats underwent sham IT (SIT) and six rats had no surgery (CON). During weeks 1-10 and 21-24, rats were fed a selection diet of protein (casein), carbohydrate (corn starch), and fat (lard) in three separate dishes. Rat chow was fed from weeks 11 to 20. IT rats had a lower weight and a lower change in weight from base line throughout most of the study. Energy intake was less in IT vs. SIT rats during the selection periods (weeks 1-10 and 21-24), but did not differ on the chow diet (weeks 11-20). Digestible energy, measured at weeks 10, 20, and 24, was lower in IT rats only at week 10. IT rats had no malabsorption by fecal calorie measurements. IT rats ate fewer fat calories at both selection periods. We conclude that IT causes long-term reduction in body weight, no malabsorption or long-term changes in digestible energy, and a persistent decrease in preference for dietary fat. Further studies are needed to determine whether increased energy expenditure is a mechanism for the long-term difference in body weight after IT.

Animals↗
PubMed1990

Circumferential quantitative analysis of planar 201T1 myocardial scintigraphy in the diagnosis of coronary artery disease.

Methodology for the computer analysis of 201T1 myocardial perfusion images has been developed by several laboratories. Substantial evidence of the advantage of this approach over visual inspection alone has been reported. The currently available computer analyses use different algorithms to analyze 201T1 kinetics in the myocardium. The authors evaluated and compared two widely used software programs, Medical Data System (MDS): a mean-count profile, and the Cedars Sinai (CS): a maximal-count profile, of planar 201T1 scintigraphy for their ability to detect coronary artery disease (CAD).

Adult↗
PubMed1990

A study of central opioid receptor involvement in nitrous oxide analgesia in mice.

This study was undertaken to assess the sensitivity of nitrous oxide (N2O) analgesia to antagonism by intrathecally (IT) and intracerebroventricularly (ICV) administered antagonists selective for kappa- and mu-opioid receptors. Male ICR mice were pretreated IT or ICV with the kappa antagonist nor-binaltorphimine (nor-BNI), 1 or 50 nmol, respectively, or distilled water (control), then exposed to N2O (50% or 75% in oxygen). Compared with IT control mice, IT nor-BNI-pretreated mice responded with significantly less analgesia. Compared with ICV control mice, ICV nor-BNI-pretreated mice also showed markedly reduced analgesic response. Other mice were pretreated IT or ICV with either the selective and irreversible mu antagonist beta-funaltrexamine (beta-FNA, 5.0 micrograms) or distilled water (control). When exposed to N2O 24 h later, beta-FNA-pretreated and control mice exhibited comparable analgesic responses. These preliminary results suggest that N2O analagesia in mice may involve spinal and supraspinal kappa-opioid receptors but not mu-opioid receptors.

Analgesia↗
PubMed1989

Noninvasive monitoring of drug biodistribution and metabolism: studies with intraarterial Pt-195m-cisplatin in humans.

We have performed a comparative evaluation of systemic (i.v.) and intraarterial (i.a.) cisplatin by using a trace dose of the radiolabeled form of this drug [( 195mPt]cisplatin) to monitor the drug's biodistribution by dynamic scintigraphic imaging. We have analyzed the drug's metabolism using a compartmental model both following i.a. and i.v. administration in patients with gliomas. Significantly larger amounts of radioactivity (up to 10 times higher than in the uninvolved brain) were measured in tumors following i.a. administration, whereas the differential localization following i.v. drug administration was, at best, only twofold that of the uninvolved brain. On the other hand, no significant differences could be detected in the pharmacokinetics of either free cisplatin or platinated proteins in blood. The washout slope in tumors following i.a. administration may be an indicator of the higher local concentration of free cisplatin; no such washout could be observed in tumors following i.v. administration. The present noninvasive methods may help document the amount and the rate of (active) drug deposition at the desired target site. They may also assist in monitoring, prospectively and/or, on line, the probable effect of chemotherapy in an individual patient. In turn it may lead to novel methods for optimizing chemotherapeutic effectiveness at specific tumor-bearing sites and in defined treatment protocols.

Cisplatin↗
PubMed1989

An unusual scintigraphic pattern in sickle cell patients.

We reviewed the nuclear medicine files of all patients enrolled in the sickle cell disease clinic who had had scans performed within the previous 5 years. We specifically looked for patterns of tracer uptake in these scans that would correlate with the severe anemia and consequent bone marrow hyperactivity of sickle cell patients. Thirty-three patients were included (21 men and 12 women) with a mean age of 26.8 years (range 17-48 years). The appearance of each of these patients' most recent scans was examined in the areas of the distal femurs, the proximal tibias and the distal tibias; a distinct triangular shaped pattern of increased activity was identified in these areas in a majority of patients. Thirty-three patients without sickle cell disease served as age-matched controls. This pattern was seen in 65.1% (95 out of 146 images) of the sickle cell patients' delayed images and 80.4% (82 out of 102 images) of their blood pool images. In contrast, the control patients demonstrated the triangular pattern in none of their blood pool studies (0%) and only 10.9% of their delayed bone images (P less than 0.001). The mean age of sickle cell patients with this pattern is 25.6 years which was significantly lower than that of those without this pattern (mean = 37.5 years, P less than 0.05). Given the high prevalence of this unique scintigraphic pattern in a group of patients with known accelerated bone marrow function, these findings may be scintigraphic evidence of bone marrow expansion. The patient's age appears to be an important factor in visualization of this pattern.

Adult↗
PubMed1989

Hepatobiliary and gallium imaging findings in gallbladder perforation: a case report and review of the literature.

Gallbladder perforation is an unusual condition with a high mortality rate. Early detection with prompt surgical intervention can increase the survival rate. Hepatobiliary imaging using Technetium-99m-labeled iminodiacetic acid has been used for the diagnosis of gallbladder perforation. However, the results vary and are somewhat confusing. The authors report a case of gallbladder perforation with hepatobiliary imaging and an unusual gallium image; review the literature; and propose a classification of three different imaging patterns: 1) visualization of the gallbladder with bile leakage, 2) nonvisualization of the gallbladder with a photopenic fluid collection, and 3) nonvisualization of the gallbladder with bile leakage. These patterns may provide pathophysiologic information for surgeon.

Adult↗
PubMed1989

Gated intracoronary thallium201 scintigraphy: feasibility and potential clinical advantages.

Visualization of ventricular walls with true global motion and myocardial thickening is not possible with use of present scintigraphic techniques. When thallium 201 (201TI) is injected intravenously (IV), only about 5% reaches the myocardium. However, if 201TI is injected intracoronarily, 100% reaches, and approximately 88% localizes in, the myocardium, which results in higher count rates than when given IV, permitting acceptable acquisition times for gated true wall motion studies. The authors describe a new technique using intracoronary (IC) 201TI to acquire high count rate, high contrast, and short acquisition time in gated true wall motion studies. Thirteen patients were studied at rest with gated IC thallium. Six of these patients also had resting IV 201TI myocardial studies. After routine coronary angiography, 0.75 mCi of 201TI was injected into each coronary artery. Multiple sequential one-minute gated studies were obtained in LAO and RAO projections, followed by sequential five-minute images for two hours to determine 201TI redistribution kinetics. Regions of interest over segments of left and right ventricles and background permitted definition of temporal and spatial distributions. Three one-minute gated studies were summed with a total count of 2,100 K for a three-minute acquisition. Myocardium-to-background ratios were as high as 13:1 with a mean of 11.4:1 in the IC study compared with 2.3:1 in the IV studies. Washout half-time in normal myocardium was 95 +/- 5 min. The detectability and size of perfusion defects were different on gated diastolic and systolic, nongated, and IV studies. Questionable defects seen on nongated studies or after IV administration were easily noted on gated diastolic images.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Vessels↗
PubMed1988

Non Hodgkins lymphoma of the breast, unusual presentation: detection by 67Ga scintigraphy.

Lymphomatous involvement of the breast is an uncommon cause of breast masses. A case is presented of a patient with bilateral breast involvement revealed by intense 67Ga uptake. Other foci of involvement were also detected scintigraphically, and confirmed by other imaging modalities. Multiagent chemotherapy resulted in significant clinical and scintigraphic regression of tumor, demonstrating the potential utility of 67Ga imaging in the follow-up of these patients.

Adult↗
PubMed1988

Gallium-67 uptake in cutaneous lesions of mycosis fungoides.

The literature on gallium imaging in mycosis fungoides is limited and conflicting. A case of mycosis fungoides with increased uptake of Ga-67 in clinically noninfected skin lesions is reported. The literature regarding mycosis fungoides and gallium imaging is reviewed.

Aged↗
PubMed1988

Hepatic photopenia in gallium imaging.

Although Ga-67 has been used extensively in imaging many different conditions, much is yet unknown about the mechanisms by which gallium concentrates preferentially in tissues such as the liver. This paper reports three patients with markedly diminished hepatic uptake of gallium. The cases are examined in light of published data demonstrating such factors as transferrin levels, radiation, and chemotherapeutic agents as altering the hepatic uptake of gallium. Of the many factors believed to influence the biodistribution of gallium, none can definitively account for the lack of hepatic uptake in these patients.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Volume calculation by means of SPECT: analysis of imaging acquisition and processing factors.

To assess the effect of image acquisition and processing factors on the volume calculated from single photon emission computed tomography (SPECT) images, the authors evaluated technical factors including image matrix size, size of the region of interest (ROI), activity concentration in the region, amount of background subtraction, type of reconstruction filter, section thickness, and number of projections. They found that the percentage of background subtraction was the single most important factor affecting volume calculation. The smaller the volume, the greater the amount of background subtraction needed before the ROI is drawn. As an acceptable means to circumvent the varying percentage of background subtraction for different volumes, a calibration curve was constructed relating the true volume with the calculated volume for a fixed percentage of background subtraction. The use of a 128 X 128 acquisition matrix and zooming of the reconstructed images were necessary for accurate calculation of volumes smaller than 300 mL.

Humans↗