Search PubMed⌕ Search

Biomedical subjects

C Miller

Publications and source records attributed to C Miller.

At least 505 records · Page 28Linked to original sources
PubMed1989

Hand-held and automated sonomammography. Clinical role relative to X-ray mammography.

A retrospective analysis of 73 patients who had undergone X-ray mammography (XRM), automated sonomammography (ASM), and hand-held sonomammography (HSM) was performed to evaluate the clinical role of both types of sonomammography (SM) relative to XRM. The results were classified on the basis of mammographic and sonographic findings. Clinical and/or surgical proof was obtained in all 73 patients. The SM was complementary to XRM, depending on the radiographic breast density. When comparison was made between ASM (4.5 MHz) and the HSM (7.5 MHz), the pathologic condition was better identified by HSM in 86% of the cases. Moreover, in no cases was ASM better than HSM.

Adult↗
PubMed1989

A realistic dynamic cardiac phantom for evaluating radionuclide ventriculography: description and initial studies with the left ventricular chamber.

A phantom was devised to validate scintigraphically determined left ventricular ejection fractions (LVEFs) and cardiac chamber volumes in the following simulated cardiac situations: normal contraction, moderately impaired left ventricular contraction, severely impaired left ventricular contraction, mitral regurgitation, and cardiomyopathy. The phantom, assembled from anatomically realistic cardiac chambers, simulated contraction and expansion using individual chamber pumps coordinated by a microcomputer. Scintigraphic studies were performed by sequential imaging of [99mTc]pertechnetate introduced into each chamber. The images were analyzed like conventional clinical studies, using both automatic and manual techniques. Scintigraphic techniques correlated with chamber volumes that were determined by weight to yield the following regression formulae: LVEF (by automatic method 1) = 1.08 x LVEF (by weight) -5.11; LVEF (by automatic method 2) = 1.00 x LVEF (by weight) -3.15; and LVEF (by manual method) = 1.04 x LVEF (by weight) -5.08 ml (Correlation coefficients greater than 0.98). The absolute left ventricular volumes (LVVs), determined by scintigraphy, correlated well with LVVs determined by weight. These correlations were performed with separations between the center of the left ventricle and the collimator varying from 5 cm to 9 cm. The regression formulae for 5, 7, and 9 cm distances were: LVV (by counts) = 0.99 x LVV (by weight) + 0.13, LVV (by counts) = 1.04 x LVV (by weight) + 9.08, LVV (by counts) = 0.88 x LVV (by weight) + 15.25, respectively. At 9 cm, slight volumetric underestimation occurred, as predicted from the work of Fearnow et al., possibly because of oversubtraction of background. Thus, this phantom provides a useful tool for validating scintigraphic cardiac blood-pool studies simulating a wide range of clinically relevant situations.

Heart↗
PubMed1989

Spontaneous gallbladder perforation.

Acute gallbladder perforation is an infrequent, although not uncommon, complication of cholecystitis. It is rarely diagnosed preoperatively and the delay in making the definitive diagnosis usually accounts for the increased incidence of morbidity and mortality associated with this complication. A case of a 92-year-old patient in whom acute gallbladder perforation was suspected peroperatively at ultrasonography of the abdomen and confirmed by technetium-99m disofenin radionuclide biliary scan is reported.

Aged↗
PubMed1989

Cystadenoma of the gallbladder.

A case of obstructive jaundice due to extrinsic common bile duct (CBD) pressure from a gallbladder mass is presented. Endoscopic retrograde cholangiopancreatography (ERCP) demonstrated a dilated CBD and a massively dilated gallbladder. Computed tomography scan of the abdomen revealed a multiseptated cystic structure originating from the gallbladder fossa. Histologic sections of the surgical specimen demonstrated a multilocular cyst lined with biliary-type epithelium. Fibromuscular proliferation of the cyst walls also was noted. A literature search did not reveal documentation of a similar gallbladder lesion. We believe this lesion represents the first reported case of gallbladder cystadenoma.

Aged↗
PubMed1989

Avoidance of injury to the left hepatic duct during parenchymal dissection for hepatic trisegmentectomy.

A simplified and safe technique is described herein for the dissection of the feedback structures to the medial segment of the left lobe, while preserving the integrity of the remaining left hepatic bile duct during the dissection for right hepatic trisegmentectomy. This is accomplished by passing a biliary probe into the main left hepatic duct from the stump of the right hepatic duct. Use of this technique during the performance of a hepatic trisegmentectomy expedites the hepatic dissection and decreases the potential for intraoperative injuries of the remaining bile duct to the lateral segment of the left lobe of the liver. In addition, irrigation of the left hepatic bile duct through the open right duct stump may demonstrate leakages of bile that may be repaired, leading to a decreased over-all morbidity in the subsequent postoperative period.

Bile Duct Diseases↗
PubMed1988

Electron spin resonance studies under dynamic mobile phase conditions on chemically modified silica.

The electron-spin resonance (ESR) techniques of spin labeling and probing are shown to be powerful methods for the study of bonded silicas used in chromatographic separations under dynamic solvent flow conditions. Microscopic information gained from these studies includes solvation composition of the bonded phase at various locales in the bonded phase, configuration of the bonded phase and solvent-flow effects. In the spin-label study, 2-(2,2-dimethyloxazolidine-N-oxy)hexylsilane (DOXYL hexyl siloxane) was used as the label. ESR spectra show changes in the motional freedom of the bonded surface as a function of mobile phase composition and elution time and demonstrate chain stiffening with the introduction of water, as inferred by other studies. In the spin-probe work, various nitroxide compounds of the 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) family were introduced under flow conditions as a 0.1 mM solution in various water-methanol mobile phases. C18 sample columns were equilibrated with this mixture. Interpretation of the spectra yielded information about the solvated environment on the surface that was sampled by the probes as a function of both the mobile phase and the polarity of the probe.

Electron Spin Resonance Spectroscopy↗
PubMed1988

Hydrolysis of thioester analogs by rat liver phospholipase A1.

The hydrolysis of thioester containing phospholipids by rat liver plasmalemma phospholipase A1 was measured in a continuous spectrophotometric assay. In this assay thioester substrates were employed which, upon hydrolysis, liberated a free thiol which was reacted with 4,4'-dithiopyridine to yield the product 4-thiopyridone that absorbs at 324 nm. Thioester substrates, prepared by chemical synthesis, were used in phospholipid and Triton X-100 micelles for kinetic analysis carried out according to the method of Hendrickson and Dennis (Hendrickson, H.S., and Dennis, E.A. (1984) J. Biol. Chem. 259, 5734-5739). Vmax, Ks, and Km values obtained for various isomers and racemic mixtures of the synthetic thioester analogs are compared with corresponding oxyester substrates. Unnatural sn-1 isomers competitively inhibited the hydrolysis of natural sn-3 isomers of phosphatidylethanolamine and phosphatidic acid. Furthermore, the sn-1 isomer of phosphatidic acid was hydrolyzed by phospholipase A1, but with lower catalytic efficiency than the sn-3 isomer. The presence of a thioester at the sn-1 position did not change the Vmax significantly, as compared to the oxyester phospholipids. When two thioesters were present on the phospholipid molecule, the Vmax was decreased significantly. A convenient synthesis of 1-monothioester analogs of phospholipids is reported. The results presented show the usefulness of the spectrophotometric assay for measuring phospholipase A1 activity as well as the influence of racemic mixtures and thioesters on the hydrolytic rate.

Animals↗
PubMed1988

Complete pathologic maturation and regression of stage IVS neuroblastoma without treatment.

Spontaneous maturation of Stage IVS neuroblastoma has been postulated as a mechanism for its favorable prognosis, but this has rarely been documented pathologically. We report on a patient with congenital Stage IVS neuroblastoma who had extensive subcutaneous and bone-marrow involvement. Serial photographs, biopsies, and vanillomandelic acid determinations documented the tumor's initial progression which was followed by spontaneous maturation and involution of the patient's disease over a 6-year period. No cytotoxic therapy was administered. Favorable biologic prognostic factors were documented, including tumor DNA and protein analyses for N-myc amplification or overexpression and analysis for serum neuron-specific enolase and ferritin. Implications for management and therapy of Stage IVS neuroblastoma are discussed with reference to this case and the recent literature.

Biomarkers, Tumor↗
PubMed1988

Duodenal and gastric delivery of levodopa in parkinsonism.

To clarify the influence of gastric emptying on levodopa-related motor fluctuations in Parkinson's disease, we assessed mobility and plasma levodopa concentrations in 10 patients during five modes of levodopa administration: (1) standard intermittent oral (SIO), (2) intermittent duodenal (ID), (3) continuous duodenal infusion (CDI), (4) continuous gastric infusion (CGI), and (5) controlled-release Sinemet (CR-4). The rank order from greatest to least for both percentage of time "on" and average mobility score was CDI, CGI, ID, CR-4, and SIO. The rank order for variance of means, a measure of fluctuation, from least to greatest for mobility was CDI, CGI, CR-4, ID, SIO, and for plasma levodopa concentrations was CDI, CGI, ID, SIO, and CR-4. The results demonstrate that it is possible to produce very steady plasma concentrations of levodopa with a corresponding reduction in motor fluctuations by continuous intraduodenal administration of the drug. This mode of delivery is an ideal model for the development of optimal continuous-release preparations of levodopa. Other enteral routes have produced a more variable plasma levodopa concentration and clinical response.

Administration, Oral↗
PubMed1988

Competition for block of a Ca2(+)-activated K+ channel by charybdotoxin and tetraethylammonium.

Single high-conductance Ca2(+)-activated K+ channels were incorporated into planar lipid bilayers, and the discrete block by charybdotoxin (CTX), a protein inhibitor of this channel, was studied. In particular, the effect of externally added tetraethylammonium (TEA) on CTX blocking kinetics was investigated. TEA decreases the on-rate of CTX in exact proportion to its blocking of the single-channel current. The CTX off-rate is unaffected by TEA. The results demonstrate that TEA and CTX are mutually exclusive in their binding to the channel. Since the site of TEA binding is known to be located on the external side of the conduction pore, this result further strengthens the proposal that the CTX binding site is located in the external mouth of the channel.

Animals↗