Kr-81m ventilation imaging: clinical utility in suspected pulmonary embolism

The results of Kr-81m/Tc-99m ventilation-perfusion (VP) lung scintigraphy were correlated with the results of pulmonary angiography for 74 patients suspected of having pulmonary embolism (PE). Among patients having a diagnostic scan, the sensitivity and specificity of scintigraphy were 91% and 94%, respectively. Also, 157 consecutive cases of Kr-81m/Tc-99m VP lung scintigraphy were reviewed, and the frequency of an indeterminate scan was found to be 22%. A similar frequency was found for VP scintigraphy with xenon-133. Of eight patients who had indeterminate scans due to the presence of a single VP mismatch, four were demonstrated to have PE by angiography. Kr-81m is an excellent agent for VP scanning in cases of suspected PE, offering accuracy in diagnosis as well as favorable physical properties.     

Negative charge distribution and density on the surface of oxygenated normal and sickle red cells

Negative charges on the external surface of red cells were visualized by colloidal iron hydroxide labelling of 50% of the membrane area after osmotic hemolysis and glutaraldehyde fixation. Counts were made over randomly selected areas on electron micrographs at 350,000 x magnification. Statistical analyses showed that at the 95% level of confidence there was no significant difference between oxygenated normal (AA) and sickle (SS) cells in either the distribution or the density of negative charges.     

Pulmonary lymphangitic spread of carcinoma: appearance on CT scans

Chest computed tomography (CT), including high-resolution CT with thin (1.5-mm) sections was used to evaluate proved (pathologically or clinically) lymphangitic spread (LS) of tumor in 12 patients. These appearances were compared with thin-section scans obtained in 11 healthy subjects. Thin-section CT demonstrated findings consistent with thickening of the normal lung interstitium. In all patients, thin sections showed an increase in the number of peripheral lines (1-2 cm in length) that were diffuse in generalized disease and localized in focal disease. Normal peripheral arcades were not increased in number, but the limbs forming the arcades were thickened in all patients. A diffuse increase in linear and curvilinear structures (reticular pattern) was seen toward the center of the lung. Polygonal structures 1-2 cm in diameter were seen in seven patients with LS but not in healthy subjects. Fissures were thickened in nine patients. Selected 1.5-mm-thick CT sections are recommended through abnormal areas (seen at CT or on chest radiographs) or if these are normal at three levels (midapex, hilus, and 3 cm above the diaphragm) when scanning patients with tumors known to cause LS.     

Volumetric rendering techniques: applications for three-dimensional imaging of the hip

Volumetric rendering is a new approach to three-dimensional (3D) imaging that overcomes many of the drawbacks of currently available surface-rendering systems. Its application on the Pixar Imaging System in two cases of acetabular fracture was assessed to illustrate the features of the technique. The fast-computing architecture and large memory of this system allow rapid generation of a series of high-quality 3D images in each plane of rotation (x or spinal axis, z or somersaulting axis) that can be viewed as independent static images or as an animated real-time video loop. Editing to remove the normal contralateral hemipelvis enhances appreciation of acetabular abnormalities. Every pixel of computed tomographic data is preserved, allowing representation of both soft tissue and bone as translucent overlap. The presentation of data also allows detection of subtle abnormalities and features and minimizes the artifact generation common in surface-rendered images.     

Radiologically guided balloon dilation of gastrointestinal strictures. Part I. Technique and factors influencing procedural success

Radiologically guided balloon catheters were used to dilate 94 gastrointestinal strictures in 92 patients over a 6-year period. Fifty strictures were esophageal and 44 nonesophageal (22 gastroenterostomies, 11 antral-pyloric strictures, four colorectal strictures, four enteroenterostomies, and three miscellaneous strictures). Factors influencing the success of stricture intubation included patient age, stricture location (esophageal vs. nonesophageal and proximal vs. distal esophageal), and association with a surgical anastomosis. Malignancy was associated with greater postdilation irregularity and a smaller increase in stricture diameter, as measured radiographically. Procedural failures occurred in 8% of cases (2% of esophageal and 30% of nonesophageal lesions). Two small, asymptomatic mucosal tears were seen after dilation (one esophageal and one colonic); no other procedural complications occurred. Following successful dilation, 16 patients (17%; six with esophageal and ten with non-esophageal strictures) had recurrence of symptoms during short-term (30-day) follow-up.     

Cytochrome P-450-dependent omega-oxidation of leukotriene B4 in rodent and human epidermis

Leukotriene B4 (LTB4,5-12-dihydroxy 6,8,10,14-eicosatetraenoic acid), an enzyme-catalyzed oxidation product of arachidonic acid, is a major inflammatory mediator. Human polymorphonuclear leukocytes and rodent hepatic microsomes catabolize LTB4 to 20-OH-LTB4 and 20-COOH-LTB4, which is mediated by a cytochrome P-450 catalyzed reaction termed the LTB4 omega-hydroxylase. In this study we investigated the catabolism of LTB4 in rat, guinea pig, and human epidermis. The incubation of 3H-LTB4 (9 microM) for 60 min in the presence of oxygen, NADPH, and epidermal microsomes prepared from neonatal fat (3.0 mg) or adult guinea pig (2.6 mg) resulted in the formation of 20-OH-LTB4 and 20-COOH-LTB4. Metabolite identification was based on co-chromatography on high pressure liquid chromatography with highly purified reference standards. The formation of 20-OH-LTB4 and 20-COOH-LTB4 was accompanied by the disappearance of LTB4. The rate of formation of 20-OH-LTB4 was 9-12-fold higher than that of 20-COOH-LTB4. Product formation was negligible with boiled microsomes, required NADPH and oxygen, was linear with respect to incubation time and protein, and was maximal at pH 7.4. LTB4-omega-hydroxylase activity was inhibited (greater than 90%) by carbon monoxide or 2-diethylaminoethyl-2,2-diphenylvalerate hydrochloride (SKF-525A) (1 mM), whereas alpha-naphthoflavone produced only moderate (13%) or no effects. Topical application of 3-methylcholanthrene and other conventional inducers of epidermal monooxygenase activities to neonatal rats (100 mg/kg, single treatment) did not result in an increase in epidermal LTB4-omega-hydroxylase activity. The addition of 3H-LTB4 (30 nmoles) to primary human keratinocytes followed by incubation at 37 degrees C resulted in time-dependent disappearance of LTB4 and appearance of 20-OH-LTB4 and 20-COOH-LTB4 in the medium. These results suggest that LTB4 is catabolized by the cytochrome P-450-dependent enzyme system in rodent and human skin and that this may participate in modulating the effects of this proinflammatory lipid in this tissue.     

Inhibition of mutagenicity in Salmonella typhimurium and skin tumor initiating and tumor promoting activities in SENCAR mice by glycyrrhetinic acid: comparison of 18 alpha- and 18 beta-stereoisomers

Licorice has been used as medicine and as sweetening agent in food products. The major water-soluble constituent of licorice is glycyrrhizin (GL), an oleanane triterpenoide, which is known to be partly hydrolyzed by glucuronidase to its aglycone glycyrrhetinic acid (GA) which exists in 18 alpha (alpha-GA) and 18 beta (beta-GA) stereoisomeric forms. In this study alpha-GA and beta-GA were found to inhibit the mutagenicity of benzo[a]pyrene (B[a]P), 2-aminofluorene and aflatoxin B1 in Salmonella typhimurium TA98 and TA100. beta-GA was more effective than alpha-GA as an antimutagen. In the two-stage skin tumorigenesis protocol using 7,12-dimethylbenz[a]anthracene (DMBA) as the tumor initiating agent followed by twice weekly applications of 12-O-tetradecanoylphorbol-13-acetate as tumor promoter, pretreatment of SENCAR mice with alpha-GA or beta-GA resulted in significant protection against tumor initiation as well as tumor promotion. As an anti-tumor initiating agent, beta-GA was found to be more effective than alpha-GA. Similarly, topical application of beta-GA was found to be more effective than alpha-GA in inhibiting the binding of both [3H]B[a]P and [3H]DMBA to epidermal DNA. However, as an anti-tumor promoter, alpha-GA and beta-GA showed comparable effects. Our results suggest that both alpha-GA and beta-GA possess substantial anti-skin tumor initiating and anti-skin tumor promoting activities.