Potential renal donors: comparison of conventional imaging with helical CT

PURPOSE

To assess helical computed tomography (CT) as a potential substitute for intravenous urography and renal angiography in the evaluation of living potential renal donors.

MATERIALS AND METHODS

Helical CT was performed in 32 potential donors both before and after administration of contrast material. Scans were reconstructed at 1.5-mm intervals for three-dimensional reconstructions. Helical CT images were blindly compared with urograms (n = 32) and renal angiograms (n = 24).

RESULTS

One small accessory artery was not depicted with helical CT, and angiography did not depict an accessory artery arising in proximity to the origin of the main renal artery. All eight kidneys with early dividing main arteries were identified with both helical CT and angiography. Three renal venous anomalies were depicted only with helical CT. Helical CT and urography equally depicted nonvascular findings.

CONCLUSION

Renal helical CT is a suitable replacement for intravenous urography and angiography in the assessment of living renal donors.

Ultrasound at scintigraphic "intermediate probability of pulmonary embolism"

For diagnosis of pulmonary embolism (PE), ventilation/perfusion lung scintigraphy is routinely used; approximately one-third of the patients will have the diagnosis "intermediate probability of PE" (inconclusive). In this group only about 33% are found to have pulmonary emboli if examined with pulmonary angiography. To evaluate the diagnostic, therapeutic, and economic consequences of ultrasound of the legs as a complementary diagnostic investigation to "intermediate probability", 72 consecutive patients were investigated with bilateral ultrasound of the proximal deep veins of the legs and pulmonary angiography in a prospective study. Ten patients had PE, of whom 7 had deep venous thrombosis, and 62 had no PE, of whom 2 had deep venous thrombosis. The negative predictive value of ultrasound was 0.95. In view of the importance of adequate treatment and rational use of public health care expenditure, complementary diagnostics should be performed, and ultrasound is an adequate complementary investigation.

Portal-phase contrast-enhanced helical CT for the detection of malignant hepatic tumors: sensitivity based on comparison with intraoperative and pathologic findings

OBJECTIVE

The purpose of this study was to determine the sensitivity of portal-phase IV contrast-enhanced helical CT in detecting malignant hepatic tumors using a lesion-by-lesion comparison with surgical and pathologic findings.

MATERIALS AND METHODS

Preoperative portal-phase contrast-enhanced helical CT studies in 21 patients (13 men, eight women) with malignant neoplasms of the liver (12 patients with primary hepatic tumors, nine patients with metastases) were reviewed retrospectively by three radiologists with the knowledge that hepatic malignancies were present in each case. Helical CT findings were compared with intraoperative findings by palpation (21 patients), sonography (15 patients), and the results of pathologic examination of resected specimens (10 patients) in a lesion-by-lesion manner. Sixty-four malignant nodules were identified in resected specimens or at surgery by palpation or intraoperative sonography. For each nodule identified by surgical or pathologic means, CT findings were reviewed for the presence of a lesion of similar size and location.

RESULTS

The readers identified 52 of 64 nodules on helical CT scans for an overall sensitivity of 81%. Sixteen of 21 primary tumors (76%) and 36 of 43 metastatic tumors (84%) were identified on CT scans. The sensitivity was 91% for nodules greater than 1 cm (42 of 46) and 56% for nodules 1 cm or less (10 of 18). False-positive findings occurred in 4% of lesions seen on helical CT scans.

CONCLUSION

Our results show that portal-phase contrast-enhanced helical CT is extremely sensitive (91%) for detecting malignant hepatic tumors greater than 1 cm, is relatively insensitive (56%) for tumors less than 1 cm, and has a low false-positive rate. These results compare favorably with published results for CT during arterial portography, the current gold standard for liver tumor detection, suggesting that portal-phase IV contrast-enhanced helical CT is an excellent noninvasive preoperative study prior to hepatic resection or cryosurgery.

Nuclear arthrography: combined scintigraphic and radiographic procedure for diagnosis of total hip prosthesis loosening

Radiographic arthrography and bone scintigraphy are common diagnostic procedures used for evaluating total hip prostheses. In this study, both techniques are combined, and nuclear contrast imaging (nuclear arthrography) is added. The efficacy of the procedures is evaluated.

METHODS

After intravenous injection of 99mTc-methylene diphosphonate (MDP), standard radiographic arthrography was performed in 105 patients (107 prostheses). The radiographic contrast medium was mixed with insoluble 111In-colloid (5 MBq/20 ml). After completion of the radiographic arthrography, nuclear arthrography was performed, and multiple-view dualisotope images (111In, 247-keV peak only) were recorded. Images were interpreted by superposition of the 111In image and the corresponding 99mTc-MDP image, the latter serving as a landmark for the position of the prosthesis and osseous structures. Findings at surgery were used as the gold standard.

RESULTS

In both cemented and uncemented acetabular and femoral components, nuclear arthrography performed better than or equal to radiographic arthrography (70%-90% and 60%-75%, respectively). Nuclear arthrography had higher diagnostic accuracy than 99mTc-MDP images alone.

CONCLUSION

Nuclear arthrography is a sensitive technique for detection of loosening of prostheses, offering added value over radiographic arthrography and bone scanning alone, especially for evaluation of the femoral component. Radiographic arthrography remains necessary not only for adequate deposition of contrast agents but also for detailed evaluation of osseous structures.

Measurement of glomerular filtration rate using nonradioactive Iohexol: comparison of two one-compartment models

Radioisotopic methods for the determination of the glomerular filtration rate (GFR) are highly accurate but require the collection of multiple blood and urine samples and are costly to perform due to personnel, material, and analysis costs. Nonradioactive methods of GFR determination have the potential of minimizing procedure costs while preserving accuracy. We determined the GFR simultaneously by 125I-iothalamate and nonradioactive iohexol clearance methods in 41 adults. The study group consisted of 54% males, with a mean age of 50.7 (range 28-79) years and a mean GFR by 125I-iothalamate clearance of 66.5 +/- 28.3 (range 10-118) ml/min. The iohexol concentrations were measured by a simplified high-performance liquid chromatography method that did not require sample preparation. The iohexol plasma clearance was calculated by both a new one-compartment model as well as by Jacobsson's one-compartment model. Using Jacobsson's single-sample model and data from the 240-min point, there was an excellent correlation between 125 I-iothalamate and nonradioactive iohexol clearance values: r2 = 0.95, standard error of the estimate = 11.4 ml/min, and intrapatient coefficient of variation = 16.9%. However, this formula tended to overestimate GFRs < 30 ml/min and to underestimate GFRs > 80 ml/min. The new one-compartment model is a modification of Bubeck's model, originally used for the determination of renal plasma blood flow. Using this modified model, there was an excellent correlation between 125I-iothalamate and nonradioactive iohexol clearance values at all levels of GFR tested: r2 = 0.95, standard error of the estimate = 9.2 ml/min, and intrapatient coefficient of variation = 13.7%. In conclusion, the determination of the plasma clearance of iohexol by a nonradioactive technique and a monoexponential model is a simple and accurate method of determining the GFR in patients with varying degrees of renal impairment.

[Visipaque: a step on the way to an ideal contrast medium]

To study tolerance of two nonionic X-ray contrasting agents Omnipaque and the iso-osmolar dimer Visipaque, changes in central hemodynamic, myocardial electrophysiological, renal nitrogen-excretory parameters were studied in 50 patients undergoing coronary angiography and ventriculography. The two contrasting agents were found to provide slight negative side effects; however, Visipaque showed better subjective tolerance and less frequently caused adverse reactions and complications. The beneficial properties of Visipaque allows the authors to recommend that it should be used in angiographic studies in high-risk patients.

Hepatocellular carcinoma: detection with double-phase helical CT during arterial portography

Retrospective analysis of findings at double-phase helical computed tomography (CT) during arterial portography was performed in 42 hepatocellular carcinomas (HCCs) in 31 patients. Phase 1 scanning started 30-35 seconds after the beginning of injection of contrast material; phase 2 scanning started 10-18 seconds after the end of phase 1. The overall detection rate for HCCs was 83% (35 of 42) in phase 1, 81% (34 of 42) in phase 2, and 90% (38 of 42) for combined phase 1 and 2 findings.

Detection of bleeding in patients with major pelvic fractures: value of contrast-enhanced CT

OBJECTIVE

We performed a retrospective review of trauma patients who had undergone both pelvic angiography and preangiographic i.v. contrast-enhanced CT to determine whether CT can accurately demonstrate the presence or absence of pelvic bleeding in patients with multisystem trauma and major pelvic fractures.

SUBJECTS AND METHODS

We reviewed the medical records and imaging studies of all patients, identified through a trauma radiology database, who had undergone pelvic angiography and preangiographic contrast-enhanced CT during a 48-month period. Results of CT scans were recorded by consensus interpretation of three radiologists without knowledge of angiographic findings. Sites of contrast material extravasation seen on CT scans were noted and compared with sites of bleeding or vascular injury identified by selective pelvic angiography.

RESULTS

Thirty patients with blunt trauma and pelvic fractures underwent both pelvic angiography and preangiographic CT studies. Findings on pelvic angiograms were positive at 26 sites in 19 patients and included contrast agent extravasation at 23 sites and vessel abnormalities without extravasation at three sites. Preangiographic pelvic CT scans showed contrast agent extravasation at 20 sites in 16 patients. Three patients had no contrast agent extravasation demonstrated by CT but had bleeding demonstrated by angiography. CT detected bleeding in 16 of 19 patients who had extravasation or vascular injury demonstrated by angiography, for a sensitivity of 84%. Results of pelvic angiography were negative in 11 patients, and none had evidence of bleeding on preangiographic CT scans. Two sites of contrast agent extravasation identified in two patients by CT did not show bleeding at angiography, for a specificity of 85% for the detection of bleeding. The overall accuracy of CT for determining the presence or absence of bleeding was 90%.

CONCLUSION

Knowledge of sites of ongoing hemorrhage is crucial for optimizing the sequence of diagnostic and therapeutic studies in patients with blunt trauma. Contrast-enhanced CT of the pelvis, which is often performed for hemodynamically stable trauma patients, is a noninvasive technique that is highly accurate in determining the presence or absence of ongoing pelvic hemorrhage. This information can assist in initial management decisions involving patients with multisystem trauma and major pelvic fractures.

Hemodynamic alterations in the paravertebral venous plexus after spinal injury

PURPOSE

To assess the prevalence of altered venous hemodynamics after spinal cord injury.

MATERIALS AND METHODS

The authors performed venography in 200 ambulant patients and 107 patients with spinal injury. The hemodynamic characteristics of the paravertebral venous plexus were documented after pedal injection of contrast material. The hemodynamic and clinical data were correlated in patients with spinal cord injury.

RESULTS

Abnormal venous return via the paravertebral venous plexus in the absence of iliac or inferior vena caval occlusion was shown in 73 (68%) of the 107 patients with spinal injury. This paravertebral venous flow route is not related to the time between injury and examination. It was demonstrable in the early as well as late post-traumatic period and was reproducible at subsequent examinations. The paravertebral venous flow route was more commonly seen in cervical than thoracolumbar injuries and was closely related to the severity of neurologic deficit (P = .0012).

CONCLUSION

Abnormal vertebral venous hemodynamics occur in most patients with spinal cord injury and are more likely to occur in patients with complete neurologic deficit and cervical injury.

Extensive extradural spread in the elderly may not relate to decreased leakage through intervertebral foramina

It has been suggested that the extensive longitudinal extradural spread of local anaesthetics in the elderly is attributed to decreased leakage through the intervertebral foramina. We have examined radiologically, in 53 patients, the relationship between leakage of iohexol through the thoracic intervertebral foramina and age. Iohexol was injected through an extradural catheter advanced 5 cm cephalad from one of the interspaces between T6 and T12. A significant correlation was observed between longitudinal spread of iohexol and age, but there was no correlation between leakage of iohexol through the intervertebral foramina and age. Our data suggest that longitudinal extradural spread of local anaesthetics in the elderly may not be attributed to decreased leakage through the intervertebral foramina.

A survey of GTP-binding proteins and other potential key regulators of exocytotic secretion in eosinophils. Apparent absence of rab3 and vesicle fusion protein homologues

We set out to identify potential key regulators of exocytotic fusion in the eosinophil, in the knowledge that granule exocytosis can be stimulated in these cells by intracellular application of nonhydrolyzable analogues of guanosine triphosphate, with Ca2+ acting as a modulator of guanine nucleotide-dependent secretion. To screen for GTP-binding proteins, guinea pig eosinophils were purified from peritoneal washings and subjected to western blotting analysis using specific immune sera raised against recombinant proteins or consensus peptide sequences within proteins of interest. We found a number of heterotrimeric G proteins (G alpha i3, G alpha o, G alpha q11, G alpha s and G beta subunits) and members of the small GTP-binding proteins expressed in eosinophils. Two subtypes of G-protein alpha subunits (G alpha i1 and G alpha z) could not be detected. Separation of subcellular organelles from homogenized eosinophils by density gradient centrifugation revealed that all of the detected GTP-binding proteins were mainly expressed in fractions containing peak plasma membrane and Golgi marker enzyme activities, while G beta subunits were also detected in secretory granule fractions. However, isoforms of Rab3, a putative GTP-binding regulator of exocytotic fusion, were undetectable in eosinophils. Neither, with the exception of syntaxin-3, could we detect any of the proteins belonging to the proposed synaptic vesicle fusion complex (SNAP-25; synaptobrevin (VAMP) and its non-neuronal homologue, cellubrevin; synaptophysin; synaptotagmin). The results from this study, based on western blotting, suggest that eosinophils express a different class of exocytotic fusion complex proteins from those found in neuronal tissues, although a number of potential candidates fulfilling the role of GE were identified in this important inflammatory cell.

Enrichment of Penicillium chrysogenum microbodies by isopycnic centrifugation in nycodenz as visualized with immuno-electron microscopy

A procedure to enrich microbodies from Penicillium chrysogenum and a method to evaluate the purity and integrity of the microbodies are described. As a P. chrysogenum microbody marker acyltransferase (AT) was used. The P. chrysogenum hyphae were converted into protoplasts with Novozym 234. In Percoll-sucrose buffer the protoplasts were separated from mycelial debris after 10,000 x g centrifugation. Purified protoplasts were lysed, and the cell homogenate was centrifuged to form a 14,000 x g pellet. After 2 h, 45,000 x g isopycnic centrifugation of the 14,000 x g pellet on a continuous 20-60% nycodenz gradient, ten fractions were collected. The fractions were analyzed for AT containing microbodies by immuno-blotting and immuno-electron microscopy. The results showed that AT-microbodies are enriched in the 38% nycodenz fraction. The microbodies had a diameter of 400 to 500 nm, revealed an intact single membrane and confined AT. The estimated equilibrium density of the P. chyrsogenum microbodies was 1.20 g ml-1 as deduced from the 38% (w/v) nycodenz concentration.

Evacuation proctography combined with positive contrast peritoneography to demonstrate pelvic floor hernias

BACKGROUND

To demonstrate the pelvic peritoneal recesses during voiding, evacuation proctography was combined with positive contrast peritoneography.

METHODS

In 30 constipated patients, peritoneography was performed, followed by proctography.

RESULTS

During evacuation rectogenital herniation developed in 20 patients (66%), without visceral filling in 12 (40%).

CONCLUSIONS

Posterior pelvic floor hernia is common during defecation. Less than half fill with bowel and many may not be apparent on standard proctography.

Contrast enhancement of the upper abdomen evaluated by CT. A comparison between iohexol 350 mg I/ml and iopamidol 370 mg I/ml

The non-ionic monomeric contrast media iopamidol and iohexol were compared concerning enhancement in the organs of the upper abdomen in CT. The average peak enhancement above the base line for the 2 contrast media in the liver, vena cava, aorta and spleen was calculated. No difference between the contrast media was found with regard to increase in contrast enhancement. No correlation between the peak enhancement and body weight and body surface was found with either of the 2 contrast media.

Digital subtraction shoulder arthrography in determining site and size of rotator cuff tear

RATIONALE AND OBJECTIVES

To evaluate the value of digital subtraction arthrographic techniques in assessing the precise size and site of rotator cuff tear.

PATIENTS AND METHODS

Prospectively interpreted findings of 29 digital arthrographs were compared with results after surgery in 22 patients and with results after arthroscopy in 7 patients.

RESULTS

Surgery or arthroscopy revealed 14 full-thickness and 2 partial-thickness tears. Digital subtraction arthrography showed 88% (14 of 16) of the rotator cuff tears, 86% (12 of 14) of the full-thickness tears, and 100% (2 of 2) of the partial-thickness tears. The site of a tear could be shown in 86% (12 of 14), but the size was evaluated to be less extensive than that seen at surgery in most tears (63%, 10 of 16).

CONCLUSIONS

The site of tears could be demonstrated in supraspinatus tendon tears, but measurements of the size of the tears were accurate only in small full-thickness and in partial-thickness tears. Very anterior and posterior tears may not be diagnosed with this method, and postexercise films were necessary to avoid false-negative findings.

Three-dimensional echocardiography: limitations of apical biplane imaging for measurement of left ventricular volume

A new three-dimensional echocardiographic system creates a "line of intersection" display to allow precise and known positioning of echocardiographic images. Our purpose was to determine whether use of the line-of-intersection display will improve positioning of the apical four-chamber and apical two-chamber views and thereby improve the agreement between estimates of left ventricular volume by apical biplane echocardiography and cineventriculography. Unguided and line of intersection-guided apical biplane views were obtained in 31 patients immediately before cardiac catheterization and single-plane cineventriculography. In 15 patients the line-of-intersection display was used to measure the position of the image plane in studies of unguided and guided methods. Linear regression and limits of agreement analysis were used to assess the agreement between cineventriculographic volumes and echocardiographic volumes determined from each set of images. The Wilcoxon test was used to compare guided and unguided image positioning. The line-of-intersection display improved four-chamber and two-chamber view positioning closer to the center of the ventricle and rotation closer to orthogonal positioning. Guided-image positioning was not able to correct displacement of the ultrasound beam anterior to the ventricular apex without deterioration of image quality in most patients. Despite improvements in image plane positioning, the agreement between echocardiographic and cineventriculographic volumes was unchanged. For end-diastole views, the unguided images had an r value = 0.84, standard error of the estimate of +/- 23.0 cc, and limits of agreement of +/- 62.4 cc. Corresponding values for the guided images at end diastole were r = 0.85, standard error of the estimate of +/- 22.9 cc, and limits of agreement of +/- 60.8 cc. At end systole the unguided results were r = 0.91, standard error of the estimate of 16.8 cc, and limits of agreement of +/- 52.2 cc. The line-of-intersection guiding of image plane positioning can improve apical image positioning but does not improve the agreement between apical biplane echocardiographic and cineventriculographic left ventricular volumes. The optimal apical imaging window is frequently occluded by the rib cage, resulting in a decrease in image quality. This reduction of image quality, combined with assumptions of left ventricular geometry, limit the accuracy of estimates of left ventricular volume from apical biplane echocardiography.

Renal masses: assessment of corticomedullary-phase and nephrographic-phase CT scans

PURPOSE

To evaluate the role of thin-section helical computed tomography (CT) performed during the corticomedullary phase (CMP) and nephrographic phase (NP) of contrast enhancement in the detection and characterization of renal masses.

MATERIALS AND METHODS

Renal CT scans and medical records of 33 patients were retrospectively reviewed. In all examinations, 5-mm-thick, contiguous, helical-mode scans were obtained before and 40 seconds after initiation of dynamic bolus injection of contrast material (CMP images); 5-mm-thick, contiguous, axial-mode scans were obtained after completion of CMP scanning (NP images).

RESULTS

At review of CMP, NP, and combination images, 259, 389, and 417 lesions, respectively, were identified. The greatest difference in detection occurred in the renal medulla, with 25 lesions identified on CMP images and 111 lesions identified on NP images. False-positive results occurred when CMP images were reviewed without NP images.

CONCLUSION

CT scans obtained only during the CMP of contrast enhancement fail to depict many renal masses that are easily seen on NP images.

Arthrography of the wrist. Assessment of the integrity of the ligaments in young asymptomatic adults

Fifty-two asymptomatic adults who were between twenty and thirty-five years old had arthrography of the wrist with use of a single injection into the radiocarpal joint. The purpose of the study was to evaluate the integrity of the triangular fibrocartilage, the scapholunate ligament, and the lunotriquetral ligament. Contrast medium was injected under fluoroscopic guidance, and posteroanterior and lateral radiographs of the wrist were made after the subjects had performed exercises of the wrist. No patient who had a history of trauma to the wrist, pain in the wrist, or inflammatory arthritis was included in the study. All of the subjects had an examination of both upper extremities that included measurement of the active motion of the wrist with a goniometer, strength-testing with a Jamar dynamometer, ballottement and testing for impingement, and palpation for tenderness. Plain radiographs were evaluated, and the ulnar variance was recorded. The arthrograms revealed an abnormal communication of the contrast medium in fourteen wrists (27 per cent), and four of the fourteen had multiple areas of communication. The abnormal communication was through the triangular fibrocartilage alone in six wrists, the scapholunate ligament alone in two wrists, the lunotriquetral ligament alone in two wrists, and in more than one of these areas in four wrists. A positive arthrogram was associated with a greater positive ulnar variance. All of the subjects had symmetrical motion of the wrists and grip strength, and none of them had tenderness in the wrist. There were no complications related to the arthrography. Perforation of a ligament in the wrist is common in young asymptomatic adults.(ABSTRACT TRUNCATED AT 250 WORDS)

Small peripheral lung carcinoma evaluated with incremental dynamic CT: radiologic-pathologic correlation

PURPOSE

To correlate incremental dynamic computed tomographic (CT) and pathologic findings in peripheral lung cancer.

MATERIALS AND METHODS

Lung lesions smaller than 3 cm in diameter were evaluated in 18 patients. CT values of the inner area of the nodule at plain CT and at 30 seconds, 2 minutes, and 5 minutes after administration of nonionic contrast material were calculated with incremental dynamic CT. Maximum attenuation was compared with pathologic type of lung carcinoma and with number of vessels and distribution of elastic fibers in the pathologic specimen.

RESULTS

Enhancement of all lesions was statistically significant (P < .0001). Maximum attenuation of lung carcinomas correlated positively with number of small vessels (diameter, 0.02-0.10 mm) (r = .77). Distribution of elastic fibers in the tumoral interstitium correlated with maximum attenuation (P = .04 between grades 1 and 3) and with number of small vessels (P = .01 between grades 1-3; P = .008 between grades 1 and 3).

CONCLUSION

Enhancement characteristics of lung carcinomas reflect the number of small tumoral vessels and the distribution of elastic fibers in the tumoral interstitium.

Hepatic hemangioma: findings with two-phase CT

PURPOSE

To characterize the appearance of hemagiomas at two-phase dynamic incremental computed tomography (CT) and to determine the cause of contrast material enhancement of adjacent parenchyma in the first series.

MATERIALS AND METHODS

Contrast-enhanced CT images of 51 hemangiomas in 20 patients were reviewed. Enhancement patterns of hemangiomas in the first series were classified as homogeneous high, peripheral high, and low attenuation; in the second series, as homogeneous high, peripheral high, iso-, and low attenuation. Correlations between arterioportal shunts and early parenchymal enhancement were evaluated in 45 hemangiomas in the 17 patients who underwent angiography.

RESULTS

Thirty-two hemangiomas progressively became enhanced. Four had low and eight had homogeneous high attenuation in both series. Seven changed from homogeneous high to isoattenuation. Early parenchymal enhancement was well correlated with presence of arterioportal shunt.

CONCLUSION

Low-attenuation hemangiomas and those that changed from homogeneous high to isoattenuation are atypical and difficult to differentiate from other neoplasms. Most early parenchymal enhancement is caused by associated arterioportal shunts.

Threshold selection for CT angiography shaded surface display of the renal arteries

The purpose of this study was to define objective criteria to calculate a tissue segmentation threshold for shaded surface display (SSD) rendering of the renal arteries with computed tomography angiography. Contrast-enhanced spiral CT scans were obtained through the renal arteries of nine patients. Six sets of SSD images were rendered for each patient with lower threshold values ranging from 80 to 130 Hounsfield units (HU) by increments of 10 HU. Visceral organ enhancement was measured in the aorta, liver, spleen, pancreas, and kidney. The segmentation threshold for each patient was determined by evaluation of the SSD images alone as well as by comparison with conventional arteriograms. The ideal threshold, as shown by comparison with conventional arteriography, was better correlated with a threshold value selected by qualitative evaluation of SSD images alone (rs = .42), than with measured enhancement in visceral organs (rs = -.289 to .009). The degree of stenosis was overestimated in a single renal artery (1 of 18) because of an inappropriate threshold selected by evaluation of the SSD images alone. In comparison with a segmentation threshold calculated from measured enhancement of visceral organs, a segmentation threshold selected by qualitative evaluation of the resulting SSD images is more likely to approximate the ideal threshold. Given the subjective nature of such threshold selection, further evaluation is warranted to determine whether threshold selection may result in inaccurate grading of stenosis.

Buoyant density of Escherichia coli is determined solely by the osmolarity of the culture medium

In previous studies, we had shown that the buoyant density of Escherichia coli is determined by the osmolarity of the growth medium by varying the osmolarity of the medium with NaCl or sucrose. However, the buoyant density of the cells always exceeded that of the growth medium. Here we determined the effect of medium with a buoyant density greater than the expected buoyant density of cells by adding Nycodenz to Luria broth. Percoll gradients of cells were analyzed by laser light scattering. The buoyant density for 125- and 375-mOsM-grown cells was 0.002 g/ml and 0.003 g/ml more, respectively, for cells grown in the presence of Nycodenz than those grown without Nycodenz, while the buoyant density of 250-mOsM-grown cells was 0.005 g/ml less for cells grown in the presence of Nycodenz than those grown without Nycodenz. Cells grown in 500-mOsM medium with or without Nycodenz had the same buoyant density. The buoyant density of cultures grown in defined medium was the same as those grown in rich medium, with only the medium osmolarity correlating to buoyant density. We conclude from these experiments that neither buoyant density nor chemical make-up of the medium determines the buoyant density of cells grown in that medium. Only the medium osmolarity determines cell buoyant density, suggesting that E. coli has no mechanisms to sense buoyant density.

Isolation of human blood dendritic cells by discontinuous Nycodenz gradient centrifugation

The most potent antigen presenting cell present in peripheral blood, lymphoid and non-lymphoid tissue is the dendritic cell (DC). The study of human DC has been restricted by their low frequency in the tissues and the lack of a truly DC specific surface marker to assist in identification and isolation. Standard techniques for the isolation of blood DC generally employ a period of in vitro culture followed by flotation on dense albumin gradients, or more recently, discontinuous gradients of metrizamide. Dense albumin gradients are time consuming to prepare, giving low and variable yields of DC. Metrizamide is more convenient, although exposure of monocytes to metrizamide can decrease the expression of CD14 and alter the accessory cell properties of antigen presenting cells. Here we demonstrate that Nycodenz gradient centrifugation of 16 h cultured, T lymphocyte depleted, peripheral blood mononuclear cells (PBMC) reliably yields a population of low density cells that is highly enriched for DC. Most B and residual T lymphocytes are depleted and NK cell numbers are reduced two-fold from the interface cell population. The high density pellet fraction exhibits very little allostimulatory activity, indicating that few DC pass into the pellet. The low density fraction contains a significant population (20 +/- 5 (SD)%, n = 8) of cells which fail to stain for the lineage markers CD3, CD11b, CD14, CD16, CD19 and CD57. Nycodenz exhibits low toxicity, does not alter the allostimulatory activity of antigen presenting cells, and is therefore ideal for the isolation of cultured DC.

[Iopentol in varix radiography. Double blind comparison with iohexol]

This trial was aimed at comparing the tolerance and the safety of Iopentol, a new nonionic monomeric contrast agent, with Iohexol, a reference compound already on the market and commonly used in similar trials. Sixty adult patients (41 women and 19 men, aged 23 to 76 years, mean age: 51.4 years) referred to our Department of Radiology for varicography 24 hours before surgery were examined; the trial was designed as a double-blind, parallel two-group comparison of Iopentol 300 mg/ml and Iohexol 300 mg/ml with 30 patients in each treatment group. No adverse reactions were observed in our series of patients. Only slight and not clinically significant changes were observed in heart rate and blood pressure values. The immunohistochemical parameters were studied for postvaricography anatomopathologic complications of the injected veins (A-Actin ML, Vimentin, Factor VIII, CD31, CD68, CK, Ulex Europaeus I, Lecitin, Desmin, Laminin) and no statistically significant differences were observed between the two groups. The histologic specimens showed only venous wall changes, as diagnosed on admission. All radiographs were classified as technically adequate and contrastographic efficacy was defined as "good" in all patients by two independent radiologists. To conclude, our trial on the efficacy and safety of the two nonionic monomeric radiographic contrast agents Iopentol and Iohexol proved the two contrast agents to be equally effective and well tolerated, which makes Iopentol a good alternative to Iohexol in varicography.