Pulmonary blood volume imaging with dual-energy computed tomography: spectrum of findings.

Dual-energy (DE) pulmonary blood volume (PBV) computed tomography (CT) has recently become available on clinical CT systems. The underlying physical principle of DECT is the fact that the photoelectric effect is strongly dependent on the CT energies resulting in different degrees of x-ray attenuation for different materials at different energy levels. DECT thus enables the characterization and quantification of iodine within tissues via imaging at different x-ray energies and analysis of attenuation differences. Technical approaches to DECT include dual-source scanners acquiring two scans with different energy levels simultaneously, and single-source CT scanners using sandwich detectors or rapid voltage switching. DE PBV CT enables the creation of iodine maps of the pulmonary parenchyma. Experience to date shows that these studies can provide additional physiological information in patients with acute or chronic pulmonary embolism beyond the pure morphological assessment a standard CT pulmonary angiography (CTPA) provides. It appears also to be promising for the evaluation of patients with obstructive airways disease. This article reviews the physics and technical aspects of DE PBV CT as well as the appearance of normal and abnormal lung tissue on these studies. Special consideration is given to pitfalls and artefacts.

Pneumonia in solid organ recipients: spectrum of pathogens in 217 episodes.

BACKGROUND: Lower respiratory tract infection (LRTI) remains a leading cause of morbidity and mortality after solid organ transplantation (SOT). PATIENTS AND METHODS: We performed a retrospective analysis of 217 episodes of LRTI in 143 SOT patients from a single center. RESULTS: There were 94 men and 49 women (85% Caucasian) of median age of 51 (range 17-79) years, including 50 renal, 86 liver, 6 pancreas, and 1 lung recipient. Forty patients experienced multiple episodes of LRTI. Median APACHE II score was 17 (range 5-40), median temperature was 38 degrees C (range 35.3 degrees C-40.2 degrees C), and median white blood cell count was 12000 (range 100-106,000). Pneumonia developed at a median of 11 (range 2-191) days after the last surgical intervention. Of the 217 LRTIs, 163 were nosocomial infections (60 ventilator-associated). Overall crude mortality of 21% was increased in patients with multiple episodes of LRTI (25%) and after liver transplantation (33%). In 40 cases, treatment was initiated without identification of a specific pathogen. Overall, 202 microorganisms were found (41 mixed infections): Staphylococcus aureus (n = 32) of which 81% were MRSA; Escherichia coli (n = 9); Klebsiella spp (n = 7); Enterobacter spp (n = 11); Serratia spp (n = 12); Pseudomonas aeruginosa (n = 15); Stenotrophomonas maltophila (n = 15); Acinetobacter spp (n = 9); fungi (n = 18), and viruses (n = 17). CONCLUSION: LRTI remains one of the most common, dangerous infections in transplant recipients with higher mortality than in other populations. MRSA is a particular problem. As a significant number of SOT patients develop multiple episodes of LRTI, a thorough reevaluation of the current guidelines for the treatment of pneumonia is urgently needed.

Postnatal expression profile of OBCAM implies its involvement in visual cortex development and plasticity.

This study examined the expression of a neuron-specific cell adhesion molecule, OBCAM (opioid-binding cell adhesion molecule), at both the mRNA and protein levels in the cat primary visual cortex at various postnatal ages, using cDNA array analysis and immunocytochemistry. Results obtained using both methods showed that the expression level of OBCAM was high in young and low in older and adult visual cortex. OBCAM-immunoreactivities were associated predominantly with perikarya and dendrites of pyramidal neurons, and OBCAM-immunopositive neurons were present in all cortical layers. Immunostaining of OBCAM in adult visual cortex showed a reduced number of immunopositive neurons and neurites and relatively lower staining intensities as compared with younger animals. In addition, the number of OBCAM-immunopositive neurons was significantly higher in the visual cortex of 4-month-old animals dark-reared from birth than those in age-matched normally reared animals. These results suggest that OBCAM may play an important role in visual cortex development and plasticity.

Kinetics of lipopolysaccharide clearance by Kupffer and parenchyma cells in perfused rat liver.

We studied the kinetics of [3H]lipopolysaccharide ([3H]LPS) (endotoxin) binding to Kupffer cells and hepatocytes at the level of the microtubular system after treatment with gadolinium chloride (GdCl(3)) and colchicine. Liver perfusion in Sprague-Dawley rats involves both portal vein and thoracic inferior vena cava cannulations as inlet and outlet, respectively. The subhepatic inferior vena cava is ligated to prevent perfusate leakage. Buffer containing 2% serum and [3H]LPS is administered at 1 ml/min and collected for 50 min. Rate constants for hepatocellular clearance of [3H]LPS in controls, colchicine-treated rats, GdCl(3)-treated rats, and colchicine plus GdCl(3)-treated rats are assessed using a simplified mathematical model. Forward-binding, reversal-binding, residency time, and influx rate constants are estimated. Results show that in GdCl(3)-treated rats, the hepatocytes effectively clear endotoxin from the circulation, and its ultimate binding affinity at the hepatocyte site is somewhat reduced compared to the Kupffer cells. In colchicine-treated rats, the disruption of the microtubule network altered [3H]LPS binding with Kupffer cells, suggesting that the microfilament-microtubular network also affects Kupffer cell function. Simultaneous treatments with colchicine and GdCl(3) increased the influx rate constant, suggesting that the compiled morphological alterations up-regulated endotoxin clearance by the liver, as indicated by a drastic increase in cellular vacuolation. In conclusion, the kinetics of the trafficking process of [3H]LPS clearance are regulated by apical-sinusoidal endocytotic and canalicular routes.