Rosette formation between immobilised human lymphocytes and erythrocytes sensitised with monoclonal anti-D

A rapid, reproducible and sensitive assay was developed to investigate the ability of human lymphocytes to form rosettes with erythrocytes sensitised with human monoclonal anti-D. Erythrocytes sensitised with a known number of anti-D molecules per cell were incubated with lymphocytes immobilised on plastic by poly(L-lysine), the resulting rosettes fixed, unbound erythrocytes removed by washing and the cell preparation stained. IgG1 and IgG3 anti-D-coated erythrocytes gave similar rosette formation at sensitisation levels in the range of 5000-15,000 molecules per cell, although at lower sensitisation levels IgG3 gave greater rosette formation than IgG1. A minimum of 500 IgG3 and 1000 IgG1 anti-D molecules per erythrocyte were required for rosetting.     

Effects of ADH on the apical and basolateral membranes of toad urinary bladder epithelial cells

Short-circuited urinary bladders from Bufo marinus were supported on their apical surface by an agar mounting method and impaled with microelectrodes via their basolateral membrane. This arrangement provided stable and long-lasting impalements of epithelial cells and yielded reliable membrane potentials and voltage divider ratios (R _a/R _b), where R _a and R _b are apical and basolateral membrane resistances respectively. The membrane potential under short-circuit conditions (V _sc) was –51.4±2.2 mV (n=59), while under open-circuit conditions apical membrane potential (V _a) and basolateral membrane potential (V _b) were –31.0±2.4 and 59.5±2.4 mV, respectively. This yields a well-shaped potential profile across the toad urinary bladder, where V _a is inversely related to the rate of transport, I _sc. Antidiuretic hormone (ADH) produced a hyperpolarisation of V _sc and V _b but had no significant effect on V _a. In addition, R _a/R _b was significantly increased by ADH (4.6±0.5 to 10.2±3.6). Calculation of individual membrane resistances following the addition of amiloride showed that ADH produced a parallel decrease in R _a and R _b membrane resistance, with the observed increase in R _a/R _b being due to a greater percentage decrease in R _b than in R _a. The ability of ADH to effect parallel changes in apical and basolateral membrane conductance helps to maintain a constant cellular volume despite an increase in transepithelial transport.     

The relationship between cyclooxygenase-2 expression and characteristics of malignant transformation in human colorectal adenomas

BACKGROUND AND AIMS: Cyclooxygenase 2 (COX-2) is a target of aspirin and other non-steroidal anti-inflammatory drugs and is implicated in the pathogenesis of colorectal cancer. The objective of this study was to evaluate the extent of COX-2 in pre-malignant colorectal polyps and to assess the relationship between COX-2 and the level of dysplasia in these lesions. METHODS: Whole polypectomy specimens were retrieved from 123 patients by endoscopic or surgical resection. Following formalin fixation and paraffin embedding, the polyps were evaluated histologically for size, type and grade of dysplasia. The extent of COX-2 expression was measured by the avidin-biotin immunohistochemical technique using a monoclonal COX-2 antibody. The extent of COX-2 expression was graded according to percentage epithelial COX-2 expression. RESULTS: The polyps were of the following histological types: 10 hyperplastic, 35 tubular adenomas, 61 tubulovillous adenomas and 17 villous adenomas. Twenty showed mild dysplasia, 65 moderate dysplasia, and 28 focal or severe dysplasia (including eight with focal invasion). The average polyp size was 1.7 cm. Nine hyperplastic polyps were COX-2-negative and one was COX-2-positive. COX-2 expression was more extensive in larger polyps and in polyps with a higher villous component. There was a significant increase in the extent of COX-2 protein with increasing severity of dysplasia. Within a polyp, there was a focal corresponding increase in COX-2 expression within epithelium showing a higher grade of dysplasia. CONCLUSIONS: COX-2 expression is related directly to colorectal adenomatous polyp size, type and grade of dysplasia. This suggests that the role of COX-2 in colorectal cancer may be at an early stage in the adenoma-to-carcinoma sequence and supports the suggestion that inhibition of COX-2 may be useful chemoprevention for this disease.     

Lipophosphoglycan is a virulence factor distinct from related glycoconjugates in the protozoan parasite Leishmania major

Protozoan parasites of the genus Leishmania undergo a complex life cycle involving transmission by biting sand flies and replication within mammalian macrophage phagolysosomes. A major component of the Leishmania surface coat is the glycosylphosphatidylinositol (GPI)-anchored polysaccharide called lipophosphoglycan (LPG). LPG has been proposed to play many roles in the infectious cycle, including protection against complement and oxidants, serving as the major ligand for macrophage adhesion, and as a key factor mitigating host responses by deactivation of macrophage signaling pathways. However, all structural domains of LPG are shared by other major surface or secretory products, providing a biochemical redundancy that compromises the ability of in vitro tests to establish whether LPG itself is a virulence factor. To study truly lpg(-) parasites, we generated Leishmania major lacking the gene LPG1 [encoding a putative galactofuranosyl (Gal(f)) transferase] by targeted gene disruption. The lpg1(-) parasites lacked LPG but contained normal levels of related glycoconjugates and GPI-anchored proteins. Infections of susceptible mice and macrophages in vitro showed that these lpg(-) Leishmania were highly attenuated. Significantly and in contrast to previous LPG mutants, reintroduction of LPG1 into the lpg(-) parasites restored virulence. Thus, genetic approaches allow dissection of the roles of this complex family of interrelated parasite virulence factors, and definitively establish the role of LPG itself as a parasite virulence factor. Because the lpg1(-) mutant continue to synthesize bulk GPI-anchored Gal(f)-containing glycolipids other than LPG, a second pathway distinct from the Golgi-associated LPG synthetic compartment must exist.     

An automated CT based lung nodule detection scheme using geometric analysis of signed distance field

The authors present a new computerized scheme to automatically detect lung nodules depicted on computed tomography (CT) images. The procedure is performed in the signed distance field of the CT images. To obtain an accurate signed distance field, CT images are first interpolated linearly along the axial direction to form an isotropic data set. Then a lung segmentation strategy is applied to smooth the lung border aiming to include as many juxtapleural nodules as possible while minimizing over segmentations of the lung regions. Potential nodule regions are then detected by locating local maximas of signed distances in each subvolume with values and the sizes larger than the smallest nodule of interest in the three-dimensional space. Finally, all detected candidates are scored by computing the similarity distance of their medial axis-like shapes obtained through a progressive clustering strategy combined with a marching cube algorithm from a sphere based shape. A free-response receiver operating characteristics curve is computed to assess the scheme performance. A performance test on 52 low-dose CT screening examinations that depict 184 verified lung nodules showed that during the initial stage the scheme achieved an asymptotic maximum sensitivity of 95.1% (175/184) with an average of 1200 suspicious voxels per CT examination. The nine missed nodules included two small solid nodules (with a diameter < or =3.1 mm) and seven nonsolid nodules. The final performance level after the similarity scoring stage was an absolute sensitivity level, namely, including the nine missed during the initial stage, of 81.5% (150/184) with 6.5 false-positive identifications per CT examination. This preliminary study demonstrates the feasibility of applying a simple and robust geometric model using the signed distance field to identify suspicious lung nodules. In the authors' data set the sensitivity of this scheme is not affected by nodule size. In addition to potentially being a stand alone approach, the signed distance field based method can be easily implemented as an initial filtering step in other computer-aided detection schemes.     

Central venous catheter infections in pediatric patients — in a community hospital

Summary We reviewed the records of 23 pediatric patients who had received at least one central venous catheter during a two-year period. Nine patients had acute lymphoblastic leukemia (ALL), nine had other hematologic/oncologic diagnoses, and five had cystic fibrosis. Twenty-nine of 65 febrile episodes in 16 patients were associated with a catheter-related infection. Twenty of 40 catheters were associated with an infection over a period of 7,229 catheter days. For every 1,000 catheter days, four episodes of infections were observed. The number of infections/1,000 catheter days, the average life of a catheter ( 180 days), and mean number of days elapsing before the first infection were not significantly different in the three diagnostic groups. Broviac catheters were used most often (24/40), followed by Quinton (9/40) and Port-a-Cath (7/40). Broviac catheters lasted twice as long (224 days, p<0.01) as Quinton and Porta-a-Cath. Grampositive cocci were isolated most frequently andStaphylococcus epidermidis was the most common pathogen. No consistent relationship between an absolute neutrophil count of <1,000/mm³ and infection with gram-positive cocci was seen. However, seven of eight episodes of gram-negative bacillary infections occurred in patients with an absolute neutrophil count of <1,000/m³ (p<0.005). Those patients who were not considered terminally ill responded well to antimicrobials. Catheter removal was necessary in only two instances.

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Zentralvenenkatheter-Infektionen bei pädiatrischen Patienten in einem städtischen Krankenhaus

Zusammenfassung Bei 23 pädiatrischen Patienten (neun Kindern mit akuter lymphoblastischer Leukämie, neun mit anderen malignen hämatologischen Erkrankungen oder Tumoren und fünf Kindern mit zystischer Fibrose) war im Zeitraum von zwei Jahren mindestens ein Zentralvenenkatheter gelegt worden. Die Krankengeschichten dieser Kinder wurden retrospektiv ausgewertet. Bei 16 Patienten traten insgesamt 65 Fieberepisoden auf, in 29 Fällen bestand eine Katheter-assoziierte Infektion. 20 von 40 Kathetern mit einer Gesamtverweildauer von 7229 Kathetertagen waren infiziert. Im Mittel kamen 4,0 Infektionen auf 1000 Kathetertage. In den drei Diagnosegruppen waren keine Unterschiede bezüglich der Anzahl der Infektionen/1000 Kathetertage, der durchschnittlichen Katheterverweildauer (etwa 180 Tage) oder der mittleren Anzahl von Tagen bis zum Auftreten der ersten Infektion festzustellen. Am häufigsten wurden Broviac-Katheter verwendet (24/40), es folgten Quinton-Katheter (9/40) und Port-a-Cath (7/40). Die Liegedauer der Broviac-Katheter war doppelt so lang (224 Tage) wie die der Quinton- oder Port-a-Cath-Modelle (p<0,01). Am häufigsten wurden grampositive Kokken aus den infizierten Kathetern isoliert, der häufigste Erreger warStaphylococcus aureus. Absolute Granulozytenzahlen unter 1000/mm³ standen nicht in Korrelation zur Infektionshäufigkeit mit grampositiven Kokken; jedoch waren sieben der acht Infektionen mit gramnegativen Stäbchen bei Patienten mit einer absoluten Granulozytenzahl von weniger als 1000/mm³ (p<0,005) aufgetreten. Patienten, die nicht im terminalen Krankheitsstadium waren, sprachen auf Antibiotika gut an. Nur in zwei Fällen mußte der Katheter entfernt werden.

     

Multiview-based computer-aided detection scheme for breast masses

In this study, we developed and tested a new multiview-based computer-aided detection (CAD) scheme that aims to maintain the same case-based sensitivity level as a single-image-based scheme while substantially increasing the number of masses being detected on both ipsilateral views. An image database of 450 four-view examinations (1800 images) was assembled. In this database, 250 cases depicted malignant masses, of which 236 masses were visible on both views and 14 masses were visible only on one view. First, we detected suspected mass regions depicted on each image in the database using a single-image-based CAD. For each identified region (with detection score > or = 0.55), we then identified a matching strip of interest on the ipsilateral view based on the projected distance to the nipple along the centerline. By lowering CAD operating threshold inside the matching strip, we searched for a region located inside the strip and paired it with the original region. A multifeature-based artificial neural network scored the likelihood of the paired "matched" regions representing true-positive masses. All single (unmatched) regions except for those either with very high detection scores (> or = 0.85) or those located near the chest wall that cannot be matched on the other view were discarded. The original single-image-based CAD scheme detected 186 masses (74.4% case-based sensitivity) and 593 false-positive regions. Of the 186 identified masses, 91 were detected on two views (48.9%) and 95 were detected only on one view (51.1%). Of the false-positive detections, 54 were paired on the ipsilateral view inside the corresponding matching strips and the remaining 485 were not, which represented 539 case-based false-positive detections (0.3 per image). Applying the multiview-based CAD scheme, the same case-based sensitivity was maintained while cueing 169 of 186 masses (90.9%) on both views and at the same time reducing the case-based false-positive detection rate by 23.7% (from 539 to 411). The study demonstrated that the new multiview-based CAD scheme could substantially increase the number of masses being cued on two ipsilateral views while reducing the case-based false-positive detection rate.