Novel phospholipase A activity secreted by Legionella species

Bacterial phospholipases are regarded as a major virulence factor in infection. In bacteria associated with pneumonia, destruction of lung surfactant and host cell membranes by bacterial phospholipases secreted during infection is thought to contribute to the disease. Phospholipase C (PLC) activity has been described in several Legionella species (W. B. Baine, J. Gen. Microbiol. 134:489-498, 1988; W. B. Baine, J. Gen. Microbiol. 131:1383-1391, 1985). By using detection methods such as thin-layer chromatography and mass spectrometry, PLC activity could not be detected in several strains of Legionella pneumophila. Instead, phospholipid degradation was identified to be caused by a novel PLA activity. We could demonstrate that PLA secretion starts at the mid-exponential-growth phase when bacteria were grown in liquid culture. Several Legionella species secreted different amounts of PLA. Legionella PLA may act as a powerful agent in the mediation of pathogenicity due to destruction of lung surfactant and epithelial cells.     

Cyclin D1 governs adhesion and motility of macrophages

The cyclin D1 gene encodes the regulatory subunit of a holoenzyme that phosphorylates and inactivates the retinoblastoma protein, thereby promoting cell-cycle progression. Cyclin D1 is overexpressed in hematopoetic and epithelial malignancies correlating with poor prognosis and metastasis in several cancer types. Because tumor-associated macrophages have been shown to enhance malignant progression and metastasis, and cyclin D1-deficient mice are resistant to oncogene-induced malignancies, we investigated the function of cyclin D1-/- bone marrow-derived macrophages. Cyclin D1 deficiency increased focal complex formation at the site of substratum contact, and enhanced macrophage adhesion, yielding a flattened, circular morphology with reduced membrane ruffles. Migration in response to wounding, cytokine-mediated chemotaxis, and transendothelial cell migration of cyclin D1-/- bone marrow-derived macrophages were all substantially reduced. Thus, apart from proliferative and possible motility defects in the tumor cells themselves, the reduced motility and invasiveness of cyclin D1-/- tumor-associated macrophages may contribute to the tumor resistance of these mice.     

Intracellular multiplication of Legionella pneumophila depends on host cell amino acid transporter SLC1A5

The infectious agent of Legionnaires' disease, Legionella (L) pneumophila, multiplies intracellularly in eukaryotic cells. This study has been performed to explore the nutrient requirements of L. pneumophila during intracellular replication. In human monocytes, bacterial replication rate was reduced by 76% in defined medium lacking L-cysteine, L-glutamine or L-serine. SLC1A5 (hATB(0,+)), a neutral amino acid transporter, was upregulated in the host cells after infection with L. pneumophila. Inhibition of SLC1A5 by BCH, a competitive inhibitor of amino acid uptake as well as siRNA silencing of the slc1a5 gene blocked intracellular multiplication of L. pneumophila without compromising viability of host cells. These observations suggest that replication of L. pneumophila depends on the function of host cell SLC1A5.     

Safe treatment of trigger finger with longitudinal and transverse landmarks: an anatomic study of the border fingers for percutaneous release

Transverse landmarks have recently been determined to predict the proximal and distal edges of the A1 pulley for trigger finger release. Percutaneous A1 pulley release has been discouraged for the border digits because of the risk of injury to the neurovascular structures of the index and small fingers. The purpose of the study was to identify longitudinal surface landmarks to prevent injury to the neurovascular bundles during percutaneous A1 pulley release of the ulnar and radial border digits. Longitudinal surface landmarks were identified and marked on 29 cadaver hands. Proximal and distal landmarks for the longitudinal vector through which the A1 pulley of the small finger was released include the midline of the proximal digital crease and the scaphoid tubercle. Proximal and distal landmarks for the longitudinal line through which the index finger A1 pulley was released include the midline of proximal digital crease and radial edge of the pisiform. Longitudinal incisions were performed between these landmarks, straight through the skin and deep enough to score the A1 pulley. The distance of the medial edge of the neurovascular structures from the longitudinal incision in the A1 pulley was measured for each small finger and index finger. Using these longitudinal landmarks for the index and small fingers, none of the neurovascular structures was injured while performing these longitudinal incisions through the skin, scoring the A1 pulley. In fact, the average distance for the neurovascular structures from the longitudinal vector of the small finger was 5.4 +/- 1.4 mm radially and 6.7 +/- 1.9 mm ulnarly. The average distance for the neurovascular structures from the longitudinal line of the index finger was 8.5 +/- 1.8 mm radially and 6.2 +/- 1.7 mm ulnarly. Based on the findings of this anatomical study, these longitudinal landmarks can be used to avoid injury to neurovascular structures in the management of trigger finger involving the border digits with steroid-injection, open, or percutaneous A1 pulley release.     

Surface landmarks to locate the thenar branch of the median nerve: an anatomical study

The thenar branch of the median nerve can be injured during carpal tunnel release. The purpose of this study was to identify surface landmarks to consistently predict the location of the thenar branch of the median nerve. Surface landmarks were marked and incised in 28 cadaveric hands. The incisions were made along the longitudinal line of the third web space and the horizontal cardinal line from the hamate hook to the ulnar border of the thumb. The origin of the thenar branch was determined in relation to these longitudinal and horizontal vectors. The origin of the thenar nerve branch was consistently observed in the radial proximal quadrant formed by the aforementioned longitudinal and horizontal vectors. The thenar branch origin was observed to be an average of 8.6 +/- 1.9 mm radial to the longitudinal axis along the third web space. The origin of the thenar branch was observed to be an average of 6.3 +/- 2.0 mm proximal to the horizontal axis between the hamate hook and the ulnar border of the thumb. The thenar branch was observed precisely at the intersection of the longitudinal vector from the second web space to the scaphoid tubercle and the horizontal vector from the hamate hook to the radial edge of the proximal metacarpophalangeal crease in all 28 cadaveric hands. On the basis of these 28 cadaveric dissections, the location of the thenar branch of the median nerve can be predicted by the intersection of the longitudinal vector from the second web space to the scaphoid tubercle and the horizontal vector from the hamate hook to the radial aspect of the metacarpophalangeal crease.     

Structure and function of the Nautilus statocyst.

The two equilibrium receptor organs (statocysts) of Nautilus are avoid sacks, half-filled with numerous small, free-moving statoconia and half with endolymph. The inner surface of each statocyst is lined with 130,000-150,000 primary sensory hair cells. The hair cells are of two morphological types. Type A hair cells carry 10-15 kinocilia arranged in a single ciliary row; they are present in the ventral half of the statocyst. Type B hair cells carry 8-10 irregularly arranged kinocilia; they are present in the dorsal half of the statocyst. Both type of hair cells are morphologically polarized. To test whether these features allow the Nautilus statocyst to sense angular accelerations, behavioural experiments were performed to measure statocyst-dependent funnel movements during sinusoidal oscillations of restrained Nautilus around a vertical body axis. Such dynamic rotatory stimulation caused horizontal phase-locked movements of the funnel. The funnel movements were either in the same direction (compensatory funnel response), or in the opposite direction (funnel follow response) to that of the applied rotation. Compensatory funnel movements were also seen during optokinetic stimulation (with a black and white stripe pattern) and during stimulations in which optokinetic and statocyst stimulations were combined. These morphological and behavioural findings show that the statocysts of Nautilus, in addition to their function as gravity receptor organs, are able to detect rotatory movements (angular accelerations) without the specialized receptor systems (crista/cupula systems) that are found in the statocysts of coleoid cephalopods. The findings further indicate that both statocyst and visual inputs control compensatory funnel movements.     

Critical evaluation of p-nitrophenylphosphorylcholine (p-NPPC) as artificial substrate for the detection of phospholipase C*

Phospholipase C (PLC) activity secreted by bacteria as a virulence factor is commonly detected by use of the artificial substrate p-nitrophenylphosphorylcholine (p-NPPC). We examined several commercially available enzymes (phosphodiesterases, phosphomonoesterases, phospholipase A, lipase, protease) for their hydrolytic activity towards p-NPPC and compared these results with those of PLC tests using phospholipid substrates. Our data indicate that, in addition to PLC, several other enzymes which can affect phosphate esters are able to hydrolyze p-NPPC. We therefore suggest to use lipid substrates for correct characterization of bacterial PLCs, especially when whole bacteria or crude enzyme preparations are investigated.