Regulation of production of type 1 pili among urinary tract isolates of Escherichia coli.

The piliation and hemagglutination properties of 54 consecutive Escherichia coli isolates from women with recurrent urinary tract infections were studied. Mannose-sensitive hemagglutination (MSHA) of guinea pig erythrocytes, characteristic of type 1-piliated bacteria, was produced by 75% of the isolates, 32% produced mannose-insensitive hemagglutination, and 14% produced no hemagglutination reaction. The production of type 1 pili was examined in those strains that produced MSHA only. Studies with antiserum prepared against purified pili suggested that at least three subtypes of type 1 hemagglutinins were represented among the isolates. All of the type 1-piliated isolates produced MSHA after serial subculture in static broth. After growth on agar, selected type 1-piliated isolates were subdivided into two groups. Many strains apparently suppressed piliation during growth on agar (regulated variants); all colonies became MSHA negative and were composed of nonpiliated cells as shown by electron microscopy. The loss of the MSHA phenotype often occurred after a single overnight passage on agar, and any remaining hemagglutinin was gradually lost with one to three additional passages. Seven strains, however, retained a significant hemagglutination titer after multiple subcultures on agar, and they produced colonies consisting of a mixed population of piliated and nonpiliated cells. These strains were apparently able to oscillate between states of pilus expression and nonexpression during growth on agar (random phase variants). When nonpiliated cells isolated from the mixed, random variant population were plated on agar, they gave rise to hemagglutination-positive colonies that consisted of both piliated and nonpiliated cells. The distinction between random variants and regulated variants was also observed in shaking broth cultures inoculated with nonpiliated cells. The random variants produced MSHA-positive cultures composed of piliated and nonpiliated cells, whereas the regulated strains remained nonpiliated. The results indicate that type 1 pili are a predominant adhesin of uropathogenic E. coli and that during growth on agar only about one-fourth of the type 1-piliated isolates regulate pilus expression by random phase variation.     

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.     

Prostaglandins and angioplasty. An experimental study in canine arteries

To prevent platelet aggregation following percutaneous transluminal angioplasty (PTA), cyclooxygenase inhibitors such as acetylsalicylic acid (ASA) and indomethacin are recommended. However, ASA blocks both the proaggregating effects of thromboxane (TXA2) and the antiaggregating and vasodilating effects of prostacyclin (PGI2). The authors measured the contractile response of dilated canine carotid arteries in situ and in vitro using an isometric force transducer. Following PTA, contraction of the arterial wall was significantly reduced (p less than 0.01). By blocking cyclooxygenase with indomethacin (3 micrograms/ml), contraction was greatly improved (p less than 0.001). These results suggest that PTA may result in marked release of prostacyclin by the damaged arterial wall, which could account for the decreased responsiveness of the artery to exogenous norepinephrine.     

Percutaneous extraction of urinary calculi: use of the intercostal approach

The authors achieved successful percutaneous extraction of urinary calculi via an intercostal approach in 24 patients. In one patient, a large hydrothorax developed and thoracentesis was required; 2 patients had moderate and 6 minimal pleural fluid collections which did not require treatment. No patient had pneumothorax. Intercostal puncture provides direct access to the upper and middle poles of the kidney when they lie above the twelfth rib and subcostal angulation is not feasible. Such an approach is advantageous for stones in the ureter, as well as renal stones which are inaccessible from the lower pole. Fluoroscopy should be performed when planning the puncture in order to avoid the lung, and a working sheath is recommended.     

Fibrosing alveolitis: CT-pathologic correlation

Computed tomography (CT) was performed within 10 days of open lung biopsy in nine patients with fibrosing alveolitis. One-centimeter collimation contiguous scans through the chest were obtained in all patients. Additional 1.5-mm collimation scans were obtained in the area in which lung biopsy was later performed in six patients. In seven patients, CT demonstrated patchy involvement of the lung parenchyma, areas with a reticular pattern being intermingled with areas of normal lung. The reticular pattern was associated with cystic spaces 2-4 mm in diameter and was more severe in the lung periphery. Histologically, the reticular pattern corresponded to areas of irregular fibrosis. One patient had diffuse honeycombing (2-20-mm cysts), and one had honeycombing only in the lung periphery. In all patients, CT clearly defined the architectural changes seen on open lung biopsy. These changes were much better seen on the 1.5-mm than on the 10-mm collimation scans. CT may be helpful in determining the pattern and distribution of lung involvement in patients with fibrosing alveolitis and in guiding the surgeon to the most appropriate area(s) for biopsy.     

The vasa vasorum and angioplasty

Interruption of flow in the vasa vasorum may lead to medial necrosis and aneurysm formation. The purpose of this study was to determine whether angioplasty produces significant alterations in the morphology or blood flow of the vasa vasorum of the dilated artery. The morphology of the canine vasa vasorum was studied before and after angioplasty; in a separate experiment vessel wall blood flow (VWBF) in canine carotid arteries was measured after angioplasty to determine whether physiologic regulation of the blood flow was disrupted by arterial dilation. No morphologic changes could be demonstrated in the vasa vasorum of the dilated artery; however, VWBF was increased by 1194 +/- 215% (mean +/- standard error, p less than 0.01) between 90 and 120 minutes after angioplasty. VWBF in the adjacent nondilated arterial segment was also increased (720 +/- 177% between 10-30 minutes, p less than 0.01) but returned toward normal after 60 minutes. Adenosine caused a "paradoxical" decrease in VWBF (p less than 0.05) of the dilated arterial segment while causing increased VWBF (p less than 0.05) in the thoracic aorta. Angioplasty appears to produce persistent hyperemia in the dilated arterial wall. A paradoxical response to adenosine suggests that vasa vasorum in the dilated arterial segment are maximally vasodilated. This may be due to mechanical disruption of vasomotor tone or to release of vasoactive substances.