No abstract

Polymorphonuclear leukocytes (PMN) labeled in vivo with 5'-bromo-2'-deoxyuridine (BrdU) in donor animals were transferred to recipients to determine the rate of clearance of labeled PMN from the circulation, their margination within the vascular space, and migration into Streptococcus pneumoniae-induced inflammatory sites. The donor animals received intravenous infusions at 25 mg/kg/day of BrdU for 7 days when cytospins of leukocyte-rich plasma (LRP) showed that 80 +/- 2.3% PMN were labeled. The BrdU labeled cells were then transfused to serum-compatible recipients as either whole blood, leukocyte-rich plasma, or PMN purified from an equal volume of whole blood. Twenty-four hours after transfer, the distribution of BrdU-labeled PMN in the lung, liver, spleen, bone marrow, and gut was determined morphometrically and by Southern blot analysis of DNA extracted from these organs. BrdU-labeled PMN transfused as either LRP or purified PMN provided no advantage over transfusing whole blood. The half-life of BrdU-labeled PMN in the recipient circulation after transfusing whole blood was 270.4 min (95% confidence intervals, 248.5 to 296.4 min). The majority of the BrdU-labeled DNA was found in the spleen, where DNA analysis showed that the white blood cells underwent programmed cell death by apoptosis. Four hours after infection with S. pneumoniae and 1 h after transfusion of labeled whole blood, BrdU-labeled PMN had migrated into the infected sites. We conclude that transfer of BrdU PMN in whole blood provides a simple, effective method of tracing labeled PMN in vivo.

We recently reported that L-selectin expression increases on circulating polymorphonuclear leukocytes (PMN) during active bone marrow release, which suggests that older cells in the circulation have lower levels of L-selectin than those recently released from the bone marrow. The present study was designed to test the hypothesis that L-selectin expression reduces on PMN as they age in the circulation. In vitro studies using flow cytometry showed that PMN L-selectin decreased to 14.6 +/- 2.3% of baseline during a 24-h incubation at 37 degrees C. To test this hypothesis in vivo, rabbit PMN, labeled in vivo with 5'-bromo-2-deoxyuridine (PMN-brdU) in donor animals, were infused into recipient rabbits as whole blood (n = 5) and followed over 24 h in the circulation with a double immunolabeling technique. These results showed that the fraction of the L-selectin-negative PMN-BrdU in the circulation increased with time (P < 0.001), and nearly all of the PMNBrdU in the circulation were L-selectin negative after 24 h. Removal of L-selectin from the surface of PMN-BrdU with chymotrypsin before infusion did not change their rate of removal from the circulation (half-life or t 1/2 262 vs. 296 min, P = NS). We conclude that there is a continuous loss of L-selectin from PMN during their life span in the circulation, which supports the hypothesis that L-selectin expression decreases on PMN as they age.

3D US of the shoulder is as accurate as 2D US when compared with MRI for the diagnosis of full- and partial-thickness supraspinatus rotator cuff tears, and 3D US examination significantly reduced the time between the initial scan and the radiologist interpretation, ultimately improving workplace efficiency.