No abstract

Abstract-Observational

L-selectin is a cell adhesion molecule that tethers free-flowing leukocytes from the blood to luminal vessel walls, facilitating the initial stages of their emigration from the circulation toward an extravascular inflammatory insult. Following shear-resistant adhesion to the vessel wall, L-selectin has frequently been reported to be rapidly cleaved from the plasma membrane (known as ectodomain shedding), with little knowledge of the timing or functional consequence of this event. Using advanced imaging techniques, we observe L-selectin shedding occurring exclusively as primary human monocytes actively engage in transendothelial migration (TEM). Moreover, the shedding was localized to transmigrating pseudopods within the subendothelial space. By capturing monocytes in midtransmigration, we could monitor the subcellular distribution of L-selectin and better understand how ectodomain shedding might contribute to TEM. Mechanistically, L-selectin loses association with calmodulin (CaM; a negative regulator of shedding) specifically within transmigrating pseudopods. In contrast, L-selectin/ CaM interaction remained intact in nontransmigrated regions of monocytes. We show phosphorylation of L-selectin at Ser 364 is critical for CaM dissociation, which is also restricted to the transmigrating pseudopod. Pharmacological or genetic inhibition of L-selectin shedding significantly increased pseudopodial extensions in transmigrating monocytes, which potentiated invasive behavior during TEM and prevented the establishment of front/back polarity for directional migration persistence once TEM was complete. We conclude that L-selectin shedding directly regulates polarity in transmigrated monocytes, which affirms an active role for this molecule in driving later stages of the multistep adhesion cascade.

A third of patients with critical limb ischemia (CLI) will eventually require limb amputation. Therapeutic neovascularization using unselected mononuclear cells to salvage ischemic limbs has produced modest results. The TIE2-expressing monocytes/macrophages (TEMs) are a myeloid cell subset known to be highly angiogenic in tumours. This study aimed to examine the kinetics of TEMs in patients with CLI and whether these cells promote neovascularization of the ischemic limb. Here we show that there are 10-fold more circulating TEMs in CLI patients, and removal of ischemia reduces their numbers to normal levels. TEM numbers in ischemic muscle are two-fold greater than normoxic muscle from the same patient. TEMs from patients with CLI display greater proangiogenic activity than TIE2-negative monocytes in vitro. Using a mouse model of hindlimb ischemia, lentiviral-based Tie2 knockdown in TEMs impaired recovery from ischemia, whereas delivery of mouse macrophages overexpressing TIE2, or human TEMs isolated from CLI patients, rescued limb ischemia. These data suggest that enhancing TEM recruitment to the ischemic muscle may have the potential to improve limb neovascularization in CLI patients.

The source of the T1 signal in the thrombus results from the oxidation of iron (released from the lysis of trapped erythrocytes in the thrombus) to its paramagnetic Fe3+ form. Quantification of T1 relaxation time appears to be a good predictor of the success of thrombolysis.

Abdominal endograft explantation is high risk but may be curative. Appropriate selection of patients for infected endograft explantation remains a major challenge.

The identification of novel genes or groups of genes expressed in prostate cancer may allow earlier diagnosis or more accurate staging of the disease. We describe the assembly and use of a 1877-member microarray representing cDNA clones from a range of prostate cancer stages and grades, precursor lesions and normal tissue. Using labelled cDNA from tumour samples obtained from TURP or radical prostatectomy, analysis of expression patterns identified many up-regulated transcripts. Cell lines were found to over-express fewer genes than diseased tissue samples. 17 known genes were found to over-express more than 4-fold in 4 or more cancers out of 15 cancers. Only 2 genes were over-expressed in 6 out of 15 cancers or more, whilst no genes were consistently found to be over-expressed in all cancer samples. Novel prostate cancer associations for several well characterized genes or full length cDNAs were identified, including PLRP1, JM27, human UbcM2, dynein light intermediate chain 2 and human homologue of rat sec61 . Novel associations with high-grade PIN include: breast carcinoma fatty acid synthase and cDNA DKFZp434B0335 . We shortlist and discuss the most significant over-expressed genes in prostate cancer and PIN, and highlight expression differences between malignant and benign samples. © 2001 Cancer Research Campaign http://www.bjcancer.com

No abstract