UMIN Clinical Trials Registry UMIN000006832 (December 4, 2011).

To cite this article: Kageyama K, Nakajima Y, Shibasaki M, Hashimoto S, Mizobe T. Increased platelet, leukocyte, and endothelial cell activity are associated with increased coagulability in patients after total knee arthroplasty. J Thromb Haemost 2007; 5: 738-45.Summary. Background: Orthopedic surgery, especially total knee and total hip arthroplasty, is considered a risk factor for peri-operative venous thromboembolism. Objectives: This study evaluates how accelerated inflammatogenic cellular interactions and the subsequent production of tissue factor and CD40 ligand play an important role in the pathogenesis of venous thromboembolism. Patients and methods: Twenty-four patients undergoing total knee arthroplasty were randomly assigned to groups with (Ti; n = 12) and without (Tn; n = 12) pneumatic tourniquet inflation. Results: Numbers of leukocyte-platelet aggregates, especially those comprising monocytes-platelets in central venous blood from the Ti group, were increased during the peri-operative period (P < 0.01), and returned to the baseline level at 24 h after starting surgery. Levels of PAC-1, P-selectin, CD40 ligand, tissue factor, Mac-1 expression on monocytes including monocyte-platelet aggregates, and the number of microparticles including those of endothelial cell origin were noticeably increased in central venous blood from the Ti group (P < 0.01). Whole blood coagulability was also obviously increased in central venous blood from the Ti group (P < 0.01). Furthermore, the concentrations of venous plasma tissue factor antigen, CD40 ligand, platelet factor 4, b-thromboglobulin, the soluble fibrin monomer complex and prothrombin fragment 1+2 were also increased (P < 0.05). Conclusions: This study showed that platelet, leukocyte and endothelium activities as well as their interactions are enhanced during the peri-operative period of total knee arthroplasty, particularly in venous blood from the lower half of the body, which consequently augments blood coagulability. Further, tourniquet inflation during surgery exaggerates these responses.

Ultrasound-guided radial artery catheterization in pediatric patients was fastest and most reliable when the artery was 2 to 4 mm below the skin surface. For arteries located <2 mm below the skin surface, increasing the depth to 2 to 4 mm by subcutaneous saline injection reduced catheterization time and improved the success rate.

G protein-coupled receptors (GPCRs) have seven hydrophobic domains, which are thought to span the lipid bilayer as ␣ helical transmembrane domains (TMDs). The tertiary structure of GPCRs has not been determined; however, molecular models of GPCRs have generally been based on bacteriorhodopsin, which is functionally unrelated to GPCRs but has a similar secondary structure. We sought to examine the validity of using bacteriorhodopsin as a scaffold for GPCR model building by experimentally determining the orientation of the TMDs of adrenergic receptors in the plasma membrane. In separate experiments, three sequential amino acid residues (Leu-310, Leu-311, Asn-312) in TMD VII of the ␤ 2 adrenoreceptor were mutated to the amino acids found in the homologous domain of the ␣ 2 adrenoreceptor (Phe, Phe, Phe). Exchange of Asn-312 and Leu-311 in the ␤ 2 adrenoreceptor resulted in nonfunctional proteins, most likely due to incompatibility of the introduced bulky phenylalanine side chain with adjacent structural domains in the ␤ 2 adrenoreceptor. This structural incompatibility was "repaired" by replacing the specific ␤ 2 TMD sequence with an ␣ 2 receptor sequence. TMD I and TMD II complemented the Asn-312 3 Phe mutation, and TMD III and TMD VI complemented the Leu-311 3 Phe mutation. These results indicate that TMDs I, II, III, and VI surround TMD VII in a counterclockwise orientation analogous to the orientation of TMDs in bacteriorhodopsin.Adrenergic receptors are one of the best characterized class of the family of G protein-coupled receptors for hormones and neurotransmitters. G protein-coupled receptors exhibit a common secondary structure consisting of seven hydrophobic segments that are thought to represent ␣ helical membrane-spanning domains. In this paper the hydrophobic segments will be referred to as transmembrane domains (TMD).1 A high resolution three-dimensional structure of adrenergic and other G protein-coupled receptors is lacking because of the difficulties inherent in producing, purifying, and crystallizing integral membrane proteins. Without these data, investigators have used the structural information from an analogous protein, bacteriorhodopsin, as a template from which to generate molecular models of adrenoreceptors (1). The rationale for using bacteriorhodopsin, a prokaryotic proton pump, as a "structural scaffold" for human adrenoreceptors is based on the seventransmembrane ␣ helices in bacteriorhodopsin, which are thought to correspond topographically to the seven hydrophobic domains present in G protein-coupled receptors. But is bacteriorhodopsin structurally similar enough to employ as a model for G protein-coupled receptors? While bacteriorhodopsin does share with rhodopsin (a G protein-coupled receptor) the photoisomerization of the retinal chromophore, it has less than 10% sequence homology with G protein-coupled receptors and is not coupled to G proteins. When bacteriorhodopsin and rhodopsin are compared at a low resolution (9 Å) the projection footprints of the helical arrangements are dif...

Abstract␣ 2 adrenergic agonists are used in the anesthetic management of the surgical patient for their sedative/hypnotic properties although the ␣ 2 adrenoceptor subtype responsible for these anesthetic effects is not known. Using a gene-targeting strategy, it is possible to specifically reduce the expression of the individual adrenoceptors expressed in the central nervous system and to thereby determine their role in hypnotic action.Stably transfected cell lines (PC 124D for rat ␣ 2A ; NIH3T3 for rat ␣ 2C adrenoceptors) were exposed to 5 M antisense oligodeoxynucleotides (ODNs) for ␣ 2A and ␣ 2C adrenergic receptor subtypes for 3 d. Individual receptor subtype expression, as determined by radiolabeled ligand binding, was selectively decreased only by the appropriate antisense ODNs and not by the "scrambled" ODNs. These antisense ODNs were then administered three times, on alternate days, into the locus coeruleus of chronically cannulated rats and their hypnotic response to dexmedetomidine (an ␣ 2 agonist) was determined.Only the ␣ 2A antisense ODNs significantly change the hypnotic response causing both an increase in latency to, and a decrease in duration of, the loss of righting reflex following dexmedetomidine; hypnotic response had normalized 8 d after stopping the ODNs. Therefore, the ␣ 2A adrenoceptor subtype is responsible for the hypnotic response to dexmedetomidine in the locus coeruleus of the rat. ( J. Clin. Invest. 1996. 98:1076-1080.)