Kalirin promotes neointimal hyperplasia by activating Rac in smooth muscle cells.

OBJECTIVE: Kalirin is a multifunctional protein that contains 2 guanine nucleotide exchange factor domains for the GTPases Rac1 and RhoA. Variants of KALRN have been associated with atherosclerosis in humans, but Kalirin's activity has been characterized almost exclusively in the central nervous system. We therefore tested the hypothesis that Kalirin functions as a Rho-guanine nucleotide exchange factor in arterial smooth muscle cells (SMCs). APPROACH AND RESULTS: Kalirin-9 protein is expressed abundantly in aorta and bone marrow, as well as in cultured SMCs, endothelial cells, and macrophages. Moreover, arterial Kalirin was upregulated during early atherogenesis in apolipoprotein E-deficient mice. In cultured SMCs, signaling was affected similarly in 3 models of Kalirin loss-of-function: heterozygous Kalrn deletion, Kalirin RNAi, and treatment with the Kalirin Rho-guanine nucleotide exchange factor -1 inhibitor 1-(3-nitrophenyl)-1H-pyrrole-2,5-dione. With reduced Kalirin function, SMCs showed normal RhoA activation but diminished Rac1 activation, assessed as reduced Rac-GTP levels, p21-activated kinase autophosphorylation, and SMC migration. Kalrn(-/+) SMCs proliferated 30% less rapidly than wild-type SMCs. Neointimal hyperplasia engendered by carotid endothelial denudation was ≈60% less in Kalrn(-/+) and SMC-specific Kalrn(-/+) mice than in control mice. CONCLUSIONS: Kalirin functions as a guanine nucleotide exchange factor for Rac1 in SMCs, and promotes SMC migration and proliferation both in vitro and in vivo.

G protein-coupled receptor kinase-5 attenuates atherosclerosis by regulating receptor tyrosine kinases and 7-transmembrane receptors.

OBJECTIVE: G protein-coupled receptor kinase-5 (GRK5) is a widely expressed Ser/Thr kinase that regulates several atherogenic receptors and may activate or inhibit nuclear factor-κB (NF-κB). This study sought to determine whether and by what mechanisms GRK5 affects atherosclerosis. METHODS AND RESULTS: Grk5(-/-)/Apoe(-/-) mice developed 50% greater aortic atherosclerosis than Apoe(-/-) mice and demonstrated greater proliferation of macrophages and smooth muscle cells (SMCs) in atherosclerotic lesions. In Apoe(-/-) mice, carotid interposition grafts from Grk5(-/-) mice demonstrated greater upregulation of cell adhesion molecules than grafts from wild-type mice and, subsequently, more atherosclerosis. By comparing Grk5(-/-) with wild-type cells, we found that GRK5 desensitized 2 key atherogenic receptor tyrosine kinases: the platelet-derived growth factor receptor-ß in SMCs, by augmenting ubiquitination/degradation; and the colony-stimulating factor-1 receptor (CSF-1R) in macrophages, by reducing CSF-1-induced tyrosyl phosphorylation. GRK5 activity in monocytes also reduced migration promoted by the 7-transmembrane receptor for monocyte chemoattractant protein-1 CC chemokine receptor-2. Whereas GRK5 diminished NF-κB-dependent gene expression in SMCs and endothelial cells, it had no effect on NF-κB activity in macrophages. CONCLUSIONS: GRK5 attenuates atherosclerosis through multiple cell type-specific mechanisms, including reduction of SMC and endothelial cell NF-κB activity and desensitization of receptor-specific signaling through the monocyte CC chemokine receptor-2, macrophage CSF-1R, and the SMC platelet-derived growth factor receptor-ß.

Nuclear structure and chromosome segregation in Drosophila male meiosis depend on the ubiquitin ligase dTopors.

In many organisms, homolog pairing and synapsis at meiotic prophase depend on interactions between chromosomes and the nuclear membrane. Male Drosophila lack synapsis, but nonetheless, their chromosomes closely associate with the nuclear periphery at prophase I. To explore the functional significance of this association, we characterize mutations in nuclear blebber (nbl), a gene required for both spermatocyte nuclear shape and meiotic chromosome transmission. We demonstrate that nbl corresponds to dtopors, the Drosophila homolog of the mammalian dual ubiquitin/small ubiquitin-related modifier (SUMO) ligase Topors. We show that mutations in dtopors cause abnormalities in lamin localizations, centriole separation, and prophase I chromatin condensation and also cause anaphase I bridges that likely result from unresolved homolog connections. Bridge formation does not require mod(mdg4) in meiosis, suggesting that bridges do not result from misregulation of the male homolog conjunction complex. At the ultrastructural level, we observe disruption of nuclear shape, an uneven perinuclear space, and excess membranous structures. We show that dTopors localizes to the nuclear lamina at prophase, and also transiently to intranuclear foci. As a role of dtopors at gypsy insulator has been reported, we also asked whether these new alleles affected expression of the gypsy-induced mutation ct(6) and found that it was unaltered in dtopors homozygotes. Our results indicate that dTopors is required for germline nuclear structure and meiotic chromosome segregation, but in contrast, is not necessary for gypsy insulator function. We suggest that dtopors plays a structural role in spermatocyte lamina that is critical for multiple aspects of meiotic chromosome transmission.

Blood conservation techniques in spinal deformity surgery: a retrospective review of patients refusing blood transfusion.

STUDY DESIGN: A retrospective review. OBJECTIVE: To review the effectiveness of blood conservation techniques in the spinal fusion of patients that refuse blood transfusion; specifically the Jehovah's witnesses population. SUMMARY OF BACKGROUND: Spinal surgery can be challenging in patients refusing blood transfusion. There is paucity in the literature examining blood conservation techniques in spinal surgery. METHODS: The radiographic and medical records of 19 Jehovah's witnesses patients who underwent spinal deformity surgery at a single institution between 2000 and 2003 were reviewed. Patients were assessed for excessive blood loss (EBL), deformity correction, operative time, perioperative complications, and hospital stay. At latest follow-up (mean, 40 months; range, 8-76) the patients were examined for radiographic fusion, progression and complications. RESULTS: Spinal fusion was attempted in 19 patients, with a mean age of 17 years (range, 10-36 years). All 19 patients were identified through the "Bloodless Surgery Program." Hypotensive anesthesia, hemodilution, and cell saver was employed for all 19 cases. Erythropoietin with supplemental iron was used in 15 patients. Aprotinin was used in 3 patients. EBL and blood returned by cell saver averaged 855 and 341 mL, respectively. Operative times average 315 minutes. The average drop in hemoglobin from after surgery was 3.1 g/dL. There were 2 intraoperative complications: (i) transient loss of somatosensory evoked potential/motor evoked potential signals; and (ii) one surgery abandoned due to EBL. The average spinal deformity correction was 58%. There were 3 postoperative complications, none related to their refusal of a transfusion. 17 patients were available for radiographic and clinic follow-up of at least 24 months. All displayed radiographic fusion without progression. CONCLUSION: These blood conservation techniques allow satisfactory completion of deformity surgery on those patients not willing to be transfused and without major anesthetic or medical complications.

Biomechanical analysis of tibial strength after harvesting unicortical tibial grafts of two different lengths.

BACKGROUND: It is not known whether the use of the proximal tibia as a source of strut graft compromises the strength of the tibia. Our hypothesis was that unicortical proximal tibial grafts in two different sizes would not significantly decrease the torsional strength of the tibia. MATERIALS AND METHODS: Ten matched pairs of human cadaver tibiae were stripped of all soft tissues. One tibia in each pair was randomly assigned to receive an osteotomy of 2 x 1.5 cm or 6 x 1.5 cm placed 1 cm dorsal to the tibial crest with the proximal graft edge 6 cm from the tibial plateau. Specimens were loaded at 720 N and in external rotational torque at 5 degrees per second to failure. Axial force or torque at failure were analyzed via T-test (p < or = 0.05). RESULTS: There was no significant difference in torque to failure between specimens with an osteotomy of 1.5 x 2 cm versus the matched intact specimens. Torque to failure for specimens with an osteotomy 1.5 x 6 cm was lower than that of the matched intact specimens (28.69 Nm +/- 4.2 Nm versus 60.95 Nm +/- 9.49 Nm; p = 0.01) and lower than that found in the 2-cm osteotomy group (p = 0.04). CONCLUSION: Torque to failure was significantly decreased with the larger 6-cm graft as compared with the intact tibia and with the graft 1.5 x 2 cm. The smaller graft did not result in a significant change in torsional strength of the tibia. CLINICAL RELEVANCE: Though this study cannot be extrapolated directly to the clinical setting, the longer graft tested in this study may raise concerns regarding the strength of the tibia after graft removal.

Radiographic parameters of increased carpal tunnel pressure with progressive wrist distraction: a cadaveric study.

PURPOSE: Increased carpal canal pressure associated with external fixation has been noted as a potential source of complications but no correlated clinical observation has been identified. We hypothesized that there would be a significant change in midcarpal distance and modified carpal height index with increasing distraction across the wrist joint and that these changes would correlate with pressure increases. METHODS: Thirteen cadaveric upper extremities were mounted vertically using 2 half pins in the midradius. Using a previously reported technique, we introduced a balloon-tipped catheter attached to a transducer into the carpal canal for pressure measurement. As weights were hung from the middle finger to create distraction across the carpus, pressure measurements and radiographs of the wrist were taken simultaneously. This sequence was performed for 4.50 kg of distraction in 0.45-kg increments and at 6.80 and 9.07 kg of distraction with the wrist in neutral position. Changes in midcarpal distance and modified carpal height index were calculated and comparisons were made with the Student t test. A 2-tailed Pearson correlation was used to determine whether there was a correlation between carpal canal pressure and radiographic indicators. Significance was set at p

Plantar-to-dorsal compared to dorsal-to-plantar screw fixation for proximal chevron osteotomy: a biomechanical analysis.

BACKGROUND: A change in screw orientation in fixing the chevron proximal first metatarsal osteotomy was noted anecdotally to improve fixation strength. The authors hypothesized that plantar-to-dorsal screw orientation would be more stable than the conventional dorsal-to-plantar screw orientation for fixation of the chevron osteotomy. The purpose of this study was to determine if the load-to-failure and stiffness of the chevron type proximal first metatarsal osteotomy stabilized using plantar-to-dorsal screw fixation were greater than with the more conventional dorsal-to-plantar screw fixation method. METHODS: One foot from each of eight matched cadaver pairs was randomly assigned to one of two groups: 1) fixation with a dorsal-to-plantar lag screw or 2) fixation with a plantar-to-dorsal lag screw. A proximal chevron osteotomy was then created using standard technique and the metatarsal was fixed according to previously established method. The bone was potted in polyester resin, and the construct was fitted into a materials testing system machine in which load was applied to the plantar aspect of the metatarsal until failure. The two groups were compared using a two-tailed Student t test. RESULTS: The average load-to-failure and stiffness of the chevron osteotomy fixed with the plantar-to-dorsal lag screw were significantly greater (p < 0.05) than the group fixed with more conventional dorsal-to-plantar lag screws. CONCLUSION: Plantar-to-dorsal screw orientation was more stable than the conventional dorsal-to-plantar screw orientation for fixation of the proximal chevron osteotomy. Plantar-to-dorsal screw orientation should be considered when using the chevron proximal first metatarsal osteotomy.

Epidemiology of lacrosse injuries in high school-aged girls and boys: a 3-year prospective study.

OBJECTIVE: To report the types, mechanisms, and circumstances of lacrosse injuries incurred by high school-aged girls and boys during organized interscholastic and summer camp games. STUDY DESIGN: Descriptive epidemiology study. METHODS: For 3 years, the authors gathered data on girls' and boys' lacrosse injuries for 359 040 high school and 28 318 summer camp athletic exposures using a lacrosse-specific computerized injury surveillance system. The most prevalent injuries were organized into multifactorial injury scenarios. RESULTS: In high school play, the injury rate for adolescent boys (2.89 per 1000 athletic exposures) was slightly higher than that for girls (2.54 per 1000 athletic exposures) (incidence rate ratio = 1.14; 95% confidence interval, 1.00-1.30). The most prevalent injuries for adolescent girls and boys were knee and ankle sprains resulting from noncontact mechanisms. Male players had significantly higher rates of shoulder, neck, trunk, and back injuries and higher game-to-practice injury ratios. In addition, they had higher rates of concussive events from player-to-player contact. Female players had higher rates of overall head injuries, many involving contusions and abrasions from stick and ball contact. CONCLUSIONS: The overall injury rates for boys' and girls' high school lacrosse were significantly lower than those for collegiate play. Significant differences existed between adolescent boys and girls with respect to injury mechanisms, body parts injured, and player and team activity at the time of injury.

Acute and recurrent patellar instability in the young athlete.

Many reports of patellofemoral instability treatment suffer the same flaws of inappropriate patient selection, poor injury definition, insufficient activity assessment, and, especially in skeletally immature patients, limited followup found in other orthopedic literature. A significant number of dogmatic statements concerning risk factors and treatment interventions continue to be recycled through the literature without adequate clinical or laboratory substantiation, even in the face of contradictory data. Traditionally, patellar instability has been treated with variable periods of immobilization, sporadic rehabilitation, and an expected full return to sports activity. The reality is that many young athletes have long-term retropatella pain and sport-limiting extensor mechanism impairment following patellar dislocations. Most athletes benefit from an initial nonoperative program that is aggressive, multidimensional, and responsive to early treatment outcomes. Concurrent osteochondral injuries are common and a major contributor to adverse outcomes. Diagnostically, MRI is improving in its ability to detail osteochondral injury and it plays an important role in determining the location and extent of MPFL injury. The primary stabilizing role of the MPFL in the normal knee and its injury as an essential lesion of patella instability has been appreciated only recently. There is growing interest in exchanging the myriad of nonanatomic extensor mechanism reconstructions for more anatomic procedures based on restitution of the MPFL.