Quantification of Microtubule-Bundling Activity of MAPs Using TIRF Microscopy.

Cross-linking of microtubules by microtubule-associated proteins (MAPs) results in the formation of microtubule bundles. It has been shown that a majority of microtubules in interphase plant cells are bundled. Bundling can contribute to maintaining structural stability and sustaining spatial organization of microtubule arrays. While bundling can be readily detected by an electron or fluorescent microscope, quantifying this activity remains technically challenging. Here we describe a method for quantifying microtubule-bundling in vitro using green and red stable microtubules. Furthermore, this method distinguishes between different types of microtubule-microtubule interactions: bundling, annealing, and branching. Our technique can be used to compare bundling activity of different MAPs and generate parameters for modeling their contribution to organization and dynamics of microtubule arrays.

Hepatitis C Is Associated With Higher Short-Term Complication Rates After Initial Aseptic and Septic Revision Total Hip Arthroplasty: A Matched Cohort Study.

BACKGROUND: It is unclear if hepatitis C virus (HCV) negatively impacts outcomes of revision total hip arthroplasty (rTHA). The purpose of this study is to trend recent rTHA utilization in patients who have HCV and compare postoperative complication rates versus a matched cohort. METHODS: All patients who underwent rTHA were retrospectively identified in a national database. Patients who had HCV (n = 1,746) were matched 1:3 with a matching group (n = 5,238) for age, gender, and several comorbidities. Cochran-Armitage tests were used to analyze trends in the annual proportion of rTHA performed in patients who had HCV from 2010 to 2019. Rates of 90-day medical and prosthesis-related complications within 2 years postoperatively were compared with multivariable logistic regressions. RESULTS: The annual proportion of rTHA performed in patients who had HCV significantly increased from 2010 to 2019 (P < .001). Patients who had HCV exhibited significantly higher rates of acute kidney injuries (7.6% versus 4.4%; odds ratio [OR] 1.50), transfusions (20.6% versus 14.6%; OR 1.38), and re-revisions for prosthetic joint infection (10.9% versus 6.5%; OR 1.73). In subgroup analyses, rates of re-revision for prosthetic joint infection after initial aseptic rTHA (7.1% versus 3.8%; OR 1.82) and periprosthetic fracture after initial septic rTHA (4.5% versus 1.6%; OR 2.77) were significantly higher in the HCV cohort. CONCLUSION: Similar to primary THA, patients who have HCV exhibit significantly increased complication rates after rTHA. With growing utilization in recent years, these data suggest that this population will comprise an increasingly larger proportion of rTHA procedures performed in the coming years.

The Impact of Hepatitis C on Complication Rates After Revision Total Knee Arthroplasty: A Matched Cohort Study.

Background: It is unclear if hepatitis C (HCV) negatively impacts outcomes of revision total knee arthroplasty (rTKA). The purpose of this study was to compare complication rates after rTKA for patients with HCV vs matched controls. Methods: A retrospective cohort study was conducted using the PearlDiver database (PearlDiver Inc., Colorado Springs, CO). Patients with HCV who underwent rTKA (n = 1448) were matched 1:4 with controls (n = 5792) on age, sex, and several comorbidities. Rates of medical complications within 90 days and prothesis-related complications within 2 years postoperatively were compared with logistic regression for (1) patients with vs without HCV and (2) HCV patients who underwent aseptic vs septic rTKA. Results: Relative to controls, patients with HCV exhibited significantly higher rates of medical complications (27.7% vs 20.9%; odds ratio [OR] 1.47), periprosthetic fractures (2.3% vs 1.1%; OR 2.20), all-cause repeat rTKA (11.7% vs 9.4%; OR 1.29), and repeat rTKA for prosthetic joint infection (PJI) (6.7% vs 3.6%; OR 1.92). Within the HCV cohort, HCV patients with initial septic rTKA exhibited significantly higher rates of medical complications (41.7% vs 22.7%; OR 2.39), all-cause subsequent rTKA (15.9% vs 10.2%; OR 1.67), and repeat rTKA for PJI (15.9% vs 3.4%; OR 5.39). Conversely, HCV patients with initial aseptic rTKA exhibited significantly higher rates of aseptic loosening (2.6% vs 7.4%; OR 0.33). Conclusions: Patients with HCV exhibited significantly higher rates of medical and prosthesis-related complications after rTKA than controls. Among patients with HCV, initial septic rTKA was associated with significantly higher rates of medical complications, repeat rTKA, and PJI.

Does pre-arthroplasty antiviral treatment for hepatitis C reduce complication rates after total shoulder arthroplasty? A matched cohort study.

Background: Hepatitis C virus (HCV) is associated with increased complications of risk after arthroplasty. The purpose of this study was to examine the impact of HCV and a pre-arthroplasty antiviral treatment on complications following total shoulder arthroplasty (TSA). Methods: A retrospective matched cohort study was conducted using an administrative claims database. Patients who underwent TSA were identified with Current Procedural Terminology -23472 and International Classification of Diseases procedural codes. A total of 1244 HCV patients were matched 1:3 with 3732 noninfected controls across age, sex, diabetes mellitus, tobacco use, and obesity. The HCV patients with treatment before TSA were identified by claims containing antiviral drug codes. Multivariable logistic regression was used to compare rates of 90-day medical complications and prosthesis-related complications within 2 years postoperatively for (1) HCV patients vs. controls, (2) antiviral-treated HCV patients vs. controls, and (3) antiviral-treated HCV patients vs. untreated HCV patients. Results: Patients with HCV exhibited significantly higher rates of blood transfusion (OR 2.12), acute kidney injuries (OR 1.86), inpatient readmission (OR 2.06), revision TSA (OR 1.48), dislocation (OR 1.92), mechanical complications (OR 1.39), and prosthetic joint infection (OR 1.53) compared to controls. Antiviral-treated HCV patients exhibited a significantly lower rate of myocardial infarction (OR 0.27) and comparable rates of all other complications relative to controls (all P > .05). Compared to untreated HCV patients, antiviral-treated HCV patients exhibited significantly lower rates of 90-day medical complications (OR 0.57) and prosthetic joint infection (OR 0.36). Conclusions: HCV is associated with significantly increased complication rates after TSA. Antiviral treatment before TSA may reduce the risk of postoperative complications.

Osteoporosis management and secondary fragility fracture rates in patients with multiple sclerosis: a matched cohort study.

This study highlights the persistent osteoporosis treatment gap following fragility fractures. Patients with multiple sclerosis sustained more primary hip fractures than controls and exhibited significantly higher rates of falls within three years post-fracture. However, multiple sclerosis (MS) patients were significantly more likely to be diagnosed with osteoporosis and treated with medications. INTRODUCTION: The purpose of this study was to compare rates of osteoporosis management, falls, and secondary fractures following primary fragility fractures among patients with MS versus matched controls. MATERIALS AND METHODS: A retrospective matched cohort study was conducted using the PearlDiver database. Patients aged ≥ 50 years with primary fragility fractures were identified (n = 120,368). Within this population, patients with MS were matched 1:10 with controls across age, sex, and US region. Rates of osteoporosis diagnoses and pharmacologic treatment, low-energy falls, and secondary fragility fractures were compared at three years post-fracture via logistic regression. RESULTS: A total of 1,232 patients with MS (mean age, 65.7 years) with primary fragility fractures were matched with 12,320 controls (mean age, 65.8 years). Primary hip fractures were significantly more common in the MS cohort (47.4% vs. 34.2%, p < 0.001). After the initial fracture, patients with MS were significantly more likely to receive a formal osteoporosis diagnosis (12.9% vs. 9.7%; OR 1.35; 95% CI, 1.13-1.61) and osteoporosis pharmacotherapy (14.4% vs. 11.9%; OR 1.24; 95% CI, 1.04-1.46). The MS cohort also exhibited significantly higher rates of falls (27.8% vs 22.7%; OR 1.15; 95% CI, 1.01-1.32). Rates of secondary fractures were comparable (6.3% vs. 5.0%; OR 1.10; 95% CI, 0.85-1.40). CONCLUSION: Primary hip fragility fractures were significantly more common in patients with MS compared to matched controls. Following an initial fracture, patients with MS exhibited a significantly higher rate of falls but were more likely to be diagnosed with osteoporosis and treated with medications.

Does Preoperative Antiviral Treatment for Hepatitis C Decrease Risk of Complications After Total Hip Arthroplasty? A Matched Cohort Study.

BACKGROUND: Hepatitis C virus (HCV) is associated with increased complication risk after elective arthroplasty. The purpose of this study is to examine the impact of HCV and prearthroplasty antiviral treatment on complications following total hip arthroplasty (THA). METHODS: A retrospective matched cohort study was conducted using an administrative claims database. In total, 6,883 HCV patients were matched 1:3 with 20,694 noninfected controls, and 920 HCV patients with antiviral treatment before THA (treated HCV) were matched 1:4 with 3,820 HCV patients without treatment (untreated HCV). Rates of 90-day medical complications and joint complications within 2 years postoperatively were compared with multivariable logistic regression. RESULTS: HCV patients exhibited significantly increased rates of medical complications within 90 days compared to noninfected controls (all P < .01). At 2 years postoperatively, HCV patients also exhibited significantly higher risk of revision THA (odds ratio [OR] 1.81), dislocation (OR 2.06), mechanical complications (OR 1.40), periprosthetic fracture (OR 1.76), and prosthetic joint infection (PJI) (OR 1.79). However, treated HCV patients exhibited statistically comparable risk of all joint complications at 2 years postoperatively relative to controls (all P > .05). Compared to untreated HCV patients, treated HCV patients exhibited significantly lower risk of inpatient readmission within 90 days (OR 0.58) and PJI at 2 years postoperatively (OR 0.62). CONCLUSION: HCV patients exhibit significantly increased risk of medical and joint complications following THA relative to controls, though prearthroplasty antiviral treatment mitigates complication risk. Treated HCV patients exhibited significantly lower risk of inpatient readmission and PJI compared to untreated HCV patients. LEVEL OF EVIDENCE: Level III.

A Review of Proximal Tibia Entry Points for Intramedullary Nailing and Validation of The Lateral Parapatellar Approach as Extra-articular.

Tibial shaft fractures are the most common long bone injury and are often treated surgically in an attempt to minimize complications. Although treatment options for tibial shaft fractures vary based on factors including open injury, severity of fracture, and soft tissue status, intramedullary nailing in adults has emerged as the preferred definitive option for stabilization. Therefore, the primary purposes of this review and cadaveric study were to evaluate the entry points for reamed tibial nails and the risks, benefits, and advantages of each approach. Due to concerns of violating the joint capsule and the generalized applicability to everyday practice of the extra-articular lateral parapatellar semi-extended technique, the secondary goal of this manuscript was to evaluate whether an intramedullary tibial nail can be consistently placed extra-articularly using the lateral parapatellar technique described by Kubiak et al. and generalizability to surgeons of varying experience.

Addition of the Sartorius Tendon Improves Biomechanics of a Four-Strand Hamstring Anterior Cruciate Ligament Autograft.

PURPOSE: The purpose of this study was to quantify and compare the biomechanical properties and change in graft size when adding the sartorius tendon as a fifth strand to a four-strand ST-G hamstring autograft. Additionally, the sartorius tendon was tested individually to quantify its independent biomechanical properties. METHODS: Four-strand and five-strand hamstring tendon grafts were harvested from matched cadaveric knees (mean age: 81.6 ± 9.8). These matched grafts were biomechanically tested using a MTS servohydraulic test system at a rate of testing representative of physiologic tears. The mean diameter, cross-sectional area, and ultimate load to failure were quantified and compared with a one-sided, paired Student's t-test. A P < .05 was considered statistically significant. RESULTS: The mean diameter of the five-strand graft was significantly larger than the four-strand graft (9.30 ± .84 mm vs 8.10 ± .42 mm; P = .002). The average ultimate load to failure of the five-strand graft was 65.3% higher than the four-strand graft (2984.05 ± 1085.11 N vs. 1805.03 ± 557.69 N; P = .009) and added 14.8% to the diameter of the four strand ST-G autograft. CONCLUSIONS: The addition of the sartorius tendon to a four-strand hamstring autograft significantly increased ultimate load to failure by 65%, graft cross-sectional area by 32%, and graft diameter by 15% compared to a traditional four-strand ST-G autograft. This information can be helpful to surgeons who wish to improve the strength of a four-strand ST-G autograft and for undersized grafts as an alternative to allograft supplementation. CLINICAL RELEVANCE: The addition of the sartorius to the four-strand ST-G hamstring autograft significantly increases the ultimate load to failure and overall graft diameter, which can be particularly helpful in undersized autografts as an alternative to allograft supplementation.

A Missed Opportunity: The Impact of Hepatitis C Treatment Prior to Total Knee Arthroplasty on Postoperative Complications.

BACKGROUND: Hepatitis C (HCV) is undertreated and increasing in prevalence. Its influence on outcomes following total knee arthroplasty (TKA) remains unclear. The purpose of this study is to examine the impact of HCV and prearthroplasty antiviral treatment on postoperative complications following TKA. METHODS: A retrospective matched cohort study was conducted using an administrative claims database to compare postoperative complication rates following TKA for (1) patients with vs without HCV and (2) among patients with HCV, patients with antiviral treatment before TKA vs no treatment. In total, 6971 patients with HCV were matched 1:4 with 27,884 controls without HCV, and 708 HCV patients with antiviral treatment before TKA were matched 1:2 with 1416 HCV patients without treatment. Rates of joint complications at 1 and 2 years postoperatively were compared via multivariable logistic regression. RESULTS: The HCV cohort exhibited significantly higher risk of prosthetic joint infection (PJI) than controls at both 1 (4.1 vs 2.1%; odds ratio [OR] 1.58) and 2 years (5.0% vs 2.7%; OR 1.55) postoperatively. Rates of revision TKA were also significantly higher for HCV patients at 1 (2.8% vs 1.8%; OR 1.40) and 2 years (4.1% vs 2.9%; OR 1.30). HCV patients with prearthroplasty antiviral treatment exhibited significantly lower risk of PJI at 1 (2.1% vs 4.1%; OR 0.50) and 2 years (2.7% vs 5.1%, OR 0.51) compared to patients without treatment. CONCLUSION: Patients with HCV have significantly increased risk of PJI and revision arthroplasty following TKA. Antiviral treatment before TKA significantly decreases the risk of PJI postoperatively. LEVEL OF EVIDENCE: Level III.

Complication Rates of Hemiarthroplasty Conversion to Total Hip Arthroplasty Versus Primary Total Hip Arthroplasty.

BACKGROUND: One of the most common surgical options for treatment of a femoral neck fracture is hemiarthroplasty (HA). However, progression of arthritis or pain can necessitate conversion to total hip arthroplasty (THA). While conversion to a THA is a viable option, it does carry multiple risks. The purpose of this study was to identify whether performing conversion from HA to THA carries an increased risk of post-operative joint complications when compared to elective THA. METHODS: An administrative claims database was queried to identify patients who underwent conversion from a HA to a THA. Incidences of prosthetic dislocation, prosthetic joint infection (PJI), periprosthetic fracture, aseptic loosening, and revision were collected and compared to elective primary THA with multivariable logistic regression. RESULTS: Patients undergoing conversion THA had significantly higher risks of all joint complications examined at both 1 and 2 years after surgery. These included prosthetic dislocation (1-year: OR 2.95; 2 years: OR 3.77), PJI (1-year: OR 1.38; 2 years: OR 2.13), periprosthetic fracture (1-year: OR 2.95; 2 years: OR 3.75), aseptic loosening (1-year: OR 6.86; 2 years: OR 7.70), and revision (1-year: OR 3.65; 2 years: OR 6.73). CONCLUSION: Performing conversion arthroplasty from HA to THA is associated with an increased risk of multiple joint complications in both the short and mid-term follow-up period. Surgeons should consider these complications when indicating HA for femoral neck fractures and elective conversion arthroplasty.

The Impact of Prior Fragility Fractures on Complications After Total Hip Arthroplasty: A Propensity Score-Matched Cohort Study.

BACKGROUND: The impact of prior fragility fractures and osteoporosis treatment before total hip arthroplasty (THA) on postoperative complications is unclear. The purpose of this study was to characterize the effect of prior fragility fractures and preoperative osteoporosis treatment on short-term complications and secondary fragility fractures after THA. METHODS: A propensity score-matched retrospective cohort study was conducted using a commercially available database to (1) characterize the impact of prior fragility fractures on rates of short-term complications after THA and (2) evaluate if osteoporosis treatment before arthroplasty reduces risk of postoperative complications. Rates of periprosthetic fracture, revision THA, and fragility fractures were compared via multivariable logistic regression. RESULTS: After 1:1 propensity score matching, 2188 patients were assigned to each cohort. Patients with a fragility fracture in the 3 years preceding THA were more likely to sustain a periprosthetic fracture (1 year: 1.7% vs 1.0%, odds ratio [OR] 1.89; 2 years: 2.1% vs 1.1%, OR 1.82), fragility fracture (1 year: 4.7% vs 1.1%, OR 3.59; 2 years: 6.7% vs 1.7%, OR 3.21), and revision THA (1 year: 2.7% vs 1.7%, OR 1.65; 2 years: 3.1% vs 1.9%, OR 1.58). Among patients with a prior fragility fracture, only 13.8% received osteoporosis pharmacotherapy before THA. Rates of all complications were statistically comparable postoperatively for patients with and without pre-THA osteoporosis treatment. CONCLUSIONS: Fragility fractures within 3 years before THA are associated with significantly increased risk of periprosthetic fracture, all-cause revision, and secondary fragility fractures postoperatively. Preoperative osteoporosis treatment may not decrease risk of postoperative complications.

Injury Profile of Mixed Martial Arts Competitions in the United States.

BACKGROUND: The popularity of mixed martial arts (MMA) continues to grow in the United States. Although prior work has provided valuable insight concerning injuries in the sport, much of the available literature is limited by factors such as small sample sizes, varying athlete demographics, and inconsistent data collection methods. PURPOSE: To report injury rates and types in MMA and analyze potential variance between competition and match variables. STUDY DESIGN: Descriptive epidemiology study. METHODS: We performed a retrospective review of injuries sustained by fighters during MMA contests between 2018 and 2019 using ringside physician postmatch injury reports from Wisconsin and Arizona. The prevalence of overall injuries and specific injury types was compared by location (Arizona vs Wisconsin), competition level (amateur vs professional), match result (decisions vs any other result), and match winners versus losers. RESULTS: In 503 contests, 285 (57%) had at least 1 injury. In these 285 matches, participants experienced 401 injuries: 197 (49%) in professional bouts and 204 (51%) in amateur bouts. The match injury rate was higher in professional bouts than in amateur contests (68% vs 51%; P < .001). Amateur fighters had more contusions and hematomas (31% vs 22%; P < .001), while professional fighters had more lacerations (39% vs 23%; P < .001). Losers exhibited a higher match injury rate than winners (48% vs 24%; P < .001). Winners experienced a higher proportion of fractures (19% vs 9%; P = .005), and losers experienced more concussions (17% vs 2%; P < .001). CONCLUSION: Professional fighters and losers of MMA bouts exhibited higher injury rates relative to amateurs and winners. The prevalence of specific injury types varied by competition level, match result, and match winners versus losers. The results of this study may be used to better understand the current injury profile in MMA and to develop targeted strategies for injury prevention.

A guide to plant TPX2-like and WAVE-DAMPENED2-like proteins.

TPX2 proteins were first identified in vertebrates as a key mitotic spindle assembly factor. Subsequent studies demonstrated that TPX2 is an intricate protein, with functionally and structurally distinct domains and motifs including Aurora kinase-binding, importin-binding, central microtubule-binding, and C-terminal TPX2 conserved domain, among others. The first plant TPX2-like protein, WAVE-DAMPENED2, was identified in Arabidopsis as a dominant mutation responsible for reducing the waviness of roots grown on slanted agar plates. Each plant genome encodes at least one 'canonical' protein with all TPX2 domains and a family of proteins (20 in Arabidopsis) that diversified to contain only some of the domains. Although all plant TPX2-family proteins to date bind microtubules, they function in distinct processes such as cell division, regulation of hypocotyl cell elongation by hormones and light signals, vascular development, or abiotic stress tolerance. Consequently, their expression patterns, regulation, and functions have diverged considerably. Here we summarize the current body of knowledge surrounding plant TPX2-family proteins.

Correction to: Transcriptome analyses of tumor-adjacent somatic tissues reveal genes co-expressed with transposable elements.

[This corrects the article DOI: 10.1186/s13100-019-0180-5.].

Transcriptome analyses of tumor-adjacent somatic tissues reveal genes co-expressed with transposable elements.

BACKGROUND: Despite the long-held assumption that transposons are normally only expressed in the germ-line, recent evidence shows that transcripts of transposable element (TE) sequences are frequently found in the somatic cells. However, the extent of variation in TE transcript levels across different tissues and different individuals are unknown, and the co-expression between TEs and host gene mRNAs have not been examined. RESULTS: Here we report the variation in TE derived transcript levels across tissues and between individuals observed in the non-tumorous tissues collected for The Cancer Genome Atlas. We found core TE co-expression modules consisting mainly of transposons, showing correlated expression across broad classes of TEs. Despite this co-expression within tissues, there are individual TE loci that exhibit tissue-specific expression patterns, when compared across tissues. The core TE modules were negatively correlated with other gene modules that consisted of immune response genes in interferon signaling. KRAB Zinc Finger Proteins (KZFPs) were over-represented gene members of the TE modules, showing positive correlation across multiple tissues. But we did not find overlap between TE-KZFP pairs that are co-expressed and TE-KZFP pairs that are bound in published ChIP-seq studies. CONCLUSIONS: We find unexpected variation in TE derived transcripts, within and across non-tumorous tissues. We describe a broad view of the RNA state for non-tumorous tissues exhibiting higher level of TE transcripts. Tissues with higher level of TE transcripts have a broad range of TEs co-expressed, with high expression of a large number of KZFPs, and lower RNA levels of immune genes.

Arctic ground squirrel neuronal progenitor cells resist oxygen and glucose deprivation-induced death.

AIM: To investigate the influence of ischemia/reperfusion on arctic ground squirrel (AGS) neuronal progenitor cells (NPCs), we subjected these cultured cells to oxygen and glucose deprivation. METHODS: AGS NPCs were expanded and differentiated into NPCs and as an ischemia vulnerable control, commercially available human NPCs (hNPCs) were seeded from thawed NPCs. NPCs, identified by expression of TUJ1 were seen at 14-21 d in vitro (DIV). Cultures were exposed to control conditions, hypoxia, oxygen and glucose deprivation or glucose deprivation alone or following return to normal conditions to model reperfusion. Cell viability and death were assessed from loss of ATP as well as from measures of alamarBlue(®) and lactate dehydrogenase in the media and from counts of TUJ1 positive cells using immunocytochemistry. Dividing cells were identified by expression of Ki67 and phenotyped by double labeling with GFAP, MAP2ab or TUJ1. RESULTS: We report that when cultured in NeuraLife™, AGS cells remain viable out to 21 DIV, continue to express TUJ1 and begin to express MAP2ab. Viability of hNPCs assessed by fluorescence alamarBlue (arbitrary units) depends on both glucose and oxygen availability [viability of hNPCs after 24 h oxygen glucose deprivation (OGD) with return of oxygen and glucose decreased from 48151 ± 4551 in control cultures to 43481 ± 2413 after OGD, P < 0.05]. By contrast, when AGS NPCs are exposed to the same OGD with reperfusion at 14 DIV, cell viability assessed by alamarBlue increased from 165305 ± 11719 in control cultures to 196054 ± 13977 after OGD. Likewise AGS NPCs recovered ATP (92766 ± 6089 in control and 92907 ± 4290 after modeled reperfusion; arbitrary luminescence units), and doubled in the ratio of TUJ1 expressing neurons to total dividing cells (0.11 ± 0.04 in control cultures vs 0.22 ± 0.2 after modeled reperfusion, P < 0.05). Maintaining AGS NPCs for a longer time in culture lowered resistance to injury, however, did not impair proliferation of NPCs relative to other cell lineages after oxygen deprivation followed by re-oxygenation. CONCLUSION: Ischemic-like insults decrease viability and increase cell death in cultures of human NPCs. Similar conditions have less affect on cell death and promote proliferation in AGS NPCs.

Arctic ground squirrel (Spermophilus parryii) hippocampal neurons tolerate prolonged oxygen-glucose deprivation and maintain baseline ERK1/2 and JNK activation despite drastic ATP loss.

Oxygen-glucose deprivation (OGD) initiates a cascade of intracellular responses that culminates in cell death in sensitive species. Neurons from Arctic ground squirrels (AGS), a hibernating species, tolerate OGD in vitro and global ischemia in vivo independent of temperature or torpor. Regulation of energy stores and activation of mitogen-activated protein kinase (MAPK) signaling pathways can regulate neuronal survival. We used acute hippocampal slices to investigate the role of ATP stores and extracellular signal-regulated kinase (ERK)1/2 and Jun NH(2)-terminal kinase (JNK) MAPKs in promoting survival. Acute hippocampal slices from AGS tolerated 30 mins of OGD and showed a small but significant increase in cell death with 2 h OGD at 37 degrees C. This tolerance is independent of hibernation state or season. Neurons from AGS survive OGD despite rapid ATP depletion by 3 mins in interbout euthermic AGS and 10 mins in hibernating AGS. Oxygen-glucose deprivation does not induce JNK activation in AGS and baseline ERK1/2 and JNK activation is maintained even after drastic depletion of ATP. Surprisingly, inhibition of ERK1/2 or JNK during OGD had no effect on survival, whereas inhibition of JNK increased cell death during normoxia. Thus, protective mechanisms promoting tolerance to OGD by AGS are downstream from ATP loss and are independent of hibernation state or season. Journal of Cerebral Blood Flow & Metabolism (2008) 28, 1307-1319; doi:10.1038/jcbfm.2008.20; published online 9 April 2008.

Potential for discovery of neuroprotective factors in serum and tissue from hibernating species.

Hibernation is a unique phenotype displayed by a phylogenetically diverse group of organisms including several species of mammals and one species of primate. Here we review evidence for blood and tissue borne signaling molecules in hibernating animals, achievements in isolating and characterizing these molecules, and potential medicinal applications.

Decreased NR1 phosphorylation and decreased NMDAR function in hibernating Arctic ground squirrels.

Heterothermic mammals such as ground squirrels tolerate ischemia and N-methyl-D-aspartate (NMDA) better than homeothermic mammals such as rats both in vivo and in vitro, and this tolerance is enhanced in the hibernating state. However, the cellular mechanisms underlying this tolerance remain unclear. NMDA receptors (NMDAR) play a key role in excitotoxicity. The purpose of the current study was therefore to test the hypothesis that NMDAR are down-regulated in hibernating Arctic ground squirrels (hAGS; Spermophilus parryii). To address this hypothesis, we used Western blot analysis to investigate NMDAR phosphorylation, an activator of NMDAR function, and internalization in naïve hippocampal tissue from hAGS, interbout euthermic AGS (ibeAGS), and rats. Furthermore, we used fura-2 calcium imaging to examine NMDAR function in cultured hippocampal slices from hAGS, ibeAGS, and rats. We report that phosphorylation of the NMDAR1 (NR1) subunit is decreased in hippocampal tissue from hAGS and that the NMDAR component of Glu-induced increase in [Ca(2+)](i) is decreased in hippocampal slices from hAGS. Moreover, the fraction of NR1 in the functional membrane pool in AGS is less than that in rats.

Persistent tolerance to oxygen and nutrient deprivation and N-methyl-D-aspartate in cultured hippocampal slices from hibernating Arctic ground squirrel.

Hibernating Arctic ground squirrel (hAGS), Spermophilus parryii, survive profound decreases in cerebral perfusion during torpor and return to normal blood flow during intermittent rewarming periods without neurologic damage. Hibernating AGS tolerate traumatic brain injury in vivo, and acute hippocampal slices from hibernating animals tolerate oxygen and glucose deprivation. It remains unclear, however, if neuroprotection results from intrinsic tissue properties or from differences in response to acute trauma associated with slice preparation. The goal of this work was therefore to determine whether an intrinsic tissue tolerance persists in chronic culture of AGS hippocampal slices at 37 degrees C. A second goal was to address N-methyl-D-aspartate (NMDA) receptor involvement and channel arrest as potential mechanisms of intrinsic tissue tolerance. Baseline neuronal survival and tolerance to oxygen and nutrient deprivation (OND), an in vitro model of ischemia-reperfusion, were assessed in the CA1 region of hippocampal slices from juvenile, hAGS and interbout euthermic AGS (ibeAGS). Early in culture (insult onset at 3 h), slices from both hAGS and ibeAGS tolerate OND (4 h deprivation followed by 20 h recovery) and 500 micromol/L NMDA plus 20 mmol/L KCl. Later in culture (insult onset at 24 h), tolerance persists in slices from hAGS but not in slices from ibeAGS. Ouabain (Na(+)K(+)ATPase inhibitor) administered 24 h in culture enhances survival of slices from hAGS (assessed 24 h later). Thus, tolerance to OND in slices from hAGS is due to intrinsic tissue properties likely involving NMDA receptors and ion channel arrest.