Cosmological baryon and lepton number in the presence of electroweak fermion-number violation

In the presence of rapid fermion-number violation due to nonperturbative electroweak effects certain relations between the baryon number of the Universe and the lepton numbers of the Universe are predicted. In some cases the electron-neutrino asymmetry is exactly specified in terms of the baryon asymmetry. Without introducing new particles, beyond the usual quarks and leptons, it is necessary that the Universe possess a nonzero value of B - L prior to the epoch of fermion-number violation if baryon and lepton asymmetries are to survive. Contrary to intuition, even though electroweak processes violate B + L, a nonzero value of B + L persists after the epoch of rapid fermion-number violation. If the standard model is extended to include lepton-number violation, for example through Majorana neutrino masses, then electroweak processes will reduce the baryon number to zero even in the presence of an initial B - L unless 20 M(sub L) approximately greater than the square root of (T(sub B - L) m(sub P1)) where M(sub L) sets the scale of lepton number violation and T(sub B - L) is the temperature at which a B - L asymmetry is produced. In many models this implies that neutrinos must be so light that they cannot contribute appreciably to the mass density of the Universe

Reestablishing a Knowledge Mens Rea Requirement for Armed Career Criminal Act Violent Felonies Post-Voisine

Until 2016, federal courts unanimously concluded that predicate offenses for the Armed Career Criminal Act (\u27ACCA ) required a knowledge mens rea. Therefore, any state law crimes that could be com- mitted with a reckless mens rea were not violent felonies and could not serve as ACCA predicates. In 2016, however, the U.S. Supreme Court\u27s opinion in Voisine v. United States disrupted that lower court consensus. The Court stated that a reckless mens rea was sufficient to violate 18 U.S.C. § 922(g)(9), which bars individuals convicted of misdemeanor domestic violence offenses from possessing firearms. The ACCA\u27s language is similar to § 922(g)(9), so, after Voisine, some lower courts overruled their prior ACCA precedents and held that reckless offenses could serve as ACCA predicates. Other courts, however, found that the purpose and context of § 922(g)(9) is significantly different than the ACCA, and ACCA predicate offenses still require a knowledge mens rea. This Note advocates for a congressional amendment to the ACCA that explicitly includes a knowledge mens rea requirement. A knowledge mens rea is most consistent with how the ACCA has been interpreted, adheres to original congressional intent, and ensures that repeated reckless offenders are not considered career criminals and are not subject to the ACCA\u27s harsh punishment

Direct Current Electrical Stimulation Increases the Fusion Rate of Spinal Fusion Cages

Study Design. A randomized experimental evaluation of direct current stimulation in a validated animal model with an experimental control group, using blinded radiographic, biomechanical, histologic, and statistical measures. Objectives. To evaluate the efficacy of the adjunctive use of direct current stimulation on the fusion rate and speed of healing of titanium interbody fusion cages packed with autograft in a sheep lumbar interbody fusion model. Summary of Background Data. Titanium lumbar interbody spinal fusion cages have been reported to be 90% effective for single-level lumbar interbody fusion. However, fusion rates are reported to be between 70% and 80% in patients with multilevel fusions or with risk factors such as obesity, tobacco use, or metabolic disorders. The authors hypothesized that direct current stimulation would increase the fusion rate of titanium interbody fusion cages packed with autograft in a sheep lumbar interbody fusion model. Methods. Twenty-two sheep underwent lumbar discectomy and fusion at L4–L5 with an 11- × 20-mm Bagby and Kuslich (BAK) cage packed with autograft. Seven sheep received a BAK cage and no current. Seven sheep had a cage and a 40-μA current applied with a direct current stimulator. Eight sheep had a BAK cage and a 100-μA current applied. All sheep were killed 4 months after surgery. The efficacy of electrical stimulation in promoting interbody fusion was assessed by performing radiographic, biomechanical, and histologic analyses in a blinded fashion. Results. The histologic fusion rate increased as the direct current dose increased from 0 μA to 40 μA to 100 μA (P \u3c 0.009). Histologically, all animals in the 100-μA group had fusions in both the right and left sides of the cage. Direct current stimulation had a significant effect on increasing the stiffness of the treated motion segment in right lateral bending (P \u3c 0.120), left lateral bending (P \u3c 0.017), right axial rotation (P \u3c 0.004), left axial rotation (P \u3c 0.073), extension (P \u3c 0.078), and flexion (P \u3c 0.029) over nonstimulated levels. Conclusion. Direct current stimulation increased the histologic and biomechanical fusion rate and the speed of healing of lumbar interbody spinal fusion cages in an ovine model at 4 months

Polyetheretherketone as a Biomaterial for Spinal Applications

Threaded lumbar interbody spinal fusion devices (TIBFD) made from titanium have been reported to be 90% effective for single-level lumbar interbody fusion, although radiographic determination of fusion has been intensely debated in the literature. Using blinded radiographic, biomechanic, histologic, and statistical measures, we evaluated a radiolucent polyetheretherketone (PEEK)-threaded interbody fusion device packed with autograft or rhBMP-2 on an absorbable collagen sponge in 13 sheep at 6 months. Radiographic fusion, increased spinal level biomechanical stiffness, and histologic fusion were demonstrated for the PEEK cages filled with autograft or rhBMP-2 on a collagen sponge. No device degradation or wear debris was observed. Only mild chronic inflammation consisting of a few macrophages was observed in peri-implant tissues. Based on these results, the polymeric biomaterial PEEK may be a useful biomaterial for interbody fusion cages due to the polymer\u27s increased radiolucency and decreased stiffness

Bioresorbable Film for the Prevention of Adhesion to the Anterior Spine After Anterolateral Discectomy

Background context The development of scar tissue and adhesions postoperatively is a natural consequence of healing but can be associated with medical complications and render reoperation difficult. Many biocompatible products have been evaluated as barriers or deterrents to adhesions. Purpose To evaluate the efficacy of a bioresorbable polylactide film as a barrier to adhesion formation after anterolateral discectomy. Study design Experimental study. Methods Seven, skeletally mature female sheep underwent a retroperitoneal approach to the anterolateral lumbar spine. A discectomy was performed at two levels with an intervening unoperated disc site. One site was treated with a polylactide film barrier (Hydrosorb Shield; MacroPore Biosurgery, San Diego, CA) affixed with tacks manufactured from the same material. The second site was left untreated. Treatment and control sites were randomly assigned. Postmortem analysis included scar tenacity scoring on five spines and histological evaluation on two spines. Results The application of the Hydrosorb film barrier allowed a definite dissection plane during scar tenacity scoring and there was a significant difference in the development of adhesions to the disc between the control and treated sites. Histological evaluation revealed evidence of barrier formation to scar tissue and no significant adverse inflammatory reactions. Conclusions Hydrosorb Shield appears to be an effective postoperative barrier to scar tissue adhesion after anterolateral discectomy. The use of polylactide tacks was beneficial to affix the barrier film in place. Safety issues associated with delayed healing or adverse response to the film or tacks were not observed. Hydrosorb film may be useful as an antiadhesion barrier facilitating dissection during surgical revision in anterior approaches to the spine. Further studies are indicated to evaluate the performance of the bioresorbable material as an antiadhesion barrier in techniques of spinal fusion and disc replacement

Bioresorbable Polylactide Interbody Implants in an Ovine Anterior Cervical Discectomy and Fusion Model: Three-Year Results

Study Design. In vivo study of anterior discectomy and fusion using a bioresorbable 70:30 poly(l-lactide-co-d,l-lactide) interbody implant in an ovine model. Objective. To evaluate the efficacy of the polylactide implant to function as an interbody fusion device, and to assess the tissue reaction to the material during the resorption process. Summary of Background Data. The use of polylactide as a cervical interbody implant has several potential advantages when compared with traditional materials. Having an elastic modulus very similar to bone minimizes the potential for stress shielding, and as the material resorbs additional loading is transferred to the developing fusion mass. Although preclinical and clinical studies have demonstrated the suitability of polylactide implants for lumbar interbody fusion, detailed information on cervical anterior cervical discectomy and fusion (ACDF) with polylactide devices is desirable. Methods. Single level ACDF was performed in 8 skeletally mature ewes. Bioresorbable 70:30 poly (l-lactide-co-d,l-lactide) interbody implants packed with autograft were used with single-level metallic plates. Radiographs were made every 3 months up to 1 year, and yearly thereafter. The animals were killed at 6 months (3 animals), 12 months (3 animals), and 36 months (2 animals). In addition to the serial plain radiographs, the specimens were evaluated by nondestructive biomechanical testing and undecalcified histologic analysis. Results. The bioresorbable polylactide implants were effective in achieving interbody fusion. The 6-month animals appeared fused radiographically and biomechanically, whereas histologic sections demonstrated partial fusion (in 3 of 3 animals). Radiographic fusion was confirmed histologically and biomechanically at 12 months (3 of 3 animals) and 36 months (2 of 2 animals). A mild chronic inflammatory response to the resorbing polylactide implant was observed at both 6 months and 12 months. At 36 months, the operative levels were solidly fused and the implants were completely resorbed. No adverse tissue response was observed in any animal at any time period. Conclusion. Interbody fusion was achieved using bioresorbable polylactide implants, with no evidence of implant collapse, extrusion, or adverse tissue response to the material. The use of polylactide as a cervical interbody device appears both safe and effective based on these ACDF animal model results

Histologic Evaluation of the Efficacy of rhBMP-2 Compared With Autograft Bone in Sheep Spinal Anterior Interbody Fusion

Study Design. The sheep anterior lumbar spinal fusion model was used to study the efficacy of recombinant human bone morphogenetic protein-2 (rhBMP-2)–collagen composite in comparison with autograft to enhance spinal interbody fusion. Comparisons were drawn from temporal radiographic and end-point biomechanical and histologic data. Objective. To analyze histologically the ability of rhBMP-2 to achieve complete arthrodesis between vertebral bodies. Summary of Background Data. Studies using rhBMP for enhancement of anterior interbody fusion have used numerous endpoints. However, systematic histologic evaluation of the fusion has not been conducted. Methods. Twelve sheep underwent single-level anterior lumbar interbody fusion performed with a cylindrical fenestrated titanium interbody fusion device (INTER FIX, Medtronic Sofamor Danek, Inc., Memphis, TN). The device was filled either with rhBMP-2–collagen (n = 6) or autogenous iliac crest bone graft (n = 6). Radiologic evaluation was carried out at 2-month intervals, and all sheep were killed 6 months after surgery. Nondestructive biomechanical testing for stiffness to flexion, extension, and lateral bending moments, un-decalcified histology, and qualitative and quantitative histologic evaluation were performed. Results. Radiographs revealed a bony bridge anterior to the cage in five of six rhBMP-2-treated animals, whereas it was present only in one of five in the autogenous bone graft group. Segments treated with rhBMP-2 were 20% stiffer in flexion than autograft-treated segments at 6 months. Six of six in the rhBMP-2 group and two of six in the autograft group showed complete fusion. There was a significantly higher rate of bony continuity observed at the fenestrations of the rhBMP-2 group. Three times more number of cage fenestrations in the rhBMP-2 group demonstrated “all-bone” when compared with the autograft group (P \u3c 0.001). Further, the scar tissue in and around the autograft-treated cages was 16-fold more (P \u3c 0.01) than that seen for rhBMP-2-treated cages. Conclusions. The study demonstrates that rhBMP-2 can lead to earlier radiologic fusion and a more consistent increased stiffness of the segments when compared with autograft in sheep anterior lumbar interbody fusion. Furthermore, a three times higher histologic fusion rate is attainable with significantly reduced fibrous tissue around the implant when rhBMP-2 is used

Axoneme-specific β-tubulin specialization a conserved C-terminal motif specifies the central pair

AbstractAxonemes are ancient organelles that mediate motility of cilia and flagella in animals, plants, and protists. The long evolutionary conservation of axoneme architecture, a cylinder of nine doublet microtubules surrounding a central pair of singlet microtubules, suggests all motile axonemes may share common assembly mechanisms. Consistent with this, α- and β-tubulins utilized in motile axonemes fall among the most conserved tubulin sequences [1, 2], and the β-tubulins contain a sequence motif at the same position in the carboxyl terminus [3]. Axoneme doublet microtubules are initiated from the corresponding triplet microtubules of the basal body [4], but the large macromolecular “central apparatus” that includes the central pair microtubules and associated structures [5] is a specialization unique to motile axonemes. In Drosophila spermatogenesis, basal bodies and axonemes utilize the same α-tubulin but different β-tubulins [6–13]. β1 is utilized for the centriole/basal body, and β2 is utilized for the motile sperm tail axoneme. β2 contains the motile axoneme-specific sequence motif, but β1 does not [3]. Here, we show that the “axoneme motif” specifies the central pair. β1 can provide partial function for axoneme assembly but cannot make the central microtubules [14]. Introducing the axoneme motif into the β1 carboxyl terminus, a two amino acid change, conferred upon β1 the ability to assemble 9 + 2 axonemes. This finding explains the conservation of the axoneme-specific sequence motif through 1.5 billion years of evolution

Cyanobacterial ribosomal RNA genes with multiple, endonuclease-encoding group I introns

<p>Abstract</p> <p>Background</p> <p>Group I introns are one of the four major classes of introns as defined by their distinct splicing mechanisms. Because they catalyze their own removal from precursor transcripts, group I introns are referred to as autocatalytic introns. Group I introns are common in fungal and protist nuclear ribosomal RNA genes and in organellar genomes. In contrast, they are rare in all other organisms and genomes, including bacteria.</p> <p>Results</p> <p>Here we report five group I introns, each containing a LAGLIDADG homing endonuclease gene (HEG), in large subunit (LSU) rRNA genes of cyanobacteria. Three of the introns are located in the LSU gene of <it>Synechococcus </it>sp. C9, and the other two are in the LSU gene of <it>Synechococcus lividus </it>strain C1. Phylogenetic analyses show that these introns and their HEGs are closely related to introns and HEGs located at homologous insertion sites in organellar and bacterial rDNA genes. We also present a compilation of group I introns with homing endonuclease genes in bacteria.</p> <p>Conclusion</p> <p>We have discovered multiple HEG-containing group I introns in a single bacterial gene. To our knowledge, these are the first cases of multiple group I introns in the same <it>bacterial </it>gene (multiple group I introns have been reported in at least one phage gene and one prophage gene). The HEGs each contain one copy of the LAGLIDADG motif and presumably function as homodimers. Phylogenetic analysis, in conjunction with their patchy taxonomic distribution, suggests that these intron-HEG elements have been transferred horizontally among organelles and bacteria. However, the mode of transfer and the nature of the biological connections among the intron-containing organisms are unknown.</p

Think outside the box: Incorporating secondary cognitive tasks into return to sport testing after ACL reconstruction

The optimal set of return to sport (RTS) tests after anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) remains elusive. Many athletes fail to pass current RTS test batteries, fail to RTS, or sustain secondary ACL injuries if they do RTS. The purpose of this review is to summarize current literature regarding functional RTS testing after ACLR and to encourage clinicians to have patients “think” (add a secondary cognitive task) outside the “box” (in reference to the box used during the drop vertical jump task) when performing functional RTS tests. We review important criteria for functional tests in RTS testing, including task-specificity and measurability. Firstly, tests should replicate the sport-specific demands the athlete will encounter when they RTS. Many ACL injuries occur when the athlete is performing a dual cognitive-motor task (e.g., attending to an opponent while performing a cutting maneuver). However, most functional RTS tests do not incorporate a secondary cognitive load. Secondly, tests should be measurable, both through the athlete’s ability to complete the task safely (through biomechanical analyses) and efficiently (through measures of performance). We highlight and critically examine three examples of functional tests that are commonly used for RTS testing: the drop vertical jump, single-leg hop tests, and cutting tasks. We discuss how biomechanics and performance can be measured during these tasks, including the relationship these variables may have with injury. We then discuss how cognitive demands can be added to these tasks, and how these demands influence both biomechanics and performance. Lastly, we provide clinicians with practical recommendations on how to implement secondary cognitive tasks into functional testing and how to assess athletes’ biomechanics and performance