New keratose sponges after the end-Permian extinction provide insights into biotic recoveries.

We challenge the prevailing view that the end-Permian extinction impeded the Triassic evolution of sponges. Here, we report a deep-water community dominated by abundant keratose sponges in the lowest Triassic strata from Southwest China. The sponge fossils occur as dark elliptical imprints in mudstone with distinct oscula on their tops. The structure of preserved fibers suggests closest affinity with the extant Dictyoceratida, an aspiculate demosponge. The exceptional preservation plays a crucial role in retaining their exquisite structures. Sedimentary, taphonomic, pyrite framboid, and trace elemental analyses indicate that the sponges proliferated in an oxygen-poor habitat, demonstrating the high tolerance of sponges to severe conditions. Sponge proliferation is a signal of environmental upheaval but they also stabilized the ecosystem, driving the first phase of biotic recovery after the end-Permian extinction.

Bayesian analyses indicate bivalves did not drive the downfall of brachiopods following the Permian-Triassic mass extinction.

Certain times of major biotic replacement have often been interpreted as broadly competitive, mediated by innovation in the succeeding clades. A classic example was the switch from brachiopods to bivalves as major seabed organisms following the Permian-Triassic mass extinction (PTME), ~252 million years ago. This was attributed to competitive exclusion of brachiopods by the better adapted bivalves or simply to the fact that brachiopods had been hit especially hard by the PTME. The brachiopod-bivalve switch is emblematic of the global turnover of marine faunas from Palaeozoic-type to Modern-type triggered by the PTME. Here, using Bayesian analyses, we find that unexpectedly the two clades displayed similar large-scale trends of diversification before the Jurassic. Insight from a multivariate birth-death model shows that the extinction of major brachiopod clades during the PTME set the stage for the brachiopod-bivalve switch, with differential responses to high ocean temperatures post-extinction further facilitating their displacement by bivalves. Our study strengthens evidence that brachiopods and bivalves were not competitors over macroevolutionary time scales, with extinction events and environmental stresses shaping their divergent fates.

The stability and collapse of marine ecosystems during the Permian-Triassic mass extinction.

The history of Earth's biodiversity is punctuated episodically by mass extinctions. These are characterized by major declines of taxon richness, but the accompanying ecological collapse has rarely been evaluated quantitatively. The Permian-Triassic mass extinction (PTME; ∼252 mya), as the greatest known extinction, permanently altered marine ecosystems and paved the way for the transition from Paleozoic to Mesozoic evolutionary faunas. Thus, the PTME offers a window into the relationship between taxon richness and ecological dynamics of ecosystems during a severe extinction. However, the accompanying ecological collapse through the PTME has not been evaluated in detail. Here, using food-web models and a marine paleocommunity dataset spanning the PTME, we show that after the first extinction phase, community stability decreased only slightly despite the loss of more than half of taxonomic diversity, while community stability significantly decreased in the second phase. Thus, taxonomic and ecological changes were unequivocally decoupled, with species richness declining severely ∼61 ka earlier than the collapse of marine ecosystem stability, implying that in major catastrophes, a biodiversity crash may be the harbinger of a more devastating ecosystem collapse.

Resilience of infaunal ecosystems during the Early Triassic greenhouse Earth.

The Permian-Triassic mass extinction severely depleted biodiversity, primarily observed in the body fossil of well-skeletonized animals. Understanding how whole ecosystems were affected and rebuilt following the crisis requires evidence from both skeletonized and soft-bodied animals; the best comprehensive information on soft-bodied animals comes from ichnofossils. We analyzed abundant trace fossils from 26 sections across the Permian-Triassic boundary in China and report key metrics of ichnodiversity, ichnodisparity, ecospace utilization, and ecosystem engineering. We find that infaunal ecologic structure was well established in the early Smithian. Decoupling of diversity between deposit feeders and suspension feeders in carbonate ramp-platform settings implies that an effect of trophic group amensalism could have delayed the recovery of nonmotile, suspension-feeding epifauna in the Early Triassic. This differential reaction of infaunal ecosystems to variable environmental controls thus played a substantial but heretofore little appreciated evolutionary and ecologic role in the overall recovery in the hot Early Triassic ocean.

Treatment of Thoracic Ossification of Posterior Longitudinal Ligament with One-Stage 360 Degree Circumferential Decompression Assisted by Piezosurgery.

OBJECTIVES: To evaluate the safety and clinical efficacy of One-Stage 360 degree circular decompression for thoracic ossification of the posterior longitudinal ligament (TOPLL) assisted by piezosurgery. MATERIALS AND METHODS: The present study enrolled 36 patients with TOPLL between August 2016 and February 2019. The average intraoperative bleeding volume of all 36 patients in this study is 1058.61 ±737.66 ml. RESULTS: All patients did not experience any intraoperative complications such as spinal cord and nerve injuries, and 22 other complications related to decompression of OPLL cited in other literature; all of which were relieved after treatment. The resection time of single laminectomy was 3.43 ±0.49 min, and circular decompression was 42.06 ±14.22 min. At the last follow-up, the modified Japanese Orthopaedic Association (mJOA) score was 8.89 ±1.56, the recovery rate of spinal cord function was 64.2 ±21.2%, and the number of cases of spinal cord function deterioration was 0 (0%). The mJOA score of the last follow-up was negatively correlated with the time of circular decompression (r = 0.368, p ＜ 0.01) and age (r = 0.412, p = 0.026). The recovery rate of the spinal cord function was negatively correlated with the operation time of circular decompression (r = -0.325, p = 0.041) and the amount of intraoperative blood loss (r = -0.555, p = 0.028). CONCLUSIONS: The use of piezosurgery can safely and effectively complete one-stage simple posterior TOPLL with 360-degree circular decompression. The incidence of complications is not high, and a good outcome can be obtained.

Ecological dynamics of terrestrial and freshwater ecosystems across three mid-Phanerozoic mass extinctions from northwest China.

The Earth has been beset by many crises during its history, and yet comparing the ecological impacts of these mass extinctions has been difficult. Key questions concern the kinds of species that go extinct and survive, how communities rebuild in the post-extinction recovery phase, and especially how the scaling of events affects these processes. Here, we explore ecological impacts of terrestrial and freshwater ecosystems in three mass extinctions through the mid-Phanerozoic, a span of 121 million years (295-174 Ma). This critical duration encompasses the largest mass extinction of all time, the Permian-Triassic (P-Tr) and is flanked by two smaller crises, the Guadalupian-Lopingian (G-L) and Triassic-Jurassic (T-J) mass extinctions. Palaeocommunity dynamics modelling of 14 terrestrial and freshwater communities through a long sedimentary succession from the lower Permian to the lower Jurassic in northern Xinjiang, northwest China, shows that the P-Tr mass extinction differed from the other two in two ways: (i) ecological recovery from this extinction was prolonged and the three post-extinction communities in the Early Triassic showed low stability and highly variable and unpredictable responses to perturbation primarily following the huge losses of species, guilds and trophic space; and (ii) the G-L and T-J extinctions were each preceded by low-stability communities, but post-extinction recovery was rapid. Our results confirm the uniqueness of the P-Tr mass extinction and shed light on the trophic structure and ecological dynamics of terrestrial and freshwater ecosystems across the three mid-Phanerozoic extinctions, and how complex communities respond to environmental stress and how communities recovered after the crisis. Comparisons with the coeval communities from the Karoo Basin, South Africa show that geographically and compositionally different communities of terrestrial ecosystems were affected in much the same way by the P-Tr extinction.

Three-dimensional navigation (O-arm) versus fluoroscopy in the treatment of thoracic spinal stenosis with ultrasonic bone curette: A retrospective comparative study.

Three-dimensional intraoperative navigation (O-arm) has been used for many years in spinal surgeries and has significantly improved its precision and safety. This retrospective study compared the efficacy and safety of spinal cord decompression surgeries performed with O-arm navigation and fluoroscopy. The clinical data of 56 patients with thoracic spinal stenosis treated from March 2015 to April 2017 were retrospectively analyzed. Spinal decompression was performed with O-arm navigation and ultrasonic bone curette in 29 patients, and with ultrasonic bone curette and fluoroscopy in 27 patients. Patients were followed-up at postoperative 1 month, 3 months, and the last clinic visit. The neurologic functions were assessed using the Japanese Orthopaedic Association (JOA) Back Pain Evaluation Questionnaire. The accuracy of screw placement was examined using three-dimensional computed tomography (CT) on postoperative day 5. There was no significant difference in the incidences of intraoperative dural tear, nerve root injury, and spinal cord injury between the two groups. The two groups showed no significant difference in postoperative JOA scores (P > .05). The O-arm navigation group had significantly higher screw placement accuracy than the fluoroscopy group (P < .05). O-arm navigation is superior to fluoroscopy in the treatment of thoracic spinal stenosis with ultrasonic bone curette in terms of screw placement accuracy. However, the two surgical modes have similar rates of intraoperative complications and postoperative neurologic functions.

Efficacy and safety of antifibrinolytic agents in spinal surgery: a network meta-analysis.

BACKGROUND: Significant blood loss is still one of the most frequent complications in spinal surgery, which often necessitates blood transfusion. Massive perioperative blood loss and blood transfusion can create additional risks. Aprotinin, tranexamic acid (TXA), and epsilon-aminocaproic acid (EACA) are antifibrinolytics currently offered as prophylactic agents to reduce surgery-associated blood loss. The aim of this study was to evaluate the efficacy and safety of aprotinin, EACA, and low/high doses of TXA in spinal surgery, and assess the use of which agent is the most optimal intervention using the network meta-analysis (NMA) method. METHODS: Five electronic databases were searched, including PubMed, Cochrane Library, ScienceDirect, Embase, and Web of Science, from the inception to March 1, 2018. Trials that were randomized and compared results between TXA, EACA, and placebo were identified. The NMA was conducted with software R 3.3.2 and STATA 14.0. RESULTS: Thirty randomized controlled trial (RCT) studies were analyzed. Aprotinin (standardized mean difference [SMD]=-0.65, 95% credibility intervals [CrI;-1.25, -0.06]), low-dose TXA (SMD = -0.58, 95% CrI [-0.92, -0.25]), and high-dose TXA (SMD = -0.70, 95% CrI [-1.04, -0.36]) were more effective than the respective placebos in reducing intraoperative blood loss. Low-dose TXA (SMD = -1.90, 95% CrI [-3.32, -0.48]) and high-dose TXA (SMD = -2.31, 95% CrI [-3.75, -0.87]) had less postoperative blood loss. Low-dose TXA (SMD = -1.07, 95% CrI [-1.82, -0.31]) and high-dose TXA (SMD = -1.07, 95% CrI [-1.82, -0.31]) significantly reduced total blood loss. However, only high-dose TXA (SMD = -2.07, 95% CrI [-3.26, -0.87]) was more effective in reducing the amount of transfusion, and was significantly superior to low-dose TXA in this regard (SMD = -1.67, 95% CrI [-3.20, -0.13]). Furthermore, aprotinin (odds ratio [OR] = 0.16, 95% CrI [0.05, 0.54]), EACA (OR = 0.46, 95% CrI [0.22, 0.97]) and high dose of TXA (OR = 0.34, 95% CrI [0.19, 0.58]) had a significant reduction in transfusion rates. Antifibrinolytics did not show a significantly increased risk of postoperative thrombosis. Results of ranking probabilities indicated that high-dose TXA had the greatest efficacy and a relatively high safety level. CONCLUSIONS: The antifibrinolytic agents are able to reduce perioperative blood loss and transfusion requirement during spine surgery. And the high-dose TXA administration might be used as the optimal treatment to reduce blood loss and transfusion.

How does the sagittal spinal balance of the scoliotic population deviate from the asymptomatic population?

BACKGROUND: Previously, the sagittal spinal balance in both asymptomatic and scoliotic Caucasian people has been characterized and compared. Very recently, the sagittal spino-pelvic parameters among asymptomatic Chinese adults have been studied, and the results were compared with Caucasian adults, indicating that a difference did exist. Unfortunately, the distribution of sagittal standing posture patterns among the Chinese population has not been characterized in either asymptomatic or scoliotic groups. METHODS: We conducted a radiographic comparison study to define the deviation of sagittal balance in scoliotic patients from that of an asymptomatic population. A total of 126 asymptomatic and 117 idiopathic scoliotic (IS) young adults were recruited. Radiographic data from each subject were reviewed, and sagittal spinopelvic parameters were measured. The Roussouly type was then determined, as well as the relative position of the C7 plumbline with respect to the sacrum and hip axis. Comparison analyses were undertaken between the two different groups. RESULTS: The IS group had a larger pelvic incidence, pelvic tilt and sacral slope, but a smaller spinal tilt than the asymptomatic group (P < 0.05), while other sagittal parameters were similar. The distribution of Roussouly types was similar between the asymptomatic and IS groups, of which 49.2% and 45.3% belonged to Roussouly Type 3, respectively. Asymptomatic males and females had a similar distribution, which was different between the two genders in the IS group (P < 0.05), with more females possessing a neutral sagittal standing posture. In addition, more IS subjects had forward displacement of the C7 plumbline than asymptomatic ones (P < 0.05), while there was no difference between the two genders in either group. CONCLUSIONS: Although sagittal pelvic parameters were greater in the IS population, their sagittal spinal balance was maintained and there was no sagittal standing posture pattern correlated with IS. The occurrence of anterior displacement of the C7 plumbline was more common in IS patients than asymptomatic adults, but did not appear to be correlated with gender in both populations.

Analysis of Spino-pelvic Sagittal Alignment in Young Chinese Patients with Lumbar Disc Herniation.

OBJECTIVE: Few studies have concentrated on the sagittal alignment of lumbar disc herniation (LDH), especially the parameters of the pelvis, and controversy exists about whether pelvic morphology is involved in the pathogenesis of LDH. The present study analyzed the characteristics of the sagittal alignment in young Chinese LDH patients and explored the impact of pelvic morphology on the pathogenesis of LDH. METHODS: A retrospective analysis was conducted on 100 young patients with LDH (69 men and 31 women, aged 18-35 years), and the clinical and imaging findings met the criteria for the diagnosis of LDH. The control group included 100 asymptomatic volunteers with matching age and gender. Coronal and sagittal parameters were measured on the anteroposterior and lateral radiographs of the whole spine, including lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), thoracic kyphosis (TK), and sagittal balance (SVA). The cases were classified into four types by the apex position of lumbar lordosis (type I, L5 or the L4-5 intervertebral space; type II, bottom or middle of L4 ; type III, upper part of L4 or the intervertebral space between L3 and L4 ; type IV, L3 or more high level), and divided into three groups by PI; namely, a low PI group (PI < 40°), a medium PI group (40° ≤ PI < 50°), and a high PI group (PI ≥ 50°). The sagittal parameters, especially PI, were compared between the LDH group and the control group. Correlations between the parameters in the LDH group were analyzed. RESULTS: The PI value of the LDH group was not different from that of the control group (46.1° ± 10.0° vs 47.2° ± 8.8°, P > 0.05). The LDH group showed lower average LL, SS, and TK (P < 0.01), as well as higher PT and SVA compared with the control group (P < 0.01). The LL (34.4° ± 15.3° vs 50.8° ± 10.2°) and SVA (21.6 ± 53.6 mm vs - 18.4 ± 32.8 mm) showed a significant difference (P < 0.01); LL was correlated with PI, SS, PT, TK and SVA (P < 0.01); and SVA was also correlated with the parameters above (P < 0.01) except PI (P > 0.05), and the lordosis apex tended to be higher. The distributions of PI groups between the LDH group and the control group were not different. Pairwise correlations were found among LL, PI, SS, and PT. In addition, TK and SVA were correlated with LL, SS, and PT. CONCLUSIONS: There is no difference in PI between young Chinese patients with lumbar disc herniation and the normal population. Young LDH patients may present flat lumbar and thoracic curves, as well as lower sacral slope. The anteversion sagittal imbalance is regulated by both the spine and the pelvis.

Effect of patient position on the lordosis and scoliosis of patients with degenerative lumbar scoliosis.

This study aimed to analyze the effect of patient positions on the lordosis and scoliosis of patients with degenerative lumbar scoliosis (DLS).Seventy-seven patients with DLS were retrospectively analyzed. We measured lordosis and Cobb's angle on preoperative upright x-rays and magnetic resonance imagings in supine position. The lordosis and scoliosis of surgical segments in intraoperative prone position were measured on intraoperative radiographs of 20 patients to compare with that in standing position. Paired t tests were performed to investigate the parameters of the sample.From standing to supine position the whole lordosis increased (29.2 ±â€Š15.7 degree vs. 34.9 ±â€Š11.2 degree), and the whole scoliosis decreased (24.3 ±â€Š11.8 degree vs. 19.0 ±â€Š10.5 degree); 53 of 77 (68.8%) cases had increased lordosis, and 67 of 77 (87%) cases had decreased scoliosis. The lordosis of surgical segments in standing position had no difference with that in intraoprerative prone position. But in changing from supine/standing position to intraoprerative prone position, the scoliosis of surgical segments decreased (14.7 ±â€Š9.4 degree vs. 11.4 ±â€Š7.0 degree; 19.0 ±â€Š11.8 degree vs. 11.4 ±â€Š7.0 degree, respectively), and 18 of 20 (90%) cases had decreased scoliosis in intraoperative prone position than that in standing position.Compared with standing position in DLS patients, supine position increased lordosis and reduced scoliosis, and intraoperative prone position reduced scoliosis significantly. When evaluating the severity of DLS and making preoperative surgical plans, lumbar lordosis in supine position should also be evaluated in addition to upright x-ray, and the effects of different positions should be taken into consideration to reduce deviation.

Mercury spikes suggest volcanic driver of the Ordovician-Silurian mass extinction.

The second largest Phanerozoic mass extinction occurred at the Ordovician-Silurian (O-S) boundary. However, unlike the other major mass extinction events, the driver for the O-S extinction remains uncertain. The abundance of mercury (Hg) and total organic carbon (TOC) of Ordovician and early Silurian marine sediments were analyzed from four sections (Huanghuachang, Chenjiahe, Wangjiawan and Dingjiapo) in the Yichang area, South China, as a test for evidence of massive volcanism associated with the O-S event. Our results indicate the Hg concentrations generally vary in parallel with TOC, and that the Hg/TOC ratios remain low and steady state through the Early and Middle Ordovician. However, Hg concentrations and the Hg/TOC ratio increased rapidly in the Late Katian, and have a second peak during the Late Hirnantian (Late Ordovician) that was temporally coincident with two main pulses of mass extinction. Hg isotope data display little to no variation associated with the Hg spikes during the extinction intervals, indicating that the observed Hg spikes are from a volcanic source. These results suggest intense volcanism occurred during the Late Ordovician, and as in other Phanerozoic extinctions, likely played an important role in the O-S event.

Expert consensus for PVCR in severe, rigid and angular spinal deformity treatment: The Kunming consensus.

In the past decades, an increasing number of surgeons started using posterior vertebral column resection (PVCR) to treat severe, rigid and angular spinal deformities. Little high-level evidence is available to guide surgical treatment. The aims of our study were to identify important surgical strategies and key technical points of Chinese experts who have extensive experience in the management of severe, rigid and angular spinal deformities using PVCR, and to standardize and unify the current core concepts. Workgroups of consensus were formed by selecting nationwide representing experts and comprehensive consultations. Eight task forces for major issues were established, then retrieval of literature, collection of expert opinions and writing of review articles were carried out. A modified Delphi process was chosen in round-table forum with three face-to-face meetings. Consensus was reached with items graded more than seven points including: indications and contraindications of PVCR; review PVCR in the evolution of spinal osteotomies; The corrective mechanism and safety of spinal cord; monitoring and responses of spinal cord crisis; characteristics and therapeutic outcome of pulmonary function; management of bleeding during PVCR; relationship of pedicle screw insertion and spinal cord safety; and analysis of non-neurologic complications and prevention strategies. In conclusion, The essential properties regarding PVCR procedure are tightly linked with various factors such as medical and surgical indication, range and level of vertebral column resection, strategies of correction, corrective efficiency and control of neurological risk. PVCR is used mainly for severe, rigid spinal deformity that is not manageable by other osteotomy techniques.

Effects of soil erosion and anoxic-euxinic ocean in the Permian-Triassic marine crisis.

The largest mass extinction of biota in the Earth's history occurred during the Permian-Triassic transition and included two extinctions, one each at the latest Permian (first phase) and earliest Triassic (second phase). High seawater temperature in the surface water accompanied by euxinic deep-intermediate water, intrusion of the euxinic water to the surface water, a decrease in pH, and hypercapnia have been proposed as direct causes of the marine crisis. For the first-phase extinction, we here add a causal mechanism beginning from massive soil and rock erosion and leading to algal blooms, release of toxic components, asphyxiation, and oxygen-depleted nearshore bottom water that created environmental stress for nearshore marine animals. For the second-phase extinction, we show that a soil and rock erosion/algal bloom event did not occur, but culmination of anoxia-euxinia in intermediate waters did occur, spanning the second-phase extinction. We investigated sedimentary organic molecules, and the results indicated a peak of a massive soil erosion proxy followed by peaks of marine productivity proxy. Anoxic proxies of surface sediments and water occurred in the shallow nearshore sea at the eastern and western margins of the Paleotethys at the first-phase extinction horizon, but not at the second-phase extinction horizon. Our reconstruction of ocean redox structure at low latitudes indicates that a gradual increase in temperature spanning the two extinctions could have induced a gradual change from a well-mixed oxic to a stratified euxinic ocean beginning immediately prior to the first-phase extinction, followed by culmination of anoxia in nearshore surface waters and of anoxia and euxinia in the shallow-intermediate waters at the second-phase extinction over a period of approximately one million years or more. Enhanced global warming, ocean acidification, and hypercapnia could have caused the second-phase extinction approximately 60 kyr after the first-phase extinction. The causes of the first-phase extinction were not only those environmental stresses but also environmental stresses caused by the soil and rock erosion/algal bloom event.

Clinical Guideline for Treatment of Symptomatic Thoracic Spinal Stenosis.

Thoracic spinal stenosis is a relatively common disorder causing paraplegia in the population of China. Until nowadays, the clinical management of thoracic spinal stenosis is still demanding and challenging with lots of questions remaining to be answered. A clinical guideline for the treatment of symptomatic thoracic spinal stenosis has been created by reaching the consensus of Chinese specialists using the best available evidence as a tool to aid practitioners involved with the care of this disease. In this guideline, many fundamental questions about thoracic spinal stenosis which were controversial have been explained clearly, including the definition of thoracic spinal stenosis, the standard procedure for diagnosing symptomatic thoracic spinal stenosis, indications for surgery, and so on. According to the consensus on the definition of thoracic spinal stenosis, the soft herniation of thoracic discs has been excluded from the pathological factors causing thoracic spinal stenosis. The procedure for diagnosing thoracic spinal stenosis has been quite mature, while the principles for selecting operative procedures remain to be improved. This guideline will be updated on a timely schedule and adhering to its recommendations should not be mandatory because it does not have the force of law.

Progress on clinical characteristics and identification of location of thoracic ossification of the ligamentum flavum.

Thoracic ossification of the ligamentum flavum (TOLF) is the most common cause for thoracic spinal stenosis. TOLF is usually complicated by thoracic disc herniation, ossification of the posterior longitudinal ligament and degenerative spinal diseases such as cervical spondylosis and lumbar spinal stenosis, and the ossification also usually has a discontinuous or continuous multi-segment distribution. The resultant superposition of several symptoms makes the clinical manifestations complex. Currently, the diagnosis of TOLF depends mainly on the patient's symptoms, physical examination and thoracic CT and MRI examinations. Identification of the location of TOLF depends more on the doctor's subjective judgement. Diagnostic problems are related to the specific region and level of surgical decompression: if the extent of decompression is insufficient, the treatment is inadequate, resulting in residual symptoms. Obversely, unnecessary trauma and a various complications will occur if the decompression is too extensive. Hence, the clinical features and process of diagnosis, especially the means of identifying the location, still require further improvement. It is necessary to establish a simple and accurate means of identifying the segment of TOLF that is responsible for the neurologic deficit: a number of spinal surgeons have been working hard on this. This article will provided an overview of the clinical features of TOLF and the related problems of clinical identification of the location of the segment causing the neurological deficit. The relationship between the imaging manifestations and clinical characteristics still need to be explored with the aim of establishing a simple and precise method for determining precisely whether TOLF is related to spinal cord injury or not, thus reducing surgical trauma and achieving an optimal prognosis.

Recombinant human bone morphogenetic protein-2-induced ossification of the ligamentum flavum in rats and the associated global modification of histone H3.

OBJECT: The primary object of this investigation was to study recombinant human bone morphogenetic protein-2 (rhBMP-2)-induced ossification of the ligamentum flavum and associated histone H3 modification in a rat model. In an additional set of studies the authors investigated spinal cord and behavioral changes in the same model. METHODS: The authors report on 2 separate sets of studies. A total of 90 rats were used for the 2 sets of studies (45 each); in each study, a lyophilized rhBMP-2 and collagen mixture (20 µg rhBMP-2 and 200 µl collagen) was implanted in the lumbar extradural space in 18 rats; another 18 animals were used for a sham-operation control group and underwent implantation of lyophilized collagen without rhBMP-2 at the same level; an additional 9 animals were used as untreated controls. Lumbar spinal samples were harvested from the rhBMP-2 groups and the shamoperation control groups at 1 week, 3 weeks, and 9 weeks after the operation. Samples were also obtained from untreated controls at the same time points. All samples were scanned using micro-CT and then made into paraffinembedded sections. The sections from the first set of 45 rats were stained using elastica van Gieson and toluidine blue, and the expression of histone modifications (H3K9ac, H3K18ac, H3K4me3, and H3K36me3) and osteogenic transcription factors (osterix, Runx2) was detected by immunohistochemistry. In the second set of studies, hindlimb motor function was assessed at 1 week, 3 weeks, and 9 weeks after surgery. After behavioral evaluation, samples were harvested, scanned using micro-CT, and then made into paraffin-embedded sections. The sections were stained using Luxol fast blue. The expression of NeuN was also detected using immunohistochemistry. RESULTS: Ossification was seen in the rhBMP-2 group from 1 week after insertion, and the volume of ossified mass increased at 3 and 9 weeks. There was no ossification seen in the sham-surgery and normal controls. The pathological changes of ossification involved ligament degeneration, cartilage formation, and, finally, bone replacement. Spinal cord evaluation showed a significant decrease in white matter content and number of neurons at 9 weeks after operation in the rhBMP-2-treated group (compared with findings in the sham-surgery and control groups as well as findings at the earlier time points in the rhBMP-2 group). Using immunohistochemical staining, histone modifications (H3K9ac, H3K18ac, H3K4me3, and H3K36me3) and osteogenic transcription factors (osterix, Runx2) all were found to be expressed in the fibrocartilage area of the rat ossified ligamentum flavum samples (rhBMP2 group). CONCLUSIONS: This rhBMP-2-induced OLF is a typical endochondral ossification, which is similar to clinical OLF. The compressed spinal cord around the ossification site showed signs of a chronic degenerative process. Histone H3 modifications (H3K9ac, H3K18ac, H3K4me3, and H3K36me3) may play an important role in OLF.

Nothosaur foraging tracks from the Middle Triassic of southwestern China.

The seas of the Mesozoic (266-66 Myr ago) were remarkable for predatory marine reptiles, but their modes of locomotion have been debated. One problem has been the absence of tracks, although there is no reason to expect that swimmers would produce tracks. We report here seabed tracks made by Mesozoic marine reptiles, produced by the paddles of nothosaurs (Reptilia, Sauropterygia) in the Middle Triassic of the Luoping localities in Yunnan, southwestern China. These show that the track-making nothosaurs used their forelimbs for propulsion, they generally rowed (both forelimbs operating in unison rather than alternately), and the forelimb entered medially, dug in as the paddle tip gained purchase, and withdrew cleanly. These inferences may provide evidence for swimming modes, or it could be argued that the locomotory modes indicated by the tracks were restricted to such contact propulsion. Such punting behaviour may have been used to flush prey from the bottom muds.

A comparison of pelagic, littoral, and riverine bacterial assemblages in Lake Bangongco, Tibetan Plateau.

Lakes of the Tibetan Plateau lack direct anthropogenic influences, providing pristine high-altitude (> 4000 m) sites to study microbial community structure. We collected samples from the pelagic, littoral, and riverine zones of Lake Bangongco, located on the western side of the Plateau, to characterize bacterial community composition and geochemistry in three distinct, but hydrologically connected aquatic environments during summer. Bacterial community composition differed significantly among zones, with communities changing from riverine zones dominated by Bacteroidetes to littoral and pelagic zones dominated by Gammaproteobacteria. Community composition was strongly related to the geochemical environment, particularly concentrations of major ions and total nitrogen. The dominance of Gammaproteobacteria in the pelagic zone contrasts with typical freshwater bacterial communities as well as other lakes on the Tibetan Plateau.

Epidemiological survey of ossification of the ligamentum flavum in thoracic spine: CT imaging observation of 993 cases.

OBJECTIVE: To investigate the characteristics of epidemiological distribution of the ossification of the ligamentum flavum (OLF) in the thoracic spine including the incidence, segmental distribution, and shape. METHODS: Chest spiral computed tomography scans of 993 cases (male 506, female 487, mean age 60 years, range 5-102 years) who presented due to chest symptoms were analyzed with axial slices combined with sagittal slices. The conditions of OLF in the thoracic spine, including segments, thickness, location, and dural sac compression, were recorded. Prevalence was standardized according to the "Age Structure of Population in Beijing 2008". RESULTS: Among the population investigated, the standardized prevalence rate was 63.9 %. The standardized prevalence rate for males (68.5 %) was higher than that for females (59.0 %). The highest prevalence rate of OLF was in the 50-59 years age group (79.2 %); however, high density originated it can be found in individuals aged 10-19 years. The comparison of different thoracic segments showed that T10-11 (44.0 %) and T11-12 (41.6 %) had the highest prevalence rates. CONCLUSION: The prevalence of ossification of the ligamentum flavum was highest in the 50-59 years group, but also occurred in early years. OLF occurs more frequently in the lower than in the upper and middle thoracic regions and its prevalence increases with aging.