3,058 research outputs found
A morphological study of the effects of cycloleucine on the central and peripheral nervous systems of the mouse
Cycloleucine (CL) is a very potent inhibitor of S-adenosyl
methionine transferase causing a rapid decline in CNS S-adenosyl
methionine levels and increase in methionine in the nervous system.
CL interrupts the transmethylation reaction in the CNS similar to that
caused by deficiency of vitamin B12 or folic acid. CL was administered as a single dose intraperitoneally (2mg/g
body weight) to mice of varying ages (21 days - 5 months). The 21
day old mice given CL 2mg/g body weight showed evidence of
toxicity within 24 hours and thereafter developed progressive muscle
weakness and ataxia. Animals did not survive longer than 1 week.
Light and electron microscopic examination o f the central and
peripheral nervous systems, from 12 hours to 7 days post-injection
showed that intramyelinic vacuolation developed in the white matter
of brain and cord within 12 hours but no myelin vacuolation occurred
in peripheral nerves. Axonal lesions in the distal parts of motor
nerves occurred within 1 2 - 2 4 hours resulting in degeneration of
intramuscular nerve fibres and terminals. Motor end-plates became
denervated. There was no degeneration of motor or sensory nerves
in the muscle spindles. Later there was evidence of axonal
degeneration in tibial and sciatic nerves. Many dorsal root ganglion
cells became vacuolated or necrotic three days after administration of
CL and numerous degenerated fibres were noted in the white matter
of the spinal cord, especially in funiculus gracilis. The intramyelinic
vacuolation in the white matter of brain and cord persisted and
became more severe during the course of the experiment.
In adult mice (6 weeks - 5 months) the pathology consisted
mainly of distal motor axonal degeneration which developed at 1 - 2
days. Only slight intramyelinic vacuolation in white matter was
noted. At 3 days later, numerous degenerated fibres were seen in the
posterior columns of cervical cord, especially in the funiculus gracilis. In a second series of experiments valine (3 mg/g body weight)
was given every 12 hours for 6 doses beginning either 24 or 48 hours
after CL. Valine (VL) is a very effective antidote against cycloleucine
and reversed its toxicity. The intramyelinic vacuolation disappeared
from the white matter in the CNS leaving little residual pathology.
Regenerating axons and remyelinated fibres were found in previously
degenerated distal peripheral nerves and denervated motor end-plates.
The reinnervation took place more rapidly in animals given VL from 24
hours after CL than 48 hours after CL.
In conclusion it can be stated that CL causes a distal motor
axonopathy and sensory ganglion cell necrosis in addition to the
previously reported myelinic vacuolation in the CNS. The mechanism
of toxicity of CL is likely to be related to the failure of
transmethylation processes affecting particularly myelin basic protein
and perhaps membrane turnover at active sites of transmitter release
such as the neuromuscular junction
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The Association between Virus Prevalence and Intercolonial Aggression Levels in the Yellow Crazy Ant, Anoplolepis Gracilipes (Jerdon).
The recent discovery of multiple viruses in ants, along with the widespread infection of their hosts across geographic ranges, provides an excellent opportunity to test whether viral prevalence in the field is associated with the complexity of social interactions in the ant population. In this study, we examined whether the association exists between the field prevalence of a virus and the intercolonial aggression of its ant host, using the yellow crazy ant (Anoplolepis gracilipes) and its natural viral pathogen (TR44839 virus) as a model system. We delimitated the colony boundary and composition of A. gracilipes in a total of 12 study sites in Japan (Okinawa), Taiwan, and Malaysia (Penang), through intercolonial aggression assay. The spatial distribution and prevalence level of the virus was then mapped for each site. The virus occurred at a high prevalence in the surveyed colonies of Okinawa and Taiwan (100% infection rate across all sites), whereas virus prevalence was variable (30%-100%) or none (0%) at the sites in Penang. Coincidentally, colonies in Okinawa and Taiwan displayed a weak intercolonial boundary, as aggression between colonies is generally low or moderate. Contrastingly, sites in Penang were found to harbor a high proportion of mutually aggressive colonies, a pattern potentially indicative of complex colony composition. Our statistical analyses further confirmed the observed correlation, implying that intercolonial interactions likely contribute as one of the effective facilitators of/barriers to virus prevalence in the field population of this ant species
Analysis of blast-induced ground vibration under surface explosion
The blasting operation is vital in the construction of tunnels and channels or in mining when encountering hard geological environments to facilitate the progress of a project. The level and range of damage due to the blast are affected by the energy of shock waves generated after explosion. The control of seismic damage is a major issue in blasting engineering and cannot be neglected. The stratum layer or buildings on the earthâs surface can be damaged when blasting-induced vibration strength exceeds the allowed range. In order to reduce the degree of damage, the patterns of blasting vibration must be studied and controlled. Therefore, the propagation characteristics of shock waves on the earthâs surface are important factors to be studied before the planning and designing of a project. This paper adopted a mutual verification method between the blasting experiment and numerical analysis results for verifying the reliability of numerical simulation based on experimental data. The numerical analysis method analyzed the dynamic mechanical behavior of blasting vibration using the finite element method. The LS-DYNA program was used to simulate TNT explosive and surface contact blasting in semi-infinite space and in propagation of the resulting seismic waves. The propagation characteristics, represented by temporal and spatial changes of surface acceleration, were investigated. The analysis results showed that post-explosion dynamic characteristics of the earthâs surface simulated by finite element method yielded promising simulation results. In addition, the propagation characteristics of stress waves were observed from the dynamic mechanical behavior of surface acceleration after explosion. That is, the maximum main stress presented a pattern of progressive attenuation with increasing distance from the blasting source. The results are able to provide reference for the protection of engineering structures from blasting vibration damages
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Semiautomated optical coherence tomography-guided robotic surgery for porcine lens removal.
PurposeTo evaluate semiautomated surgical lens extraction procedures using the optical coherence tomography (OCT)-integrated Intraocular Robotic Interventional Surgical System.SettingStein Eye Institute and Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, USA.DesignExperimental study.MethodsSemiautomated lens extraction was performed on postmortem pig eyes using a robotic platform integrated with an OCT imaging system. Lens extraction was performed using a series of automated steps including robot-to-eye alignment, irrigation/aspiration (I/A) handpiece insertion, anatomic modeling, surgical path planning, and I/A handpiece navigation. Intraoperative surgical supervision and human intervention were enabled by real-time OCT image feedback to the surgeon via a graphical user interface. Manual preparation of the pig-eye models, including the corneal incision and capsulorhexis, was performed by a trained cataract surgeon before the semiautomated lens extraction procedures. A scoring system was used to assess surgical complications in a postoperative evaluation.ResultsComplete lens extraction was achieved in 25 of 30 eyes. In the remaining 5 eyes, small lens pieces (â€1.0 mm3) were detected near the lens equator, where transpupillary OCT could not image. No posterior capsule rupture or corneal leakage occurred. The mean surgical duration was 277 seconds ± 42 (SD). Based on a 3-point scale (0 = no damage), damage to the iris was 0.33 ± 0.20, damage to the cornea was 1.47 ± 0.20 (due to tissue dehydration), and stress at the incision was 0.97 ± 0.11.ConclusionsNo posterior capsule rupture was reported. Complete lens removal was achieved in 25 trials without significant surgical complications. Refinements to the procedures are required before fully automated lens extraction can be realized
Non-destructive quantitation of spermine in human prostate tissue samples using HRMAS 1H NMR spectroscopy at 9.4 T
AbstractWe present the results of a study of human prostate specimens evaluated by high resolution magic angle spinning 1H nuclear magnetic resonance (NMR) spectroscopy at 400 MHz (9.4 T) and by quantitative histopathology. We demonstrate that NMR and pathology data can be obtained from the same intact specimens, and report for the first time a linear correlation between the NMR measured concentration of spermine, a proposed endogenous inhibitor to prostate cancer growth, and the volume percentage of normal prostatic epithelial cells as quantified by histopathology. Our results show that NMR may serve as a critical tool for the investigation of the inhibitory mechanism of spermine in human subjects
The complete mitochondrial genome of a parthenogenetic ant Monomorium triviale (Hymenoptera: Formicidae)
Monomorium is one of the most species-rich yet taxonomically problematic ant genus. An East Asian species, M. triviale Wheeler, W.M., 1906, is reproduced by obligate thelytokous parthenogenesis and performs strict reproductive division of labor. We sequenced the M. triviale mitogenome using next-generation sequencing methods. The circular mitogenome of M. triviale was 16, 290âbp in length, consisting of 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNAs, and a single non-coding region of 568âbp. The base composition was AT-biased (82%). Gene order rearrangements were detected and likely to be unique to the genus Monomorium. We announce the M. triviale mitogenome as additional genomic resources for elucidating phylogenetic and taxonomic problems of Monomorium and comparative genomics of parthenogenetic ant species
EVALUATION OF ELBOW AND FOREARM MOTION BETWEEN SIDEARM AND OVERHAND PITCHING
This study is to analyze the differences in kinematics, electromyography (EMG) and ultrasonography between two types of pitchers. We intend to observe and simulate the muscles around glenohumeral and elbow joints in different pitching motions and hope to discover the connections and differences in between. 12 pitchers from the top level were recruited. Larger elbow flexion was found in sidearm pitchers during the acceleration phase. Decrease of the distance of nerve to medial epicondyle was also found as the elbow moved to a more flexed position. More anterior translation of the ulnar nerve might occur during acceleration phase. Slightly lower flexor carpi radialis (FCR) activity was displayed in sidearm pitchers, showing that FCR might play a less crucial role in protecting medial elbow by providing less varus torque
A General Procedure for the Regioselective Synthesis of Aryl Thioethers and Aryl Selenides Through CâH Activation of Arenes
A general procedure for the synthesis of aryl thioethers and aryl selenides in one-pot through sequential iridium-catalyzed CâH borylation and copper-promoted CâS and CâSe bond formation is described. Functional groups including chloro, nitro, fluoro, trifluoromethyl, and nitrogen-containing heterocycles were all tolerated under the reaction conditions. Importantly, not only aryl thiols and selenides but also their alkyl analogs were suitable coupling partners, and the products were obtained in good yields with high meta regioselectivity
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