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  • 1
    ISSN: 1432-1106
    Keywords: Key words Medial geniculate nucleus ; Brachium of the inferior colliculus ; AP5 ; CNQX ; NMDA-mediated synaptic transmission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Previous work from this laboratory has demonstrated that monosynaptic inputs from the brachium of the inferior colliculus (BIC) to the medial subdivision of the medial geniculate nucleus (mMG) strengthen as a result of associative conditioning with an acoustic conditioned stimulus (i.e., fear conditioning). One model that has been proposed to underlie certain types of neuronal plasticity involves the recruitment of N-methyl-d-aspartic acid (NMDA)-type glutamate receptors. The purpose of the present study was to examine the relative contributions of glutamatergic NMDA and non-NMDA receptors to synaptic transmission within this pathway. Individual contributions of the specific receptor types were assessed through the use of 2-amino-5-phosphonovaleric acid (AP5), a selective NMDA receptor antagonist, and 6-cyano-5-nitroquinoxaline-2,3-dione (CNQX), a non-NMDA receptor antagonist. Bipolar stimulating electrodes were stereotaxically implanted in BIC and recording electrodes (attached to dual 32-gauge cannulae for delivery of drug) were positioned in mMG of New Zealand albino rabbits. Single pulses (150 µs, 100–350 µA) delivered to BIC resulted in short-latency (〈4 ms) responses in mMG. BIC-evoked single-unit activity was recorded from mMG before, during, and at several intervals after injection of AP5, CNQX, and/or artificial cerebrospinal fluid (ACSF). Injection of either AP5 or CNQX, but not ACSF, significantly attenuated the short-latency BIC-evoked responses in the vast majority of cells tested. These findings suggest that the monosynaptic pathway from BIC to mMG is glutamatergic and that this pathway frequently employs NMDA-type receptors during electrically stimulated synaptic transmission. Due to the NMDA receptors’ proposed role in plasticity (e.g., long-term potentiation), these results may have implications for understanding the mechanisms of synaptic plasticity observed at this synapse during associative learning.
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  • 2
    ISSN: 1432-0932
    Keywords: Key words Vascularized bone graft ; Spinal reconstruction ; Vertebrectomy ; Kyphosis ; Vessel anastomosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In selected spinal deformities the use of a vascularized graft to establish fusion may be considered: compared to a non-vascularized graft it has superior mechanical properties, resulting in greater graft strength and stiffness, and greater effectiveness in facilitating union. Eight patients with a progressive spinal deformity (four cases) and malignancy (four cases) were treated with resection and/or correction and stabilization. To facilitate (multi)level fusion vascularized fibular grafts were used in two cervical and two thoracolumbar deformities. Fibular (two cases) or iliac grafts (two cases) were used in four cases of spinal reconstruction after vertebrectomy for malignancy. In all patients complete incorporation of the graft was obtained within 5 weeks to 8 months postoperatively. Complications occurred in three cases: one patient had a transient laryngeal edema and laryngeal nerve palsy. Another patient had a non-fatal deep vein thrombosis with pulmonary embolisms, successfully treated with anticoagulants. A third patient developed a lung infection and subsequently a deep infection around the dorsal instrumentation; after hardware removal the infection was controlled. At the latest follow-up (mean 30 months, range 24– 48 months) six out of eight patients are alive. One patient died 2.5 years after the intervention due to widespread metastases, while another patient died in the postoperative period due to unknown reasons. Vascularized bone graft in spinal surgery facilitates primary mechanical stability and rapid fusion, and it has higher resistance to infection. The variety of applications of a vascularized graft may extend the range of indications for the use of grafts in spinal surgery.
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  • 3
    ISSN: 1573-9686
    Keywords: Biomimetics ; Pneumatic artificial muscles ; Neural networks ; Motor control ; Human movment control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract This paper reports the design, construction, and testing of a replica of the human arm, which aims to be dynamically as well as kinematically accurate. The arm model is actuated with McKibben pneumatic artificial muscles, and controlled by a special purpose digital signal processing system designed to simulate spinal neural networks in real time. An artificial muscle spindle has also been designed and tested. Design and test data are reviewed, and the paper describes how we hope to use the system to improve our understanding of the reflexive control of human movement and posture.
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  • 4
    ISSN: 1573-9686
    Keywords: Neuromuscular ; Muscle mechanics ; Muscle spindle ; Posture ; Movement ; Stability ; Biomechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract This paper extends the systematic approach described in Winters and Stark (62) for developing muscle models. The underlying motivation is our finding that for larger scale shoulder and head-neck postural systems to be mechanically stable, open-loop muscle properties are often not sufficient. There are three primary contributions. First, the previous muscle mechanical model structure and parameter estimation process of (62) is updated to reflect recent experimental findings. Second, an intrafusal (IF) muscle model is developed that includes a γ static motoneuron (MN) drive, a Hill muscle model, and a muscle spindle sensor across the IF series element; this provides a more appropriate muscle spindle output signal, especially for studies of posture. Third, the conceptual cut between the neurocontrol input and the actuator is raised from just below the MN summing junction to a higher location, allowing a “musclereflex actuator” to be defined that satisfies the formal theoretical requirement for possessing passive spring-like behavior when the neurocontrol input is constant. α−ψ MN coactivation is assumed, and three types of intrinsic autogenic reflex responses (spindle, Golgi tendon organ, Rhenshaw cell) are developed. Default feedback gains are set based on the criteria that inherent feedback should not sculpt the feedforward excitation drive by more than ±10% of maximum. This new actuator model only mildly affects voluntary goal-directed dynamic performance, but enhances spring-like performance around the postural equilibrium state, in line with available animal and human studies and with several theories on postural regulation.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 0-0 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
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  • 6
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
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  • 7
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The anaerobic fungus Neocallimastix frontalis L2 does not carry out oxidative phosphorylation but instead obtains energy from a fermentative metabolism. It does not have mitochondria, but does contain specialised redox organelles, the hydrogenosomes. With the aid of confocal laser scanning microscopy, we were able to follow the compartmentalisation of the ΔpH probe BCECF-AM (bis-(3-propyl-5-oxoisoxazol-4-yl)pentamethine(oxonolVi),2′,7′-bis-(2-carboxyethyl)-5-carboxyfluorescein acetomethyl ester) into hydrogenosomes in situ. Association of the Ca2+-specific dye Fluo-3AM (1-[2-amino-5-(2,7-dichloro 6-hydroxy-3-oxy-9-xanthenyl)-phenoxyl]-2-[2-amino-5-methylphenoxy]ethane-N,N,N′,N′-tetraacetic acid acetomethyl ester) within the lumen of the hydrogenosomes was also observed. In addition, transmission electron microscopy revealed that the hydrogenosomes contained electron-dense inclusions. X-ray microanalysis of these granules indicated the presence of calcium and phosphate. Our results indicate that hydrogenosomes from N. frontalis L2 maintain an internal alkaline pH and are involved in the calcium regulation of the cell. These physiological features resemble those of mitochondria from aerobic fungi.
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  • 8
    ISSN: 1573-904X
    Keywords: supercritical fluid antisolvent ; protein precipitation ; secondary structure ; solid state ; long-term storage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The long-term and high-temperature storage of dry, micron-sized particles of lysozyme, trypsin, and insulin was investigated. Subsequent to using supercritical carbon dioxide as an antisolvent to induce their precipitation from a dimethylsulfoxide solution, protein microparticles were stored in sealed containers at -25, -15, 0, 3, 20, 22, and 60°C. The purpose of this study was to investigate the suitability of supercritical antisolvent precipitation as a finishing step in protein processing. Methods. Karl Fisher titrations were used to determine the residual moisture content of commercial and supercritically-processed protein powders. The secondary structure of the dry protein particles was determined periodically during storage using Raman spectroscopy. The proteins were also redissolved periodically in aqueous buffers and assayed spectrophotometrically for biological activity and by circular dichroism for structural conformation in solution. Results. Amide I band Raman spectra indicate that the secondary structure of the protein particles, while perturbed from that of the solution state, remained constant in time, regardless of the storage temperature. The recoverable biological activity upon reconstitution for the supercritically-processed lysozyme and trypsin microparticles was also preserved and found to be independent of storage temperature. Far UV circular dichroism spectra support the bioactivity assays and further suggest that adverse structural changes, with potential to hinder renaturation upon redissolution, do not take place during storage. Conclusions. The present study suggests that protein precipitation using supercritical fluids may yield particles suitable for long-term storage at ambient conditions.
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  • 9
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Protocols for in situ hybridization (ISH) of cultured cells often include storage in alcohol at −20°C between fixation of the cultures and the ISH procedure. In experiments aimed at localizing ferritin mRNA in C2 muscle cultures by ISH with digoxigenin-labelled riboprobes, we have noticed that omission of the ethanol storage dramatically changed the pattern of mRNA localization. In cultures stored in 50%, 70%, or 90% ethanol for at least 15 min, ferritin signal was stronger on myotubes than myoblasts but was uniformly distributed over both. In untreated cultures, the signal was patchy, concentrated on the extremities of the elongated myoblasts and very sparse in myotubes. Similar results were obtained with a probe to β-actin used as a control, except that signal was higher in myoblasts in all conditions. When the probes were reduced in size to 〈100 bases from 561 for ferritin and 1150 for actin, the pattern became uniform, regardless of prehybridization treatment. The patchy pattern disappeared when cells were treated with RNase A following hybridization, suggesting that it is non-specific, despite its absence in cultures hybridized with a sense probe. We conclude that incomplete access of RNA probes can result not only in a reduced ISH signal but also in artefactual patterns of mRNA localization.
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  • 10
    ISSN: 1573-7705
    Keywords: NETWORK MANAGEMENT ; RMON ; SNMP ; MIB ; INTERNETWORK
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The Remote network-MONitoring (RMON) standard isa valuable addition to the Simple Network ManagementProtocol (SNMP), providing network managers withimportant global network information. Unlike SNMPagents, RMON agents operate in promiscuous mode andprocess all packets traversing the local net. The RMONmanagement information base (MIB) supplements the SNMPMIB-II standard MIB. We present common network problems that cannot be solved using existing MIB-II orRMON objects. To solve these problems, we developextensions to the RMON matrix group to gather networklayer statistics that result in a view of packet traffic beyond the local network. Our extensionsincrease the ability to analyze and solve networkconfiguration problems and perform troubleshooting. Wedemonstrate our results by implementing and analyzingtwo “live” internetworking problems. Datacollected from these experiments showed that networktraffic patterns can be isolated by individual subnets,thus more easily identifying sources ofcongestion.
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