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  • 1
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: S-Adenosyl-l-methionine decarboxylase (SAMdc) and l-ornithine decarboxylase (ODC) are major enzymes regulating polyamine synthesis. Following ischemia, putrescine content increases as a result of post-traumatic activation of ODC and inhibition of SAMdc. These alterations are thought to mediate edema and cell death. The purpose of this study was to quantify SAMdc activity and edema in the brain following controlled cortical impact injury. Anesthetized adult male rats underwent a right parietal craniectomy and were subjected to cortical impact injury. Tissues were obtained from three bilateral regions: parietal cortex, motor area (CPm); parietal cortex, somatosensory area (CPs); and the pyriform cortex (CPF). SAMdc activity was determined in the postmitochondrial fraction from homogenates of fresh, unfrozen tissues by measuring the decarboxylation of S-adenosyl-l-[carboxyl-14C]methionine. Basal SAMdc activity was determined in unoperated rats, and regional differences were noted: Activity was lower in the CPF than in the CPm and CPs. SAMdc activity decreased to the greatest extent in the ipsilateral CPm (impact site) from 1 to 72 h following traumatic brain injury. Significant edema was found in the ipsilateral CPm 1, 8, 16, 24, and 48 h after injury. Decreased SAMdc activity impairs the conversion of putrescine to polyamines and may contribute to delayed pathological changes in the brain after traumatic injury.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Neurochemical research 16 (1991), S. 89-94 
    ISSN: 1573-6903
    Schlagwort(e): Amino acid neurotransmitters ; spinal cord ; transcranial stimulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The present study used microdialysis techniques in an intact rabbit model to measure the release of amino acids within the lumbar spinal cord in response to transcranial electrical stimulation. Dialysis samples from the extracellular space were obtained over a stimulation period of 90 minutes and were examined using high pressure liquid chromatography. Neuronal excitation was verified by recerding corticomotor evoked potentials (CMEPs) from the spinal cord. A significant increase in the release of glycine and taurine compared to sham animals was measured after 90 minutes of transcranial stimulation. Glutamate and aspartate release was not significantly elevated. GABA concentrations were consistently low. CMEP components repeatedly showed adequate activation of descending fiber pathways and segmental interneuron pools during dialysis sampling. Since glycine, and to a lesser extent taurine, have been shown to inhibit motor neuron activity and are closely associated with segmental interneuron pools, suprasegmental modulation of motor activity may be, in part, through these inhibitory amino acid neurotransmitters in the rabbit lumbar spinal cord.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1573-6903
    Schlagwort(e): Glycine ; NMDA ; thermal receptors ; neuropathic pain
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We have previously shown in animal models that enhanced segmental glycine release is produced by neuroaugmentation techniques commonly used to control pain in humans. Our current hypothesis is that glycine administered intrathecally reduces the pain response evoked by the hotplate analgesia meter method. Neuropathic rats created by unilateral partial ligation of the sciatic nerve were treated with intrathecal infusion of glycine, strychnine, MK-801, or 5–7 DKA at 0.1 μmol for 2 hours at a rate of 10 μl/min. Time required for limb withdrawal at 42°C was significantly increased after glycine administration but not altered by strychnine, a specific glycine receptor antagonist. Administration of the NMDA receptor antagonist, MK-801, blocked the influence of glycine, with a less obvious antagonistic response from 5,7 DKA. Our results provide evidence that glycine and related compounds significantly modify thermal hyperalgesia, and may operate primarily through the NMDA receptor complex.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Neurochemical research 15 (1990), S. 635-639 
    ISSN: 1573-6903
    Schlagwort(e): Excitatory amino acids ; spinal cord ischemia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Excitatory amino acids have been implicated in the production of calcium mediated neuronal death following central nervous system ischemia. We have used microdialysis to investigate changes in the extracellular concentrations of amino acids in the spinal cord after aortic occlusion in the rabbit. Glutamate, aspartate, glutamine, asparagine, glycine, taurine, valine, and leucine were measured in the micordialysis perfusate by high pressure liquid chromatography. The concentrations of glutamate, glycine, and taurine were significantly higher during ischemia and reperfusion than controls. Delayed elevations in the concentrations of asparagine and valine were also detected. The elevation of glutamate is consistent with the hypothesis that excitotoxins may mediate neuronal damage in the ischemic spinal cord. Increased extracellular concentrations of asparagine and valine may reflect preferential use of amino acids for energy metabolism under ischemic conditions. The significance of increased concentrations of inhibitory amino acid neurotransmitters is unclear.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Neurochemical research 18 (1993), S. 887-892 
    ISSN: 1573-6903
    Schlagwort(e): Glycine ; spinal shock ; spasticity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Amino acid neurotransmitters (AANTs) play a major role in maintenance of muscle tone. Abnormal AANT concentrations are associated with hyper- or hypotonic states. Flaccidity from spinal shock commonly occurs after spinal cord injury (SCI) and may be associated with changes in AANT concentrations. Ischemic SCIs created in the lumbar region of rabbits by intraaortic balloon occlusion produced spastic or flaccid injuries. Microdialysis sampling of AANTs from the injured segmental structures was done 3 days after SCI. Evoked potentials were used to monitor spinal cord stability. No significant changes in AANT levels occurred in the spastic or flaccid group after 4 hour sampling. However, flaccid animals had baseline glycine levels 2–3 times higher (p〈0.001) than spastic animals or controls. High concentrations of the inhibitory AANT glycine is associated with flaccidity following SCI, or spinal shock, but not spasticity. Glycinergic compounds directed toward suppression of excess muscle tone deserve further study.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1573-6903
    Schlagwort(e): Intrathecal infusion ; glycine ; strychnine ; NMDA ; spasticity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Spasticity is a frequent and complex sequel to spinal cord injury. The neurochemical basis for the origin of spasticity is largely unknown. Glycine is among the most abundant neurotransmitters in the spinal cord. However, the role of glycine and related compounds in spasticity have received little attention. An ischemic spinal cord injury was created in rabbits, by an intraaortic balloon occlusion technique, which produced lower limb spasticity. A catheter was inserted into the cisterna magna and the spinal cord was bathed with 100 μM solutions of glycine, strychnine,d-serine, β-alanine, MK-801, or artificial CSF for 4 hours at a rate of 10 μl/min. H-reflexes were monitored before and during infusion by stimulating the posterior tibial nerve and recording from the plantar surface of the foot. Glycine,d-serine, and MK-801 depressed the H wave, strychnine produced a heightened H wave, and β-alanine caused no significant changes. These results indicate that glycine and related compounds may influence spasticity.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of clinical monitoring and computing 12 (1996), S. 285-291 
    ISSN: 1573-2614
    Schlagwort(e): Head injury ; oxygen saturation ; jugular bulb catheter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Medizin
    Notizen: Abstract Objectives. Monitoring jugular venous oxygen saturation (SjvO2) has been useful for the early identification and treatment of cerebral ischemia in patients with severe head injury. However, the catheters that have been used for this purpose have not performed optimally. The purpose of this study was to evaluate the performance of a new regional oxygen saturation catheter for monitoring SjvO2.Methods. Eighteen regional oxygen saturation catheters, 4-Fr in diameter (Baxter Healthcare Corporation, Edward Critical Care), were used in this study. Each catheter was inserted percutaneously into the dominant jugular vein and the catheter's tip position in the jugular bulb was verified by radiograph. The catheter was calibratedin vitro prior to insertion using the optic calibrator provided by the manufacturer. The catheter was recalibrated every 8 to 12 hours by comparing the oxygen saturation value from the catheter with that measured by a cooximeter in a blood sample drawn through the catheter.Results. In vitro calibration using the optic calibrator was not always successful. Five catheters could not be calibrated. The remaining 13 catheters could all be calibrated, but only 9 provided a value that was within 4% of the oxygen saturation derived from the blond sample. After the firstin vivo calibration, the correlation between the catheter and the blond sample values was improved. A total of 196 comparisons were made. The median, 25th, and 75th quartile differences between the catheter and the blond sample measurement of SjvO2 were 0.00, −1.15, and 1.25%, respectively. Using longitudinal data regression, the overall slope of the regression between the catheter and blood values was 0.997 (p = 0.001).Conclusions. The new regional oxygen saturation catheter provided reliable measurement of SjvO2 83% of the time when the signal quality index was ≤3, and may be useful for continuous monitoring of SjvO2.
    Materialart: Digitale Medien
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