Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Stochastic processes in postural center-of-pressure profiles (1997)
    Springer
    Experimental brain research 113 (1997), S. 158-164 
    Details
    ISSN: 1432-1106
    Keywords: Posture ; Center of pressure ; Stochastic processes ; Development ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The stochastic processes of postural center-of-pressure profiles were examined in 3- and 5-year-old children, young adult students (mean 20 years), and an elderly age group (mean 67 years). Subjects stood still in an upright bipedal stance on a force platform under vision and nonvision conditions. The time evolutionary properties of the center-of-pressure dynamic were examined using basic stochastic process models. The amount of motion of the center of pressure decreased with increments of age from 3 to 5 years to young adult but increased again in the elderly age group. The availability of vision decreased the amount of motion of the center of pressure in all groups except the 3-year-old group, where there was less motion of the center of pressure with no vision. The stochastic properties of the center-of-pressure dynamic were assessed using both a two-process, random-walk model of Collins and De Luca and an Ornstein-Uhlenbeck model that is linear and has displacement governed only by a single stiffness term in the random walk. The two-process open- and closed-loop model accounted for about 96% and the Ornstein-Uhlenbeck model 92% of the variance of the diffusion term. Diffusion parameters in both models showed that the data were correlated and that they varied with age in a fashion consistent with developmental accounts of the changing regulation of the degrees of freedom in action. The findings suggest that it is premature to consider the trajectory of the center-of-pressure as a two-process, open- and closed-loop random-walk model given that: (a) the linear Ornstein-Uhlenbeck dynamic equation with only two parameters accommodates almost as much of the variance of the random walk; and (b) the linkage of a discontinuity in the diffusion process with the transition of open- to closed-loop processes is poorly founded. It appears that the nature of the stochastic properties of the random walk of the center-of-pressure trajectory in quiet, upright standing remains to be elucidated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02454152
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Passive Transfer of Lambert-Eaton Myasthenic Syndrome in Mice: Decreased Rates of Resting and Evoked Release of Acetylcholine from Skeletal Muscle (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 42 (1984), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Mice were injected for 1–2 months daily with 10 mg immunoglobulin G (IgG) from four patients with Lambert-Eaton myasthenic syndrome (LEMS); control mice were injected with pooled human IgG from normal donors. Gastrocnemius muscles were homogenised for the assay of acetylcholine (ACh), choline acetyltrans-ferase (ChAT), and cholinesterase (ChE). The ACh, ChAT, and ChE contents of gastrocnemius muscles from “LEMS mice” were about the same as the control values, which were 180 pmol, 40 nmol * h−1 (37°C), and 15 μmol * h−1 (37°C), respectively. Hemidiaphragms were treated with an irreversible ChE inhibitor (Soman) and incubated at 20°C for estimation of ACh release. Resting ACh release from experimental muscles was reduced by about 25% (P2 〈 0.05) and the release evoked by 3 s−1 nervous stimulation by 50% (P2 〈 0.05). On the other hand, 50 mM KCl-induced transmitter release was not abnormal in LEMS mice. The findings indicate that IgG antibody from patients with LEMS may bind to nerve terminal determinants that are involved in quantal and nonquantal ACh release.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1984.tb02733.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Choline Acetyltransferase in Skeletal Muscle from Patients with Myasthenia Gravis (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 37 (1981), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Acetylcholine synthesis in homogenates of human intercostal muscle was measured by a radiochemical method. Choline acetyltransferase activity in control muscle was about 20 nmol.g−1.h−1. The enzyme was found only in the endplate area of the muscle. At high substrate concentrations its activity was overshadowed by the acetylcholine synthesizing activity of a different enzyme not saturated by 10 mm-choline. The nonspecific enzyme was present at and away from the endplate area. Choline acetyltransferase in parasternal samples of intercostal muscle from myasthenia gravis patients was about 2.5 times higher than in samples, taken from a more lateral location, of control patients, but the Km for choline was not altered (0.24 mm). It is suggested that in myasthenia gravis the shortage of acetylcholine receptors is partially compensated for by increased synthesis, storage, and release of the transmitter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1981.tb04657.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Acetylcholine Synthesizing Enzymes in Frog Skeletal Muscle (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 35 (1980), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Acetylcholine synthesis in homogenates of frog sartorius muscle was measured by a radiometric method with a low blank. Choline acetyltransferase activity was very low (Vmax, 2 nmol g1 h−1, Kmfor choline, approx. 50 μ, m). The enzyme was found only in the endplate area and disappeared after denervation; it was inactivated by 4-(1-naphthylvinyl)pyridine. At high substrate concentrations its activity was overshadowed by the acetylcholine-synthesizing activity of a different enzyme not saturated by 10 mm-choline. The non-specific enzyme was present at and away from the endplate area, and it was not affected by denervation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1980.tb07855.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    SUBCELLULAR LOCALIZATION OF NEWLY-FORMED [3H]ACETYLCHOLINE IN RAT CEREBRAL CORTEX IN VITRO (1973)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 21 (1973), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —Slices from rat brain cortex were incubated for either 5 or 60 min in a medium containing [3H]choline and 4·7 or 25 mm-KCl. Bioassayable ACh and labelled ACh were determined in the incubation medium, in the total tissue homogenate and in subcellular fractions. Raising the KCl concentration from 4·7 to 25 mm stimulated the release and synthesis of total and of labelled ACh. In medium containing 25 mm-KCl the amounts of ACh decreased in the tissue and in the nerve ending cytoplasm, but remained constant in the synaptic vesicles. After incubation in 25 mm-KCl medium the ACh in the vesicles was labelled to the same extent as the cytoplasmic ACh but after incubation in 4·7 mm-KCl medium vesicular ACh was labelled less than cytoplasmic ACh. During 5 min incubation in medium containing 25 mm-KCl the ratio of labelled to total ACh was much higher in the medium than in the homogenate, the vesicles or the cytoplasm. During the last 15 min of the 60 min incubation the ratio of labelled to total ACh in the medium was still higher than that in the tissue fractions, but less so than during the 5 min incubation. It is concluded that the vesicular and cytoplasmic fractions are not identical with the store in the tissue from which newly-synthesized ACh is preferentially released.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1973.tb06011.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    A METHOD FOR DETERMINATION OF ACETYLCHOLINE BY SLOW PYROLYSIS COMBINED WITH MASS FRAGMENTOGRAPHY ON A PACKED CAPILLARY COLUMN (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 32 (1979), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A new procedure is described for the estimation of ACh by pyrolysis-gas chromatography/ mass spectrometry.ACh iodide and the iodides of ACh-d16 or propionylcholine are slowly demethylated at 250°C by pyrolysis on the tip of a glass probe after insertion into the heated entrance of a glass tube leading to a packed capillary column. The volatile tertiary amines are then carried by helium to the column and trapped in its initial part which is kept at about 60°C. After 2–3 min the chromatography is started when the amines are released by heating this part to the ambient temperature in the oven (165°C).Peaks due to demethylated ACh and propionylcholine are well separated. The limit of detection is about 0.3pmol. After pyrolysis of mixtures of ACh and either ACh-d16 or propionylcholine the peak amplitudes are linearly related to the doses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1979.tb00364.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    ACETYLCHOLINE METABOLISM AND CHOLINE UPTAKE IN CORTICAL SLICES (1977)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The uptake of [14C]choline was studied in cortical slices from rat brain after their incubation in a Krebs-Henseleit medium containing either 4.7 mm-KCl (low K), 25 mm-KCl (high K) or 25 mm-KCl without calcium (Ca free, high K). With 0.84 μm-[14C]choline in the medium the uptake per gram of tissue was 0.62 nmol after incubation in low K medium, 1.13 nmol after incubation in high K medium and 0.78 nmol after incubation in a Ca free, high K medium. The differences caused by potassium were greater in fraction P2 than in fractions P1 and S2. With 17 and 50μm-[14C]choline in the medium greater amounts of [14C]choline were taken up, but the effect of potassium on the uptake almost disappeared. The amount of radioactive material in fraction P2 followed Michaelis-Menten kinetics with Km values of 2.1 and 2.3 μm after incubation in low and high K medium, respectively. Hemicholinium-3 only slightly inhibited choline uptake from a medium with 0.84μm-[14C]choline, but it abolished the extra-uptake induced by high K medium. The radioactivity in the slices consisted mainly of unchanged choline and little ACh was formed after incubation in low K medium, but after incubation in high K medium 50% of the choline taken up was converted into ACh. The hemicholinium-3 sensitive uptake of choline, the conversion of choline into ACh and the synthesis of total ACh, were stimulated about 7–8-fold by potassium. It is concluded that in cortical slices from rat brain all choline used for the synthesis of ACh is supplied by the high-affinity uptake system, of which the activity is geared to the rate of ACh synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1977.tb10696.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    ANALYSIS OF THE PREFERENTIAL RELEASE OF NEWLY SYNTHESIZED ACETYLCHOLINE BY CORTICAL SLICES FROM RAT BRAIN WITH THE AID OF TWO DIFFERENT LABELLED PRECURSORS (1976)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 26 (1976), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —The release of newly synthesized acetylcholine (ACh) by cortical slices from rat brain in the presence of 25 mm-KCl was studied. The slices were incubated for 5 min in a medium containing both [2-14C]pyruvate and choline labelled with 3 deuterium atoms (choline-d3) in order to label at the same time the acetyl moiety and the choline moiety of ACh. The non-labelled ACh and the ACh-d3 were measured by pyrolysis-gas chromatography/mass spectrometry, and the [I4C]ACh by liquid scintillation counting. It was found that the newly formed [4C]ACh as well as the newly formed ACh-d3 had a more than 2.5 times greater probability of being released than the preformed non-labelled ACh. These findings strongly suggest that it is not simply the ACh synthesized immediately inside the nerve ending membrane from incoming undiluted labelled choline, which is preferentially released, but that all newly formed ACh has a greater probability of being released than preformed ACh. No preferential release of newly formed ACh was observed when the incubation medium contained 5.6 mm-pyruvate instead of 10 mm-glucose + 0.6 mm-pyruvate. The cause of this difference remains unexplained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1976.tb04441.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Acetylcholinesterase activity of skeletal muscle in a non-immunogenic model for myasthenia gravis in rats (1999)
    Springer
    Journal of neural transmission 106 (1999), S. 423-431 
    Details
    ISSN: 1435-1463
    Keywords: Keywords: Acetylcholine receptor (nicotinic) ; acetylcholinesterase ; α-bungarotoxin ; skeletal muscle ; myasthenia gravis.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. Myasthenia gravis is caused by an autoimmune attack to acetylcholine receptors of skeletal muscle. Acetylcholine release from motor nerve terminals is upregulated in patients with myasthenia gravis and also in rat "myasthenic" models, dependent on the reduction of the number of acetylcholine receptors. This study addresses the question as to whether at "myasthenic" endplates there are changes in the activity of acetylcholinesterase. To this end we studied acetylcholinesterase activity in junctional and extrajunctional regions of dilator naris, extensor digitorum longus, and hemidiaphragm muscles from rats with α-bungarotoxin-induced myasth-enia gravis. In all studied muscles from "myasthenic" rats there was no significant change of junctional acetylcholinesterase activity. In contrast, in dilator naris and extensor digitorum longus muscles, there was a 60% and 30% increase of extrajunctional acetylcholinesterase activity. There was no significant change in the extrajunctional activity in hemidiaphragm muscles. Velocity sedimentation analysis revealed that the increase in extrajunctional activity in extensor digitorum longus muscles could be attributed to an increase of the activity of the G4 form of acetylcholinesterase. Treatment of rats with 6.4 μg h−1 neostigmine bromide for 29 days had no influence on junctional and extrajunctional acetylcholinesterase activity of extensor digitorum longus muscles from rats with α-bungarotoxin-induced myasthenia gravis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007020050169
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Effect of estradiol and progesterone on muscle weight and acetylcholine receptors in “myasthenic” rats (1992)
    Springer
    Journal of neural transmission 87 (1992), S. 193-197 
    Details
    ISSN: 1435-1463
    Keywords: Acetylcholine receptors ; estradiol ; myasthenia gravis ; neuromuscular junction ; progesterone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Clinical evidence suggests that endocrinal factors are involved in fluctuations of the symptoms of women with myasthenia gravis. We studied the effect of estradiol and progesterone in an animal model for myasthenia gravis in rats. Although it was found that the mass of muscles was dependent on sex, and in female rats affected by estradiol, the number of acetylcholine receptors in these muscles was independent of sex and hormone administration. Sex hormones failed to influence the severity of muscle weakness in myasthenic rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01245365
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...