Perceptual errors increase with movement duration and may contribute to hypokinesia in Parkinson's disease.

People with Parkinson's disease (PD) perceive that their movement amplitude is greater than what they actually perform. The neural mechanisms underlying one's perception of movement are believed to involve the sensorimotor integration process (SIP). How PD affects the SIP is not well understood. A previous study interrogating the SIP showed healthy adults (HAs) overestimated their limb position in the direction of movement and the error and its variance (VOE) depended on movement duration. We asked if PDs showed errors in perceived limb position and if the dependence on movement duration was different from HAs. We used an existing computational model of the SIP to explore mechanisms for the error and VOE as a function of movement duration. Twenty PDs, off medication, and 20 age-matched HAs were asked to estimate the position of their hand after performing 50, slow, non-visually guided wrist flexion or extension movements for a random period of time (<4.0 s). Both groups overestimated the amount they moved; however, the PDs' error and VOE were larger (p<0.001). HAs showed increasing error/VOE for small movement durations that reduced/stabilized for longer movement durations. PDs however showed increasing error/VOE with increasing movement duration that did not significantly improve/stabilize. The model suggested that the basis for such perceptual deficits may be abnormal proprioceptive feedback and/or processing of an abnormal internal impression (prediction) that underestimates movement amplitude. Simulation results imply that the PD's SIP could no longer effectively access sensory (proprioceptive) feedback to correct errors in other components of the SIP due to the abnormal processing of sensory feedback. We suggest from this study that an impaired perception of movement amplitude and sensory processing deficits contribute to hypokinesia in PD.

Surfactant-encapsulated clusters (SECs): (DODA)20(NH4)[H3Mo57V6(NO)6O183(H2O)18], a case study.

We present a comprehensive study of the partially reduced polyoxomolybdate [H3-Mo57V6(NO)6O183(H2O)18]21-encapsulated in a shell of dimethyldioctadecylammonium (DODA) surfacmolecules. Treatment of an aqueous solution of (NH4)21[H3Mo57V6-(NO)6O183(H2O)18] . 65H2O (1a) with a trichloromethane solution of the surfactant leads to instant transfer of the encapsulated complex anion into the organic phase. Results from vibrational spectroscopy. analytical ultracentrifugation, small-angle X-ray scattering, transmission electron microscopy, elemental analysis, and Langmuir compression isotherms are consistent with a single polyoxometalate core encapsulated within a shell of 20 DODA molecules. The molar mass of the supramolecular assembly is 20249 gmol(-1) and the diameter is 3.5 nm. A material with the empirical formula (DODA)20(NH4)[H3-Mo57V6NO)6O183(H2O)18] (2) was isolated as a dark violet solid, which readily dissolves in organic solvents. Slow evaporation of solutions of 2 on solid substrates forces the hydrophobic particles to aggregate into a cubic lattice. Annealing these so-formed films at elevated temperature causes de-wetting with terrace formation similar to liquid crystals and block copolymers. Compound 2 forms a stable Langmuir monolayer at the air-water interface; Langmuir-Blodgett multilayers are readily prepared by repeated transfer of monolayers on solid substrates. The films were characterized by optical ellipsometry, Brewster angle microscopy, transmission electron microscopy, and X-ray reflectance.

Kinetic studies on hybridoma cells immobilized in fixed bed reactors.

Cultures with immobilized hybridoma cells were performed in fixed bed systems. "Steady state" values for volume-specific substrate uptake and metabolite production rates were determined at various perfusion rates and superficial flow velocities of the medium within the carrier matrix. Data from fixed bed volumes between 50 and 600 ml did not show any difference. The volume-specific glutamine and glucose uptake rate turned out to be independent of the superficial flow velocity, but decreased with decreasing glutamine and glucose concentration. The volume-specific oxygen uptake rate increased with increasing superficial flow velocity and substrate concentration, respectively. A similar behavior was observed for the ratio between oxygen and glucose uptake rate. The production rate for monoclonal antibodies was neither affected by the substrate concentration nor by the superficial flow velocity. The metabolic parameters of the immobilized cells were put into kinetic equations and compared to those of suspended cells. It could be concluded that the metabolism of the immobilized cells is determined by the oxygen supply within the macroporous carriers.

Specific catalytic activity of cathepsin S in comparison to cathepsins B and L along the rat nephron.

Assay conditions were elaborated to determine the catalytic activity of cathepsin S fluorometrically for direct comparison with the activities of cathepsins B + L(+S) and B along the nephron of the normal rat. These conditions include the use of 0.5 mM Z-Phe-Arg-AMC as substrate, which is saturating for the three enzymes. The stability of cathepsin S at pH 7.5 and the resistance of cathepsin B against inactivation by 0.5 microM Z-Phe-Phe-CHN2 permitted differentiation of these enzyme activities. The catalytic activity of cathepsin S in rat kidney homogenate (1.11 mumol/min x g protein) amounted to 2.1% of that of cathepsins B + L(+S) and to 3.2% of that of cathepsin B. It was ten-fold higher in the cortex (1.54 mumol/min x g protein) than in the medulla resembling the activity ratio of cathepsins B + L(+S) and B. In suspensions of isolated glomeruli and isolated proximal tubules the activities of cathepsin S were 0.76 and 3.21 mumol/min x g protein, respectively. The corresponding activities of cathepsins B + L(+S) amounted to 80.0 and 211.7 mumol/min x g protein consisting of 71% cathepsin B activity. In nephron segments microdissected from lyophilized renal sections, highest cathepsin S activity was found in the proximal convoluted tubules (4.21 mumol/min x g dry weight) followed by 0.83 mumol/min x g dry weight in proximal straight tubules of the superficial cortex. In the remaining segments cathepsin S activity was hardly detectable. Unlike cathepsin S activity, the activity of cathepsin B was distributed in parallel to that of cathepsins B + L(+S). The presence of relatively high cathepsin S activity in proximal convoluted tubules in co-localization with the activities of cathepsins B + L(+S) and B suggests a primary role of these enzymes in heterophagocytosis of proteins from the ultrafiltrate.

Volumetric development of the fetal telencephalon, cerebral cortex, diencephalon, and rhombencephalon including the cerebellum in man.

Fresh volumes of the human telencephalon, cerebral cortex, diencephalon, and of the rhombencephalon including cerebellum were determined in a series of 10 normal specimens ranging in age from 63 to 176 days after conception. The volumetric growth of these parts shows a nonlinear dependence on age with a smaller increase during the 3d ontogenetic month and a stronger increase from the 4th month on. These data were analyzed together with previous measurements of 28 brains taken from the Yakovlev Collection in Washington, D.C., and the Vogt Collection in Düsseldorf. These brains range in age from 137 to 22,900 days after conception. These samples were reproduced in a model using sigmoid logistic functions. The entire brain and all analyzed parts show a monotonous growth. The individual regions develop heterochronously. The diencephalon is the first part to reach its ideal volume, with a main growth spurt between 100 and 420 days after conception. The rhombencephalon including the cerebellum is the last, with its main growth spurt between 240 and 650 days after conception. The growth of the entire brain is determined to a great extent by that of the telencephalon, having a main growth spurt between 175 and 580 days after conception. The prenatal growth is described separately with the asymmetric sigmoid function according to Gompertz. This yields a better approximation of the data collected from the early prenatal period.