Abstract Recessively inherited loss-of-function mutations in the PTEN-induced putative kinase 1(Pink1), DJ-1 (Park7) and Parkin (Park2) genes are linked to familial cases of early-onset Parkinson's ...disease (PD). As part of its strategy to provide more tools for the research community, The Michael J. Fox Foundation for Parkinson's Research (MJFF) funded the generation of novel rat models with targeted disruption ofPink1, DJ-1 or Parkin genes and determined if the loss of these proteins would result in a progressive PD-like phenotype. Pathological, neurochemical and behavioral outcome measures were collected at 4, 6 and 8 months of age in homozygous KO rats and compared to wild-type (WT) rats. Both Pink1 and DJ-1 KO rats showed progressive nigral neurodegeneration with about 50% dopaminergic cell loss observed at 8 months of age. ThePink1 KO and DJ-1 KO rats also showed a two to three fold increase in striatal dopamine and serotonin content at 8 months of age. Both Pink1 KO and DJ-1 KO rats exhibited significant motor deficits starting at 4 months of age. However, Parkin KO rats displayed normal behaviors with no neurochemical or pathological changes. These results demonstrate that inactivation of the Pink1 or DJ-1 genes in the rat produces progressive neurodegeneration and early behavioral deficits, suggesting that these recessive genes may be essential for the survival of dopaminergic neurons in the substantia nigra (SN). These MJFF-generated novel rat models will assist the research community to elucidate the mechanisms by which these recessive genes produce PD pathology and potentially aid in therapeutic development.
Approaches to improve resolution in chiral separation of several basic pharmaceutical compounds by capillary electrophoresis (CE) via a cyclodextrin (CD) inclusion complexation are described. ...Tetraalkylammonium reagents, including long-chain cationic surfactants and short-chain alkylammonium hydroxides, are examined for controlling the electroosmotic flow in order to improve resolution of the cationic enantiomers. In this regard, short-chain tetraalkylammonium cations (such as tetrabutylammonium and tetramethylammonium are more effective. First, the short-chain tetraalkylammonium cations can be used at much higher concentrations than the long-chain cationic surfactants, which form micelles in the few millimolar concentration range. As a result, a better capillary wall coverage is provided with the short-chain reagents, which leads to reduction or reversal of the direction of the electroosmotic flow at the acidic pH 2.5. Second, the short-chain tetraalkylammonium cations are relatively less hydrophobic and less likely to occupy the hydrophobic cavity of beta-CD than the long-chain cationic surfactants, leaving the enantioselective interaction sites more available for the analytes. The presence of these tetraalkylammonium cations was essential in many chiral separations that were reportedly not achieved by using the buffer electrolytes containing only the beta-CD as a chiral selector. In addition, a mechanism of chiral recognition by beta-CD for a group of stereoisomers is discussed.
The migration of metal cations in capillary electrophoresis with indirect UV detection was investigated. A mathematical model was used to relate the electrophoretic mobility of a metal cation with ...two background electrolyte factors: the pH and the concentration of a complexing agent. Imidazole, which has an electrophoretic mobility close to those of metal cations, was used as the visualization agent, and 2-hydroxyisobutyric acid (HIBA) was used as the complexing agent. Through computer modeling, the electrophoretic mobilities of fourteen metal cations were predicted on the basis of five initial experiments within the factor space of pH and HIBA concentration. Good agreement was observed between the predicted electrophoretic mobilities and the observed values of the metal cations. Subsequently, the separation of a complex mixture of metal cations was successfully optimized. A complete separation of 14 metal cations including alkali, alkaline earth and transition metal(II) cations was achieved within 4 min. In addition, the effectiveness of other visualization agents and complexing agents for the separation of metal cations was examined.
Previously, the use of phenomenological models to describe the migration behavior of acidic solutes in micellar electrokinetic chromatography (MEKC) was reported. In this paper, the phenomenological ...approach is further extended by including both acidic and basic solutes and simultaneously taking two important experimental factors (pH and micelle concentration) into consideration. In addition, a general method is described to model the migration behavior of ionizable (both acidic and basic) solutes in MEKC with anionic and cationic micelles. The practical implication of the phenomenological approaches is that they will provide quantitative relationships between solute migration and experimental factors such that the migration behavior can be predicted on the basis of a few initial experiments and that physicochemical parameters of solutes can also be estimated from model fitting. Through computer-assisted modeling, migration behavior of several acidic and basic solutes over a pH-micelle concentration factor space was successfully predicted on the basis of only five experiments. Furthermore, this phenomenological approach was used to predict the separation of a group of aromatic amines in MEKC with anionic micelles, which resulted in a successful separation of 18 aromatic amines in less than 15 min.
A method for improving separations of peptides and other positively charged species in capillary zone electrophoresis with untreated capillaries using acidic buffers containing tetraalkylammonium ...cations is described. Tetramethylammonium and tetrabutylammonium cations dynamically modify the capillary surface, leading to a reversal in the direction of the electroosmotic flow. As a result, the adsorption of positively charged peptides and proteins is minimized, and resolution and peak capacity are improved as the migration of cationic analytes is counterbalanced by the electroosmotic flow. The combining effect of reversing electroosmotic flow and cyclodextrin inclusion complexation on separations of closely related peptides and a protein mixture, as well as tryptic digest of hemoglobin is demonstrated.
In a previous paper on cyclodextrin-mediated capillary zone electrophoresis, it was shown that the use of short-chain tetraalkylammonium cations leads to a reversal in the direction of the ...electroosmotic flow without an adverse effect on enantioselectivity. As a result, enantiomeric resolution of basic (cationic) compounds can be improved as the electroosmotic flow counteracts the migration of solute enantiomers. It is demonstrated in this report that the scope of chiral separation of basic compounds can be further extended by a combination of reversing the electroosmotic flow and enhancing enantioselectivity through the chemical modifications of β-cyclodextrin. Therefore, β-cyclodextrin and its derivatives were evaluated as chiral recognition agents for the chiral separations of 22 basic compounds with rather complex molecular structures. The differences in enantioselectivity displayed by β-cyclodextrin and derivatives are discussed in order to achieve a better understanding of the chiral interactions involved in the discrimination of solute enantiomers.
Approaches to improve resolution in chiral separation of several basic pharmaceutical compounds by capillary electrophoresis via a cyclodextrin inclusion complexation are described.
This article is concerned with the robust formation tracking control of a group of underactuated surface vessels whose formation is characterized by the relative bearings between the vessels. Control ...protocols are proposed to asymptotically steer certain points on the vessels, called hand points , which lie ahead of their centers of mass along the longitudinal axes, to track the desired moving formation; such a control method is called an output regulation approach . The moving formation is guided by the motions of two or more agents, which are referred to as leaders , and the other follower agents track the leaders by maintaining bearing constraints to neighbors. The proposed control schemes are designed based on a backstepping technique and sliding mode control. The latter is employed to attenuate known bounded disturbances present in the vessels' dynamics. When the bounds of the disturbances are unknown, an adaptive control protocol is subsequently investigated, under which the system is shown to converge to a small neighborhood of the target formation. Further, sufficient conditions on the upper bound of the hand points' desired velocities are provided for the uniform ultimate boundedness of the vessels' internal sway-yaw dynamics. Simulation results are provided to support the theoretical analysis.
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