Spaced training improves learning in Ts65Dn and Ube3a mouse models of intellectual disabilities

Benefits of distributed learning strategies have been extensively described in the human literature, but minimally investigated in intellectual disability syndromes. We tested the hypothesis that training trials spaced apart in time could improve learning in two distinct genetic mouse models of neurodevelopmental disorders characterized by intellectual impairments. As compared to training with massed trials, spaced training significantly improved learning in both the Ts65Dn trisomy mouse model of Down syndrome and the maternally inherited Ube3a mutant mouse model of Angelman syndrome. Spacing the training trials at 1 h intervals accelerated acquisition of three cognitive tasks by Ts65Dn mice: (1) object location memory, (2) novel object recognition, (3) water maze spatial learning. Further, (4) spaced training improved water maze spatial learning by Ube3a mice. In contrast, (5) cerebellar-mediated rotarod motor learning was not improved by spaced training. Corroborations in three assays, conducted in two model systems, replicated within and across two laboratories, confirm the strength of the findings. Our results indicate strong translational relevance of a behavioral intervention strategy for improving the standard of care in treating the learning difficulties that are characteristic and clinically intractable features of many neurodevelopmental disorders.

An origin of transfer from Lactococcus lactis subsp. lactis causes rearrangement in the temperature sensitive plasmids pUCB3522 and pJRS290

Cloning of the oriT region derived from Lactococcus lactis subsp. lactis into plasmids is expected to convert them into mobilizable plasmids in a suitable genetic background. In some cases, however, the cloning of oriT causes deleterious DNA rearrangements. In the work presented, oriT was cloned into two temperature sensitive plasmids, pJRS290 and pUCB3522. The plasmids were transformed into E. coli and electroporated into L. lactis. Restriction digestion of the plasmids derived from the cloned transformed cells showed fragment sizes different from those expected, indicating that rearrangements had occurred. Furthermore, the inability to successfully transform E. coli with one of the plasmids supports this conclusion.

Effects of acetylcysteine and dexamethasone on experimental corneal wounds in rabbits

Corneal wound healing often leads to the development of scar tissue with loss of transparency. Reconstitution of transparent corneal stroma depends on the regulation of the biosynthetic activities of post-lesional keratocytes as well as to a large extent on the limitation of matrix degradation. It has been shown that 3% concentration of N-acetylcysteine (NAC) improves the healing time of corneal wounds but some corneal haze remains. On the other hand, topical corticosteroids may retard the corneal wound healing but decrease the haze. Thus, the aim of the study was to evaluate whether adding dexamethasone to NAC could reduce the side effects of the two drugs. In this study, experimental corneal wounds were created surgically, up to the depth of one half of the stroma in the center of both eyes of all rabbits. The left eyes were treated topically with 0.9% NaCl as controls and the right eyes were treated with a combination of one drop of 3% NAC and one drop of 0.1% dexamethasone, 6 times per day. Corneal wounds were measured by fluorescein staining every day. The results indicated that the combination of acetylcysteine and dexamethasone significantly increased the mean healing time compared to the control group (p < 0.05). Clinical and histopathologic examinations revealed that the corneal haze in the treatment group was greater than in the control group. It is concluded that treatment of the eyes by a combination of 3% acetylcysteine and 0.1% dexamethasone (if used from the first day of ulceration) may retard the corneal wound healing in rabbits.

Fibril formation of lysozyme upon interaction with sodium dodecyl sulfate at pH 9.2

Fibril formation seems to be a general property of all proteins. Its occurrence in hen or human lysozyme depends on certain conditions, namely acidic pHs or the presence of some additives. This paper studies the interaction of lysozyme with sodium dodecyl sulfate (SDS) at pH 9.2, using UV-visible spectrophotometry, circular dichroism (CD) spectropolarimetry, electron microscopy (EM) and chemometry. Based on observations such as the strange increase in absorbance at 650nm (pH 9.2) and the presence of intermediates, it is assumed that lysozyme fibrils have been formed at pH 9.2 in the presence of SDS as an anionic surfactant. Thioflavin T emission fluorescence and an EM image confirmed this assumption. beta-cyclodextrin was then used as a turbidity inhibitor to establish its effect on the distribution of intermediates that participate in fibril formation.

The Correlation of RNase A Enzymatic Activity with the Changes in the Distance between Nε2-His12 and Nδ1-His119 Upon Addition of Stabilizing and Destabilizing Salts

The effect of stabilizing and destabilizing salts on the catalytic behavior of ribonuclease A (RNase A) was investigated at pH 7.5 and 25 degrees C, using spectrophotometric, viscometric and molecular dynamic methods. The changes in the distance between N(epsilon2) of His(12) and N(delta1) of His(119) at the catalytic center of RNase A upon the addition of sodium sulfate, sodium hydrogen sulfate and sodium thiocyanate were evaluated by molecular dynamic methods. The compactness and expansion in terms of Stokes radius of RNase A upon the addition of sulfate ions as kosmotropic salts, and thiocyanate ion as a chaotropic salt, were estimated by viscometric measurements. Enzyme activity was measured using cytidine 2', 3'-cyclic monophosphate as a substrate. The results from the measurements of distances between N(epsilon2) of His(12) and N(delta1) of His(119) and Stokes radius suggest (i) that the presence of sulfate ions decreases the distance between the catalytic His residues and increases the globular compactness, and (ii) that there is an expansion of the enzyme surface as well as elongation of the catalytic center in the presence of thiocyanate ion. These findings are in agreement with activity measurements.

Thermal Dissociation and Conformational Lock of Superoxide Dismutase

The kinetics of thermal dissociation of superoxide dismutase (SOD) was studied in 0.05 M Tris-HCl buffer at pH 7.4 containing 10(-4) M EDTA. The number of conformational locks and contact areas and amino acid residues of dimers of SOD were obtained by kinetic analysis and biochemical calculation. The cleavage bonds between dimers of SOD during thermal dissociation and type of interactions between specific amino acid residues were also simulated. Two identical contact areas between two subunits were identified. Cleavage of these contact areas resulted in dissociation of the subunits, with destruction of the active centers, and thus, lost of activity. It is suggested that the contact areas interact with active centers by conformational changes involving secondary structural elements.

Comparative Study of the Conformational Lock, Dissociative Thermal Inactivation and Stability of Euphorbia Latex and Lentil Seedling Amine Oxidases

The thermal stability of copper/quinone containing amine oxidases from Euphorbia characias latex (ELAO) and lentil seedlings (LSAO) was measured in 100 mM potassium phosphate buffer (pH 7.0) following changes in absorbance at 292 nm. ELAO was shown to be about 10 degrees C more stable than LSAO. The dissociative thermal inactivation of ELAO was studied using putrescine as substrate at different temperatures in the range 47-70 degrees C, and a "conformational lock" was developed using the theory pertaining to oligomeric enzyme. Moreover ELAO was shown to be more stable towards denaturants than LSAO, as confirmed by dodecyl trimethylammonium bromide denaturation curves. A comparison of the numbers of contact sites in inter-subunits of ELAO relative to LSAO led us to conclude that the higher stability of ELAO to temperature and towards denaturants was due to the presence of larger number of contact sites in the conformational lock of the enzyme. This study also gives a putative common mechanism for thermal inactivation of amine oxidases and explains the importance of C-terminal conserved amino acids residues in this class of enzymes.