Seven star polymers with degrees of polymerization (DPs) of the arms from 10 to 100 and dimensions in the nanometer range were prepared using sequential group transfer polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA, hydrophilic positively ionizable monomer) and ethylene glycol dimethacrylate (hydrophobic neutral cross-linker). The polymers were characterized in tetrahydrofuran by gel permeation chromatography and static light scattering to determine the molecular weights and the weight-average number of arms for each sample. The number of arms of the star polymers varied from 20 to 72. Aqueous solutions of the star polymers were studied by turbidimetry, hydrogen ion titration, and dynamic light scattering to determine their cloud points, pKs, and hydrodynamic diameters. The cloud points of the larger star polymers, with arm DP 30-100, were found to be 29-34 degrees C, almost independent of the DP of the arms. Similarly, the pKs of all star polymers were calculated to range between 6.7 and 7.0, again independent of the arm DP. In contrast, the hydrodynamic diameters of the star polymers strongly depended on the DP of the arms. In particular, by increasing the DP of the arms from 20 to 100, the hydrodynamic diameters in water increased from 7 to 31 nm. All star polymers were evaluated for their ability to transfect human cervical HeLa cancer cells with the modified plasmid pRLSV40 with the enhanced green fluorescent protein as the reporter gene. Our results showed that as the DP of the arms of the DMAEMA star homopolymers increased from 10 to 100, the overall transfection efficiency decreased, with the star polymer with DP of the arms of 10 emerging as the best transfection reagent. Systematic variation of the amounts of star polymer and plasmid DNA used in the transfections led to an optimization of the performance of this star polymer, yielding overall transfection efficiencies of 15%, comparable to the optimum overall transfection efficiency of the commercially available transfection reagent SuperFect of 13%.

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In the present work, we have characterized the maturation of the GABAergic system in mammalian retina. Immunoreactivity for GABA, GAD (glutamic acid decarboxylase, EC 4.1.1.15) -65 and -67 in the adult rat retina was localized in cells in the inner nuclear and ganglion cell layers. This pattern was established around postnatal day 8 and included transient GABA and GAD-67 expression in horizontal cells. GAD activity was very low at P1 and P4, increasing after P8, reaching maximal activity by P21 and decreasing to attain adult values by P30. GABA content was approximately constant from P1 to P13, increasing thereafter to reach adult levels. GAD protein content increased progressively with postnatal development and the two isoforms could be distinguished at P8. The disparity between retinal GABA content vs. presence and activity of the synthesizing enzyme, led us to investigate the alternative pathway for GABA synthesis that utilizes putrescine as a substrate. Highest levels of ornithine decarboxylase activity (the limiting step for putrescine synthesis) were found between P1 and P4, decreasing to very low levels after P13. The same pattern was observed for putrescine content in the retina. Highest amounts were found at P1, that decreased and remained constant after P13. Additionally, approximately 40% of tritiated putrescine incorporated by P1, P4 and adult retinas was converted into GABA. Our results suggest the existence of two different sources of GABA in mammalian retina, one that uses glutamate as a precursor and predominates in the mature nervous system and another that utilizes putrescine and is present transiently at early developmental stages.

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Investigation of the morphology of ganglion cells in the cat retina has shown that a remarkable reduction in the number of dendritic spines and branches occurs during development of the alpha and beta cell classes. To learn whether dendritic remodelling represents a generalized mechanism of mammalian retinal ganglion cell development, we have examined the morphology of ganglion cells in the retina of the developing rat. The present study has concentrated on type II cells, which retain a great number of dendritic spines and branches in the adult and comprise a large proportion of the population of rat retinal ganglion cells. To reveal fine dendritic and axonal processes, Lucifer yellow was injected intracellularly in living retinae maintained in vitro. Size and complexity of the dendritic trees were found to increase rapidly during an initial stage of development lasting from late fetal life until approximately postnatal day 12 (P12). Dendrites and axons of immature ganglion cells expressed several transient morphological features comprising an excessive number of dendritic branches and spine-like processes, and short, delicate axonal sidebranches. The following developmental stage was characterized by a remarkable decrease in the morphological complexity of retinal ganglion cells and a slowed growth of their dendritic fields. The number of dendritic branches and spines of types I and II retinal ganglion cells declined after P12 to reach a mature level by the end of the first postnatal month. Thus, even cells that retain a highly complex dendritic tree into the adult state undergo extensive remodelling. These results suggest that regressive modifications at the level of the dendritic field constitute a generalized mechanism of maturation in mammalian retinal ganglion cells.

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Introduction:Use of Integrated Health Information Systems (IHIS) for the provision of healthcare services benefits both healthcare professionals and patients, while requiring continuous evaluation and upgrading to fully support its role.Aim:The main purpose of the study was to develop an evaluation framework for hospitals utilizing IHIS, within the three main areas identified as Human factor, Technology and Organization.Material and methods:The questionnaire consisted of 43 questions, with 17 questions (related to categories procedures, system quality and satisfaction), 25 questions (related to categories, safety and collaboration) and 1 question related to accessibility to the system (within the category system quality). Three open questions were added to evaluate users’ perception on what was needed for the improvement of health services in their respective hospitals for all 3 variables being evaluated. The open questions were included to allow participants to express their opinion in a more detailed setting. A database was developed, and the data were processed and analyzed.Results:Factor analysis formed 5 categories for the evaluation framework. Cronbach’s alpha coefficient was found in all categories to be above > 0.85.Conclusion:Evaluation frameworks can be designed, developed and implemented by using different methodologies. For an evaluation framework to be effective it should be designed and implemented based on the aims and purpose of the research and the specific needs of the particular healthcare setting or hospital. Considering the categories satisfaction, collaboration, safety, system quality, procedures, and by using Likert scale and open questions in the current study, DIPSA can provide a holistic image of IHIS by evaluating any hospital system.