Archive of Journal
Volume 71, Issue 5, May. 2015

Distinct Cell Cycle Proteins Control Schwann Cell Proliferation in Health and Disease

Volume 71, May 2015

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Abstract: Proliferating Schwann cells, the glial cells of the peripheral nervous system, are a prominent feature during early development and after damage to peripheral nerves. Altered Schwann cell proliferation is also associated with diseases and pathological states including inherited peripheral neuropathies, peripheral nerve tumors, and peripheral neuropathies secondary to diabetes, cancer chemotherapeutic agents, or toxins. To gain more insight into the molecular processes governing Schwann cell proliferation in health and disease, we examined the Schwann cell cycle and its regulation in vivo. Methods: We have examined the expression, regulation, and localization of cyclins, cyclin-dependent kinases (cdk), and cell cycle inhibitors in Schwann cells of developing and adult peripheral nerves using immunohistochemistry. In addition, we used appropriate mutant mice to examine the functional requirement for the respective cell cycle proteins in Schwann cell proliferation. Results: Proliferating Schwann cells during development express cyclin D1 in the cytoplasm. After injury, cyclin D1 becomes localized to the nuclei of proliferating Schwann cells. Cyclin D1-deficient animals revealed that developmentally regulated proliferation is not affected by the absence of cyclin D1, whereas injury-induced proliferation is impaired. We further found that the cell cycle inhibitor p21 appears first in the cytoplasm of Schwann cells at postnatal day 7 when most cells have already ceased dividing. After nerve injury, however, p21 is localized mainly in nuclei of dedifferentiated Schwann cells. Consistently, p21-deficient Schwann cells do not undergo proper growth arrest in later phases of nerve development. In contrast, after nerve injury, nuclear p21 is required for correct cell cycle control at the peak of Schwann cell proliferation. We next investigated the requirements for cdk2, 4, and 6 during Schwann cell proliferation. We show that only cdk2 and 4 are expressed in peripheral nerves. Our data from cdk-deficient mice indicate that postnatal Schwann cell proliferation is abolished in the absence of cdk4 but not in the absence of cdk2 or 6. Conclusions: We find that distinct components of the cell cycle machinery that regulate Schwann cell proliferation during development differ fundamentally from those activated following nerve injury or in peripheral neuropathies.

Author(s): ATANASOSKI S

Mapping Many Voices - Self-Organizing Maps as a Tool for Creating Dialogue Among Visitors and Stakeholders

Volume 71, May 2015

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Abstract: The paper analyzes a new kind of visitor feedback tool, a self-organizing map (SOM), which was tried out by Heureka, the Finnish Science Centre, when exhibiting Scenes of Silence (or Dialogue in Silence) in 2007-2008. SOM is a visualisation technique that shows multidimensional information on a two-dimensional map, enabling to get the big picture without losing nuances of the data. The paper will evaluate the potential of this new technology in the light of the Dialogue in Silence experience, and how it should be further developed. Prior Perspectives or Theory When Heureka presented the powerful exhibition Dialogue in the Dark (2000-2001), the guest books were filled with thrilled comments, reflecting the immersive, emotional and transformative experience of being guided by a blind person in total darkness. The need to express was an obvious impact of the dark, but enlightening, experience. For the other socially powerful experience, Scenes of Silence (or Dialogue in Silence), where hearing visitors are guided by deaf guides through a silent experience, Heureka wanted to widen and deepen the ways of collecting visitor feedback. We wanted to go further and set a platform for dialogue for visitors, non-visitors and the deaf ambassadors, the animators of the experience. For this goal a virtual guest book was set up. It collected personal data ? age, gender, level of sign language skills ? and then asked the user about how she/he relates to silence, sign language, deaf people and hearing implants. This multidimensional information (answers to 8 questions) was then used to locate all the persons on an attitude map. The map showed the user his/her individual location in relation to all the other people who have answered the questions. The closer the people are on the map, the more similarly they have answered the questions. Importance The use of self-organizing map was designed to map the attitudes of the Dialogue in Silence visitors and to offer them a platform for communication among themselves and with the deaf guides of the exhibition. The attitude map attracted 2500 people, out of whom 1615 completed the whole survey and received their location on the attitude map. The sign language users, 281 people, formed quite a clear group on the attitude map. On the other hand, some of them were a bit in the margins and indicated the fact that the group is not totally homogenous. Our next SOM application at Heureka, the Science Changing the World exhibition (opening April 2010), will invite visitors to share their opinions about ethical and societal issues deriving from modern research. In this application, opinion leaders (e.g. intellectuals, politicians and religious leaders) will serve as reference points on the attitude maps for visitors.

Author(s): Mikko Myllykoski

TEMPERATURE AND FREQUENCY DEPENDENT CONDUCTIVITY STUDIES ON ULTRANANOCRYSTALLINE DIAMOND

Volume 71, May 2015

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Abstract: Analysis of conductivity dependence on temperature and frequency has demonstrated to be a powerful tool to infer the electrical properties of nanostructured materials. Such approach enables to evaluate charge transport mechanisms and discriminate grain boundary and grain interior contributions to their limitation. Different contributions can be identified and separated by reference to a physical model also using equivalent electric schemes suitable to address the whole DC and AC electrical response. The paper is aimed to report on the work carried out on intrinsic and lightly nitrogenated ultrananocrystalline diamond (UNCD) deposited by a microwave assisted CVD process using Ar/H2/CH4/N2 gas mixtures [1]. Thin films on silicon were investigated in DC and AC regime in the range 10 mHz-10 MHz at different temperature in the 115K - 550K range. The electrical response has been modeled either by a series or a parallel equivalent scheme also considering the contribution of a contact resistance in series with the equivalent material?s scheme. These schemes fairly agree with the experimentally observed low-frequency data, but cannot completely explain trends observed in the high-frequency range. Effects associated to the formation of a distributed junction at the interface of the p-type nanocrystalline diamond grain and n-type grain boundary is proposed to justify observed trends.

Author(s): G. Conte, V. Ralchenko

Effect of gentamicin on serum digoxin level in patients with congestive heart failure.

Volume 71, May 2015

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Abstract: receiving digitalis therapy. The aim of this study is to evaluate the effect of gentamicin on serum digoxin level. Methods: Twenty-four diabetic patients and patients with congestive heart failure and twelve normal healthy volunteers were enrolled in this study. The patients received digoxin treatment 0.25 mg/day. Gentamicin in a dose of 80 mg i.m. twice a day for 7 days was prescribed for these patients to treat chest infection. Serum digoxin and creatinine levels were determined before and after gentamicin administration. Results: Gentamicin induced a significant increase in serum digoxin level of diabetic patients and patients with congestive heart failure. Serum creatinine level increased significantly before and after i.m. injection of gentamicin. Conclusions: The present study indicated that increase serum digoxin level when combined with gentamicin should be considered a risk factor for digitalis toxicity.

Author(s): ALKADI HO, MAJED AN, YAHIA AR