| 131. |
- Abbas, Abdul-Karim, 1959, et al.
(författare)
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Temporal phases of long-term potentiation (LTP): myth or fact?
- 2015
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Ingår i: Reviews in the Neurosciences. - : Walter de Gruyter GmbH. - 0334-1763 .- 2191-0200. ; 26:5, s. 507-546
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Tidskriftsartikel (refereegranskat)abstract
- Long-term potentiation (LTP) remains the most widely accepted model for learning and memory. In accordance with this belief, the temporal differentiation of LTP into early and late phases is accepted as reflecting the differentiation of short-term and long-term memory. Moreover, during the past 30 years, protein synthesis inhibitors have been used to separate the early, protein synthesis-independent (E-LTP) phase and the late, protein synthesis-dependent (L-LTP) phase. However, the role of these proteins has not been formally identified. Additionally, several reports failed to show an effect of protein synthesis inhibitors on LTP. In this review, a detailed analysis of extensive behavioral and electrophysiological data reveals that the presumed correspondence of LTP temporal phases to memory phases is neither experimentally nor theoretically consistent. Moreover, an overview of the time courses of E-LTP in hippocampal slices reveals a wide variability ranging from <1 h to more than 5 h. The existence of all these conflictual findings should lead to a new vision of LTP. We believe that the E-LTP vs. L-LTP distinction, established with protein synthesis inhibitor studies, reflects a false dichotomy. We suggest that the duration of LTP and its dependency on protein synthesis are related to the availability of a set of proteins at synapses and not to the de novo synthesis of plasticity-related proteins. This availability is determined by protein turnover kinetics, which is regulated by previous and ongoing electrical activities and by energy store availability. RAHAM WC, 1991, MOLECULAR NEUROBIOLOGYSATELLITE MEETING ON MOLECULAR MECHANISMS RAHAM WC, 1995, MOLECULAR BRAIN RESEARCH, V30, P367 RAHAM WC, 1993, NEUROSCIENCE, V56, P717
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| 132. |
- Abbas, Abdul-Karim, 1959
(författare)
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Testing the conditions of long-term potentiation vulnerability for enhancement and interruption in CA1 area from mice hippocampal slices
- 2015
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Ingår i: The 12th International Meeting of Society of Neuroscientists of Africa (SONA) 25-30 March 2015.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Based on the recent findings that show that both long-term potentiation (LTP) and long-term depression (LTD) can be stabilized for several hours in hippocampal slices obtained from rat or mice, we have developed a theoretical model that explain these contradictory findings to the major literature. Our model conceded, in contrast to the prevalent dogma in the neuroscience of synaptic plasticity, that protein turnover rather than the presumed triggered protein synthesis has predictive power for the outcome of synaptic plasticity under conditions of protein synthesis inhibition (Abbas et al., Rev. Neurosci., Submitted). We predicted that when the degree of ATP perturbation produced by the LTP-inducing stimulation was not very high, either due to the type of LTP-inducing protocol (e.g. “weak”) or if the compensatory non-neuronal energy sources alleviate the state of transient ATP disturbance, the rate of activity-dependent degradation will be generally low and protein synthesis inhibitors might have no effect unless the protein synthesis inhibition interval covers the half-life of necessary proteins. To empirically verify our proposed model, we conducted experiments testing the conditions under which LTP can be vulnerable to enhancement or interruption by application of protein degradation inhibitor. Benefiting from the drug characteristics of dose-dependent selective targeting of the components of the proteasome system, S20 and S26, we treated hippocampal slices obtained from adult mice with the proteasome inhibitor MG-115. Low concentrations (10-20 µM) of the drug improved the magnitude and duration of LTP induced by weak induction protocol. However, higher concentration (50 µM) diminished the magnitude of LTP induced by either weak or strong protocol. Taken together, the findings indicate that, blocking degradation of some protein components (e.g. negative proteins) improves LTP in its magnitude and/or lifetime. Conversely, when the LTP induction is associated with an increase in turnover, blocking degradation exhibits a decaying effect on LTP stabilization in similar pattern to that achieved by protein synthesis inhibitors.
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| 133. |
- Abbas, Abdul-Karim, 1959
(författare)
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The Evidence-Based Medicine Condition: A Report on Uses and Abuses
- 2017
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Ingår i: Iraqi New Medical Journal. - 2521-7429 .- 2409-5931. ; 3:1, s. 8-16
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Tidskriftsartikel (refereegranskat)abstract
- This article is not questioning the validity or even the usefulness of evidence-based medicine (EBM) technical developments. Rather, the author is engaging with the conceptual framework within which EBM has been developed, interpreted and presented. Thus, this article explores the sociopolitical conditions that underlie characterizing EBM as paradigm and the implications of this label on practicing it in the developed as well as developing world. As medicine does not belong to pure sciences, it is believed here that the claim of paradigmatic characteristic is implanted to fulfil authoritative symbolic function rather than expressing a presumed revolutionary and radical change. This authoritative function, which enables EBM to transcend the clinical epidemiology it established on, could articulate three axes: the demise of welfare state, the postmodernist assault on the classical notions of truth and certainty, and the crisis of the medical professions. One prominent evidence that supports our proposal is the dynamicity of the movement and its capacity to “engulf” everything in its way including pseudoscience. It is noted that a major consequence of assigning EBM as paradigm is to give it a legitimized and rationalized potentiality for abuse by the profit-oriented medicalpharmaceutical complex. Another major impact is on the developing countries, which because they follow the educational and practical systems of medicine in the West, are in more positive attitude to both the drug companies and to new fashions. Beyond these issues, it is argued in the current paper that the claim of paradigm attains efficiently the control and power functions of EBM via achieving “ totalizing ” discourse creating norms for the consciousness and moral identity of the clinician. In short, it is via the paradigmatic characterization EBM engages in reasserting its hegemony in the face of a variety of challenges, and at the same time, assimilates as much as possible the sources of such challenges. It is assumed that the susceptibility of EBM for corruption will continue unless the disguising power of EBM is dismantled via humanist and medical critiques.
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| 134. |
- Abbas, F, et al.
(författare)
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Surgical treatment of gingival recessions using emdogain gel: clinical procedure and case reports
- 2003
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Ingår i: Int J Periodontics Restorative Dent. ; 23, s. 607-613
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Tidskriftsartikel (refereegranskat)abstract
- This article describes the clinical procedure and outcome of surgical treatment of gingival recessions with the adjunctive use of Emdogain gel, an enamel matrix derivative bioactive material for periodontal reconstructive surgery. Six cases with gingival recession on maxillary canines are presented with 12 months of follow-up. Initial gingival recession averaged 4.8 mm, with a mean probing pocket depth of 2.2 mm. At the 12-month follow-up, a mean of 3.5 mm of root coverage was observed (ie, 73% root coverage, range 60% to 100%). Probing pocket depth averaged 1.7 mm, indicating a 4-mm gain of clinical attachment (range 3 to 5 mm). On a clinical level, mucogingival surgery in combination with the application of Emdogain gel results in predictable root coverage and gain of clinical attachment while maintaining shallow pockets.
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| 135. |
- Abbas, M., et al.
(författare)
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Family Transmission of COVID-19 Including a Child with MIS-C and Acute Pancreatitis
- 2021
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Ingår i: International Medical Case Reports Journal. - 1179-142X. ; 14, s. 55-65
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Spread of the novel coronavirus SARS-CoV-2, since at least December 2019, has caused a pandemic. SARS-CoV-2 causes the disease COVID-19, which can affect several human organs. Abdominal pain is one of the known symptoms, but little is known about acute pancreatitis as a complication. As well, knowledge about viral transmission in families is limited. This case report describes MIS-C and acalculous acute pancreatitis in a child who was a member of a family in which four of five members had COVID-19. Case Report: A previously healthy family was infected by SARS-CoV-2 from an unknown source. The 13-year-old daughter was infected by SARS-CoV-2 and symptomatic during two periods, with an asymptomatic interval in-between. During the first period, she had transient and mild upper respiratory symptoms which was followed four weeks later by a secondary severe illness. At that point, there was inflammation in multiple organs and signs of Multisystem Inflammatory Syndrome in Children (MIS-C) and a Kawasaki-like disease with skin rash, scalded skin in hands and conjunctivitis. Myocarditis, bronchopneumonia, pancreatitis, and hepatopathy without encephalopathy were noted. She required assisted ventilation for 5 days. There were laboratory signs of disseminated intravascular coagulopathy. The multisystem inflammation was treated with intravenous immunoglobulin (IVIG) once a day for four days and immunotherapy (high dose methylprednisolone (IV) once a day, for 12 days, then tapered over 4 weeks, anakinra (IV) four times daily for 12 days), low molecular weight heparin for 22 days and salicylates for 6 weeks leading to full restoration of health. The two brothers and mother in the family had mild to moderate COVID-19 infections. The father was not affected despite close contact with his children. The household transmission and clinical course and outcome are described. No further known COVID-19 infection occurred in the neighborhood during or immediately after the family cluster was discovered. Conclusion: Penetrance and severity of COVID-19 can vary in family clusters. One adolescent showed a two-phase course with severe infection. This case report highlights MIS-C and acute pancreatitis as a complication associated with COVID-19 in children.
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| 136. |
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| 137. |
- Abbas, Zareen, 1962, et al.
(författare)
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Activity Coefficients of Concentrated Salt Solutions: A Monte Carlo Investigation
- 2019
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Ingår i: Journal of Solution Chemistry. - : Springer Science and Business Media LLC. - 0095-9782 .- 1572-8927. ; 48:8-9
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Tidskriftsartikel (refereegranskat)abstract
- Monte Carlo (MC) simulations were used to calculate single ion and mean ionic activity coefficients and water activity in concentrated electrolytes and at elevated temperatures. By using a concentration dependent dielectric constant, the applicability range of the MC method was extended to 3 mol·L−1 or beyond, depending on the salt. The calculated activity coefficients were fitted to experimental data by adjusting only one parameter, i.e., the cation radius. Fitted ionic radii obtained by such a procedure indicate the extent of cation–anion interaction in a salt solution. For example, the fitted radii of Li+ and Na+ in LiClO3 and NaClO3 indicate that Li+ is strongly hydrated and has a weak interaction with the ClO3− ion whereas Na+ forms ion pairs and loses its hydration. The single ion activity coefficients for protons and chloride ions in HCl were calculated by MC simulations and compared with experimental values obtained by ion selective electrodes. The calculated single ion activity coefficients for protons and chloride ions are much lower and higher, respectively, than the experimental values. However, the mean activity coefficients of HCl obtained by the MC simulations, ion selective electrodes and vapor pressure measurements are in good agreement. In the case of NaCl and KCl the calculated single ion activity coefficients of Na+, K+, and Cl− are much closer to the values obtained by ion selective electrodes. The results in HCl indicate that the hydrated proton is large and includes the chloride ion within the hydration shell, i.e., the apparent size of the chloride ion is negligible.
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| 138. |
- Abbas, Zareen, 1962, et al.
(författare)
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From restricted towards realistic models of salt solutions: Corrected Debye–Hückel theory and Monte Carlo simulations
- 2007
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Ingår i: Journal of Mathematical Fluid Mechanics. - : Elsevier BV. - 1422-6952 .- 1422-6928 .- 0378-3812. ; 260:2, s. 233-247
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Tidskriftsartikel (refereegranskat)abstract
- The properties of bulk salt solutions over wide concentration ranges are explored by a combination of simple physical theory and Monte Carlo (MC) simulations. The corrected Debye–Hückel (CDH) theory which incorporates ion size effects in a linear response approximation is extended to yield free energy and other thermodynamic properties by integration of the chemical potential over concentration. Charging integration which is usually used to obtain an electrostatic contribution of total free energy of electrolytes is avoided in this new direct approach. MC simulations are performed with a modified Widom particle insertion method, which also provides directly the ionic activity coefficients. The validity of the CDH theory is tested by comparison with the MC simulation data for 1:1, 2:1, 2:2 and 3:1 restricted primitive model (RPM) electrolytes over a wide concentration range and at various ion sizes. Mean ionic activity and osmotic coefficients calculated by the CDH theory in RPM approximation of electrolyte are fitted to experimental data by adjusting only a mean ionic diameter. Good fits up to 1 molal (m) concentration are obtained for a large number of salt solutions. MC simulations data for unrestricted primitive model (UPM) of 1:1 and 2:1 electrolytes are also fitted to the experimental data by varying the cation radius while keeping the anion radius fixed at a crystallographic value. The success of this approach is found to be salt specific. For example good fits up to 2 and 3.5 m concentrations were obtained for LiCl and LiBr, respectively. However in the case of less dissociated salts such as NaCl and KI the experimental data could only be fitted up to one molal concentration. Possibility of extending the applicability range of the CDH theory to concentrations >2 m is explored by including a concentration dependent dielectric constant as measured in experiments. Mean ionic activity coefficients for a number of salts could successfully be fitted up to 3 m concentration by adjusting only a mean ionic diameter. Difficulties encountered in simultaneously fitting the mean ionic activity and osmotic coefficients at salt concentrations >2 m are discussed.
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| 139. |
- Abbas, Zareen, 1962, et al.
(författare)
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Monte Carlo simulation of the dissociation constants of CO2 in 0 to 1 molal sodium chloride between 0 and 25 °C
- 2013
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 150:1, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Stoichiometric dissociation constants of the carbon dioxide system in NaCl solution between 0 and 1 mol and 0 to 25 °C were estimated by Monte Carlo (MC) simulations, and compared with Pitzer calculations and experimental measurements. The MC simulations used experimentally determined dielectric constants of water at different temperatures, and optimal agreement with the experimental data and Pitzer calculations was achieved by adjusting the ionic radii. This simple procedure resulted in effective ionic radii which were further used to simulate the activity coefficients of salt mixtures. The first and second stoichiometric dissociation constants of carbonic acid in NaCl solution (pK1⁎ and pK2⁎) were estimated from the MC-derived activity coefficients of mixed salts in NaCl. The MC results are in good agreement with the experimental data as well as with the Pitzer calculations. This study shows that Monte Carlo simulations in the temperature and ionic strength range relevant to seawater can provide pK values of the same quality as Pitzer calculations, and constitutes the first step in developing a temperature-dependent MC model for seawater. While MC calculations require greater computing resources, the number of parameters derived by fitting to thermodynamic data is substantially smaller than for Pitzer calculations.
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| 140. |
- Abbas, Zareen, 1962, et al.
(författare)
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Monte Carlo Simulations of Salt Solutions: Exploring the Validity of Primitive Models
- 2009
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 113:17, s. 5905-5916
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Tidskriftsartikel (refereegranskat)abstract
- An extensive series of Monte Carlo (MC) simulations were performed in order to explore the validity of simple primitive models of electrolyte solutions and in particular the effect of ion size asymmetry on the bulk thermodynamic properties of real salt solutions. Ionic activity and osmotic coefficients were calculated for 1:1, 2:1, and 3:1 electrolytes by using the unrestricted primitive model (UPM); i.e., ions are considered as charged hard spheres of different sizes dissolved in a dielectric continuum. Mean ionic activity and osmotic coefficients calculated by the MC simulations were fitted simultaneously to the experimental data by adjusting only the cation radius while keeping the anion radius fixed at its crystallographic value. Ionic radii were further optimized by systematically varying the cation and anion radii at a fixed sum of ionic radii. The success of this approach is found to be highly salt specific. For example, experimental data (mean ionic activity and osmotic coefficients) of salts which are usually considered as dissociated such as HCl, HBr, LiCl, LiBr, LiClO4, and KOH were successfully fitted up to 1.9, 2.5, 1.9, 3, 2.5, and 4.5 M concentrations, respectively. In the case of partially dissociated salts such as NaCl, the successful fits were only obtained in a more restricted concentration range. Consistent sets of the best fitted cation radii were obtained for acids, alkali, and alkaline earth halides. A list of recommended ionic radii is also provided. The reliability of the optimized ionic radii was further tested in simulations of the osmotic coefficients of LiCl−NaCl−KCl salt mixtures. A very good agreement between the simulated and experimental data was obtained up to ionic strength of 4.5 M.
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