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Smith AM, Grayson BE. A strike to the head: Parallels between the pediatric and adult human and the rodent in traumatic brain injury. J Neurosci Res 2024; 102:e25364. [PMID: 38953607 DOI: 10.1002/jnr.25364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 06/05/2024] [Accepted: 06/16/2024] [Indexed: 07/04/2024]
Abstract
Traumatic brain injury (TBI) is a condition that occurs commonly in children from infancy through adolescence and is a global health concern. Pediatric TBI presents with a bimodal age distribution, with very young children (0-4 years) and adolescents (15-19 years) more commonly injured. Because children's brains are still developing, there is increased vulnerability to the effects of head trauma, which results in entirely different patterns of injury than in adults. Pediatric TBI has a profound and lasting impact on a child's development and quality of life, resulting in long-lasting consequences to physical, cognitive, and emotional development. Chronic issues like learning disabilities, behavioral problems, and emotional disturbances can develop. Early intervention and ongoing support are critical for minimizing these long-term deficits. Many animal models of TBI exist, and each varies significantly, displaying different characteristics of clinical TBI. The neurodevelopment differs in the rodent from the human in timing and effect, so TBI outcomes in the juvenile rodent can thus vary from the human child. The current review compares findings from preclinical TBI work in juvenile and adult rodents to clinical TBI research in pediatric and adult humans. We focus on the four brain regions most affected by TBI: the prefrontal cortex, corpus callosum, hippocampus, and hypothalamus. Each has its unique developmental projections and thus is impacted by TBI differently. This review aims to compare the healthy neurodevelopment of these four brain regions in humans to the developmental processes in rodents.
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Affiliation(s)
- Allie M Smith
- Department of Neurology, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Bernadette E Grayson
- Department of Neurology, University of Mississippi Medical Center, Jackson, Mississippi, USA
- Department of Population Health Science, University of Mississippi Medical Center, Jackson, Mississippi, USA
- Department of Anesthesiology, University of Mississippi Medical Center, Jackson, Mississippi, USA
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2
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Barbaresi P, Fabri M, Lorenzi T, Sagrati A, Morroni M. Intrinsic organization of the corpus callosum. Front Physiol 2024; 15:1393000. [PMID: 39035452 PMCID: PMC11259024 DOI: 10.3389/fphys.2024.1393000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Accepted: 05/16/2024] [Indexed: 07/23/2024] Open
Abstract
The corpus callosum-the largest commissural fiber system connecting the two cerebral hemispheres-is considered essential for bilateral sensory integration and higher cognitive functions. Most studies exploring the corpus callosum have examined either the anatomical, physiological, and neurochemical organization of callosal projections or the functional and/or behavioral aspects of the callosal connections after complete/partial callosotomy or callosal lesion. There are no works that address the intrinsic organization of the corpus callosum. We review the existing information on the activities that take place in the commissure in three sections: I) the topographical and neurochemical organization of the intracallosal fibers, II) the role of glia in the corpus callosum, and III) the role of the intracallosal neurons.
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Affiliation(s)
- Paolo Barbaresi
- Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, Marche Polytechnic University, Ancona, Italy
| | - Mara Fabri
- Department of Life and Environmental Sciences, Marche Polytechnic University, Ancona, Italy
| | - Teresa Lorenzi
- Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, Marche Polytechnic University, Ancona, Italy
| | - Andrea Sagrati
- Department of Life and Environmental Sciences, Marche Polytechnic University, Ancona, Italy
| | - Manrico Morroni
- Electron Microscopy Unit, Azienda Ospedaliero-Universitaria, Ancona, Italy
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3
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Cho H, Han S, Cho HJ. Empirical relationship between TEM-derived myelin volume fraction and MRI-R 2 values in aging ex vivo rat corpus callosum. Magn Reson Imaging 2023; 103:75-83. [PMID: 37451521 DOI: 10.1016/j.mri.2023.07.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 05/26/2023] [Accepted: 07/09/2023] [Indexed: 07/18/2023]
Abstract
Ex vivo ratiometric measurements of short- and long-T2 components using the multiple spin echo sequence of MRI are often employed to evaluate alterations in myelin content in the white matter (WM) of the brain. However, the relationship between absolute MRI-T2 values (long-T2 component) and myelin volumetric information in aged ex vivo rodent WM appears to be influenced by factors such as animal species, field strength, and fixation durations/washing. Here, multiple spin echo sequence-based MRI-R2 (the reciprocal of T2) values were measured in the corpus callosum (CC) region in the post-mortem rat brains (n = 9) of different age groups with common fixation techniques without washing at 7 T. Transmission electron microscopy (TEM)-based quantification of myelin volume fraction (MVF) and corresponding Monte-Carlo simulation to estimate relaxation rates (R2,IE) due to diffusion in the presence of inhomogeneous magnetic field perturbation in intra- and extra-cellular (IE) spaces were respectively performed. To determine whether the short-T2 components originating from myelin water were mixed with long-T2 components from IE water or were undetectable, the MVF values obtained from TEM results were respectively compared with MRI-R2 and R2,IE values. A significant correlation (Pearson's correlation coefficient r = 0.8763; p < 0.01) of average MRI-R2 and MVF values was observed. Estimated R2,IE values from Monte-Carlo simulations in IE water signals were also positively correlated (r = 0.8281; p < 0.01) with MVF values. However, the magnitudes of R2,IE values were much smaller than those observed for MRI-R2 values, indicating that changes in R2 related MVF are likely dominated by myelin water components. Such comparisons between independent parameters from MRI, TEM, and simulations support the suggestion that myelin water signals were indistinguishably mixed to exhibit mono-exponential T2 relaxation, and multiple spin echo sequence-based MRI-R2 values in aging ex vivo rat CC without prolonged washing still reflect the volumetric information of myelin, likely due to enhanced water exchange across the myelin.
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Affiliation(s)
- Hwapyeong Cho
- Department of Biomedical Engineering, Ulsan National Institute of Science and Technology, Ulsan, South Korea
| | - Sohyun Han
- Research Equipment Operations Division, Korea Basic Science Institute, Cheongju, South Korea.
| | - Hyung Joon Cho
- Department of Biomedical Engineering, Ulsan National Institute of Science and Technology, Ulsan, South Korea.
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4
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Cho H, Lee H, Gong Y, Kim YR, Cho J, Cho HJ. Quantitative susceptibility mapping and R1 measurement: Determination of the myelin volume fraction in the aging ex vivo rat corpus callosum. NMR IN BIOMEDICINE 2022; 35:e4645. [PMID: 34739153 DOI: 10.1002/nbm.4645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Revised: 10/03/2021] [Accepted: 10/16/2021] [Indexed: 06/13/2023]
Abstract
In studies of the white matter (WM) in aging brains, both quantitative susceptibility mapping (QSM) and direct R1 measurement offer potentially useful ex vivo MRI tools that allow volumetric characterization of myelin content changes. Despite the technical importance of such MRI methods in numerous age-related diseases, the supposed linear relationship between the estimates of either the QSM or R1 method and age-affected myelin contents has not been validated. In this study, the absolute myelin volume fraction (MVF) was determined by transmission electron microscopy (TEM) as a gold standard measure for comparison with the values obtained by the aforementioned MR methods. To theoretically evaluate and understand the MR signal characteristics, QSM simulations were performed using the finite perturber method (FPM). Specifically, the simulation geometry modeling was based on TEM-derived structures aligned orthogonally to the main magnetic field, the construct of which was used to estimate the magnetic field shift (ΔB) changes arising from the conjectured myelin structures. Experimentally, ex vivo corpus callosum (CC) samples from rat brains obtained at 6 weeks (n = 3), 4 months (n = 3), and 20 months (n = 3) after birth were used to establish the relationship between changes quantified by either QSM or R1 with the absolute MVF by TEM. From the ex vivo brain samples, the scatterplot of mean MVF versus R1 was fitted to a linear equation, where R1mean = 0.7948 × MVFmean + 0.8118 (Pearson's correlation coefficient r = 0.9138; p < 0.01), while the scatterplot of mean MVF versus MRI-derived magnetic susceptibility (χ) was also fitted to a line where χmeasured,mean = -0.1218 × MVFmean - 0.006345 (r = -0.8435; p < 0.01). As a result of the FPM-based QSM simulations, a linearly proportional relationship between the simulated magnetic susceptibility, χsimulated,mean , and MVF (r = -0.9648; p < 0.01) was established. Such a statistically significant linear correlation between MRI-derived values by the QSM (or R1 ) method and MVF demonstrated that variable myelin contents in the WM (i.e., CC) can be quantified across multiple stages of aging. These findings further support that both techniques based on QSM and R1 provide an efficient means of studying the brain-aging process with accurate volumetric quantification of the myelin content in WM.
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Affiliation(s)
- Hwapyeong Cho
- Department of Biomedical Engineering, Ulsan National Institute of Science and Technology, Ulsan, South Korea
| | - Hansol Lee
- Department of Biomedical Engineering, Ulsan National Institute of Science and Technology, Ulsan, South Korea
| | - Yelim Gong
- Department of Biomedical Engineering, Ulsan National Institute of Science and Technology, Ulsan, South Korea
| | - Young Ro Kim
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts, USA
| | - Junghun Cho
- Department of Radiology, Weill Cornell Medical College, New York, New York, USA
| | - Hyung Joon Cho
- Department of Biomedical Engineering, Ulsan National Institute of Science and Technology, Ulsan, South Korea
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5
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Sams E. Oligodendrocytes in the aging brain. Neuronal Signal 2021; 5:NS20210008. [PMID: 34290887 PMCID: PMC8264650 DOI: 10.1042/ns20210008] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 05/25/2021] [Accepted: 05/26/2021] [Indexed: 12/22/2022] Open
Abstract
More than half of the human brain volume is made up of white matter: regions where axons are coated in myelin, which primarily functions to increase the conduction speed of axon potentials. White matter volume significantly decreases with age, correlating with cognitive decline. Much research in the field of non-pathological brain aging mechanisms has taken a neuron-centric approach, with relatively little attention paid to other neural cells. This review discusses white matter changes, with focus on oligodendrocyte lineage cells and their ability to produce and maintain myelin to support normal brain homoeostasis. Improved understanding of intrinsic cellular changes, general senescence mechanisms, intercellular interactions and alterations in extracellular environment which occur with aging and impact oligodendrocyte cells is paramount. This may lead to strategies to support oligodendrocytes in aging, for example by supporting myelin synthesis, protecting against oxidative stress and promoting the rejuvenation of the intrinsic regenerative potential of progenitor cells. Ultimately, this will enable the protection of white matter integrity thus protecting cognitive function into the later years of life.
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Affiliation(s)
- Eleanor Catherine Sams
- Blizard Institute, Barts and The London School of Medicine and Dentistry Centre for Neuroscience, Surgery and Trauma, Blizard Institute, 4 Newark Street, Whitechapel E1 2AT, London
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6
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Kerkenberg N, Wachsmuth L, Zhang M, Schettler C, Ponimaskin E, Faber C, Baune BT, Zhang W, Hohoff C. Brain microstructural changes in mice persist in adulthood and are modulated by the palmitoyl acyltransferase ZDHHC7. Eur J Neurosci 2021; 54:5951-5967. [PMID: 34355442 DOI: 10.1111/ejn.15415] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 07/25/2021] [Indexed: 11/30/2022]
Abstract
For a long time, mice have been classified as adults with completely mature brains at 8 weeks of age, but recent research suggests that developmental brain changes occur for up to 6 months. In particular, adolescence coincides with dramatic changes of neuronal structure and function in the brain that influence the connectivity between areas like hippocampus and medial prefrontal cortex (mPFC). Neuronal development and plasticity are regulated in part by the palmitoyl acyltransferase ZDHHC7, which modulates structural connectivity between hippocampus and mPFC. The aim of the current study was to investigate whether developmental changes take place in hippocampus and mPFC microstructure even after 8 weeks of age and whether deficiency of ZDHHC7 impacts such age-dependent alterations. Altogether, 46 mice at 11, 14 or 17 weeks of age with a genetic Zdhhc7 knockout (KO) or wild type (WT) were analysed with neuroimaging and diffusion tensor-based fibre tractography. The hippocampus and mPFC regions were compared regarding fibre metrics, supplemented by volumetric and immunohistological analyses of the hippocampus. In WT animals, we identified age-dependent changes in hippocampal fibre lengths that followed a U-shaped pattern, whereas in mPFC, changes were linear. In Zdhhc7-deficient animals, the fibre statistics were reduced in both regions, whereas the hippocampus volume and the intensities of myelin and neurofilament were higher in 11-week-old KO mice compared to WTs. Our results confirmed ongoing changes of microstructure in mice up to 17 weeks old and demonstrate that deleting the Zdhhc7 gene impairs fibre development, suggesting that palmitoylation is important in this process.
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Affiliation(s)
- Nicole Kerkenberg
- Department of Mental Health, University of Münster, Münster, Germany.,Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Münster, Münster, Germany
| | - Lydia Wachsmuth
- Clinic of Radiology, University of Münster, Münster, Germany
| | - Mingyue Zhang
- Department of Mental Health, University of Münster, Münster, Germany
| | | | - Evgeni Ponimaskin
- Cellular Neurophysiology, Hannover Medical School, Hannover, Germany
| | - Cornelius Faber
- Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Münster, Münster, Germany.,Clinic of Radiology, University of Münster, Münster, Germany
| | - Bernhard T Baune
- Department of Mental Health, University of Münster, Münster, Germany.,Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Münster, Münster, Germany.,Department of Psychiatry, Melbourne Medical School, University of Melbourne, Melbourne, Victoria, Australia.,Florey Institute for Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia
| | - Weiqi Zhang
- Department of Mental Health, University of Münster, Münster, Germany.,Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Münster, Münster, Germany
| | - Christa Hohoff
- Department of Mental Health, University of Münster, Münster, Germany
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7
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Sun M, Brady RD, Casillas-Espinosa PM, Wright DK, Semple BD, Kim HA, Mychasiuk R, Sobey CG, O'Brien TJ, Vinh A, McDonald SJ, Shultz SR. Aged rats have an altered immune response and worse outcomes after traumatic brain injury. Brain Behav Immun 2019; 80:536-550. [PMID: 31039431 DOI: 10.1016/j.bbi.2019.04.038] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 03/28/2019] [Accepted: 04/26/2019] [Indexed: 12/14/2022] Open
Abstract
Initial studies suggest that increased age is associated with worse outcomes after traumatic brain injury (TBI), though the pathophysiological mechanisms responsible for this remain unclear. Immunosenescence (i.e., dysregulation of the immune system due to aging) may play a significant role in influencing TBI outcomes. This study therefore examined neurological outcomes and immune response in young-adult (i.e., 10 weeks old) compared to middle-aged (i.e., 1 year old) rats following a TBI (i.e., fluid percussion) or sham-injury. Rats were euthanized at either 24 h or one-week post-injury to analyze immune cell populations in the brain and periphery via flow cytometry, as well as telomere length (i.e., a biomarker of neurological health). Behavioral testing, as well as volumetric and diffusion-weighted MRI, were also performed in the one-week recovery rats to assess for functional deficits and brain damage. Middle-aged rats had worse sensorimotor deficits and shorter telomeres after TBI compared to young rats. Both aging and TBI independently worsened cognitive function and cortical volume. These changes occurred in the presence of fewer total leukocytes, fewer infiltrating myeloid cells, and fewer microglia in the brains of middle-aged TBI rats compared to young rats. These findings indicate that middle-aged rats have worse sensorimotor deficits and shorter telomeres after TBI than young rats, and this may be related to an altered neuroimmune response. Although further studies are required, these findings have important implications for understanding the pathophysiology and optimal treatment strategies in TBI patients across the life span.
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Affiliation(s)
- Mujun Sun
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia; Department of Medicine, The Royal Melbourne Hospital, The University of Melbourne, Melbourne, VIC, Australia
| | - Rhys D Brady
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia; Department of Medicine, The Royal Melbourne Hospital, The University of Melbourne, Melbourne, VIC, Australia
| | - Pablo M Casillas-Espinosa
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia; Department of Medicine, The Royal Melbourne Hospital, The University of Melbourne, Melbourne, VIC, Australia
| | - David K Wright
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Bridgette D Semple
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia; Department of Medicine, The Royal Melbourne Hospital, The University of Melbourne, Melbourne, VIC, Australia
| | - Hyun Ah Kim
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora, VIC, Australia
| | - Richelle Mychasiuk
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia; Department of Psychology, University of Calgary, Calgary, AB, Canada
| | - Christopher G Sobey
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora, VIC, Australia
| | - Terence J O'Brien
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia; Department of Medicine, The Royal Melbourne Hospital, The University of Melbourne, Melbourne, VIC, Australia
| | - Antony Vinh
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora, VIC, Australia
| | - Stuart J McDonald
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia; Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora, VIC, Australia
| | - Sandy R Shultz
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia; Department of Medicine, The Royal Melbourne Hospital, The University of Melbourne, Melbourne, VIC, Australia.
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8
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Neely CLC, Lippi SLP, Lanzirotti A, Flinn JM. Localization of Free and Bound Metal Species through X-Ray Synchrotron Fluorescence Microscopy in the Rodent Brain and Their Relation to Behavior. Brain Sci 2019; 9:E74. [PMID: 30925761 PMCID: PMC6523809 DOI: 10.3390/brainsci9040074] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 03/23/2019] [Accepted: 03/26/2019] [Indexed: 12/27/2022] Open
Abstract
Biometals in the brain, such as zinc, copper, and iron, are often discussed in cases of neurological disorders; however, these metals also have important regulatory functions and mediate cell signaling and plasticity. With the use of synchrotron X-ray fluorescence, our lab localized total, both bound and free, levels of zinc, copper, and iron in a cross section of one hemisphere of a rat brain, which also showed differing metal distributions in different regions within the hippocampus, the site in the brain known to be crucial for certain types of memory. This review discusses the several roles of these metals in brain regions with an emphasis on hippocampal cell signaling, based on spatial mapping obtained from X-ray fluorescence microscopy. We also discuss the localization of these metals and emphasize different cell types and receptors in regions with metal accumulation, as well as the potential relationship between this physiology and behavior.
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Affiliation(s)
- Caroline L C Neely
- Department of Psychology, George Mason University, 4400 University Drive, Fairfax, VA 22030, USA.
| | - Stephen L P Lippi
- Department of Psychology & Sociology, Angelo State University, 2601 W. Avenue N, ASU Station #10907, San Angelo, TX 76909, USA.
| | - Antonio Lanzirotti
- Center for Advanced Radiation Sources, University of Chicago, 9700 South Cass Avenue, Argonne, IL 60439, USA.
| | - Jane M Flinn
- Department of Psychology, George Mason University, 4400 University Drive, Fairfax, VA 22030, USA.
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9
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Begolly S, Olschowka JA, Love T, Williams JP, O'Banion MK. Fractionation enhances acute oligodendrocyte progenitor cell radiation sensitivity and leads to long term depletion. Glia 2017; 66:846-861. [PMID: 29288597 DOI: 10.1002/glia.23288] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 12/13/2017] [Accepted: 12/13/2017] [Indexed: 12/18/2022]
Abstract
Ionizing radiation (IR) is commonly used to treat central nervous system (CNS) cancers and metastases. While IR promotes remission, frequent side effects including impaired cognition and white matter loss occur following treatment. Fractionation is used to minimize these CNS late side effects, as it reduces IR effects in differentiated normal tissue, but not rapidly proliferating normal or tumor tissue. However, side effects occur even with the use of fractionated paradigms. Oligodendrocyte progenitor cells (OPCs) are a proliferative population within the CNS affected by radiation. We hypothesized that fractionated radiation would lead to OPC loss, which could contribute to the delayed white matter loss seen after radiation exposure. We found that fractionated IR induced a greater early loss of OPCs than an equivalent single dose exposure. Furthermore, OPC recovery was impaired following fractionated IR. Finally, reduced OPC differentiation and mature oligodendrocyte numbers occurred in single dose and fractionated IR paradigms. This work demonstrates that fractionation does not spare normal brain tissue and, importantly, highlights the sensitivity of OPCs to fractionated IR, suggesting that fractionated schedules may promote white matter dysfunction, a point that should be considered in radiotherapy.
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Affiliation(s)
- Sage Begolly
- Departments of Environmental Medicine, University of Rochester School of Medicine & Dentistry, Rochester, New York
| | - John A Olschowka
- Department of Neuroscience and Del Monte Neuroscience Institute, University of Rochester School of Medicine & Dentistry, Rochester, New York
| | - Tanzy Love
- Department of Biostatistics and Computational Biology, University of Rochester School of Medicine & Dentistry, Rochester, New York
| | - Jacqueline P Williams
- Departments of Environmental Medicine, University of Rochester School of Medicine & Dentistry, Rochester, New York.,Department of Radiation Oncology, University of Rochester School of Medicine & Dentistry, Rochester, New York
| | - M Kerry O'Banion
- Department of Neuroscience and Del Monte Neuroscience Institute, University of Rochester School of Medicine & Dentistry, Rochester, New York.,Department of Neurology, University of Rochester School of Medicine & Dentistry, Rochester, New York
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10
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Begolly S, Shrager PG, Olschowka JA, Williams JP, O'Banion MK. Fractionation Spares Mice From Radiation-Induced Reductions in Weight Gain But Does Not Prevent Late Oligodendrocyte Lineage Side Effects. Int J Radiat Oncol Biol Phys 2016; 96:449-457. [PMID: 27478169 DOI: 10.1016/j.ijrobp.2016.05.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 04/28/2016] [Accepted: 05/04/2016] [Indexed: 01/05/2023]
Abstract
PURPOSE To determine the late effects of fractionated versus single-dose cranial radiation on murine white matter. METHODS AND MATERIALS Mice were exposed to 0 Gy, 6 × 6 Gy, or 1 × 20 Gy cranial irradiation at 10 to 12 weeks of age. Endpoints were assessed through 18 months from exposure using immunohistochemistry, electron microscopy, and electrophysiology. RESULTS Weight gain was temporarily reduced after irradiation; greater loss was seen after single versus fractionated doses. Oligodendrocyte progenitor cells were reduced early and late after both single and fractionated irradiation. Both protocols also increased myelin g-ratio, reduced the number of nodes of Ranvier, and promoted a shift in the proportion of small, unmyelinated versus large, myelinated axon fibers. CONCLUSIONS Fractionation does not adequately spare normal white matter from late radiation side effects.
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Affiliation(s)
- Sage Begolly
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York
| | - Peter G Shrager
- Department of Neuroscience, University of Rochester School of Medicine and Dentistry, Rochester, New York; Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York
| | - John A Olschowka
- Department of Neuroscience, University of Rochester School of Medicine and Dentistry, Rochester, New York
| | - Jacqueline P Williams
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York; Department of Radiation Oncology, University of Rochester School of Medicine and Dentistry, Rochester, New York
| | - M Kerry O'Banion
- Department of Neuroscience, University of Rochester School of Medicine and Dentistry, Rochester, New York; Department of Neurology, University of Rochester School of Medicine and Dentistry, Rochester, New York.
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11
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Juraska JM, Willing J. Pubertal onset as a critical transition for neural development and cognition. Brain Res 2016; 1654:87-94. [PMID: 27060769 DOI: 10.1016/j.brainres.2016.04.012] [Citation(s) in RCA: 140] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 04/02/2016] [Accepted: 04/05/2016] [Indexed: 12/26/2022]
Abstract
Adolescence, broadly defined as the period between childhood and adulthood, is characterized by a variety of neuroanatomical and behavioral changes. In human adolescents, the cerebral cortex, especially the prefrontal cortex, decreases in size while the cortical white matter increases. Puberty appears to be an important factor in both of these changes. However, the white matter continues to grow beyond what is thought to be adolescence, while the gray matter of the cortex stabilizes by young adulthood. The size changes that are the manifestation of cortical reorganization during human adolescence are also seen in cellular reorganization in the rat cortex. The prefrontal cortex loses neurons, dendrites and synapses while myelination in the white matter continues to increase. All of this reorganization is more marked in female rats, and there is evidence both from pubertal timing and from removal of the ovaries that puberty plays an important role in initiating these changes in females. The maturation of behavioral functions of the prefrontal cortex, such as inhibitory control, occurs in both humans and rats across adolescence. There is also evidence for puberty as a major factor in decreasing perseveration in rats, but few studies have been done using pubertal status as an experimental variable, and the role of the gonadal steroids in modulating behavior throughout life makes clear effects more difficult to document. In all, puberty appears to be so essential to the changes occurring during adolescence that it should be recorded when possible, especially given the sex difference in pubertal timing. This article is part of a Special Issue entitled SI: Adolescent plasticity.
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Affiliation(s)
- Janice M Juraska
- Department of Psychology and Neuroscience Program University of Illinois, 603 E. Daniel St., Champaign, IL 61820, United States.
| | - Jari Willing
- Department of Psychology and Neuroscience Program University of Illinois, 603 E. Daniel St., Champaign, IL 61820, United States
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12
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Developmental neurotoxicity of inhaled ambient ultrafine particle air pollution: Parallels with neuropathological and behavioral features of autism and other neurodevelopmental disorders. Neurotoxicology 2015; 59:140-154. [PMID: 26721665 DOI: 10.1016/j.neuro.2015.12.014] [Citation(s) in RCA: 153] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 12/18/2015] [Accepted: 12/18/2015] [Indexed: 12/25/2022]
Abstract
Accumulating evidence from both human and animal studies show that brain is a target of air pollution. Multiple epidemiological studies have now linked components of air pollution to diagnosis of autism spectrum disorder (ASD), a linkage with plausibility based on the shared mechanisms of inflammation. Additional plausibility appears to be provided by findings from our studies in mice of exposures from postnatal day (PND) 4-7 and 10-13 (human 3rd trimester equivalent), to concentrated ambient ultrafine (UFP) particles, considered the most reactive component of air pollution, at levels consistent with high traffic areas of major U.S. cities and thus highly relevant to human exposures. These exposures, occurring during a period of marked neuro- and gliogenesis, unexpectedly produced a pattern of developmental neurotoxicity notably similar to multiple hypothesized mechanistic underpinnings of ASD, including its greater impact in males. UFP exposures induced inflammation/microglial activation, reductions in size of the corpus callosum (CC) and associated hypomyelination, aberrant white matter development and/or structural integrity with ventriculomegaly (VM), elevated glutamate and excitatory/inhibitory imbalance, increased amygdala astrocytic activation, and repetitive and impulsive behaviors. Collectively, these findings suggest the human 3rd trimester equivalent as a period of potential vulnerability to neurodevelopmental toxicity to UFP, particularly in males, and point to the possibility that UFP air pollution exposure during periods of rapid neuro- and gliogenesis may be a risk factor not only for ASD, but also for other neurodevelopmental disorders that share features with ASD, such as schizophrenia, attention deficit disorder, and periventricular leukomalacia.
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13
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Altered contralateral sensorimotor system organization after experimental hemispherectomy: a structural and functional connectivity study. J Cereb Blood Flow Metab 2015; 35:1358-67. [PMID: 25966942 PMCID: PMC4527994 DOI: 10.1038/jcbfm.2015.101] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 04/10/2015] [Indexed: 12/18/2022]
Abstract
Hemispherectomy is often followed by remarkable recovery of cognitive and motor functions. This reflects plastic capacities of the remaining hemisphere, involving large-scale structural and functional adaptations. Better understanding of these adaptations may (1) provide new insights in the neuronal configuration and rewiring that underlies sensorimotor outcome restoration, and (2) guide development of rehabilitation strategies to enhance recovery after hemispheric lesioning. We assessed brain structure and function in a hemispherectomy model. With MRI we mapped changes in white matter structural integrity and gray matter functional connectivity in eight hemispherectomized rats, compared with 12 controls. Behavioral testing involved sensorimotor performance scoring. Diffusion tensor imaging and resting-state functional magnetic resonance imaging were acquired 7 and 49 days post surgery. Hemispherectomy caused significant sensorimotor deficits that largely recovered within 2 weeks. During the recovery period, fractional anisotropy was maintained and white matter volume and axial diffusivity increased in the contralateral cerebral peduncle, suggestive of preserved or improved white matter integrity despite overall reduced white matter volume. This was accompanied by functional adaptations in the contralateral sensorimotor network. The observed white matter modifications and reorganization of functional network regions may provide handles for rehabilitation strategies improving functional recovery following large lesions.
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Ali-Rahmani F, Grigson PS, Lee S, Neely E, Connor JR, Schengrund CL. H63D mutation in hemochromatosis alters cholesterol metabolism and induces memory impairment. Neurobiol Aging 2014; 35:1511.e1-12. [DOI: 10.1016/j.neurobiolaging.2013.12.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2013] [Revised: 12/19/2013] [Accepted: 12/19/2013] [Indexed: 12/30/2022]
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15
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Bocci T, Pietrasanta M, Cerri C, Restani L, Caleo M, Sartucci F. Visual callosal connections: role in visual processing in health and disease. Rev Neurosci 2014; 25:113-27. [DOI: 10.1515/revneuro-2013-0025] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 09/07/2013] [Indexed: 11/15/2022]
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16
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Wang S, Young KM. White matter plasticity in adulthood. Neuroscience 2013; 276:148-60. [PMID: 24161723 DOI: 10.1016/j.neuroscience.2013.10.018] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 10/09/2013] [Accepted: 10/10/2013] [Indexed: 01/24/2023]
Abstract
CNS white matter is subject to a novel form of neural plasticity which has been termed "myelin plasticity". It is well established that oligodendrocyte generation and the addition of new myelin internodes continue throughout normal adulthood. These new myelin internodes maybe required for the de novo myelination of previously unmyelinated axons, myelin sheath replacement, or even myelin remodeling. Each process could alter axonal conduction velocity, but to what end? We review the changes that occur within the white matter over the lifetime, the known regulators and mediators of white matter plasticity in the mature CNS, and the physiological role this plasticity may play in CNS function.
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Affiliation(s)
- S Wang
- Menzies Research Institute Tasmania, University of Tasmania, Hobart 7000, Australia
| | - K M Young
- Menzies Research Institute Tasmania, University of Tasmania, Hobart 7000, Australia.
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17
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Juraska JM, Sisk CL, DonCarlos LL. Sexual differentiation of the adolescent rodent brain: hormonal influences and developmental mechanisms. Horm Behav 2013; 64:203-10. [PMID: 23998664 DOI: 10.1016/j.yhbeh.2013.05.010] [Citation(s) in RCA: 144] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2013] [Revised: 05/03/2013] [Accepted: 05/28/2013] [Indexed: 11/24/2022]
Abstract
This article is part of a Special Issue "Puberty and Adolescence". Sexual differentiation is the process by which the nervous system becomes structurally and functionally dissimilar in females and males. In mammals, this process has been thought to occur during prenatal and early postnatal development, when a transient increase in testosterone secretion masculinizes and defeminizes the developing male nervous system. Decades of research have led to the views that structural sexual dimorphisms created during perinatal development are passively maintained throughout life, and that ovarian hormones do not play an active role in feminization of the nervous system. Furthermore, perinatal testosterone was thought to determine sex differences in neuron number by regulating cell death and cell survival, and not by regulating cell proliferation. As investigations of neural development during adolescence became more prominent in the late 20th century and revealed the extent of brain remodeling during this time, each of these tenets has been challenged and modified. Here we review evidence from the animal literature that 1) the brain is further sexually differentiated during puberty and adolescence; 2) ovarian hormones play an active role in the feminization of the brain during puberty; and 3) hormonally modulated, sex-specific addition of new neurons and glial cells, as well as loss of neurons, contribute to sexual differentiation of hypothalamic, limbic, and cortical regions during adolescence. This architectural remodeling during the adolescent phase of sexual differentiation of the brain may underlie the known sex differences in vulnerability to addiction and psychiatric disorders that emerge during this developmental period.
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Affiliation(s)
- Janice M Juraska
- Department of Psychology and Neuroscience Program, University of Illinois, 603 E Daniel St., Champaign, IL 61820, United States.
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18
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Yang S, Li C, Qiu X, Zhang L, Lu W, Chen L, Zhao Y, Shi X, Huang C, Cheng G, Tang Y. Effects of an enriched environment on myelin sheaths in the white matter of rats during normal aging: A stereological study. Neuroscience 2013; 234:13-21. [DOI: 10.1016/j.neuroscience.2013.01.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 12/25/2012] [Accepted: 01/03/2013] [Indexed: 11/25/2022]
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19
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Chareyron LJ, Lavenex PB, Lavenex P. Postnatal development of the amygdala: A stereological study in rats. J Comp Neurol 2012; 520:3745-63. [DOI: 10.1002/cne.23132] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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20
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The corpus callosum and the visual cortex: plasticity is a game for two. Neural Plast 2012; 2012:838672. [PMID: 22792494 PMCID: PMC3388387 DOI: 10.1155/2012/838672] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 04/19/2012] [Indexed: 01/03/2023] Open
Abstract
Throughout life, experience shapes and selects the most appropriate brain functional connectivity to adapt to a changing environment. An ideal system to study experience-dependent plasticity is the visual cortex, because visual experience can be easily manipulated. In this paper, we focus on the role of interhemispheric, transcallosal projections in experience-dependent plasticity of the visual cortex. We review data showing that deprivation of sensory experience can modify the morphology of callosal fibres, thus altering the communication between the two hemispheres. More importantly, manipulation of callosal input activity during an early critical period alters developmental maturation of functional properties in visual cortex and modifies its ability to remodel in response to experience. We also discuss recent data in rat visual cortex, demonstrating that the corpus callosum plays a role in binocularity of cortical neurons and is involved in the plastic shift of eye preference that follows a period of monocular eyelid suture (monocular deprivation) in early age. Thus, experience can modify the fine connectivity of the corpus callosum, and callosal connections represent a major pathway through which experience can mediate functional maturation and plastic rearrangements in the visual cortex.
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Abstract
The literature on the neuroanatomical changes that occur during normal, non-demented aging is reviewed here with an emphasis on the improved accuracy of studies that use stereological techniques. Loss of neural tissue involved in cognition occurs during aging of humans as well as the other mammals that have been examined. There is considerable regional specificity within the cerebral cortex and the hippocampus in both the degree and cellular basis for loss. The anatomy of the prefrontal cortex is especially vulnerable to the effects of aging while the major subfields of the hippocampus are not. A loss of neurons, dendrites and synapses has been documented, as well as changes in neurotransmitter systems, in some regions of the cortex and hippocampus but not others. Species differences are also apparent in the cortical white matter and the corpus callosum where there are indications of loss of myelin in humans, but most evidence favors preservation in rats. The examination of whether the course of neuroanatomical aging is altered by hormone replacement in females is just beginning. When hormone replacement is started close to the time of cycle cessation, there are indications in humans and rats that replacement can preserve neural tissue but there is some variability due to the type of hormones and regimen of administration.
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Affiliation(s)
- Janice M Juraska
- Department of Psychology and Program in Neuroscience, University of Illinois, 603 E Daniel, Champaign, IL, 61820, USA,
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22
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Latimer CS, Searcy JL, Bridges MT, Brewer LD, Popović J, Blalock EM, Landfield PW, Thibault O, Porter NM. Reversal of glial and neurovascular markers of unhealthy brain aging by exercise in middle-aged female mice. PLoS One 2011; 6:e26812. [PMID: 22046366 PMCID: PMC3201977 DOI: 10.1371/journal.pone.0026812] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Accepted: 10/04/2011] [Indexed: 01/14/2023] Open
Abstract
Healthy brain aging and cognitive function are promoted by exercise. The benefits of exercise are attributed to several mechanisms, many which highlight its neuroprotective role via actions that enhance neurogenesis, neuronal morphology and/or neurotrophin release. However, the brain is also composed of glial and vascular elements, and comparatively less is known regarding the effects of exercise on these components in the aging brain. Here, we show that aerobic exercise at mid-age decreased markers of unhealthy brain aging including astrocyte hypertrophy, a hallmark of brain aging. Middle-aged female mice were assigned to a sedentary group or provided a running wheel for six weeks. Exercise decreased hippocampal astrocyte and myelin markers of aging but increased VEGF, a marker of angiogenesis. Brain vascular casts revealed exercise-induced structural modifications associated with improved endothelial function in the periphery. Our results suggest that age-related astrocyte hypertrophy/reactivity and myelin dysregulation are aggravated by a sedentary lifestyle and accompanying reductions in vascular function. However, these effects appear reversible with exercise initiated at mid-age. As this period of the lifespan coincides with the appearance of multiple markers of brain aging, including initial signs of cognitive decline, it may represent a window of opportunity for intervention as the brain appears to still possess significant vascular plasticity. These results may also have particular implications for aging females who are more susceptible than males to certain risk factors which contribute to vascular aging.
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Affiliation(s)
- Caitlin S. Latimer
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, Lexington, Kentucky, United States of America
| | - James L. Searcy
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, Lexington, Kentucky, United States of America
| | - Michael T. Bridges
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, Lexington, Kentucky, United States of America
| | - Lawrence D. Brewer
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, Lexington, Kentucky, United States of America
| | - Jelena Popović
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, Lexington, Kentucky, United States of America
| | - Eric M. Blalock
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, Lexington, Kentucky, United States of America
| | - Philip W. Landfield
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, Lexington, Kentucky, United States of America
| | - Olivier Thibault
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, Lexington, Kentucky, United States of America
| | - Nada M. Porter
- Department of Molecular and Biomedical Pharmacology, University of Kentucky College of Medicine, Lexington, Kentucky, United States of America
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23
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Age related changes in the myelinated fibers of corpus callosum. Neurosci Lett 2011; 499:208-12. [DOI: 10.1016/j.neulet.2011.05.229] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 05/22/2011] [Accepted: 05/25/2011] [Indexed: 11/20/2022]
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24
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Midsagittal structural differences and sexual dimorphism of the corpus callosum in obsessive-compulsive disorder. Psychiatry Res 2011; 192:147-53. [PMID: 21543190 DOI: 10.1016/j.pscychresns.2010.12.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Revised: 12/07/2010] [Accepted: 12/08/2010] [Indexed: 11/21/2022]
Abstract
Neurobiological abnormalities in various brain regions, including the orbitofrontal cortex, basal ganglia, and thalamus, have been found in patients with obsessive-compulsive disorder (OCD), and impairment in white matter connectivity in these regions has recently been suggested. To investigate structural connectivity in OCD, we used the midsagittal area and thickness to assess the morphology of the corpus callosum (CC), the largest connecting fiber tract in the human brain. Midsagittal magnetic resonance images of the CC were acquired from 69 adult patients with OCD and 69 matched normal controls. We calculated and compared the total area and the areas of five subregions of the CC as well as the distances between 200 equidistant points on the top and bottom of lines on the surface of the CC in the two groups. The absolute total area of the CC was significantly larger in OCD patients than in controls when brain size, age, gender, and IQ were controlled. Significant enlargements in CC1, CC2, and CC5 were seen in OCD patients before correction for multiple comparisons. The thickness of the caudal part of the splenium was greater in OCD patients than in controls. The analysis according to gender showed that only male OCD patients differed from male controls with respect to the area of the CC. These findings reflect structural abnormalities in the CC, and especially in the splenium, in adult patients with OCD. Abnormal interhemispheric connectivity, including the parietotemporal and occipital areas, may affect the pathophysiology of OCD. Sexual dimorphism in the CC of OCD patients should be considered.
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25
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Richardson WD, Young KM, Tripathi RB, McKenzie I. NG2-glia as multipotent neural stem cells: fact or fantasy? Neuron 2011; 70:661-73. [PMID: 21609823 PMCID: PMC3119948 DOI: 10.1016/j.neuron.2011.05.013] [Citation(s) in RCA: 226] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/10/2011] [Indexed: 12/23/2022]
Abstract
Cycling glial precursors-"NG2-glia"-are abundant in the developing and mature central nervous system (CNS). During development, they generate oligodendrocytes. In culture, they can revert to a multipotent state, suggesting that they might have latent stem cell potential that could be harnessed to treat neurodegenerative disease. This hope has been subdued recently by a series of fate-mapping studies that cast NG2-glia as dedicated oligodendrocyte precursors in the healthy adult CNS-though rare, neuron production in the piriform cortex remains a possibility. Following CNS damage, the repertoire of NG2-glia expands to include Schwann cells and possibly astrocytes-but so far not neurons. This reaffirms the central role of NG2-glia in myelin repair. The realization that oligodendrocyte generation continues throughout normal adulthood has seeded the idea that myelin genesis might also be involved in neural plasticity. We review these developments, highlighting areas of current interest, contention, and speculation.
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Affiliation(s)
- William D Richardson
- Wolfson Institute for Biomedical Research and Research Department of Cell and Developmental Biology, University College London (UCL), UK.
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26
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Peiffer AM, Shi L, Olson J, Brunso-Bechtold JK. Differential effects of radiation and age on diffusion tensor imaging in rats. Brain Res 2010; 1351:23-31. [PMID: 20599817 DOI: 10.1016/j.brainres.2010.06.049] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 05/28/2010] [Accepted: 06/21/2010] [Indexed: 02/08/2023]
Abstract
Greater than 50% of adults and approximately 100% of children who survive >6 months after fractionated partial or whole-brain radiotherapy develop cognitive impairments. Noninvasive methods are needed for detecting and tracking the radiation-induced brain injury associated with these impairments. Using magnetic resonance imaging, we sought to detect structural changes associated with brain injury in our rodent model of fractionated whole-brain irradiation (fWBI) induced cognitive impairment and to compare those changes with alterations that occur during the aging process. Middle aged rats were given a clinically relevant dose of fWBI (40 Gy: two 5 Gy fractions/week for 4 weeks) and scanned approximately 1 year post-irradiation to obtain whole-brain T2 and diffusion tensor images (DTI); control groups of sham-irradiated age-matched and young rats were also scanned. No gross structural changes were evident in the T2 structural images, and no detectable fWBI-induced DTI changes in fractional anisotropy (FA) were found in heavily myelinated white matter (corpus callosum, cingulum, and deep cortical white matter). However, significant fWBI-induced variability in FA distribution was present in the superficial parietal cortex due to an fWBI-induced decline in FA in the more anterior slices through parietal cortex. Young rats had significantly lower FA values relative to both groups of older rats, but only within the corpus callosum. These findings suggest that targets of the fWBI-induced change in this model may be the less myelinated or unmyelinated axons, extracellular matrix, or synaptic fields rather than heavily myelinated tracts.
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Affiliation(s)
- Ann M Peiffer
- Department of Radiology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
| | - Lei Shi
- Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | - John Olson
- Center for Biomolecular Imaging, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | - Judy K Brunso-Bechtold
- Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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27
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Cerghet M, Skoff RP, Swamydas M, Bessert D. Sexual dimorphism in the white matter of rodents. J Neurol Sci 2009; 286:76-80. [PMID: 19625027 DOI: 10.1016/j.jns.2009.06.039] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2009] [Revised: 06/10/2009] [Accepted: 06/22/2009] [Indexed: 10/20/2022]
Abstract
Sexual dimorphism of astrocytes and neurons is well documented in many brain and spinal cord structures. Sexual dimorphism of oligodendrocytes (Olgs) and myelin has received less attention. We recently showed that density of Olgs in corpus callosum, fornix, and spinal cord of wild-type male rodents is more densely packed than in females; myelin proteins and myelin gene expression are likewise greater in males than in female rodents. However, glial cell proliferation and cell death were two times greater in female corpus callosum. Endogenous sex hormones, specifically lack of androgens, produce an Olg female phenotype in castrated male mouse. In vitro studies using Olgs culture also showed differences between males and females Olg survival and signaling pathways in response to sexual hormones. Sexual dimorphism of white matter tracts and glia in rodents indicates the necessity for controlling gender in the experimental studies of neurodegenerative disorders. Most importantly, our studies suggest that hormones may contribute to sexual dimorphism observed in certain human diseases including multiple sclerosis.
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Affiliation(s)
- Mirela Cerghet
- Henry Ford Health System, Detroit, MI 48202, United States.
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28
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Markham JA, Herting MM, Luszpak AE, Juraska JM, Greenough WT. Myelination of the corpus callosum in male and female rats following complex environment housing during adulthood. Brain Res 2009; 1288:9-17. [PMID: 19596280 DOI: 10.1016/j.brainres.2009.06.087] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2007] [Revised: 06/24/2009] [Accepted: 06/26/2009] [Indexed: 02/08/2023]
Abstract
Myelination is an important process in brain development, and delays or abnormalities in this process have been associated with a number of conditions including autism, developmental delay, attention deficit disorder, and schizophrenia. Myelination can be sensitive to developmental experience; however, although the adult brain remains highly plastic, it is unknown whether myelination continues to be sensitive to experience during adulthood. Male and female rats were socially housed until four months of age, at which time they were moved into either a complex or "enriched" environment (EC) or an isolated condition (IC). Although the area of the splenium (posterior 20% of the callosum, which contains axons from visual cortical neurons) increased by about 10% following two months of EC housing, the area occupied by myelinated axons was not influenced by adult housing condition. Instead, it was the area occupied by glial cell processes and unmyelinated axons which significantly increased following EC housing. Neither the size nor the myelin content of the genu (anterior 15% of the callosum) was sensitive to manipulations of adult housing condition, but males had more area occupied by myelinated axons in both callosal regions. Finally, the inability of two months of complex environment housing during adulthood to impact the number of myelinated axons in the splenium was confirmed in a subset of animals using quantitative electron microscopy. We conclude that the sensitivity of myelination to experience is reduced in adulthood relative to development in both sexes.
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Affiliation(s)
- Julie A Markham
- Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
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29
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Jito J, Nakasu S, Ito R, Fukami T, Morikawa S, Inubushi T. Maturational changes in diffusion anisotropy in the rat corpus callosum: Comparison with quantitative histological evaluation. J Magn Reson Imaging 2008; 28:847-54. [DOI: 10.1002/jmri.21496] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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30
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Flores AI, Narayanan SP, Morse EN, Shick HE, Yin X, Kidd G, Avila RL, Kirschner DA, Macklin WB. Constitutively active Akt induces enhanced myelination in the CNS. J Neurosci 2008; 28:7174-83. [PMID: 18614687 PMCID: PMC4395496 DOI: 10.1523/jneurosci.0150-08.2008] [Citation(s) in RCA: 288] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The serine/threonine kinase Akt regulates multiple cellular functions. The current studies identify a new role for Akt in CNS myelination. In earlier studies on cultured oligodendrocytes, we showed that neuregulin signals through phosphatidylinositol-3'-OH kinase and Akt to enhance survival of oligodendrocytes. However, when transgenic animals were generated that overexpressed constitutively active Akt in oligodendrocytes and their progenitor cells, no enhanced survival of oligodendrocytes or progenitors was found. No alteration in the proliferation or death of progenitors was noted. In contrast, the major impact of Akt overexpression in oligodendrocytes was enhanced myelination. Most interestingly, oligodendrocytes in these mice continued actively myelinating throughout life. Thus, expression of constitutively active Akt in oligodendrocytes and their progenitor cells generated no more oligodendrocytes, but dramatically more myelin. The increased myelination continued as these mice aged, resulting in enlarged optic nerves and white matter areas. In older animals with enlarged white matter areas, the density of oligodendrocytes was reduced, but because of the increased area, the total number of oligodendrocytes remained comparable with wild-type controls. Interestingly, in these animals, overexpression of Akt in Schwann cells did not impact myelination. Thus, in vivo, constitutively active Akt enhances CNS myelination but not PNS myelination and has no impact developmentally on oligodendrocyte number. Understanding the unique aspects of Akt signal transduction in oligodendrocytes that lead to myelination rather than uncontrolled proliferation of oligodendrocyte progenitor cells may have important implications for understanding remyelination in the adult nervous system.
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Affiliation(s)
- Ana I. Flores
- 1Department of Neurosciences, Cleveland Clinic, Cleveland, Ohio 44195, and
| | | | - Emily N. Morse
- 1Department of Neurosciences, Cleveland Clinic, Cleveland, Ohio 44195, and
| | - H. Elizabeth Shick
- 1Department of Neurosciences, Cleveland Clinic, Cleveland, Ohio 44195, and
| | - Xinghua Yin
- 1Department of Neurosciences, Cleveland Clinic, Cleveland, Ohio 44195, and
| | - Grahame Kidd
- 1Department of Neurosciences, Cleveland Clinic, Cleveland, Ohio 44195, and
| | - Robin L. Avila
- 2Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467
| | | | - Wendy B. Macklin
- 1Department of Neurosciences, Cleveland Clinic, Cleveland, Ohio 44195, and
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31
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Yang S, Li C, Zhang W, Wang W, Tang Y. Sex differences in the white matter and myelinated nerve fibers of Long-Evans rats. Brain Res 2008; 1216:16-23. [DOI: 10.1016/j.brainres.2008.03.052] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2008] [Revised: 03/19/2008] [Accepted: 03/21/2008] [Indexed: 11/29/2022]
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32
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Yates MA, Markham JA, Anderson SE, Morris JR, Juraska JM. Regional variability in age-related loss of neurons from the primary visual cortex and medial prefrontal cortex of male and female rats. Brain Res 2008; 1218:1-12. [PMID: 18513705 DOI: 10.1016/j.brainres.2008.04.055] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2007] [Revised: 11/16/2007] [Accepted: 04/23/2008] [Indexed: 11/17/2022]
Abstract
During aging, changes in the structure of the cerebral cortex of the rat have been seen, but potential changes in neuron number remain largely unexplored. In the present study, stereological methods were used to examine neuron number in the medial prefrontal cortex and primary visual cortex of young adult (85-90 days of age) and aged (19-22 months old) male and female rats in order to investigate any age-related losses. Possible sex differences in aging were also examined since sexually dimorphic patterns of aging have been seen in other measures. An age-related loss of neurons (18-20%), which was mirrored in volume losses, was found to occur in the primary visual cortex in both sexes in all layers except IV. Males, but not females, also lost neurons (15%) from layer V/VI of the ventral medial prefrontal cortex and showed an overall decrease in volume of this region. In contrast, dorsal medial prefrontal cortex showed no age-related changes. The effects of aging clearly differ among regions of the rat brain and to some degree, between the sexes.
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Affiliation(s)
- M A Yates
- Psychology Department, University of Illinois Urbana-Champaign, Champaign, IL 61820, USA
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