51
|
Siriphorn A, Dunham KA, Chompoopong S, Floyd CL. Postinjury administration of 17β-estradiol induces protection in the gray and white matter with associated functional recovery after cervical spinal cord injury in male rats. J Comp Neurol 2013; 520:2630-46. [PMID: 22684936 DOI: 10.1002/cne.23056] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The majority of spinal cord injuries (SCIs) in the clinic occur at the lower cervical levels, resulting in both white and gray matter disruption. In contrast, most experimental models of SCI in rodents induce damage in the thoracic cord, resulting primarily in white matter disruption. To address this disparity, experimental cervical SCI models have been developed. Thus, we used a recently characterized model of cervical hemicontusion SCI in adult male rats to assess the potential therapeutic effect of post-SCI administration of 17β-estradiol. Rats received a hemicontusion at the level of the fifth cervical vertebra (C5) followed by administration of 17β-estradiol via a slow release pellet (0.5 or 5.0 mg/pellet) beginning at 30 minutes post-SCI. Behavioral evaluation of skilled and unskilled forelimb function and locomotor function were conducted for 7 weeks after SCI. Upon conclusion of the behavioral assessments, spinal cords were collected and histochemistry and stereology were conducted to evaluate the effect of treatment on the lesion characteristics. We found that post-SCI administration of 17β-estradiol decreased neuronal loss in the ventral horn, decreased reactive astrogliosis, decreased the immune response, and increased white mater sparing at the lesion epicenter. Additionally, post-SCI administration of 17β-estradiol improved skilled forelimb function and locomotor function. Taken together, these data suggest that post-SCI administration of 17β-estradiol protected both the gray and white matter in cervical SCI. Moreover, this treatment improved function on skilled motor tasks that involve both gray and white matter components, suggesting that this is likely a highly clinically relevant protective strategy.
Collapse
Affiliation(s)
- Akkradate Siriphorn
- Center for Glial Biology in Medicine and Department of Physical Medicine and Rehabilitation, University of Alabama at Birmingham, Alabama 35249, USA
| | | | | | | |
Collapse
|
52
|
Satoh JI, Tabunoki H, Ishida T, Saito Y, Konno H, Arima K. Reactive astrocytes express the potassium channel Kir4.1 in active multiple sclerosis lesions. ACTA ACUST UNITED AC 2013. [DOI: 10.1111/cen3.12011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jun-ichi Satoh
- Department of Bioinformatics, Molecular Neuropathology; Meiji Pharmaceutical University; Tokyo; Japan
| | - Hiroko Tabunoki
- Department of Bioinformatics, Molecular Neuropathology; Meiji Pharmaceutical University; Tokyo; Japan
| | - Tsuyoshi Ishida
- Department of Pathology, Laboratory Medicine; Kohnodai Hospital; NCGM; Chiba; Japan
| | - Yuko Saito
- Department of Laboratory Medicine; National Center Hospital; NCNP; Tokyo; Japan
| | - Hidehiko Konno
- Department of Neurology; Nishitaga National Hospital; Sendai; Japan
| | - Kunimasa Arima
- Department of Psychiatry; National Center Hospital; NCNP; Tokyo; Japan
| |
Collapse
|
53
|
Spatio-temporal spread of neuronal death after focal photolysis of caged glutamate in neuron/astrocyte co-cultures. Neurochem Int 2013; 62:1020-7. [PMID: 23538265 DOI: 10.1016/j.neuint.2013.03.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 03/13/2013] [Accepted: 03/15/2013] [Indexed: 11/22/2022]
Abstract
Glutamate-mediated excitotoxicity is now accepted as a major mechanism of ischemic neuronal damage. In the infarct core region, massive neuronal death is observed, but neurons in the surroundings of the core (ischemic penumbra) seem viable at the time of stroke. Several hours or days after a stroke, however, many neurons in the penumbra will undergo delayed neuronal death (DND). The mechanisms responsible for such DND are not fully understood. In this study, we investigated whether and how glutamate-mediated localized excitotoxic neuronal death affects surrounding neurons and astrocytes. To induce spatially-restricted excitotoxic neuronal death, a caged glutamate was focally photolyzed by a UV flash in neuron/astrocyte co-cultures. Uncaging of the glutamate resulted in acute neuronal death in the flashed area. After that, DND was observed in the surroundings of the flashed area late after the uncaging. In contrast, DND was not observed in neuron-enriched cultures, suggesting that functional changes in astrocytes, not neurons, after focal acute neuronal death were involved in the induction of DND. The present in vitro study showed that the spatially-restricted excitotoxic neuronal death resulted in DND in the surroundings of the flashed area, and suggested that the nitric oxide (NO)-induced reduction in the expression of astrocytic GLT-1 was responsible for the occurrence of the DND.
Collapse
|
54
|
Guptarak J, Wanchoo S, Durham-Lee J, Wu Y, Zivadinovic D, Paulucci-Holthauzen A, Nesic O. Inhibition of IL-6 signaling: A novel therapeutic approach to treating spinal cord injury pain. Pain 2013; 154:1115-28. [PMID: 23639820 DOI: 10.1016/j.pain.2013.03.026] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 02/03/2013] [Accepted: 03/15/2013] [Indexed: 01/13/2023]
Abstract
To characterize the contribution of interleukin-6 (IL-6) to spinal cord injury pain (SCIP), we employed a clinically relevant rat contusion model of SCIP. Using Western blots, we measured IL-6 levels in lumbar segments (L1-L5), at the lesion site (T10), and in the corresponding lumbar and thoracic dorsal root ganglia (DRG) in 2 groups of similarly injured rats: (a) SCI rats that developed hind-limb mechanical allodynia (SCIP), and (b) SCI rats that did not develop SCIP. Only in SCIP rats did we find significantly increased IL-6 levels. Immunocytochemistry showed elevated IL-6 predominantly in reactive astrocytes. Our data also showed that increased production of IL-6 in hyperreactive astrocytes in SCIP rats may explain still-poorly understood astrocytic contribution to SCIP. To test the hypothesis that IL-6 contributes to mechanical allodynia, we treated SCIP rats with neutralizing IL-6 receptor antibody (IL-6-R Ab), and found that one systemic injection abolished allodynia and associated weight loss; in contrast to gabapentin, the analgesic effect lasted for at least 2weeks after the injection, despite the shorter presence of the Ab in the circulation. We also showed that IL-6-R Ab partially reversed SCI-induced decreases in the protein levels of the glutamate transporter GLT-1 12hours and 8days after Ab injection, which may explain the lasting analgesic effect of the Ab in SCIP rats. A link between reactive astrocytes IL-6-GLT-1 has not been previously shown. Given that the humanized IL-6-R Ab tocilizumab is Food and Drug Administration-approved for rheumatoid arthritis, we are proposing tocilizumab as a novel and potentially effective treatment for SCIP.
Collapse
Affiliation(s)
- Jutatip Guptarak
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555-1072, USA
| | | | | | | | | | | | | |
Collapse
|
55
|
Zurolo E, de Groot M, Iyer A, Anink J, van Vliet EA, Heimans JJ, Reijneveld JC, Gorter JA, Aronica E. Regulation of Kir4.1 expression in astrocytes and astrocytic tumors: a role for interleukin-1 β. J Neuroinflammation 2012; 9:280. [PMID: 23270518 PMCID: PMC3538650 DOI: 10.1186/1742-2094-9-280] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Accepted: 12/09/2012] [Indexed: 01/08/2023] Open
Abstract
OBJECTIVE Decreased expression of inwardly rectifying potassium (Kir) channels in astrocytes and glioma cells may contribute to impaired K⁺ buffering and increased propensity for seizures. Here, we evaluated the potential effect of inflammatory molecules, such as interleukin-1β (IL-1β) on Kir4.1 mRNA and protein expression. METHODS We investigated Kir4.1 (Kcnj10) and IL-1β mRNA expression in the temporal cortex in a rat model of temporal lobe epilepsy 24 h and 1 week after induction of status epilepticus (SE), using real-time PCR and western blot analysis. The U373 glioblastoma cell line and human fetal astrocytes were used to study the regulation of Kir4.1 expression in response to pro-inflammatory cytokines. Expression of Kir4.1 protein was also evaluated by means of immunohistochemistry in surgical specimens of patients with astrocytic tumors (n = 64), comparing the expression in tumor patients with (n = 38) and without epilepsy (n = 26). RESULTS Twenty-four hours after onset of SE, Kir4.1 mRNA and protein were significantly down-regulated in temporal cortex of epileptic rats. This decrease in expression was followed by a return to control level at 1 week after SE. The transient downregulation of Kir4.1 corresponded to the time of prominent upregulation of IL-1β mRNA. Expression of Kir4.1 mRNA and protein in glial cells in culture was downregulated after exposure to IL-1β. Evaluation of Kir4.1 in tumor specimens showed a significantly lower Kir4.1 expression in the specimens of patients with epilepsy compared to patients without epilepsy. This paralleled the increased presence of activated microglial cells, as well as the increased expression of IL-1β and the cytoplasmic translocation of high mobility group box 1 (HMGB1). CONCLUSIONS Taken together, these findings indicate that alterations in expression of Kir4.1 occurring in epilepsy-associated lesions are possibly influenced by the local inflammatory environment and in particular by the inflammatory cytokine IL-1β.
Collapse
Affiliation(s)
- Emanuele Zurolo
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, AZ 1105, The Netherlands
| | - Marjolein de Groot
- Department of Neurology, VU University Medical Center, Amsterdam, The Netherlands
| | - Anand Iyer
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, AZ 1105, The Netherlands
| | - Jasper Anink
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, AZ 1105, The Netherlands
| | - Erwin A van Vliet
- Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, The Netherlands
| | - Jan J Heimans
- Department of Neurology, VU University Medical Center, Amsterdam, The Netherlands
| | - Jaap C Reijneveld
- Department of Neurology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
- Department of Neurology, VU University Medical Center, Amsterdam, The Netherlands
| | - Jan A Gorter
- Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, The Netherlands
- Epilepsy Institute in The Netherlands Foundation (Stichting Epilepsie Instellingen Nederland, SEIN), Heemstede, The Netherlands
| | - Eleonora Aronica
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, AZ 1105, The Netherlands
- Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, The Netherlands
- Epilepsy Institute in The Netherlands Foundation (Stichting Epilepsie Instellingen Nederland, SEIN), Heemstede, The Netherlands
| |
Collapse
|
56
|
Astrocyte dysfunction in temporal lobe epilepsy: K+ channels and gap junction coupling. Glia 2012; 60:1192-202. [DOI: 10.1002/glia.22313] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 01/27/2012] [Accepted: 01/27/2012] [Indexed: 12/11/2022]
|
57
|
Unger T, Lakowa N, Bette S, Engele J. Transcriptional regulation of the GLAST/EAAT-1 gene in rat and man. Cell Mol Neurobiol 2012; 32:539-47. [PMID: 22252783 DOI: 10.1007/s10571-011-9790-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Accepted: 12/21/2011] [Indexed: 01/09/2023]
Abstract
Various acute and chronic brain diseases result in disturbed expression of the glial glutamate transporters, GLAST/EAAT-1 and GLT-1/EAAT-2, and subsequent secondary neuronal cell death. The idea that glutamate-induced brain damage can be prevented by restoring glutamate homeostasis in the injured brain, focussed previous efforts on identifying the network controlling astrocytic glutamate transport. Since most of this work was performed with rat astrocytes, we now sought to compare the transcriptional regulation of the GLAST/EAAT-1 gene in rat and man. Reporter gene assay demonstrated that the human GLAST/EAAT-1 promoter comprises the 2.3 kb region immediately flanking the 5'-end of the human GLAST/EAAT-1 gene. Cloning of the previously unknown promoter of rat GLAST/EAAT-1 gene demonstrated maximal reporter gene activity with a sequence comprising the 1.5 kb region flanking the 5'-end of the gene as well as non-coding exon 1, and intron 1-2. Although the promoter regions from both species lacked sequence homology, they contained numerous identical consensus motifs. In human promoter constructs, dbcAMP, PACAP, EGF, and TGFα, which represent potent stimulators of endogenous GLAST/EAAT-1 expression, only further increased reporter gene activity in the presence of the GLAST/EAAT-1 3'-UTR. By contrast, the rat GLAST/EAAT-1 3'-UTR only mediated the stimulatory increases of dbcAMP. Moreover, the GLAST/EAAT-1 3'-UTR repressed constitutive GLAST/EAAT-1 expression in man, but enhanced GLAST/EAAT-1 transcription in rat. Together, our findings suggest the existence of close functional similarities of the GLAST/EAAT-1 promoter regions in man and rat and further point to a species-specific function of the GLAST/EAAT-1 3'-UTR in constitutive and regulated GLAST/EAAT-1 expression.
Collapse
Affiliation(s)
- Tina Unger
- Medical Faculty, Institute of Anatomy, University of Leipzig, Leipzig, Germany
| | | | | | | |
Collapse
|
58
|
Gwak YS, Kang J, Unabia GC, Hulsebosch CE. Spatial and temporal activation of spinal glial cells: role of gliopathy in central neuropathic pain following spinal cord injury in rats. Exp Neurol 2011; 234:362-72. [PMID: 22036747 DOI: 10.1016/j.expneurol.2011.10.010] [Citation(s) in RCA: 193] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 10/05/2011] [Accepted: 10/13/2011] [Indexed: 01/27/2023]
Abstract
In the spinal cord, neuron and glial cells actively interact and contribute to neurofunction. Surprisingly, both cell types have similar receptors, transporters and ion channels and also produce similar neurotransmitters and cytokines. The neuroanatomical and neurochemical similarities work synergistically to maintain physiological homeostasis in the normal spinal cord. However, in trauma or disease states, spinal glia become activated, dorsal horn neurons become hyperexcitable contributing to sensitized neuronal-glial circuits. The maladaptive spinal circuits directly affect synaptic excitability, including activation of intracellular downstream cascades that result in enhanced evoked and spontaneous activity in dorsal horn neurons with the result that abnormal pain syndromes develop. Recent literature reported that spinal cord injury produces glial activation in the dorsal horn; however, the majority of glial activation studies after SCI have focused on transient and/or acute time points, from a few hours to 1 month, and peri-lesion sites, a few millimeters rostral and caudal to the lesion site. In addition, thoracic spinal cord injury produces activation of astrocytes and microglia that contributes to dorsal horn neuronal hyperexcitability and central neuropathic pain in above-level, at-level and below-level segments remote from the lesion in the spinal cord. The cellular and molecular events of glial activation are not simple events, rather they are the consequence of a combination of several neurochemical and neurophysiological changes following SCI. The ionic imbalances, neuroinflammation and alterations of cell cycle proteins after SCI are predominant components for neuroanatomical and neurochemical changes that result in glial activation. More importantly, SCI induced release of glutamate, proinflammatory cytokines, ATP, reactive oxygen species (ROS) and neurotrophic factors trigger activation of postsynaptic neuron and glial cells via their own receptors and channels that, in turn, contribute to neuronal-neuronal and neuronal-glial interaction as well as microglia-astrocytic interactions. However, a systematic review of temporal and spatial glial activation following SCI has not been done. In this review, we describe time and regional dependence of glial activation and describe activation mechanisms in various SCI models in rats. These data are placed in the broader context of glial activation mechanisms and chronic pain states. Our work in the context of work by others in SCI models demonstrates that dysfunctional glia, a condition called "gliopathy", is a key contributor in the underlying cellular mechanisms contributing to neuropathic pain.
Collapse
Affiliation(s)
- Young S Gwak
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch at Galveston, TX 77555, USA.
| | | | | | | |
Collapse
|
59
|
Lepore AC, O'Donnell J, Kim AS, Yang EJ, Tuteja A, Haidet-Phillips A, O'Banion CP, Maragakis NJ. Reduction in expression of the astrocyte glutamate transporter, GLT1, worsens functional and histological outcomes following traumatic spinal cord injury. Glia 2011; 59:1996-2005. [PMID: 21882244 DOI: 10.1002/glia.21241] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Accepted: 08/04/2011] [Indexed: 12/23/2022]
Abstract
The astrocyte glutamate transporter, GLT1, is responsible for the vast majority of glutamate uptake in the adult central nervous system (CNS), thereby regulating extracellular glutamate homeostasis and preventing excitotoxicity. Glutamate dysregulation plays a central role in outcome following traumatic spinal cord injury (SCI). To determine the role of GLT1 in secondary cell loss following SCI, mice heterozygous for the GLT1 astrocyte glutamate transporter (GLT1+/-) and wild-type mice received thoracic crush SCI. Compared with wild-type controls, GLT1+/- mice had an attenuated recovery in hindlimb motor function, increased lesion size, and decreased tissue sparing. GLT1+/- mice showed a decrease in intraspinal GLT1 protein and functional glutamate uptake compared with wild-type mice, accompanied by increased apoptosis and neuronal loss following crush injury. These results suggest that astrocyte GLT1 plays a role in limiting secondary cell death following SCI, and also show that compromise of key astrocyte functions has significant effects on outcome following traumatic CNS injury. These findings also suggest that increasing intraspinal GLT1 expression may represent a therapeutically relevant target for SCI treatment.
Collapse
Affiliation(s)
- Angelo C Lepore
- Department of Neuroscience, Thomas Jefferson University Medical College, 900 Walnut St., Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, USA
| | | | | | | | | | | | | | | |
Collapse
|
60
|
Lepore AC, O'Donnell J, Bonner JF, Paul C, Miller ME, Rauck B, Kushner RA, Rothstein JD, Fischer I, Maragakis NJ. Spatial and temporal changes in promoter activity of the astrocyte glutamate transporter GLT1 following traumatic spinal cord injury. J Neurosci Res 2011; 89:1001-17. [PMID: 21488085 DOI: 10.1002/jnr.22624] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Revised: 12/20/2010] [Accepted: 01/19/2011] [Indexed: 12/21/2022]
Abstract
After traumatic spinal cord injury (SCI), there is an opportunity for preserving function by attenuating secondary cell loss. Astrocytes play crucial roles in the adult CNS and are responsible for the vast majority of glutamate buffering, potentially preventing excitotoxic loss of neurons and oligodendrocytes. We examined spatial and temporal changes in gene expression of the major astrocyte glutamate transporter GLT1 following moderate thoracic contusion SCI using transgenic BAC-GLT1-eGFP promoter reporter mice. In dorsal column white matter, total intensity of GLT1-eGFP expression per region was significantly reduced following SCI at both lesion epicenter and at rostral and caudal areas where no tissue loss occurred. This regional decrease in GLT1 expression was due to significant loss of GLT1-eGFP(+) cells, partially accounted for by apoptosis of eGFP(+) /GFAP(+) astrocytes in both white and gray matter. There were also decreased numbers of GLT1-eGFP-expressing cells in multiple gray matter regions following injury; nevertheless, there was sustained or even increased regional GLT1-eGFP expression in gray matter as a result of up-regulation in astrocytes that continued to express GLT1-eGFP. Although there were increased numbers of GFAP(+) cells both at the lesion site and in surrounding intact spinal cord following SCI, the majority of proliferating Ki67(+) /GFAP(+) astrocytes did not express GLT1-eGFP. These findings demonstrate that spatial and temporal alterations in GLT1 expression observed after SCI result from both astrocyte death and gene expression changes in surviving astrocytes. Results also suggest that following SCI a significant portion of astrocytes lacks GLT1 expression, possibly compromising the important role of astrocytes in glutamate homeostasis.
Collapse
Affiliation(s)
- Angelo C Lepore
- Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
61
|
Gwak YS, Hulsebosch CE. GABA and central neuropathic pain following spinal cord injury. Neuropharmacology 2011; 60:799-808. [PMID: 21216257 DOI: 10.1016/j.neuropharm.2010.12.030] [Citation(s) in RCA: 146] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Revised: 12/02/2010] [Accepted: 12/22/2010] [Indexed: 12/31/2022]
Abstract
Spinal cord injury induces maladaptive synaptic transmission in the somatosensory system that results in chronic central neuropathic pain. Recent literature suggests that glial-neuronal interactions are important modulators in synaptic transmission following spinal cord injury. Neuronal hyperexcitability is one of the predominant phenomenon caused by maladaptive synaptic transmission via altered glial-neuronal interactions after spinal cord injury. In the somatosensory system, spinal inhibitory neurons counter balance the enhanced synaptic transmission from peripheral input. For a decade, the literature suggests that hypofunction of GABAergic inhibitory tone is an important factor in the enhanced synaptic transmission that often results in neuronal hyperexcitability in dorsal horn neurons following spinal cord injury. Neurons and glial cells synergistically control intracellular chloride ion gradients via modulation of chloride transporters, extracellular glutamate and GABA concentrations via uptake mechanisms. Thus, the intracellular "GABA-glutamate-glutamine cycle" is maintained for normal physiological homeostasis. However, hyperexcitable neurons and glial activation after spinal cord injury disrupts the balance of chloride ions, glutamate and GABA distribution in the spinal dorsal horn and results in chronic neuropathic pain. In this review, we address spinal cord injury induced mechanisms in hypofunction of GABAergic tone that results in chronic central neuropathic pain. This article is part of a Special Issue entitled 'Synaptic Plasticity & Interneurons'.
Collapse
Affiliation(s)
- Young S Gwak
- Department of Neuroscience & Cell Biology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-1043, USA.
| | | |
Collapse
|