Development of nitrergic neurons in the nervous system of the locust embryo

We followed the development of the nitric oxide‐cyclic guanosine monophosphate (NO‐cGMP) system during locust embryogenesis in whole mount nervous systems and brain sections by using various cytochemical techniques. We visualized NO‐sensitive neurons by cGMP immunofluorescence after incubation with an NO donor in the presence of the soluble guanylyl cyclase (sGC) activator YC‐1 and the phosphodiesterase‐inhibitor isobutyl‐methyl‐xanthine (IBMX). Central nervous system (CNS) cells respond to NO as early as 38% embryogenesis. By using the NADPH‐diaphorase technique, we identified somata and neurites of possible NO‐synthesizing cells in the CNS. The first NADPH‐diaphorase‐positive cell bodies appear around 40% embryogenesis in the brain and at 47% in the ventral nerve cord. The number of positive cells reaches the full complement of adult cells at 80%. In the brain, some structures, e.g., the mushroom bodies acquire NADPH‐diaphorase staining only postembryonically. Immunolocalization of L‐citrulline confirmed the presence of NOS in NADPH‐diaphorase‐stained neurons and, in addition, indicated enzymatic activity in vivo. In whole mount ventral nerve cords, citrulline immunolabeling was present in varying subsets of NADPH‐diaphorase‐positive cells, but staining was very variable and often weak. However, in a regeneration paradigm in which one of the two connectives between ganglia had been crushed, strong, reliable staining was observed as early as 60% embryogenesis. Thus, citrulline immunolabeling appears to reflect specific activity of NOS. However, in younger embryos, NOS may not always be constitutively active or may be so at a very low level, below the citrulline antibody detection threshold. For the CNS, histochemical markers for NOS do not provide conclusive evidence for a developmental role of this enzyme. J. Comp. Neurol. 518:1157–1175, 2010. © 2009 Wiley‐Liss, Inc.     

Apocynin attenuate spatial learning deficits and oxidative responses to intermittent hypoxia

Rationale: The long-term intermittent hypoxia (LTIH) that characterizes sleep-disordered breathing impairs spatial learning and increases oxidative stress in rodents. We hypothesized that LTIH activated brain NADPH oxidase, which served as a critical source of superoxide in the oxidation injury, and that apocynin might attenuate LTIH-induced spatial learning deficits by reducing LTIH-induced NADPH oxidase expression. Objective: To investigate the effects of apocynin on spatial learning and oxidative responses to LTIH in rats. Methods: Forty healthy male Sprague–Dawley (SD) rats were randomly divided into four groups of 10 each: a LTIH group, an apocynin-treated LTIH group, a sham LTIH group and an apocynin-treated sham group. Spatial learning in each group was assessed with the Morris water maze test. RT-PCR and Western blot were used to examine mRNA and protein expression of NADPH oxidase subunit p47phox and p22phox in the hippocampus region. The level of MDA and SOD were detected by colorimetric method. The terminal deoxynucleotidyl transferase-mediated dUTP-nick end-labeling (TUNEL) method was used to display the apoptotic cells of the hippocampus tissue. Results: Apocynin treatment prevented LTIH-induced decreases in spatial learning during the Morris water maze as well as LTIH-induced decrease in SOD levels. In untreated animals, LTIH exposure was related to increase of MDA levels in comparison to sham LTIH animals, and apocynin-treated animal exposure to LTIH showed reduction in MDA levels. Increases in hippocampus NADPH oxidase subunit p47phox mRNA and protein expression were observed in LTIH-exposed animals; there was no statistical difference of p47phox mRNA and protein expression between LTIH group and apocynin treatment group. Treatment with apocynin significantly ameliorated cell apoptosis in LTIH-exposed animals. Conclusion: These results indicate that apocynin attenuates LTIH-induced spatial learning deficits and mitigates LTIH-induced oxidative stress through multiple beneficial effects on oxidant pathways. NADPH oxidase up-expression is closely associated with oxidative processes in LTIH rats, and inhibition of NADPH oxidase activity may hopefully serve as a useful strategy for cognitive function impairment from chronic intermittent hypoxia.     

Glucose-6-phosphate dehydrogenase and glutathione reductase support antioxidant enzymes in nerves and muscles of rats during nerve regeneration

The effects of the rat sciatic nerve crush on the activities of glucose-6-phosphate dehydrogenase (G6PD), glutathione reductase (GR), glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase (CAT) were examined in regenerating nerve and in two reinnervating muscles: the slow twitch soleus and the fast twitch extensor digitorum longus (edl). The enzyme activities in the crushed side, were compared with the contralateral homologue tissues and basal values, determined in uncrushed animals. In the crushed side, the activity of G6PD, GR, GPX and CAT of the sciatic nerve and both muscles markedly increased in comparison with the uncrushed side. In the nerve and in both muscles, SOD activity decreased at 13 days, then rose to values higher than normal, but the pattern of the crushed side was not significantly different from that of the uncrushed. In the uncrushed side, we observed a significant increase of nerve G6PD, GPX and CAT activities compared to basal values, while in both muscles, values fluctuated around the normal without any significant variation. The mechanism of these enzymatic changes is unknown, however our work suggests that: (i) during nerve regeneration, an oxidative stress occurs in nerve and muscle, which causes adaptive responses in antioxidant enzymes; (ii) the maximum antioxidant power is expressed during the period of synaptic retraction; (iii) G6PD and GR activities are synergistically modulated with GPX and CAT, while SOD activity appears independently regulated.     

Reduced efficacy of nitrergic neurotransmission exacerbates erectile dysfunction after penile nerve injury despite axonal regeneration

Penile (cavernous) nerves are readily damaged during radical prostatectomy, invariably causing impotence. Erectile function can return, however this may take months or years and capacity often remains poor. Many studies have attempted to improve penile nerve regeneration but have not explored mechanisms underlying the delay in functional recovery. This is assumed to be due to slow growth of axons, although penile tissues also change following loss of erectile activity. We have asked whether delayed recovery of the nitrergic nerve-evoked erectile response is due to pre-synaptic (slow axonal growth) or post-synaptic (changes in tissue responsiveness) mechanisms. These components were dissected in vitro following penile nerve injury in adult rats. Following crush of both penile nerves, excellent regeneration of nitrergic axons occurred after 10-12 weeks but neurogenic relaxation of cavernosum muscle was still relatively poor. This was at least partly due to attenuated tissue responsiveness to nitric oxide (using sodium nitroprusside as a donor) from 3 weeks after injury. Western blotting also revealed a modest reduction of soluble guanylyl cyclase. A second model of penile nerve injury, unilateral cut, completely denervated one side but retained potential for penile erection. Some anatomical and functional recovery occurred after 9-11 weeks (probably due to sprouting from contralateral uninjured axons), but nitroprusside-evoked relaxations were unaltered from at least 3 weeks onward. These data suggest that erectile dysfunction following extensive nerve injury may be exacerbated by postsynaptic changes in nitric oxide signaling, even when nerve regeneration occurs. This may be prevented by continued activation of penile tissues to retain normal perfusion.     

Dimethylarginine dimethylaminohydrolase (DDAH) as a nerve-injury-associated molecule: mRNA localization in the rat brain and its coincident up-regulation with neuronal NO synthase (nNOS) in axotomized motoneurons.

As part of a project to identify genes up-regulated by injury of the motor neuron, a clone encoding dimethylarginine dimethylaminohydrolase (DDAH) was isolated. This enzyme is known to metabolize methylarginines, which are endogenous inhibitors of NOS activity. DDAH may therefore contribute to the control of NO synthesis. The present study demonstrated that both DDAH and nNOS mRNAs are up-regulated after axotomy in injured hypoglossal motor neurons. The profile of DDAH mRNA up-regulation in the injured hypoglossal motor neurons paralleled that of NADPH diaphorase staining. While the expression of both DDAH and nNOS was upregulated in motor neurons following nerve injury, the normal distribution of DDAH and nNOS mRNAs in the noninjured central nervous system were distinctly different. We speculate that both genes are involved in the upregulation of NO production following nerve transection, although the role of NO in the process of nerve regeneration is so far unknown.     

Upregulation of mucosal 5-HT3 receptors is involved in restoration of colonic transit after pelvic nerve transection

Background Colonic dysfunction occurs after pelvic autonomic nerve damage. The enteric nervous system can compensate. We investigated the role of mucosal serotonin receptors, 5‐HT₃ and 5‐HT₄, in the colonic motility restoration over 2 weeks after parasympathetic pelvic nerve transection in a rat model. Methods Male Sprague‐Dawley rats underwent pelvic nerve transection or sham operation. Colonic transit was expressed as the geometric center of ⁵¹Cr distribution. Mucosal 5‐HT₃ and 5‐HT₄ receptor expression was evaluated by Western blot. Intraluminal pressure increase was measured after 5‐HT₃ (ondansetron) or 5‐HT₄ receptor antagonist (GR125487) administration in vitro in sham and denervated distal colons. Key Results At 2 weeks, colonic transit in the denervated group was 30% slower compared to the sham group (P < 0.01). At 1 and 2 weeks, 5‐HT₃ receptor expression was increased two‐fold in the denervated group, compared to shams (P < 0.05). A three‐fold smaller dose of ondansetron was required in denervated tissues to inhibit intraluminal pressure rise than in sham colons (P < 0.01). There was no difference in the expression of 5‐HT₄ receptor or the response to GR125487 in denervated vs sham colons. Conclusions & Inferences Colonic motility was restored to approximately 70% normal over 1 week without further improvement at 2 weeks. Enteric nervous system compensated by upregulating mucosal 5‐HT_3, but not 5‐HT_4, receptors.     

Effect of ionotropic glutamate receptor antagonists on Fos-like immunoreactivity in the dorsal horn following transection of the rat sciatic nerve

Fos-like immunoreactivity (FLI) was investigated in the lumbar dorsal horn 2 h after transection of the rat sciatic nerve and sham operation. FLI following nerve transection was distributed through the medio-lateral extension of the superficial layer of the dorsal horn, while FLI after sham operation, tissue injury, was restricted to the lateral one-third of this layer. The number of FLI neurons in the lateral one-third was similar in the two operations, indicating that neurons expressing FLI in the medial two-thirds and in the lateral one-third of the superficial layer after nerve transection are derived from nerve injury and tissue injury, respectively. FLI in the lateral one-third, but not the medial two-thirds, after nerve transection was significantly reduced by pretreatment with NMDA and AMPA/KA receptor antagonists, indicating that there is a considerable difference in the contributions of ionotropic glutamate receptors to FLI in this layer induced by nerve injury and tissue injury.     

Functional recovery and vitamin E level following sciatic nerve crush injury in normal and diabetic rats

Extensive biochemical data document the involvement of oxygen derived free radicals (ODFR) in recovery following neurotrauma as well as diabetic neuropathy. Vitamin E is considered as one of the principle protective mechanism against oxidative damage in neuronal tissue. The present study was undertaken to determine the association between functional recovery and vitamin E levels following sciatic nerve crush injury in normal and diabetic rats. The sciatic nerve of normal and streptozotocin (STZ) induced diabetic rats was crushed using a haemostat. The walking track analysis and vitamin E levels were recorded on 10, 20 and 30th day. Maximum functional deficiency and depletion of vitamin E in sciatic nerve was observed on 10th day following crush injury in both normal and diabetic animals. A progressive motor recovery and repletion of vitamin E was observed on day 20 and 30 following injury in both diabetic and normal rats. The functional recovery was slower whereas vitamin E level was higher in diabetic animals as compared to normal injured rats during healing phase suggesting that vitamin E alone may not be an efficient indicator of oxidative stress during regeneration of axons following trauma in diabetic rats.     

Changes in GABA and GABA(B) receptor expressions are involved in neuropathy in the rat cuneate nucleus following median nerve transection

This study examined the relationship between changes in GABA transmission and behavioral abnormalities after median nerve transection. Following unilateral median nerve transection, the percentage of GABA‐like immunoreactive neurons in the cuneate nucleus and that of GABA_B receptor‐like immunoreactive neurons in the dorsal root ganglion in the injured side decreased and reached a nadir at 4 weeks after median nerve transection. Four weeks after bilateral median nerve transection and intraperitoneal application with saline, baclofen (2 mg kg^?1), or phaclofen (2 mg kg^?1) before unilateral electrical stimulation of the injured median nerve, we investigated the level of neuropeptide Y release and c‐Fos expression in the stimulated side of the cuneate nucleus. The neuropeptide Y release level and the number of c‐Fos‐like immunoreactive neurons in the baclofen group were significantly attenuated, whereas those in the phaclofen group had increased compared to the saline group. These findings indicate that median nerve transection reduces GABA transmission, promoting injury‐induced neuropeptide Y release and consequently evoking c‐Fos expression in cuneate nucleus neurons. Furthermore, this study used the CatWalk method to assess behavioral abnormalities in rats following median nerve transection. These abnormalities were reversed by baclofen treatment. Overall, the results suggest that baclofen treatment block neuropeptide Y release, subsequently lessening c‐Fos expression in cuneate neurons and consequently attenuating neuropathic signal transmission to the thalamus. Synapse, 2012. © 2012 Wiley Periodicals, Inc.     

Neuroprotective effects of brain‐derived neurotrophic factor against amyloid beta 1‐40‐induced retinal and optic nerve damage

Brain‐derived neurotrophic factor (BDNF) could be considered a potential neuroprotective therapy in amyloid beta (Aβ)‐associated retinal and optic nerve degeneration. Hence, in this study we investigated the neuroprotective effect of BDNF against Aβ1‐40‐induced retinal and optic nerve injury. In this study, exposure to Aβ1‐40 was associated with retinal and optic nerve injury. TUNEL staining showed significant reduction in the apoptotic cell count in the BDNF‐treated group compared with Aβ1‐40 group. H&E‐stained retinal sections also showed a striking reduction in neuronal cells in the ganglion cell layer (GCL) of retinas fourteen days after Aβ1‐40 exposure. By contrast, number of retinal cells was preserved in the retinas of BDNF‐treated animals. After Aβ1‐40 exposure, visible axonal swelling was observed in optic nerve sections. However, the BDNF‐treated group showed fewer changes in optic nerve; axonal swelling was less frequent and less marked. In the present study, exposure to Aβ was associated with oxidative stress, whereas levels of retinal glutathione (GSH), superoxide dismutase (SOD) and catalase were significantly increased in BDNF‐treated than in Aβ1‐40‐treated rats. Both visual object recognition tests using an open‐field arena and a Morris water maze showed that BDNF improved rats’ ability to recognise visual cues (objects with different shapes) after Aβ1‐40 exposure, thus demonstrating that the visual performance of rats was relatively preserved following BDNF treatment. In conclusion, intravitreal treatment with BDNF prevents Aβ1‐40‐induced retinal cell apoptosis and axon loss in the optic nerve of rats by reducing retinal oxidative stress and restoring retinal BDNF levels.     

Schwann cell is a target in ischemia-reperfusion injury to peripheral nerve

Ischemia-reperfusion (IR) causes oxidative injury and ischemic fiber degeneration due to injury of the neuron and axon. In this study, we explore the effect of oxidative stress on Schwann cells, as a specific peripheral nerve target, using our established rat model for IR injury. Fifty-six rats were used. Six groups (N = 8 each) underwent complete hindlimb ischemia for 4 h, followed by reperfusion durations of 0 h, 3 h, 7 days, 14 days, 28 days, and 42 days. One group underwent sham operation (N = 8). We evaluated immunohistochemical labeling for oxidative injury using anti-8-hydroxydeoxyguanosine (8-OHdG). To identify cells committed to apoptosis, we studied immunolabeling to caspase-3 and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) positivity. Only minimal positivity was seen in the sham, 0-h, and 3-h groups. Positivity to 8-OHdG, caspase-3, and TUNEL increased significantly in groups undergoing longer reperfusion (8-OHdG, 7-28 days; caspase-3, 14-42 days; TUNEL, 14-42 days). The positive cells surrounding axons were identified as being Schwann cells by their configuration and colabeling with S-100. We conclude that apoptosis of Schwann cells occurs during reperfusion and continues even when axons regenerate. Schwann cell apoptosis could contribute to impairment of axonal function and efficiency of fiber regeneration. Both these abnormalities are known to occur in experimental and human diabetic nerves.     

弥漫性脑损伤大鼠颅内压及脑灌注压的变化及DCLHb治疗作用

目的：研究大鼠加速性弥慢性脑损伤合并低血压及脑缺血、缺氧时，颅内压（ＩＣＰ）及脑灌注压（ＣＰＰ）变化与双阿斯匹林联偶血红蛋白液（ＤＣＬＨｂ）治疗作用。方法：２４只ＳＤ大鼠随机分为假手术对照、脑损伤并低血压与脑缺血及治疗三组。采用Ｍａｒｍａｒｏｕ大鼠加速性弥慢性脑损伤模型，抽血及颈动脉结扎造成低血压及脑缺血、缺氧。所有动物均气管内插管并实施同步生理监护。结果：伤后４小时，与假手术组对比，合并低血压与脑缺血组出现ＩＣＰ增高及ＣＰＰ降低（Ｐ＜０．０５），ＤＣＬＨｂ治疗组二者接近正常。结论：合并低血压与脑缺血组出现ＩＣＰ增高及ＣＰＰ降低提示低血压或脑缺血参予脑损害的加重过程，ＤＣＬＨｂ则可能通过提高ＣＰＰ发挥脑保护作用。     

Early in vivo changes in calcium ions, oxidative stress markers, and ion channel immunoreactivity following partial injury to the optic nerve

CNS injury is often localized but can be followed by more widespread secondary degenerative events that usually result in greater functional loss. Using a partial transection model in rat optic nerve (ON). we recently demonstrated in vivo increases in the oxidative stress-associated enzyme MnSOD 5 min after injury. However, mechanisms by which early oxidative stress spreads remain unclear. In the present study, we assessed ion distributions, additional oxidative stress indicators, and ion channel immunoreactivity in ON in the first 24 hr after partial transection. Using nanoscale secondary ion mass spectroscopy (NanoSIMS), we demonstrate changes in the distribution pattern of Ca ions following partial ON transection. Regions of elevated Ca ions in normal ON in vivo rapidly decrease following partial ON transection, but there is an increasingly punctate distribution at 5 min and 24 hr after injury. We also show rapid decreases in catalase activity and later increases in immunoreactivity of the advanced glycation end product carboxymethyl lysine in astrocytes. Increased oxidative stress in astrocytes is accompanied by significantly increased immunoreactivity of the AMPA receptor subunit GluR1 and aquaporin 4 (AQP4). Taken together, the results indicate that Ca ion changes and oxidative stress are early events following partial ON injury that are associated with changes in GluR1 AMPA receptor subunits and altered ionic balance resulting from increased AQP4.     

Effects of crush and axotomy on oxidative stress and some trace element levels in phrenic nerve of rats

This study was designed to investigate the effect of crush and axotomy on oxidative stress and some trace element levels in phrenic nerve of rats. Eighteen male Wistar-albino rats were divided randomly into three groups, each consisting of 6 rats. The animals in the first group were not crushed or axotomized and served as control. Phrenic nerves of the animals in the second and third groups were crushed and axotomized, respectively. Animals in all groups were sacrificed one week after the crush or axotomy, and degenerated phrenic nerves were harvested for the determination of tissue oxidative stress and trace element levels. Lipid peroxidation product malondialdehyde and antioxidant glutathione levels increased in both crushed and axotomized phrenic nerves. The activities of antioxidant enzymes such as superoxide dismutase, catalase and glutathione peroxidase were lower in crushed and axotomized phrenic nerves than in controls. The levels of Fe, Pb, Mn, Cd and Co increased, and Mg and Cu levels decreased in crushed phrenic nerves. The levels of Fe and Mg decreased, Pb and Co levels increased in axotomized phrenic nerves. It was concluded that crushing or axotomizing the phrenic nerves may produce oxidative stress by increasing lipid peroxidation and decreasing antioxidant enzyme activities. It was also concluded that while crush to phrenic nerves causes accumulation of minerals, axotomizing phrenic nerves causes depletion of minerals in the tissues.     

Dynamic changes in glypican-1 expression in dorsal root ganglion neurons after peripheral and central axonal injury

Glypican-1, a glycosyl phosphatidyl inositol (GPI)-anchored heparan sulphate proteoglycan expressed in the developing and mature cells of the central nervous system, acts as a coreceptor for diverse ligands, including slit axonal guidance proteins, fibroblast growth factors and laminin. We have examined its expression in primary sensory dorsal root ganglion (DRG) neurons and spinal cord after axonal injury. In noninjured rats, glypican-1 mRNA and protein are constitutively expressed at low levels in lumbar DRGs. Sciatic nerve transection results in a two-fold increase in mRNA and protein expression. High glypican-1 expression persists until the injured axons reinnervate their peripheral targets, as in the case of a crushed nerve. Injury to the central axons of DRG neurons by either a dorsal column injury or a dorsal root transection also up-regulates glypican-1, a feature that differs from most DRG axonal injury-induced genes, whose regulation changes only after peripheral and not central axonal injury. After axonal injury, the cellular localization of glypican-1 changes from a nuclear pattern restricted to neurons in noninjured DRGs, to the cytoplasm and membrane of injured neurons, as well as neighbouring non-neuronal cells. Sciatic nerve transection also leads to an accumulation of glypican-1 in the proximal nerve segment of injured axons. Glypican-1 is coexpressed with robo 2 and its up-regulation after axonal injury may contribute to an altered sensitivity to axonal growth or guidance cues.     

Effects of endogenous neurotrophins on sympathetic sprouting in the dorsal root ganglia and allodynia following spinal nerve injury

Peripheral nerve injury is often complicated by a chronic pain syndrome that is difficult to treat. In animal models of peripheral nerve injury, sympathetic nerve terminals in the dorsal root ganglia (DRG) sprout to form baskets around large diameter neurons, an anatomical change that has been implicated in the induction of neuropathic pain. In the present study, we have investigated whether neurotrophins derived from peripheral sources play any roles in sympathetic sprouting and neuropathic pain in a rat model of peripheral nerve injury. After transection of the left lumbar (L) 5 spinal nerve, antisera specific to neurotrophins were injected intraperitoneally twice a week for 2 weeks. The foot withdrawal response to von Frey hairs was examined on days 1, 3, 7, 10, and 14 postlesion. After completion of behavioral tests, sympathetic sprouting in DRG was examined by tyrosine hydroxylase (TH) immunohistochemistry. The number of TH-immunoreactive (ir) fibers and baskets around large neurons within the lesioned DRG was dramatically increased in the rats treated with control normal sheep serum. Antisera specific to nerve growth factor (NGF), neurotrophin-3 (NT3), and brain-derived neurotrophic factor (BDNF) significantly reduced the sympathetic sprouting and the formation of baskets. L5 spinal nerve lesion induced a significant increase in foot withdrawal responses to von Frey hair stimuli, which was attenuated by treatment of antisera to neurotrophins with a different time sequential. The effect of BDNF antiserum occurred earlier and lasted longer than those of NGF and NT3 antisera. These results implicate that peripherally derived neurotrophins are involved in the induction of sympathetic sprouting and neuropathic pain following peripheral nerve injury.     

Sustained release of neurotrophin‐3 via calcium phosphate‐coated sutures promotes axonal regeneration after spinal cord injury

Because of the dynamics of spinal cord injury (SCI), the optimal treatment will almost certainly be a combination approach to control the environment and promote axonal growth. This study uses peripheral nerve grafts (PNGs) as scaffolds for axonal growth while delivering neurotrophin‐3 (NT‐3) via calcium phosphate (CaP) coatings on surgical sutures. CaP coating was grown on sutures, and NT‐3 binding and release were characterized in vitro. Then, the NT‐3‐loaded sutures were tested in a complete SCI model. Rats were analyzed for functional improvement and axonal growth into the grafts. The CaP‐coated sutures exhibited a burst release of NT‐3, followed by a sustained release for at least 20 days. Functionally, the rats with PNGs + NT‐3‐loaded sutures and the rats treated with PNGs scored significantly higher than controls on day 56 postoperatively. However, functional scores in rats treated with PNGs + NT‐3‐loaded suture were not significantly different from those of rats treated with PNGs alone. Cholera toxin subunit B (CTB) labeling rostral to the graft was not observed in any controls, but CTB labeling rostral to the graft was observed in almost all rats that had had a PNG. Neurofilament labeling on transverse sections of the graft revealed that the rats treated with the NT‐3‐loaded sutures had significantly more axons per graft than rats treated with an NT‐3 injection and rats without NT‐3. These data demonstrate that PNGs serve as scaffolds for axonal growth after SCI and that CaP‐coated sutures can efficiently release NT‐3 to increase axonal regeneration. © 2016 Wiley Periodicals, Inc.     

NAD(P)H oxidase, superoxide dismutase, catalase, glutathione peroxidase and nitric oxide synthase expression in subacute spinal cord injury

Primary trauma to the spinal cord triggers a cascade of cellular and molecular events that promote continued tissue damage and expansion of the lesion for extended periods following the initial injury. Oxidative and nitrosative stresses play an important role in progression of spinal cord injury (SCI). In an attempt to explore the biochemical origin of oxidative/nitrosative stress associated with secondary SCI, we studied expression of the superoxide (O2*-)-generating enzyme, NAD(P)H oxidase, antioxidant enzymes [superoxide dismutase (CuZn SOD, Mn SOD), catalase, glutathione peroxidase (GPX)], nitric oxide synthases (NOS) and a byproduct of NO-O2*- interaction (nitrotyrosine) in the spinal cord tissues of rats 16 h and 14 days after surgical resections of a 5-mm segment of the cord below T8 or sham-operation. Immunodetectable NAD(P)H oxidase subunits (gp91phox and P67phox), Mn SOD, inducible NOS (iNOS), endothelial NOS (eNOS), and nitrotyrosine were elevated in the transected cords on day 1 and day 14. Neuronal NOS (nNOS) was unchanged on day 1 and significantly depressed on day 14. GPX was unchanged on day 1 and significantly elevated on day 14. Catalase was unchanged in the cord tissue surrounding the transection site at both points. Thus, concurrent upregulations of NAD(P)H oxidase, eNOS and iNOS (but not nNOS), work in concert to maintain oxidative and nitrosative stress in the injured cord tissue.     

Postnatal development of NT3 and TrkC in mouse ventral cochlear nucleus

In the developing nervous system, neurotrophin 3 (NT3) and brain‐derived neurotrophic factor (BDNF) have been shown to interact with each other and with different parts of a neuron or glia and over considerable distances in time and space. The auditory system provides a useful model for analyzing these events, insofar as it is subdivided into well‐defined groups of specific neuronal types that are readily related to each other at each stage of development. Previous work in our laboratory suggested that NT3 and its receptor TrkC in the mouse cochlear nucleus (CN) may be involved in directing neuronal migration and initial targeting of inputs from cochlear nerve axons in the embryo. NT3 is hard to detect soon after birth, but TrkC lingers longer. Here we found NT3 and TrkC around P8 and the peak around P30. Prominent in ventral CN, associated with globular bushy cells and stellate cells, they were localized to different subcellular sites. The TrkC immunostain was cytoplasmic, and that of NT3 was axonal and perisomatic. TrkC may be made by CN neurons, whereas NT3 has a cochlear origin. The temporal pattern of their development and the likelihood of activity‐dependent release of NT3 from cochlear axons suggest that it may not be critical in early synaptogenesis; it may provide long‐term trophic effects, including stabilization of synapses once established. Activity‐related regulation could coordinate the supply of NT3 with inner ear activity. This may require interaction with other neurotrophins, such as BDNF. © 2009 Wiley‐Liss, Inc.