Parkinson's disease (PD) is characterized by degeneration of the dopaminergic neurons in substantia nigra (SN). The motor symptoms of PD include tremor, rigidity, bradykinesia and postural impairment. In rodents, central administration of neuropeptide-S (NPS) has been shown to induce locomotor activity, dopamine release and neuronal survival by decreasing lipid peroxidation, additionally, the NPS receptor (NPSR) was detected in SN. Accumulating findings suggest that central NPS may ameliorate the parkinsonian symptoms, however, this has been explored incompletely due to the scarcity of experimental studies. Therefore, the present study was designed to test whether central NPS treatment exerts protective and/or alleviative effects on 6-OHDA-induced rat experimental PD model. Adult male Wistar rats received acute (alleviate; 10 nmol, icv) or chronic (protective; 1 nmol, icv for 7 days) NPS treatment following the central injection of 6-OHDA in medial forebrain bundle. Motor performance tests and in vivo nigral microdialysis were performed before and 7 days after the central 6-OHDA injection. The immunoreactivities for tyrosine hydroxylase (TH), NPSR, 4-hydroxynonenal (4-HNE) and c-Fos were detected by immunohistochemistry in frozen SN sections. Our double immunofluorescence labeling studies demonstrated that NPSR is present in the nigral TH-positive neurons. Central NPS injection caused a remarkable c-Fos expression in SN; whereas, no change was observed following vehicle injection. In both chronic and acute treatment groups, the 6-OHDA-induced motor dysfunction and impaired nigral dopamine release were improved significantly. However, only chronic, but not acute treatment restored the loss of nigral TH-positive cells, while decreasing the 4-HNE immunoreactivity in SN. Our findings demonstrate that central NPS treatment not only exerts a neuroprotective action on nigral dopaminergic neurons, it also improves the striatal dopaminergic signaling. Therefore, the present study candidates the NPSR agonism as a novel therapeutic approach for PD treatment.
DOI : 10.1016/j.expneurol.2019.02.015
Sayı :317 Sayfa :78-86
Early life stress leads to psychopathological processes correlated with the predisposition of individuals. Prolonged development of the prefrontal cortex (PFC), playing a critical role in the cognition, personality and social behavior, makes it susceptible to adverse conditions. In this study, we evaluated the dendritic morphology of medial PFC neurons in rats subjected to perinatal stress exposure.
DOI : 10.1016/j.expneurol.2015.06.005
Sayi :275 Sayfa :274-284
With neuroprotective approaches having failed until recently, current focus on experimental stroke research has switched towards manipulation of post-ischemic neuroregeneration. Transplantation of subventricular zone (SVZ) derived neural progenitor cells (NPCs) is a promising strategy for promotion of neurological recovery. Yet, fundamental questions including the optimal cell delivery route still have to be addressed. Consequently, male C57BL6 mice were exposed to transient focal cerebral ischemia and allowed to survive for as long as 84 days post-stroke. At 6 h post-stroke, NPCs were grafted using six different cell delivery routes, i.e., intravenous, intraarterial, ipsilateral intrastriatal, contralateral intrastriatal, ipsilateral intraventricular and ipsilateral intracortical injection. Control mice received PBS only using the aforementioned delivery routes. Intralesional numbers of GFP(+) NPCs were high only after ipsilateral intrastriatal transplantation, whereas other injection paradigms only yielded comparatively small numbers of grafted cells. However, acute neuroprotection and improved functional outcome were observed after both systemic (i.e., intraarterial and intravenous) and ipsilateral intrastriatal transplantation only. Whereas systemic cell delivery induced acute and long-term neuroprotection, reduction of brain injury after ipsilateral intrastriatal cell grafting was only temporary, in line with the loss of transplanted NPCs in the brain. Both systemic and ipsilateral intrastriatal NPC delivery reduced microglial activation and leukocyte invasion, thus reducing free radical formation within the ischemic brain. On the contrary, only systemic NPC administration stabilized the blood-brain-barrier and reduced leukocytosis in the blood. Although intraarterial NPC transplantation was as effective as intravenous cell grafting, mortality of stroke mice was high using the intraarterial delivery route. Consequently, intravenous delivery of native NPCs in our experimental model is an attractive and effective strategy for stroke therapy that deserves further proof-of-concept studies. (C) 2015 Elsevier Inc. All rights reserved.
DOI : 10.1016/j.expneurol.2015.07.023
Sayi :273 Sayfa :45-56
Thymoma-associated Myasthenia gravis (TAMG) is one of the anti-acetylcholine receptor MG (AChR-MG) sub-types. The clinico-pathological features of TAMG and its pathogenesis are described here in comparison with pathogenetic models suggested for the more common non-thymoma AChR-MG subtypes, early onset MG and late onset MG. Emphasis is put on the role of abnormal intratumorous T cell selection and activation, lack of intratumorous myoid cells and regulatory T cells as well as deficient expression of the autoimmune regulator (AIRE) by neoplastic thymic epithelial cells. We review spontaneous and genetically engineered thymoma models in a spectrum of animals and the extensive clinical and immunological overlap between canine, feline and human TAMG. Finally, limitations and perspectives of the transplantation of human and murine thymoma tissue into nude mice, as potential models for TAMG, are addressed. (C) 2015 Elsevier Inc. All rights reserved.
DOI : 10.1016/j.expneurol.2015.02.010
Sayi :270 Sayfa :55-65
Seizures induced in animals by the kindling procedure have been described as an effective model of human epilepsy, principally because of the long lasting nature of this phenomenon (J. O. McNamara, 1984, Ann. Neurol. 16: 572–576). Permanent changes in the central nervous system associated with kindling should therefore provide insight onto of some forms of naturally occurring epilepsy. We report here the observation that in rats with fully developed kindled seizures, the exposure of the stimulation site to artificial cerebral spinal fluid (CSF) containing normal levels of calcium is able to block completely the seizure event. Exposure of the stimulation site to artificial CSF without calcium resulted in the return of the complete seizure. This implies that extracellular calcium levels are chronically reduced at the stimulation site of kindled rats and that this change in ion levels is necessary for the expression of the seizure.
At least two forms of actomyosin adenosine triphosphatase (ATPase) have been demonstrated in mammalian skeletal muscles. One form is relatively alkalistabile: acid-labile, and is found in most muscle fibers of fast-twitch muscles, while the other is relatively acid-stabile: alkali-labile, and is present in the majority of fibers of slow-twitch muscles. Each singly efferented muscle fiber of the general somatic musculature usually possesses only one of the two enzyme forms. A histochemical survey of the intrafusal and extraocular musculature of the rat indicates that a substantial minority of the fibers comprising these muscles contain both forms of actomyosin ATPase (dual-activity). Many fibers of these specialized muscles are known to have complex innervations and to exhibit tonic, graded contractions. In light of the known neural regulation of actomyosin ATPase, it may be that dual enzyme activity is a consequence of dual innervation by efferents having qualitatively different regulatory capabilities.
End-to-end nerve repair is a widely used and successful experimental microsurgical technique via which a denervated nerve stump is supplied with reinnervating motor or sensory axons. On the other hand, questions are still raised as concerns the reliability and usefulness of the end-to-side coaptation technique. This study had the aim of the reinnervation of the denervated forearm flexor muscles in baboons through the use of an end-to-side coaptation technique and the synergistic action of the radial nerve. The median and ulnar nerves were transected, and the motor branch of the radial nerve supplying the extensor carpi radialis muscles (MBECR) was used as an axon donor for the denervated superficial forearm flexors. A nerve graft was connected to the axon donor nerve through end-to-side coaptation, while at the other end of the graft an end-to-end connection was established so as to reinnervate the motor branch of the forearm flexors. Electrophysiological investigations and functional tests indicated successful reinnervation of the forearm flexors and recovery of the flexor function. The axon counts in the nerve segments proximal (1038 ± 172 S.E.M.) and distal (1050 ± 116 S.E.M.) to the end-to-side coaptation site and in the nerve graft revealed that motor axon collaterals were given to the graft without the loss or appreciable misdirection of the axons in the MBECR nerve distal to the coaptation site. The nerve graft was found to contain varying, but satisfactory numbers of axons (269 ± 59 S.E.M.) which induced morphological reinnervation of the end-plates in the flexor muscles. Accordingly, we have provided evidence that end-to-side coaptation can be a useful technique when no free donor nerve is available. This technique is able to induce limited, but still useful reinnervation for the flexor muscles, thereby producing a synergistic action of the flexor and extensor muscles which allows the hand to achieve a basic gripping function.
Silver staining, acetycholinesterase, and fluorescence histochemical studies on the atrial septum of the monkey heart reveal the presence of numerous ganglia, specially in the region of the coronary sinus and the fossa ovalus and near the origin of the great vessels. Three types of neurons were seen in the ganglia: first, a group of large multipolar neurons with a deeply impregnated cytoplasm; second, light silver-staining neurons possessing one or two processes; and finally, an intermediate neuron characterized by a large densely silver-impregnated nucleus which contrasted markedly with the pale cytoplasm. In addition, the ganglia contained “argyrophilic particles” composed of a body and single elongated process. The majority of the neurons were acetycholinesterase-positive; however, the acetycholinesterase staining reaction showed considerable variation. At one end of the spectrum the ganglia were so intensely stained that all intraganglionic detail was lost; whereas, in others the acetycholinesterase reaction was barely visible. The specific fluorescence studies demonstrated that a few of the neurons contained an autofluorescent granular cytoplasm. The fluorescence of these cells was enhanced after exposure to paraformaldehyde, and this increase in fluorescence could be interpreted as either an enhancement of the autofluorescence or evidence for the existence of a system of adrenergic neurons in the heart. The significance of these findings and the relationship to sensory nerves, and the sympathetic and parasympathetic nervous system are discussed.
Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) characterized by progressive neuronal demyelination and degeneration. Much of this damage can be attributed to microglia, the resident innate immune cells of the CNS, as well as monocyte-derived macrophages, which breach the blood-brain barrier in this inflammatory state. Upon activation, both microglia and macrophages release a variety of factors that greatly contribute to disease progression, and thus therapeutic approaches in MS focus on diminishing their activity. We use the CSF1R inhibitor PLX5622, administered in mouse chow, to ablate microglia and macrophages during the course of experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Here, we show that ablation of these cells significantly improves animal mobility and weight gain in EAE. Further, we show that this treatment addresses the pathological hallmarks of MS, as it reduces demyelination and immune activation. White matter lesion areas in microglia/macrophage-depleted animals show substantial preservation of mature, myelinating oligodendrocytes in comparison to control animals. Taken together, these findings suggest that ablation of microglia/macrophages during the symptomatic phase of EAE reduces CNS inflammation and may also promote a more permissive environment for remyelination and recovery. This microglia and macrophage-targeted therapy could be a promising avenue for treatment of MS.
Intracellular recordings were made in 69 L-7 dorsal horn cells in spinal cats. Cells in Rexed's layers IV–VI responding to single shocks to the sural nerve were studied. Three types of short latency (5–10 msec) PSP and spike responses were evoked by low-intensity nerve stimulation: Initial EPSP followed by a long IPSP (31 cells); EPSP only (21 cells); and spikes from baseline only (17 cells). Increasing stimulus intensity to excite both A and C nerve fibers elicited both short-latency and long-latency (> 200 msec) PSP sequences and spikes in 31 cells. Long-latency PSP and spike responses were similar to the shorterlatency responses, but were more frequently followed by spike discharges lasting for several hundred milliseconds. Recruitment of additional spikes per response was sometimes produced by stimulation of C fibers at rates greater than 0.3/sec (“windup”). This phenomenon was related in most cases to a recruitment of additional EPSP per stimulus and was often related to a progressive membrane depolarization. Responses to constant intensity heat were positively accelerating functions of time. These data point to the existence of long-term postsynaptic facilitatory responses activated by small-fiber inputs.
Research into neonatal ischemic brain damage is impeded by the lack of a complete understanding of the initial hemodynamic mechanisms resulting in a lesion, particularly that of NO-mediated vascular mechanisms. In a neonatal stroke rat model, we recently show that collateral recruitment contributes to infarct size variability. Non-specific and selective NO synthase (NOS) inhibition was evaluated on cerebral blood-flow changes and outcome in a P7 rat model of arterial occlusion (left middle cerebral artery electrocoagulation with 50 min occlusion of both common carotid arteries). Blood-flow changes were measured by using ultrasound imaging with sequential Doppler recordings in both internal carotid arteries and basilar trunk. Cortical perfusion was measured by using laser Doppler flowmetry. We showed that global NOS inhibition significantly reduced collateral support and cortical perfusion (collateral failure), and worsened the ischemic injury in both gender. Conversely, endothelial NOS inhibition increased blood-flows and aggravated volume lesion in males, whereas in females blood-flows did not change and infarct lesion was significantly reduced. These changes were associated with decreased phosphorylation of neuronal NOS at Ser847 in males and increased phosphorylation in females at 24 h, respectively. Neuronal NOS inhibition also increased blood-flows in males but not in females, and did not significantly change infarct volumes compared to their respective PBS-treated controls. In conclusion, both nNOS and eNOS appear to play a key role in modulating arterial blood flow during ischemia mainly in male pups with subsequent modifications in infarct lesion.
This research was prompted by conflicting data in earlier studies of the role of the septum in affective behavior wherein a noxious stimulus was used as behavioral reinforcement. Water-deprived rats were trained to bar-press for water delivered on two alternating intermittent reinforcement schedules. On one, reinforcement was delivered after a fixed number of bar-presses had been emitted fixed ratio) while on the other, a reinforcement was delivered after a 2-min period had elapsed since the previous reinforcement (fixed interval). Septal lesions were placed either prior or subsequent to training on this schedule, permitting evaluation of lesion effects on acquisition or retention of behavior. Controls consisted of animals with gyrus-cinguli lesions, caudate lesions, and nonoperated animals. During acquisition, animals with septal lesions learned the behavior pattern as readily as did nonoperated animals; however, during the fixed interval component, animals with septal lesions had a significantly higher behavioral output than the controls. On the retention testing, the animals with septal lesions showed a loss of their preoperative behavior pattern, and upon recovery manifested the behavior characteristic of such animals during initial acquisition. However, controls showed none or only transitory changes and quickly returned to the preoperative behavior patterns. The results suggest that the hyperexcitability displayed by animals with septal lesions depends not only on the presence of the lesion but also on the occurrence or presence of stimuli the significance of which has been established by particular reinforcement programming.
Changes in the sleep pattern were investigated in rats given actinomycin S3 (AcS3, 0.25 mg/kg, intraventricularly), an inhibitor of RNA synthesis, at 0000, 0600, 1200, and 1800. The amounts of slow-wave (SS) and paradoxical sleep (PS) were increased during the dark period (1800 to 0600) in the groups treated at 0000, 0600, and 1200. In the 1800 injected group, PS was decreased. 5-Hydroxytryptamine (5-HT) was determined in the 0600 injected group. The 5-HT concentration in the AcS3-treated group was twofold higher than in the control group at 1800 (12 h after administration) in the cerebral cortex and lower brain stem but returned to control values at 0000 (18 h after) while sleep time continued to increase. Thus, AcS3 affected the circadian rhythm of the sleep-wake cycle. The increase of sleep time in the dark period was independent of changes in brain 5-HT content.
High-gain intracellular recordings of spinal cord motoneurons were obtained in the chronically prepared cat during wakefulness, quiet sleep, and active sleep. Discrete hyperpolarizing postsynaptic potentials were found to occur repetitively throughout active sleep in conjunction with the presence of somatomotor atonia. These potentials were most prominent in the transition period from quiet to active sleep as well as during episodes of rapid eye movements during active sleep. Their polarity was reversed after the intracellular injection of chloride ions. We propose that these are inhibitory potentials which are responsible for or contribute significantly to the postsynaptic inhibition of spinal cord motoneurons during active sleep.
This study investigated the relationships between changes in intracranial pressure and the activity of cortical epileptogenic foci in cats. Epileptiform spiking was produced by focal freezing and/or topical application of penicillin. Increases in intracranial pressure were produced by infusion of mock cerebrospinal fluid into the cisterna magna. We found that increases in intracranial pressure always produced decreases in epileptiform spike discharge rate. Some preparations also showed an enhancement or “rebound” of spike discharge rate soon after the intracranial pressure was returned to normal. We concluded that it is unlikely that compression or distortion of cerebral tissue play any role in these results. Decreases in cerebral blood flow may be a factor but only for the higher values of intracranial pressure in the less sensitive preparations. We suggest that the most important mechanism responsible for these findings is the desynchronizing effect of afferent input related to increased intracranial pressure. The source of this sensory activity may be from receptors in the cerebrospinal meninges and blood vessels.
Cortical influences, conducted in the pyramidal tract, can modify the amplitude and form of the evoked response in dorsal-column nuclei. Both an increase and a decrease in magnitude of responses can be produced by direct cortical stimulation. When the cortex is excited indirectly, through specific thalamocortical connections, only facilitation occurs. This study has explored further ways in which the response can be modified. In the encéphale isolé of the cat, evoked response in dorsal column nuclei can be reduced by stimulation of midbrain tegmentum. When sensorimotor cortex is ablated, this reduction can no longer be obtained; instead, facilitation occurs. Additionally, serially evoked responses in dorsal-column nuclei display a pronounced increase in amplitude after ablation of the sensorimotor cortex. In low pyramidal preparations, the depressor effect continues functioning, showing that this is a direct action through the pyramidal tract. It is concluded that: the cerebral cortex exerts an inhibitory influence upon afferent potentials in the gracile and cuneate nuclei; stimulation of the reticular formation is capable of activating this mechanism; and the reticular formation also has a direct facilitatory effect on these responses in the dorsal-column nuclei.
We have previously observed that the delivery of an adenoviral vector encoding for glial cell line-derived neurotrophic factor (AdGDNF) into the substantia nigra (SN) 7 days after intrastriatal administration of 6-hydroxydopamine (6-OHDA) protects dopamine (DA)-dependent behaviors, tyrosine hydroxylase immunoreactive (TH+) cells in SN, and amphetamine-induced c-fos induction in striatum. In the present study, we sought to determine if the behavioral protection observed in 6-OHDA-treated rats receiving AdGDNF was associated with an increase in DA availability in the striatum as measured by microdialysis. Rats received intrastriatal 6-OHDA (16 μg/2.8 μl) or vehicle followed 7 days later by intranigral AdGDNF (3.2 × 107 pfu/2 μl), AdLacZ (3.2 × 107 pfu/2 μl), or phosphate buffered saline (PBS). Three weeks later, microdialysis samples were collected from the same striatal region under basal conditions, following KCl (100 mM) or amphetamine (250 μM) administered via the striatal microdialysis probe, or amphetamine administered systemically (6.8 mg/kg i.p). Animals given 6-OHDA followed by either PBS or AdLacZ showed a decrease in basal extracellular striatal DA levels to 24% of control. In contrast, basal extracellular DA in 6-OHDA-lesioned rats with a nigral injection of AdGDNF was almost 3-fold higher than 6-OHDA-vehicle treated animals, 65% of control DA levels. Moreover, although KCl and amphetamine produced no increase in striatal DA release in 6-OHDA-treated rats that subsequently were given either PBS or AdLacZ, these manipulations increased DA levels significantly in 6-OHDA-treated rats later given AdGDNF. Thus, DA neurotransmission within the striatum of 6-OHDA treated rats appears to be enhanced by increased expression of GDNF in the nigra.
Dysfunctional glial glutamate transporters and over production of pro-inflammatory cytokines (including interleukin-1β, IL-1β) are two prominent mechanisms by which glial cells enhance neuronal activities in the spinal dorsal horn in neuropathic pain conditions. Endogenous molecules regulating production of IL-1β and glial glutamate functions remain poorly understood. In this study, we revealed a dynamic alteration of GSK3β activities and its role in regulating glial glutamate transporter 1 (GLT-1) protein expression in the spinal dorsal horn and nociceptive behaviors following the nerve injury. Specifically, GSK3β was expressed in both neurons and astrocytes in the spinal dorsal horn. GSK3β activities were suppressed on day 3 but increased on day 10 following the nerve injury. In parallel, protein expression of GLT-1 in the spinal dorsal horn was enhanced on day 3 but reduced on day 10. In contrast to these time-dependent changes, the activation of astrocytes and over-production of IL-1β were found on both day 3 and day 10. Meanwhile, thermal hyperalgesia was observed from day 2 through day 10 and mechanical allodynia from day 4 through day 10. Pre-emptive pharmacological inhibition of GSK3β activities significantly ameliorated thermal hyperalgesia and mechanical allodynia at the late stage but did not have effects at the early stage. These were accompanied with the suppression of GSK3β activities, prevention of decreased GLT-1 protein expression, inhibition of astrocytic activation, and reduction of IL-1β in the spinal dorsal horn on day 10. These data indicate that the increased GSK3β activity in the spinal dorsal horn is attributable to the downregulation of GLT-1 protein expression in neuropathic rats at the late stage. Further, we also demonstrated that the nerve-injury-induced thermal hyperalgesia on day 10 was transiently suppressed by pharmacological inhibition of GSK3β. Our study suggests that GSK3β may be a potential target for the development of analgesics for chronic neuropathic pain.
Motor nerve excitability studies by “threshold tracking” in amyotrophic lateral sclerosis (ALS) revealed heterogeneous abnormalities in motor axon membrane function possibly depending on disease stage. It remains unclear to which extent the excitability deviations reflect a pathogenic mechanism in ALS or are merely a consequence of axonal degeneration. We investigated motor axon excitability in presymptomatic and symptomatic SOD1G127X mutants, a mouse model of ALS with late clinical onset and rapid disease progression. After clinical onset, there was a rapid loss of functional motor units associated with an increase in rheobase and strength–duration time constant, an increase in refractoriness at the expense of the superexcitability, larger than normal threshold deviations during both depolarizing and hyperpolarizing threshold electrotonus with impaired accommodation and reduction of the input conductance. These abnormalities progressed rapidly over a few days and were associated with morphological evidence of ongoing axonal degeneration. Presymptomatic mice with unaltered motor performance at rotor-rod measurement also had an increase in refractoriness at the expense of the superexcitability during the recovery cycle. This was, however, associated with smaller than normal deviations during threshold electrotonus, and a steeper resting current–threshold slope indicating slight axonal depolarization in agreement with motoneuronal hyperexcitability indicated by enhanced F-waves. Our data suggest that SOD1G127X motor axons undergo a state of membrane depolarization; however, during rapid motoneuron loss disease-specific nerve excitability measures are confounded by excitability changes in degenerating but still conducting axons. These findings should be considered in the interpretation of disease-stage-related nerve excitability changes in ALS.
DOI : 10.1016/j.expneurol.2011.11.008 Anahtar Kelimeler :
Nerve activity, Regeneration, Ion channels, Excitability, Node of Ranvier, Internode, Mouse model, Motor neuron disease
ISSN: 0014-4886 Sayı: 1 Cilt: 233 Sayfa: 408-420
The effect of age at the time of spinal lesion on the response of the tracts descending from the ventromedial portion of the midbrain was examined. Degeneration resulting from sequential lesions (T6 hemisection, then electrolytic midline mesencephalon lesion) administered 7 to 9 months apart was studied in sections of spinal cord stained by the Fink-Heimer technique. There was an increased density of the projection field which was demonstrated two and three segments rostral to a midthoracic funiculotomy in newborn, 21-day-old, and adult rats. Unexpectedly, the increased density was similar in the three age groups. No sprouting was demonstrated in the cervical cord. In all age groups the projection remained confined to its normal terminal fields. There was no statistically significant difference in area on the two sides destroyed by the midbrain lesion and no shrinkage in the upper thoracic gray matter in any age group as demonstrated by planimetric measurements of sections. In animals which sustained lesions as infants, there was a massive reduction in area of the lateral white matter including that occupied by the rubrospinal tract. Therefore, in rats with lesions administered in infancy, a comparable (to adult) amount of sprouting may have been from fewer axons. Two possible explanations for these results are considered. First, there may be proportionately more sprouting per axon in the animals with first lesions at birth. On the other hand, the amount of sprouting per axon may be similar in both age groups if only some axons sprout in animals with first lesions as adults.
Chronic paralysis of the duck embryo with α-bungarotoxin increases the number of trochlear motor neurons that survive by decreasing the magnitude of embryonic cell death. The present study examined how such an increase in the motor neuron projection is accommodated at the peripheral target. The results indicate that the overall size of the duck superior oblique muscle was drastically reduced following chronic paralysis with α-bungarotoxin. The number of motor end-plates was reduced to about 25% of the control. Although the total number of end-plates was significantly reduced, their size was larger and they became innervated by far more nerve terminals than in the control. Thus, increased motor neuron survival occurred while the size of the periphery and the number of synaptic sites (end-plates) were greatly reduced. These observations suggest that the cause of embryonic cell death may not be related to the availability of adequate numbers of synapses with the periphery. They also suggest that the physiologic activity of the embryo may play a significant role in regulation of cell number in the developing nervous system.
The entire presumptive nervous system of stage 24 Amblystoma maculatum embryos was surgically excised to produce aneurogenic larvae. For controls, embryos of the same age were operated in an identical fashion except that a segment of neural tube (about 1 mm) dorsal to the limb bud anlagen was left intact. The number of peripherally situated muscle nuclei (a measure of myofiber differentiation) peaked at the four-digit stage of aneurogenic limb development. The number of peripheral nuclei in the controls also peaked at the same time but remained at that maximum. With the exception of Day 13, the number of peripheral nuclei was always greater in control than in aneurogenic muscle. The total number of muscle nuclei per limb cross section gradually decreased in aneurogenic muscle to a number significantly lower than in controls at 31 days after the operation and thereafter. The cross-sectional size of aneurogenic muscle nuclei seemed to decrease at a faster rate than control nuclei. Reflecting nuclear density, the myonuclear area per muscle area in aneurogenic limbs was smallest at 21 days after the operation. After 21 days, aneurogenic nuclear densities progressively increased whereas control densities remained at the low, Day-21 value. From Day 13 to 21 the muscle nuclear density in control and aneurogenic limbs was statistically equal. Aneurogenic myofibers in an advanced state of degeneration incorporated more [3H]leucine or [3H]uridine than fibers where cross striations were still visible with the light microscope. With the electron microscope, acid phosphatase-stained lysosomes were found adjacent to disintegrating myofibrillar material in degenerating aneurogenic myofibers. Ruthenium red staining indicated that myofiber basement laminae developed normally in aneurogenic muscle and persisted.
Objective To establish an animal model for posttraumatic stress disorder in burn-injured patients. Methods Thermal-injured mice with 15% total body surface area were subjected to a series of neurobehavioral tests at 1 and 3 months postburn. Brains were collected for analysis of key molecules expression, spleens for T cell function analysis, and blood for biochemistry and hormones detection. Results Comparison with sham mice, burn mice showed extremely high locomotion in homecage, open field, and forced swimming tests, indicating a hyper-arousal state. Burn mice exhibited improved spatial memory in Morris Water Maze test and heightened context fear memory in context fear conditioning, suggesting re-experiencing behavior. Although burn mice showed pronounced passive avoidance in the step-through test, their active avoidance capability in response to the conditional stimulus in the shuttle box test was relatively deteriorated. Likewise, the retention of cue-feared memory was impaired in fear conditioning test. The above negative alterations in mood were recapitulated in open-field test, in which the burn mice displayed an anxiety-like behavior with less time spent in the center. However, no sign of depression was found in the forced swimming and sucrose preference tests. The negative mood of burn mice was reinforced by a deficit in sociality and preference for social novelty in social interaction test. These neurobehavioral alterations were associated with an increased expression of brain-derived neurotrophic factor along with a remarkable microgliosis and a moderate astrocytosis in the brain of burn vs. sham mice. Moreover, a prominent Th2 switch and consequent increased nuclear NF-κB translocation were seen in the splenic T cells from burn relative to sham mice. Conclusions We conclude that even mild burn injury could lead to long-lasting cognitive and effective alterations in mice. These findings shed light on the interactions among neuropsychology, neurobiology, and immunology throughout the recovery period of burn injury.
DOI : 10.1016/j.expneurol.2019.113084 Anahtar Kelimeler :
Burn injury, Neurobehavior, Posttraumatic stress disorder, CD4+ T cell, Brain-derived neurotrophic factor, PTSD posttraumatic stress disorder, posttraumatic stress disorder, BDNF brain-derived neurotrophic factor, brain-derived neurotrophic factor, CNS central nervous system, central nervous system, TBSA total body surface area, total body surface area, MWM Morris Water Maze, Morris Water Maze, pb postburn, postburn, CS conditioned stimulus, conditioned stimulus, US unconditioned stimulus, unconditioned stimulus, GFAP glial fibrillary acidic protein, glial fibrillary acidic protein, PFA paraformaldehyde, paraformaldehyde, BSA bovine serum albumin, bovine serum albumin, PVDF polyvinylidene difluoride, polyvinylidene difluoride, i.p. intraperitoneally, intraperitoneally, Iba-1 ionized calcium binding adaptor protein 1, ionized calcium binding adaptor protein 1, DR dopamine receptor, dopamine receptor, TBI traumatic brain injury, traumatic brain injury, AST aspartate transaminase, aspartate transaminase, ALT alanine aminotransferase, alanine aminotransferase, HDL high density lipoprotein, high density lipoprotein, LDL low density lipoprotein, low density lipoprotein, VLDL very low density lipoprotein, very low density lipoprotein
ISSN: 0014-4886 Cilt: 323 Sayfa: 113084
The effects of various concentrations of bupivacaine on the extensor muscles of rats were studied. The drug was applied to the muscles either in situ or in a bath through perfusion. Bupivacaine produced a concentration- and temperature-dependent depolarization of surface fibers which could not be antagonized by blockers of sodium and potassium conductance or by altering the concentrations of sodium, calcium, or chloride ions. Concentrations of bupivacaine above 50 μm blocked nerve-evoked muscle action potentials. The blockade of nerve conduction recovered within 12 h of drug application in vivo. When bath-applied, 50 to 100 μm bupivacaine increased miniature end-plate potential frequency two- to threefold, decreased the amplitude, and shortened the decay phase of the transient potential. When applied to the muscle in vivo, and studied at periods beyond 24 h, concentrations of bupivacaine to 1 mm had no effect on the membrane potential or spontaneous and evoked transmitter release. Additionally, no signs of denervation appeared when the extensor muscle was studied at 24-h or longer intervals. Muscles exposed to 5 mm bupivacaine were significantly depolarized by day 3 but at that time had miniature end-plate potentials of normal amplitude and time course. The synaptic apparatus remained intact throughout the period of degeneration and subsequent regeneration of muscle fibers as confirmed by light microscopy. At 50 μm bupivacaine, no fiber degeneration was observed, yet as early as 12 h after its application a significant degree of terminal sprouting was seen in all muscles. As many as 35% of the end-plates showed terminal sprouts at day 10 with 5 mm bupivacaine and a significant number of those sprouts made neuromuscular contacts at distances greater than 800 μm from an end-plate. A low-profile extrajunctional acetylcholine sensitivity was recorded at 3 and 10 days after application of bupivacaine (5 mm) in vivo. The results ruled out muscle inactivity and degeneration per se as possible stimuli for terminal sprouting. Induction of terminal sprouting by bupivacaine in the absence of degeneration of the muscle fiber and in the presence of an apparently intact neuromuscular apparatus was the most significant finding.
Repetition of seizures appears to increase severity in a number of seizure models, but the nature of these severity increases has not been elucidated in naturally occurring genetic epilepsy models. The genetically epilepsy-prone rat (GEPR) is highly susceptible to many seizure provoking stimuli, and high intensity acoustic stimuli induce audiogenic seizures (AGS). The role of forebrain structures in AGS in the GEPR has not been clear, and the presence of cortical epileptiform EEG activity in the GEPR is controversial. The present study examined the effects of 21 daily AGS repetitions on behavior and EEG activity recorded from the cortex of two GEPR substrains that exhibit moderate (GEPR-3) or severe AGS (GEPR-9). The results indicated that AGS repetition induced seizure severity increases in both GEPR substrains and resulted in prominent cortical epileptiform EEG activity. The AGS behavioral patterns remained distinctly different in the two substrains throughout seizure repetition. In each substrain a different additional behavioral phase was expressed; the GEPR-9 exhibited post-tonic clonus, and the GEPR-3 exhibited facial and forelimb clonus. These findings indicate that seizure repetition results in expansion of the neuronal network subserving AGS to involve forebrain structures. The medial geniculate body and amygdala appear to be part of this expanded network, and long-term potentiation, which was reported in the pathway between the latter brain structures, may be involved. These data suggest that recruitment of forebrain structures into the AGS neuronal network appears to be essential for production of the additional ictal behaviors evoked by AGS repetition.
Neural progenitor cells (NPCs) have shown modest potential and some side effects (e.g. allodynia) for treatment of spinal cord injury (SCI). In only a few cases, however, have NPCs shown promise at the chronic stage. Given the 1.275 million people living with chronic paralysis, there is a significant need to rigorously evaluate the cell types and methods for safe and efficacious treatment of this devastating condition. For the first time, we examined the pre-clinical potential of NPCs derived from human induced pluripotent stem cells (hiPSCs) to repair chronic SCI. hiPSCs were differentiated into region-specific (i.e. caudal) NPCs, then transplanted into a new, clinically relevant model of early chronic cervical SCI. We established the conditions for successful transplantation of caudalized hiPSC-NPCs and demonstrate their remarkable ability to integrate and produce multiple neural lineages in the early chronic injury environment. In contrast to prior reports in acute and sub-acute injury models, survival and integration of hiPSC-derived neural cells in the early chronic cervical model did not lead to significant improvement in forelimb function or induce allodynia. These data indicate that while hiPSCs show promise, future work needs to focus on the specific hiPSC-derivatives or co-therapies that will restore function in the early chronic injury setting.
The heads of infant rats were irradiated with 200 r X-ray. In one group the animals were injected with thymidine-3H immediately after irradiation, in the other, 24 hours before irradiation. All were killed at 3 days of age, 6 hours after irradiation and 6 or 30 hours after injection. In autoradiograms from the brains of unirradiated animals killed 6 hours after injection, the proportion of labeled cells, reflecting regional rate of cell poliferation, was determined at several brain sites. The relative reduction in the rate of cell proliferation in irradiated animals was also established. In matched stained sections the proportion of pyknotic cells, reflecting rate of cell death, was determined in the same brain regions. Finally, pyknosis index/labeling index ratios were calculated to relate radiation-induced cell death to rate of cell proliferation at different loci. It was established that migrating cells and prospective migratory cells, whether mitotic or postmitotic, are extremely radiosensitive, with a large proportion of them killed by exposure to 200 r. Relatively few of the stationary proliferating cells were killed with this dose. Stationary differentiating cells, and mature cells were not visibly affected. These results suggest that damage to the cellular mechanisms that enable primitive cells to locomote, rather than damage to DNA, is the principal cause of cell death in the nervous system exposed to low-level radiation. Moreover, the selective effect of this procedure could provide a technique for the identification of migratory cells at different brain sites during different stages of development.