Functional recovery after brain infarction: plasticity and neural transplantation

Stem Cell Treatment for Ischemic Stroke Recovery

The role of cellular transplantation to promote functional recovery after stroke has been evaluated over the last two decades. Preclinical studies first established the potential for cultured neuronal cells derived from a teratocarcinoma cell line to be tested for safety and efficacy in the treatment of human stroke. In animal models of stroke that caused reproducible learning and motor deficits, injection of neuronal cells resulted in a return of learning behavior, retention time, and motor function. Clinical trials followed. Additional work with cells derived from a bone marrow neuroprogenitor line, fetal cortical stem cells, and other cell sources showed promise in preclinical studies and then these cells were tested in clinical studies. This report reviews the different biological repair approaches using cell implants, discusses clinical trial design and surgical methods, and the current state of research.

Deficits in motor and cognitive functions in an adult mouse model of hypoxia-ischemia induced stroke

Ischemic strokes cause devastating brain damage and functional deficits with few treatments available. Previous studies have shown that the ischemia-hypoxia rapidly induces clinically similar thrombosis and neuronal loss, but any resulting behavioral changes are largely unknown. The goal of this study was to evaluate motor and cognitive deficits in adult HI mice. Following a previously established procedure, HI mouse models were induced by first ligating the right common carotid artery and followed by hypoxia. Histological data showed significant long-term neuronal losses and reactive glial cells in the ipsilateral striatum and hippocampus of the HI mice. Whereas the open field test and the rotarod test could not reliably distinguish between the sham and HI mice, in the tapered beam and wire-hanging tests, the HI mice showed short-term and long-term deficits, as evidenced by the increased number of foot faults and decreased hanging time respectively. In cognitive tests, the HI mice swam longer distances and needed more time to find the platform in the Morris water maze test and showed shorter freezing time in fear contextual tests after fear training. In conclusion, this study demonstrates that adult HI mice have motor and cognitive deficits and could be useful models for preclinical stroke research.

Acupuncture in Stroke Rehabilitation

This paper summarises earlier published data on acupuncture and electroacupuncture in stroke patients and discusses possible mechanisms behind the enhanced recovery obtained. Severely hemiparetic patients were entered into a randomised trial within 10 days of their stroke. Acupuncture, including electroacupuncture, was given twice a week for ten weeks to half of the patients, in addition to the daily physiotherapy and occupational therapy given to all. Patients given acupuncture recovered faster and more fully than the control stroke patients, with a significant difference in balance, mobility, activity of daily living and quality of life, an effect that persisted one year after stoke onset. In a follow-up 2 to 3.8 years after the stroke, the postural control of stroke survivors was compared with that of 23, age-matched, healthy subjects. Only half of the control stroke patients could perform the test, and the postural control pattern in those who could take part was significantly different from the healthy controls and acupuncture treated stroke patients, whereas there was no significant difference between acupuncture treated patients and healthy controls. The possible psychological effects of a greater expectation in patients given acupuncture has to be considered. Other studies have shown that special attention given to stroke patients in the early rehabilitation period can accelerate their recovery, but that the difference is usually lost at follow-up. Our results need confirmation, but we have hypothesised that sensory stimulation in the form of acupuncture may release substances that enhance brain plasticity after stroke, an hypothesis than can be tested in experimental studies. Whether or not the effects are specific for acupuncture, or can be obtained also by other kinds of sensory stimuli such as transcutaneous nerve stimulation is currently being investigated.

Dressing Ability after Stroke: A Review of the Literature

Despite regular occupational therapy, many stroke patients remain dependent for dressing. The latter half of the 20th century has witnessed considerable debate in the literature as to the underlying deficits that influence a person's ability to relearn to dress. This paper critiques the relationship between cognitive and physical skills and recovery in dressing. The implications for occupational therapy are discussed.

Angiogenesis in Ischemic Stroke and Angiogenic Effects of Chinese Herbal Medicine

Stroke is one of the major causes of death and adult disability worldwide. The underlying pathophysiology of stroke is highly complicated, consisting of impairments of multiple signalling pathways, and numerous pathological processes such as acidosis, glutamate excitotoxicity, calcium overload, cerebral inflammation and reactive oxygen species (ROS) generation. The current treatment for ischemic stroke is limited to thromolytics such as recombinant tissue plasminogen activator (tPA). tPA has a very narrow therapeutic window, making it suitable to only a minority of stroke patients. Hence, there is great urgency to develop new therapies that can protect brain tissue from ischemic damage. Recent studies have shown that new vessel formation after stroke not only replenishes blood flow to the ischemic area of the brain, but also promotes neurogenesis and improves neurological functions in both animal models and patients. Therefore, drugs that can promote angiogenesis after ischemic stroke can provide therapeutic benefits in stroke management. In this regard, Chinese herbal medicine (CHM) has a long history in treating stroke and the associated diseases. A number of studies have demonstrated the pro-angiogenic effects of various Chinese herbs and herbal formulations in both in vitro and in vivo settings. In this article, we present a comprehensive review of the current knowledge on angiogenesis in the context of ischemic stroke and discuss the potential use of CHM in stroke management through modulation of angiogenesis.

Cortical plasticity induced by different degrees of peripheral nerve injuries: a rat functional magnetic resonance imaging study under 9.4 Tesla

BACKGROUND

Major peripheral nerve injuries not only result in local deficits but may also cause distal atrophy of target muscles or permanent loss of sensation. Likewise, these injuries have been shown to instigate long-lasting central cortical reorganization.

METHODS

Cortical plasticity changes induced after various types of major peripheral nerve injury using an electrical stimulation technique to the rat upper extremity and functional magnetic resonance imaging (fMRI) were examined. Studies were completed out immediately after injury (acute stage) and at two weeks (subacute stage) to evaluate time affect on plasticity.

RESULTS

After right-side median nerve transection, cortical representation of activation of the right-side ulnar nerve expanded intra-hemispherically into the cortical region that had been occupied by the median nerve representation After unilateral transection of both median and ulnar nerves, cortical representation of activation of the radial nerve on the same side of the body also demonstrated intra-hemispheric expansion. However, simultaneous electrical stimulation of the contralateral uninjured median and ulnar nerves resulted in a representation that had expanded both intra- and inter-hemispherically into the cortical region previously occupied by the two transected nerve representations.

CONCLUSIONS

After major peripheral nerve injury, an adjacent nerve, with similar function to the injured nerve, may become significantly over-activated in the cortex when stimulated. This results in intra-hemispheric cortical expansion as the only component of cortical plasticity. When all nerves responsible for a certain function are injured, the same nerves on the contralateral side of the body are affected and become significantly over-activated during a task. Both intra- and inter-hemispheric cortical expansion exist, while the latter dominates cortical plasticity.

Neural tissue transplantation, repair, and rehabilitation

Transplants of cells and tissues to the central nervous system of adult mammals can, under appropriate conditions, survive, integrate, and function. In particular, the grafted cells can sustain functional recovery in animal models of a range of neurodegenerative conditions including genetic and idiopathic neurodegenerative diseases of adulthood and aging, ischemic stroke, and brain and spinal cord trauma. In a restricted subset of such conditions, cell transplantation has progressed to application in humans in early-stage clinical trials. At the present stage of play, there is clear evidence of clinical efficacy of fetal cell transplants in Parkinson disease (notwithstanding a range of technical difficulties still to be fully resolved), and preliminary claims of promising outcomes in several other severe neurodegenerative conditions, including Huntington disease and stroke. Moreover, the experimental literature is increasingly suggesting that the experience and training of the graft recipient materially affects the functional outcome. For example, environmental enrichment, behavioral activity, and specific training can enhance the recovery process to maximize functional recovery. There are even circumstances where the grafted cells have been demonstrated to restore the neural substrate for new learning. Consequently, it is not sufficient to replace lost cells anatomically; rather, for the grafts to be effective, they need to be integrated functionally into the host circuitry, and the host animal requires training and rehabilitation to maximize function of the reconstructed graft-host circuitry. Such observations require reconsideration of the design of the next generation of clinical trials and subsequent service delivery, to include physiotherapists, cognitive therapists, and rehabilitation experts as core members of the transplant team, along with the neurologists and neurosurgeons that have conventionally led the field.

Chapter 55: neural transplantation

The history of cell transplantation in the nervous system is reviewed in four main sections. The "early era" spans the period from 1890 to 1940, during which the first attempts at cell transplantation in the brain were undertaken. Many contemporary themes were first addressed such as surgical factors to achieve survival of grafted cells and how that should be assessed, immunological factors, use of tumors as a readily viable cell source; and use of the anterior eye chamber as a model transplantation site. However, such studies generally exhibited only low levels of viability or successful implantation. The "middle era" from 1940 to 1970 spans the period when the techniques for viable and reliable cell transplantation using embryonic donor tissues implanted into sites with effective vascularization were first established in brain and neuroendocrine systems in a limited number of specialist centers. However, although sometimes impressive, these results were at variance with the prevailing view that the adult mammalian brain is immutable and resistant to plasticity, growth or regeneration, and were largely ignored. The "modern era," since 1970, began with the pioneering studies that combined cell transplantation with the use of improved histochemical and ultrastructural anatomical techniques to demonstrate selectivity, specificity and regenerative capacity of implanted cells, and the slow acceptance that the adult brain does exhibit considerable potential for plasticity and repair. The last three decades have witnessed the identification of reliable and efficient transplantation technologies combined with progressively refined methods of molecular, cellular, biochemical, physiological and functional analysis. This now enables the ready use of cell transplantation as a powerful novel method within the neuroscience tool-kit, which is being used: to analyze normal organization and function of the nervous system; to reveal the biological mechanisms and principles of neuronal development, regeneration and plasticity; and to study the principles of surgically directed cell therapies for promoting plasticity, replacement and repair in response to injury and disease. The final section reviews recent progress in translating cell transplantation to the clinic for application in Parkinson's and other central nervous system diseases.

Early motor balance and coordination training increased synaptophysin in subcortical regions of the ischemic rat brain

The aim of this study was to evaluate the effect of early motor balance and coordination training on functional recovery and brain plasticity in an ischemic rat stroke model, compared with simple locomotor exercise. Adult male Sprague-Dawley rats with cortical infarcts were trained under one of four conditions: nontrained control, treadmill training, motor training on the Rota-rod, or both Rota-rod and treadmill training. All types of training were performed from post-operation day 1 to 14. Neurological and behavioral performance was evaluated by Menzies' scale, the prehensile test, and the limb placement test, at post-operation day 1, 7, and 14. Both Rota-rod and treadmill training increased the expression of synaptophysin in subcortical regions of the ischemic hemisphere including the hippocampus, dentate gyrus, and thalamus, but did not affect levels of brain-derived neurotrophic factor or tyrosin kinase receptor B. The Rota-rod training also improved Menzies' scale and limb placement test scores, whereas the simple treadmill training did neither. The control group showed significant change only in Menzies' scale score. This study suggests that early motor balance and coordination training may induce plastic changes in subcortical regions of the ischemic hemisphere after stroke accompanied with the recovery of sensorimotor performance.

Is acupuncture an acceptable option in stroke rehabilitation? A survey of stroke patients

OBJECTIVE

Stroke is a leading cause of morbidity and mortality and stroke survivors make up the largest group of patients in rehabilitation. These individuals also have one of the longest lengths of stay in rehabilitation. It has been suggested that acupuncture may be beneficial in post-stroke rehabilitation and in this study we examine how stroke patients value acupuncture and their perceptions of acupuncture as a rehabilitation treatment option.

DESIGN AND SETTING

A questionnaire was distributed to individuals undergoing post-stroke rehabilitation at three rehabilitation centers attached to hospitals in Toronto, Canada.

RESULTS

Two hundred and seventy-three individuals completed the questionnaire with the respondent group comprising mainly males (62%) over 65 years of age (68%). Overall 29% had used acupuncture with 16% receiving acupuncture treatment for stroke related conditions. Almost all respondents (98%) wanted to know more about acupuncture in stroke rehabilitation and 87% would consider acupuncture as a treatment option. Few (8%) reported that they had advanced level knowledge about acupuncture, with most reporting a basic (48%) or intermediate (33%) level which recognized that acupuncture used fine needles to produce a therapeutic response. Those with prior acupuncture experience expected to pay more for treatment. The main factors influencing decisions to use acupuncture were practitioner competency (84%), cost (65%) and sterilization concerns (40%).

CONCLUSION

This study demonstrates that there is willingness by patients attending conventional hospital-based rehabilitation centers to consider acupuncture in stroke rehabilitation and that lack of knowledge about this treatment is not a barrier to use.

Stroke repair with cell transplantation: neuronal cells, neuroprogenitor cells, and stem cells

Stroke is a common cause of death and disability. The role of cellular transplantation to promote functional recovery has been explored. Preclinical studies first established the potential for cultured neuronal cells derived from a teratocarcinoma cell line to be tested for safety and efficacy in the treatment of human stroke. In animal models of stroke that caused reproducible learning and motor deficits, injection of neuronal cells resulted in a return of learning behavior retention time and motor function. In this report the authors review several current concepts for cellular repair, discuss important patient selection and surgical technique issues, and discuss plans for future experiments.

In peripheral nerve regeneration environment enriched with activity stimulating factors improves functional recovery

Enriched environment stimulates brain plasticity processes after brain lesion. Less is known about the influence of enriched environment with activity stimulating factors as determinants of functional outcome after peripheral nerve repair. BDNF (brain-derived neurotrophic factor) plays a role in activity-dependent neuronal plasticity and changes in motor cortex in rats learning complex motor skills. Our study aimed to elucidate if enriched environment influences functional results after peripheral nerve repair. The results in this rat sciatic nerve transection and repair model showed that environment enriched with activity stimulating factors can improve functional results.

Circuit training in community-living "younger" men after stroke

OBJECTIVES

We sought to assess a training program focused on muscle strength and endurance in persons with prior stroke.

METHODS

Thirty men with a slight hemiparesis caused by a first occurrence of stroke at least 6 months earlier were included with an average age of 54 years. The following was assessed before and after an 8-week period: muscle strength, endurance, work capacity, and activity level. The training group consisted of 21 persons and 9 served as control subjects. There were no differences between the groups in the various assessments from the start. The training was set up as circuit training with 5 stations aiming to strengthen the muscles and increase endurance in the bilateral lower limbs. The session lasted for 45 minutes, 3 times per week, for 8 weeks. On eligible persons in the training group, double-sided muscle biopsies were also performed before and after.

RESULTS

There was significance in improved muscle strength and improved peak oxygen uptake for the paretic leg, which was reflected in the muscle enzymes. The nonparetic side also showed improvement, but to a lesser extent. The control group remained unchanged.

CONCLUSIONS

Stroke survivors can improve muscle strength, endurance, and work capacity in both the paretic and nonparetic leg with a circuit training program.

Survival and early differentiation of human neural stem cells transplanted in a nonhuman primate model of stroke

OBJECT

Neural cell transplantation has been proposed as a treatment after stroke. The purpose of this study was to establish if human neural stem cells (HNSCs) could survive in the nonhuman primate brain after an ischemic event.

METHODS

Three adult cynomolgus monkeys received a unilateral occlusion of the M, segment of the right middle cerebral artery (MCA). One week later each animal received five magnetic resonance (MR) image-guided stereotactic intracerebral injections of HNSC neurospheres labeled with bromodeoxyuridine (BrdU) in the areas surrounding the ischemic lesion as defined in T1- and T2-weighted images. On the day of transplantation and throughout the study the monkeys received oral cyclosporine (10 mg/kg twice a day), and plasma levels were monitored routinely. The animals were killed at 45, 75, or 105 days after transplantation. Magnetic resonance images revealed a cortical and subcortical infarction in the MCA distribution area. Postmortem morphological brain analyses confirmed the distribution of the infarcted area seen in the MR images, with loss of tissue and necrosis in the ischemic region. Cells that were positive for BrdU were present in the three experimental monkeys, mainly along injection tracks. Double-label immunofluorescence for BrdU and betaIII-tubulin (a marker of young neurons) revealed colocalization of few HNSCs, most of which were observed outside the immediate injection site. Colocalization with nestin was also observed, indicating an early neural/glial fate.

CONCLUSIONS

In a model of stroke in nonhuman primates, HNSCs can survive up to 105 days when transplanted 1 week after an ischemic event and can partly undergo neuronal differentiation.

Challenges of Neuroprotection and Neurorestoration in Ischemic Stroke Treatment

Currently, the most important therapeutic approaches in the acute phase of ischemic stroke are focused on the restoration of regional cerebral blood flow, early admission to a stroke unit and the attempt to block, using neuroprotective drugs, the biochemical and metabolic changes involved in the 'ischemic cascade'. Treatment with rt-PA in the acute phase, although very effective, is still limited to a small number of patients and positive preclinical results of neuroprotective treatment have not, as yet, been endorsed in clinical trials. The remarkable lack of concordance between the positive results in experimental models and the negative results obtained in clinical trials has led to a change in attitude in the conduct of preclinical studies as well as to a modification of the design of clinical trials, with special attention being paid to patient selection criteria and clinical evaluation. Some neuroprotective drugs, such as citicoline, have shown some efficacy in subgroups of patients with cerebral infarction, even with a therapeutic window of up to 24 h, which would suggest a possible neurorestorative effect. Different degrees of functional recovery, weeks or months after the ischemic event, are currently observed in clinical practice and have been related to endogenous self-repair mechanisms. The growing understanding of the mechanisms involved in the phenomena of brain plasticity and their modulation, together with the possibility of restoring functional deficits by encouraging endogenous neurogenesis or by cell therapy, open up new directions in the treatment of stroke patients.

Transplantation of embryonic stem cells overexpressing Bcl-2 promotes functional recovery after transient cerebral ischemia

The study tested the hypothesis that transplantation of embryonic stem (ES) cells into rat cortex after a severe focal ischemia would promote structural repair and functional recovery. Overexpression of the human anti-apoptotic gene bcl-2 in ES cells was tested for increasing survival and differentiation of transplanted cells and promoting functional benefits. Mouse ES cells, pretreated with retinoic acid to induce differentiation down neural lineages, were transplanted into the post-infarct brain cavity of adult rats 7 days after 2-h occlusion of the middle cerebral artery (MCA). Over 1-8 weeks after transplantation, the lesion cavity filled with ES cell-derived cells that expressed markers for neurons, astrocytes, oligodendrocytes, and endothelial cells. ES cell-derived neurons exhibited dendrite outgrowth and formed a neuropil. ES cell-transplanted animals exhibited enhanced functional recovery on neurological and behavioral tests, compared to control animals injected with adult mouse cortical cells or vehicle. Furthermore, transplantation with ES cells overexpressing Bcl-2 further increased the survival of transplanted ES cells, neuronal differentiation, and functional outcome. This study supports that ES cell transplantation and gene modification may have values for enhancing recovery after stroke.

Neurotransplantation for patients with subcortical motor stroke: a Phase 2 randomized trial

OBJECT

No definitive treatment exists to restore lost brain function following a stroke. Transplantation of cultured neuronal cells has been shown to be safe and effective in animal models of stroke and safe in a Phase 1 human trial. In the present study the authors tested the usefulness of human neuron transplantation followed by participation in a 2-month stroke rehabilitation program compared with rehabilitation alone in patients with substantial fixed motor deficits associated with a basal ganglia stroke.

METHODS

Human neuronal cells (LBS-Neurons; Layton BioScience, Inc.) were delivered frozen and then thawed and formulated on the morning of surgery. The entry criteria in this randomized, observer-blinded trial of 18 patients included age between 18 and 75 years, completed stroke duration of 1 to 6 years, presence of a fixed motor deficit that was stable for at least 2 months, and no contraindications to stereotactic surgery. Patients were randomized at two centers to receive either 5 or 10 million implanted cells in 25 sites (seven patients per group) followed by participation in a stroke rehabilitation program, or to serve as a nonsurgical control group (rehabilitation only; four patients). The surgical techniques used were the same at both centers. All patients underwent extensive pre- and postoperative motor testing and imaging. Patients received cyclosporine A for 1 week before and 6 months after surgery. The primary efficacy measure was a change in the European Stroke Scale (ESS) motor score at 6 months. Secondary outcomes included Fugl-Meyer, Action Research Arm Test, and Stroke Impact Scale scores, as well as the results of other motor tests. Nine strokes were ischemic in origin and nine were hemorrhagic. All 14 patients who underwent surgery (ages 40-70 years) underwent uncomplicated surgeries. Serial evaluations (maximum duration 24 months) demonstrated no cell-related adverse serological or imaging-defined effects. One patient suffered a single seizure, another had a syncopal event, and in another there was burr-hole drainage of an asymptomatic chronic subdural hematoma. Four of seven patients who received 5 million cells (mean improvement 6.9 points) and two of seven who received 10 million cells had improved ESS scores at 6 months; however, there was no significant change in the ESS motor score in patients who received cell implants (p = 0.756) compared with control or baseline values (p = 0.06). Compared with baseline, wrist movement and hand movement scores recorded on the Fugl-Meyer Stroke Assessment instrument were not improved (p = 0.06). The Action Research Arm Test gross hand-movement scores improved compared with control (p = 0.017) and baseline (p = 0.001) values. On the Stroke Impact Scale, the 6-month daily activities score changed compared with baseline (p = 0.045) but not control (p = 0.056) scores, and the Everyday Memory test score improved in comparison with baseline (p = 0.004) values.

CONCLUSIONS

Human neuronal cells can be produced in culture and implanted stereotactically into the brains of patients with motor deficits due to stroke. Although a measurable improvement was noted in some patients and this translated into improved activities of daily living in some patients as well, this study did not find evidence of a significant benefit in motor function as determined by the primary outcome measure. This experimental trial indicates the safety and feasibility of neuron transplantation for patients with motor stroke.

Angiogenesis and stem cell transplantation as potential treatments of cerebral ischemic stroke

Ischemic stroke is a leading cause of human death and disability. Although stroke survivors may gain spontaneous partial functional recovery, they often suffer from sensory-motor dysfunctions, behavioral/neurological alterations, and various degrees of paralysis. Currently, limited clinical intervention is available to prevent ischemic damage and restore lost function in stroke victims. In addition to the extensive research on protective maneuvers against ischemia-induced cell death, increasing attention has been focused on potential strategies of promoting tissue repair and functional recovery in the damaged post-ischemic brain. Angiogenesis, or the growth of new blood vessels, may contribute to cell survival and functional recovery of the area of insult. The study of angiogenesis will increase the understanding of the mechanism underlying post-ischemia neurovascular plasticity and regeneration. Additionally, stem cell transplantation has emerged in the last few years as a potential therapy for ischemic stroke, because of their capability to differentiate into multiple cell types and the possibility that they may provide trophic support for cell survival, tissue repair, and functional recovery.

One-legged bicycling as an assessment tool for patients with stroke

OBJECTIVE

To assess whether one-legged bicycling correlates with muscle strength and thereby could work as an outcome measure for persons with stroke.

METHODS

The study comprised 29 men (age 35-65) with a first occurrence of stroke 6-35 months earlier. Each leg was evaluated separately. A ramp protocol was used (10 W/min), with continuous recording of the ventilatory uptake (Vo(2)) and heart rate. An isokinetic dynamometer was used to assess strength and endurance. Enzyme assays were performed on muscle biopsy samples.

RESULTS

The peak isometric strength and isokinetic strength of the paretic leg correlated with the max. W on the bicycle. The oxidative enzyme citrate synthase correlated with the workload for both legs on the bicycle and lactate dehydrogenase correlated with peak isometric strength in both legs.

CONCLUSIONS

The one-legged bicycle exercise test can be used to assess endurance in persons with a previous stroke as it correlates with dynamometer testing and muscle biopsies.

Prospective demonstration of short-term motor plasticity following acquired central pareses

The effect of newly acquired central pareses on functional MRI (fMRI) signal pattern is not known, since up to now all investigated patients were examined while they already experienced the motor weakness. We describe the first prospective and controlled study demonstrating the impact of new, acquired central pareses on fMRI motor activation pattern. Six patients suffering from a new central paresis after resection of a brain tumor infiltrating the central region were prospectively compared with a control group of five patients without postoperative paresis and a group of six healthy, age-matched controls who were investigated at two time points. fMRI signal was postoperatively analyzed during the performance of hand motor tasks and compared to the preoperative fMRI results. The relative signal change between rest and activation was evaluated for five cortical regions: the primary motor cortex (M1) and the ipsilateral primary motor cortex (M1i), the supplementary motor area (SMA), the premotor area (PMA), and the superior parietal lobule (SPL). In the patients with new postoperative central pareses, significant (P = 0.0313) decreases in fMRI activation were found in M1, whereas significant (P = 0.0313) increases were found in SMA and PMA. For M1i and SPL, there was a signal increase on average as well, but it failed to reach significance (P = 0.1250). In both control groups, no significant changes between both examinations were seen. Even though the number of investigated patients is too small to draw definite conclusions, our results support the concept of short-term motor plasticity being mediated by redundant systems that may take over function after damage of the primary motor cortex. The findings potentially also reflect increased functional demands imposed upon the motor network subsequent to a loss of dexterity.

Motor balance and coordination training enhances functional outcome in rat with transient middle cerebral artery occlusion

The goal of this study was to determine if relatively complex motor training on Rota-rod involving balance and coordination plays an essential role in improving motor function in ischemic rats, as compared with simple locomotor exercise on treadmill. Adult male Sprague-Dawley rats with (n=40) or without (n=40) ischemia were trained under each of three conditions: (1) motor balance and coordination training on Rota-rod; (2) simple exercise on treadmill; and (3) non-trained controls. Motor function was evaluated by a series of tests (foot fault placing, parallel bar crossing, rope and ladder climbing) before and at 14 or 28 days after training procedures in both ischemic and normal animals. Infarct volume in ischemic animals was determined with Nissl staining. Compared with both treadmill exercised and non-trained animals, Rota-rod-trained animals with or without ischemia significantly (P<0.01) improved motor performance of all tasks except for foot fault placing after 14 days of training, with normal rats having better performance. Animals trained for up to 28 days on the treadmill did not show significantly improved function. With regard to foot fault placing task, performance on foot placing was improved in ischemic rats across the three measurements at 0, 14 and 28 days regardless of training condition, while the normal group reached their best performance at the beginning of measurement. No significant differences in infarct volume were found in rats trained either with Rota-rod (47+/-4%; mean+/-S.E.), treadmill (45+/-5%) or non-exercised control (45+/-3%). In addition, no obvious difference could be detected in the location of the damage which included the dorso-lateral portion of the neostriatum and the frontoparietal cortex, the main regions supplied by the middle cerebral artery. The data suggest that complex motor training rather than simple exercise effectively improves functional outcome.

Biologic Transplantation and Neurotrophin-Induced Neuroplasticity After Traumatic Brain Injury

OBJECTIVE

In this review, we analyze progress in the treatment of traumatic brain injury with neurotrophins, growth factors and cell and tissue neurotransplantation. The primary objective of these therapies is to reduce neurologic deficits associated with the trauma by inducing neuroplasticity. These therapies are restorative and not necessarily neuroprotective.

MAIN OUTCOME MEASURES

An extensive literature on administration of neurotrophics factors and cell and tissue cerebral transplantation is reviewed. The effects of these therapeutic approaches on brain biochemical, molecular, cellular, and tissue responses are summarized.

CONCLUSION

The cumulative data indicate that cell therapy shows substantial promise in the treatment of neural injury.

Synaptic plasticity in thalamic nuclei enhanced by motor skill training in rat with transient middle cerebral artery occlusion

The goal of this study was to determine if synaptic plasticity in the thalamus of rats subjected to stroke could be altered by motor training. Transient occlusion of right middle cerebral artery in adult female Sprague-Dawley rats (n = 35) was induced with an intraluminal filament followed by three training conditions, 1. motor skill training on Rota-rod requiring balance and coordination skills, 2. simple exercise on treadmill, and 3. nontrained controls. Synaptic plasticity in brain was evaluated by synapotophysin immunocytochemistry at 14 or 28 days after training procedures. Infarct volume was determined in Nissl stained sections. Both at 14 and 28 days after Rota-rod training, intense synaptophysin immunoreactivity was present in the right but not the left mediodorsal and ventromedial nuclei of thalamus of ischemic rats. In treadmill-trained animals, however, similarly intense synaptic plasticity in these two thalamic nuclei was seen only at 28 days. Immunostaining was found also in other brain regions adjacent to or remote from infarct site. The data suggest that motor training, particularly motor skill training involving balance and coordination, facilitates a uniquely lateralized synaptogenesis in the thalamus.

Neuronal transplantation for motor stroke: from the laboratory to the clinic

Laboratory studies have established the potential for neuronal transplantation to be of benefit to patients. Experimental studies in normal animals indicate that brain implantation of neurons seems safe. Implanted neurons integrated with the host brain, sent out axonal processes to communicate with other nerve cells, released transmitters (the chemical messengers of nerve cell communication), and demonstrated typical neuronal proteins. This article discusses phase I and II trials of neuronal transplantation in humans with small strokes in critical brain locations such as the basal ganglia region. More work is needed to confirm safety and to identify optimal measures of efficacy in this setting.

Functional improvement after motor training is correlated with synaptic plasticity in rat thalamus

The goals of this study were to determine whether functional outcome after motor training in rats was linked to synaptic plasticity in thalamus, and whether the Rota-rod apparatus, widely used to test motor function, could be used as an easy and quantitative motor skill training procedure. Adult female Sprague-Dawley rats (n = 39) were evaluated under three training conditions: 1. Movement requiring balance and coordination skills on Rota-rod; 2. simple exercise on treadmill; 3. nontrained controls. Motor function was evaluated by a series of motor tests (foot fault placing, parallel bar crossing, rope and ladder climbing) before and 14 or 28 days after training procedure. Synaptic strength in brain was assessed by synaptophysin immunocytochemistry. After 14 days of training, Rota-rod-trained animals significantly (p < 0.01) improved motor performance, compared to treadmill and nontrained animals. Animals with up to 28 days of simple exercises on the treadmill did not show a significantly improved performance on most motor tasks, except for an improvement in foot fault placing. Intensive synaptophysin immunoreactivity was present in the right but not the left mediodorsal and ventromedial nuclei of thalamus in Rota-rod-trained rats at 14 and 28 days, and in treadmill-trained rats at 28 days. The data suggested that functional outcome is effectively improved by motor skill training rather than by simple exercises, and this may be related, at least partially, to uniquely lateralized synaptogenesis in the thalamus. Both Rota-rod and treadmill could be quantitatively used in rats for motor training of different complexity.

A test for detecting long-term sensorimotor dysfunction in the mouse after focal cerebral ischemia

The mouse is an excellent model for investigations of stroke and neural injury. However, there is a paucity of long term functional outcome measurements for the mouse. We, therefore, developed a sensorimotor functional test (corner test) and applied this test to a model of focal cerebral ischemia in the mouse. Male C57/6J mice (n=20) were subjected to embolic middle cerebral artery (MCA) occlusion. Reduction of cerebral blood flow (CBF) was measured by perfusion weighted MRI at 1 h after ischemia. The corner test, which is sensitive to chronic sensorimotor and postural symmetries, a general neurological test battery, and a foot fault test were performed between 2 and 90 days after ischemia. Infarct volume was measured at 90 days after ischemia. Multivariable analysis revealed that the corner test was highly predictive for infarct volume measured at 90 days after stroke, with R(2) values ranging from 0.73 to 0.93. The foot-fault test and neurological score did not detect chronic behavioral impairments. A significant (P<0.001) correlation between the infarct volume and the corner test was detected at 90 days after mild focal cerebral ischemia, whereas, there was no correlation between the infarct volume and neurological score or foot-fault. The data demonstrate that the corner test is a sensitive and objective test, which can be applied to evaluate long term functional outcome after stroke in the mouse.

Preliminary study of the behavioral effects of LBS-neuron implantation on seizure susceptibility following middle cerebral artery occlusion in the rats

Neural transplantation is a promising treatment strategy that can restore the motor, sensory and cognitive functions in the rat middle cerebral artery occlusion (MCAO) model of stroke. In particular, neuronal cells derived from a human teratocarcinoma cell line, called hNT neurons or LBS neurons (clinical grade preparation), are effective in improving behavioral recovery after stroke. In the elderly, epilepsy is a common sequela of stroke, especially if the infarction involves cerebral cortex. However, the effect of implanting neural cells on seizure susceptibility in the MCAO model has not yet been determined. The purpose of this study was to determine the susceptibility to pentylenetetrazol (PTZ)-induced seizures in normal, MCAO-lesioned and MCAO-lesioned rats in which the LBS neurons were injected. Adult, male Sprague-Dawley rats were subjected to 60 min of MCAO using the intraluminal filament technique followed 3-4 weeks later by transplantation of 80,000 LBS-neurons into the ipsilateral cortex. Susceptibility to PTZ-induced seizures was tested 4-6 weeks post-transplant at doses of 35, 50 and 70 mg/kg, administered subcutaneously. Latency to the first lethal response, latency to first generalized seizure, duration of the first generalized seizure, and the number of generalized seizures in an hour post-PTZ treatment observation period was determined. Even thought there was a tendency for groups that underwent MCAO to be more susceptible to seizures, there were no statistically significant differences between the groups and no differences between MCAO alone and MCAO animals in which cells had been implanted. While grafted cells were identified in all but one injected animal, the results suggest that the grafts may not have been healthy either from immunological rejection or PTZ-induced injury. These results suggest that while placing cells within the cortex does not reduce seizure susceptibility, it also does not increase the incidence of seizures. Further investigations are warranted.

PET evaluation of bilingual language compensation following early childhood brain damage

We report a positron emission tomography (PET) study in a 37-year-old, right handed, bilingual (English and American Sign Language) male with left frontal lobe damage, without evidence of language or general intellectual dysfunction. A brain MRI scan demonstrated an atrophic lesion of the left dorsolateral prefrontal, orbital, and opercular cortices extending from the frontal pole to precentral gyrus and including parts of anterior cingulate cortex, due to an probable infantile encephalitis. H(2) (15)O PET scans found evidence of increased right hemisphere activity compared to normal controls during spontaneous generation of narrative in both English and ASL. Neuropsychological data were within normal limits with the exception of visuospatial function. The results suggest the possibility that plasticity, unmasking of neural pathways, and or other adaptations of language function in the right hemisphere may have occurred, and are discussed with regard to the crowding hypothesis.

Restoration of function by neural transplantation in the ischemic brain

Stroke remains a major brain disorder that often renders patients severely impaired and permanently disabled. There is no available treatment for reversing these deficits. Hippocampal, striatal and cortical grafting studies demonstrate that fetal cells/tissues, immortalized cells, and engineered cell lines can survive grafting into the ischemic adult brain, correct neurotransmitter release, establish both afferent and efferent connections with the host brain, and restore functional and cognitive deficits in specific models of stroke. The success of neural transplantation depends on several factors: the stroke model (location, extent, and degree of infarction), the donor cell viability and survival at pre- and post-transplantation, and the surgical technique, among others. Further exploitation of knowledge of neural transplantation therapy already available from our experience in treating Parkinson's disease needs to be critically considered for stroke therapy. While the consensus is to create a functional neuronal circuitry in the damaged host brain, there is growing evidence that trophic action of the grafts and host, as well as exogenous application of trophic factors may facilitate functional recovery in stroke. Current treatment modules, specifically that of rehabilitative medicine, should also be explored with neural transplantation therapy. However, validation of neural transplantation and any other treatment for stroke should be critically assessed in laboratory experiments and limited clinical trials. No direct treatment is recognized as safe and effective for reversing the stroke-induced brain damage and functional/cognitive deficits. The first clinical trial of neural transplantation in stroke patients is a mile-stone in stroke therapy, but subsequent large-scale trials should be approached with caution.

Early and delayed induction of immediate early gene expression in a novel focal cerebral ischemia model in the rat

This study aimed at evaluating changes in expression of immediate early genes in a new photothrombotic focal ischemia model that exhibits late spontaneous reperfusion and morphological restoration in the region-at-risk within the cerebral cortex. Gene expression was studied with Northern blots, in situ hybridization and immunohistochemistry. At early time points (1-4 h), nerve growth factor-induced gene A and B, and c-fos mRNAs, were quickly induced throughout the ipsilateral cortex, with no obvious differences between the region-at-risk and remote cortical areas. High concentrations of nerve growth factor-induced gene A and c-Fos proteins were present within the region-at-risk even when cortical cerebral blood flow was as low as 40% of control values. At 4 h the nerve growth factor-induced gene A mRNA and protein expression was significantly decreased in the hippocampus vs. naive controls. However, a small decrease was also found in sham-operated and anaesthetized controls. A late induction, at 5 days, of c-fos and nerve growth factor-induced gene B mRNAs was seen bilaterally in the hippocampus and also, in the case of nerve growth factor induced-gene B, in the contralateral cortex. A complex pattern of changes in immediate early gene expression occurs after reversible focal cortical ischemia. This may be important for tissue recovery as well as neuropsychiatric symptoms after stroke.

Protection by a manganese porphyrin of endogenous peroxynitrite-induced death of glial cells via inhibition of mitochondrial transmembrane potential decrease

In the cerebral ischemic penumbra, progressive metabolic deterioration eventually leads to death of glial cells. The exact mechanism for the death of glial cells is unclear. Here we report that under glucose-deprived conditions immunostimulated glial cells rapidly underwent death via production of large amounts of peroxynitrite. The cell-permeable Mn(III)tetrakis(N-methyl-4'-pyridyl)porphyrin (MnTMPyP) caused a concentration-dependent attenuation of the increased death in glucose-deprived immunostimulated glial cells. The structurally related compound H(2)TMPyP, which lacks metals, did not attenuate this augmented cell death. MnTMPyP prevented the elevation in nitrotyrosine immunoreactivity (a marker of ONOO(-)) in glucose-deprived immunostimulated glial cells. In glucose-deprived glial cells, MnTMPyP also completely blocked the augmented death and nitrotyrosine immunoreactivity induced by the ONOO(-)-producing reagent 3-morpholinosydnonimine (SIN-1). The mitochondrial transmembrane potential (MTP), as measured using the dye JC-1, was rapidly decreased in immunostimulated or SIN-1-treated glial cells deprived of glucose. MnTMPyP, but not H(2)TMPyP, blocked the depolarization of MTP in those glial cells. The present data, at least in part, provide evidence for how glial cells die in the postischemic and/or recurrent ischemic brain.

Environmental influence on brain-derived neurotrophic factor messenger RNA expression after middle cerebral artery occlusion in spontaneously hypertensive rats

Enriched environment significantly enhances postischemic functional outcome. We have tested the hypothesis that housing in enriched environment stimulates gene expression for brain-derived neurotrophic factor. After ligation of the middle cerebral artery in male spontaneously hypertensive rats, they were housed in individual cages for 30h, then housed either in standard cages or in an enriched environment. The rats were killed two to 30days after the ischemic event. Cryostat coronal sections through the dorsal hippocampus (Bregma -3.3) were processed for in situ hybridization using a rat-brain-derived neurotrophic factor messenger RNA antisense oligonucleotide probe. Postischemic gene expression was significantly higher in standard rats than in enriched rats in contralateral and peri-infarct cortex and in most parts of the hippocampus two, three and 12days after the ischemic event, with a trend for higher-than-baseline levels in standard rats and lower-than-baseline levels in enriched rats. At 20 and 30days the values for both groups were below baseline levels. Contrary to our hypothesis, gene expression in rats postoperatively housed in enriched environment was significantly lower than in standard rats at a time when other studies have reported hyperexcitability in the ipsilateral and contralateral cortex. Should the low messenger RNA levels correspond to low protein synthesis, this might indicate that dampening of the early postischemic hyperexcitability may be beneficial. Low levels in both groups at 20 and 30days may correspond to loss of callosal connections in the opposite hemisphere and to horizontal cortical connections in the lesioned hemisphere.

Brain plasticity and hand surgery: an overview

The hand is an extension of the brain, and the hand is projected and represented in large areas of the motor and sensory cortex. The brain is a complicated neural network which continuously remodels itself as a result of changes in sensory input. Such synaptic reorganizational changes may be activity-dependent, based on alterations in hand activity and tactile experience, or a result of deafferentiation such as nerve injury or amputation. Inferior recovery of functional sensibility following nerve repair, as well as phantom experiences in virtual, amputated limbs are phenomena reflecting profound cortical reorganizational changes. Surgical procedures on the hand are always accompanied by synaptic reorganizational changes in the brain cortex, and the outcome from many hand surgical procedures is to a large extent dependent on brain plasticity.

Quantitative measurement of motor and somatosensory impairments after mild (30 min) and severe (2 h) transient middle cerebral artery occlusion in rats

We tested the hypothesis that mild and severe ischemic cell damage are reflected in neurological and functional recovery after stroke. Rats were subjected to either 30 min or 120 min of middle cerebral artery occlusion or sham operation. Neurological and functional tests including, gross neurological score, and rotarod and adhesive removal tests were performed at various time points up to 21 days after stroke. Significant differences between groups of animals were detected using the rotarod and adhesive removal test. A significant correlation between lesion volume and adhesive removal test was detected in rats subjected to 30 min of ischemia. Our data indicate that quantitative rotarod and adhesive removal tests measure different aspects of functional recovery after stroke, and both are useful in characterizing functional recovery from an ischemic insult.

Changes in brain nerve growth factor levels and nerve growth factor receptors in rats exposed to environmental enrichment for one year

This study examined the effects of long-term differential rearing on levels of brain nerve growth factor, its receptors, and their relationships to cognitive function. Adult rats (two months old) were placed into either enriched or standard housing conditions where they remained for 12 months. Animals from the enriched condition group had significantly higher levels of nerve growth factor in hippocampus, visual and entorhinal cortices compared with animals housed in isolated condition. Immunohistochemical analysis of brain tissue from the medial septal area revealed higher staining intensity and fibre density with both the low-affinity and the high-affinity nerve growth factor receptors. Enriched rats performed better than isolated rats in acquisition of spatial learning and had lower locomotion scores in the open field. These results provide further evidence that experimental stimulation results in increased production of trophic factors and structural reorganization in specific brain regions known to be involved in cognitive function.

Environmental influence on gene expression and recovery from cerebral ischemia

An emerging concept in neurobiology is that the adult brain retains a capacity for plasticity and functional reorganization throughout the life span. Experimental data from electrophysiological, morphological and behavioral studies have documented experience dependent plasticity in the intact and injured adult brain. Neuroimaging clinical studies indicate altered post stroke functional activation patterns, usually including activation of the intact hemisphere. However, there is some disagreement regarding their functional significance and longitudinal studies correlating outcome and activation pattern are needed to solve some controversies. Postoperative housing of rats in activity stimulating environment after ligation of the middle cerebral artery significantly enhances outcome. Gene expression for brain derived neurotrophic factor and Ca2+/calmodulin-dependent protein kinase II, two substances with potential role in brain plasticity, show different patterns in animals housed in standard and in enriched environment. The functional significance of altered gene expression needs to be evaluated.

Ondine's curse in association with diabetes insipidus following transient vertebrobasilar ischemia

Ischemic lesions of the brainstem can lead to complex neurologic deficits. Failure of the automatic control of ventilation (Ondine's curse syndrome) is a possible but rare syndrome following localized brainstem dysfunction. We report on a 49-year-old man with intermittent bradycardia, cranial nerves' dysfunctions and a slight right-sided hemiparesis. An acute brainstem ischemia was diagnosed and treated immediately with high-dose heparin. Cerebral angiography revealed a proximal occlusion of the left vertebral artery but a normal right vertebral artery and a hyperplastic right posterior inferior cerebellar artery. Cranial Computed Tomography and MRI scan demonstrated multiple ischemic lesions in the posterior circulation. During a 4-week treatment course the patient underwent six episodes of acute severe hypoxia and hypercapnia requiring orotracheal intubation twice and manual ventilation by air mask over a few minutes for four times after a tracheostomy had been performed. Twice a short-term episode of hypothalamic Diabetes insipidus was observed following hypoventilation. We conclude that both Ondine's curse syndrome and diabetes insipidus were due to transient vertebrobasilar ischemia.

Inflammatory mediators and stroke: new opportunities for novel therapeutics

Contrary to previous dogmas, it is now well established that brain cells can produce cytokines and chemokines, and can express adhesion molecules that enable an in situ inflammatory reaction. The accumulation of neutrophils early after brain injury is believed to contribute to the degree of brain tissue loss. Support for this hypothesis has been drawn from many studies where neutrophil-depletion blockade of endothelial-leukocyte interactions has been achieved by various techniques. The inflammation reaction is an attractive pharmacologic opportunity, considering its rapid initiation and progression over many hours after stroke and its contribution to evolution of tissue injury. While the expression of inflammatory cytokines that may contribute to ischemic injury has been repeatedly demonstrated, cytokines may also provide "neuroprotection" in certain conditions by promoting growth, repair, and ultimately, enhanced functional recovery. Significant additional basic work is required to understand the dynamic, complex, and time-dependent destructive and protective processes associated with inflammation mediators produced after brain injury. The realization that brain ischemia and trauma elicit robust inflammation in the brain provides fertile ground for discovery of novel therapeutic agents for stroke and neurotrauma. Inhibition of the mitogen-activated protein kinase (MAPK) cascade via cytokine suppressive anti-inflammatory drugs, which block p38 MAPK and hence the production of interleukin-1 and tumor necrosis factor-alpha, are most promising new opportunities. However, spatial and temporal considerations need to be exercised to elucidate the best opportunities for selective inhibitors for specific inflammatory mediators.

Immunostimulated glial cells potentiate glucose deprivation-induced death of cultured rat cerebellar granule cells

The present study investigates whether immunostimulated glial expression of inducible nitric oxide synthase influences the glucose deprivation-induced death of rat cerebellar granule cells (CGC). CGC/glia cocultures were immunostimulated by interferon-gamma (200 U/ml) and lipopolysaccharides (1 microg/ml) and 2 days later were challenged by glucose deprivation. Neurotoxicity was assessed by measuring the release of lactate dehydrogenase. Neither a 2-h glucose deprivation nor a 2-day immunostimulation altered the viability of CGC. A 2-day immunostimulation, however, markedly potentiated the glucose deprivation-induced death of CGC. The increased death of glucose-deprived CGC after immunostimulation was mimicked by the nitric oxide (NO) releasing reagent 3-morpholinosydnonimine (SIN-1) and was partially prevented by the NO synthase (NOS) inhibitor N(G)-nitroarginine. The increased death of glucose-deprived CGC either after immunostimulation or by SIN-1 was not altered by various N-methyl-D-aspartate (NMDA) and non-NMDA receptor antagonists. Because superoxide dismutase and catalase, which remove superoxide anion, decreased the augmented death of glucose-deprived immunostimulated CGC, the reaction of NO with superoxide to form peroxynitrite appears to be implicated in the potentiated neurotoxicity. Our data indicate that immunostimulated glial cells potentiate the death of glucose-deprived neurons in part through the expression of inducible NOS but not through NMDA receptor activation. Potentiation of glucose-deprived CGC death by immunostimulated glial cells may be clinically implicated in the tendency of recurrent ischemic insults to be more severe and fatal than an initial ischemic insult.

Are neuronal markers and neocortical graft-host interface influenced by housing conditions in rats with cortical infarct cavity?

The aim was to study if exposure to an enriched environment influenced graft-host interface and neuronal markers in neocortical grafts implanted in cortical infarct cavities 3 weeks after distal ligation of the middle cerebral artery in adult hypertensive rats. Half the rats were exposed to an enriched environment for 2 h daily 5 days a week starting 1 week after the arterial ligation. The brain was fixed by perfusion 4 weeks postgrafting. The immunoreactivity to glial fibrillary acidic protein, microtubule associated protein 2, and synaptophysin was studied in coronal paraffin-embedded sections. A distinct glial border separated the infarct cavity from the surrounding brain in sham-transplanted rats. Most grafts filled the larger part of the infarct cavity. In 8 of 18 transplants, 4 in each experimental group, part of the transplants protruded through the thin glial membrane that delineated the transplant-host interface into the adjacent host brain tissue. Microtubule associated protein 2 immunostained sections indicated bridging of dendrites in the host-transplant interface. Synaptophysin immunoreactivity was significantly higher in grafts than in contralateral cortex. However, graft morphology and neuronal marker immunoreactivity did not differ between rats housed in standard and activity stimulating cages.

Quantitative analysis of synaptophysin immunoreactivity in human neocortex after cardiac arrest: confocal laser scanning microscopy study

Transient global ischaemia caused by cardiac arrest results in lesions that involve all brain structures. The aim of this study was to investigate the condition of synapses in patients surviving, but remaining in a persistent vegetative state, following resuscitation after cardiac arrest. We performed a quantitative analysis of the distribution and density of elements containing a synaptic vesicle protein--synaptophysin (p38)--in human neocortex in cases which survived for 1 week, 2 months, and 1 year after the cardiac arrest. Neurologically healthy cases that died following an accident served as control. Dual-channel confocal laser scanning microscopy (CLSM) was used to image p38-immunoreactivity (IR) and lipofuscin autofluorescence. In control cases no statistically significant differences were found for p38-IR between layers II-III and V-VII. However, the temporal cortex had a higher density of p38-immunoreactive structures than the motor cortex. In postischaemic cases a reduction in the density of p38-IR elements was apparent, mainly in the frontal and motor cortices and less pronounced in the temporal cortex. The least decrease compared with controls was observed in the visual cortex. In the 1 week survival case, a maximal decrease in p38-IR (35% below control) was found. In this case, the number of p38-IR elements per visual field was decreased, and big aggregates of p38-IR structures were observed. In general, the amounts of p38-IR structures were higher in all of the control cases compared with the postischaemic cases.

Neurotrophin-mediated neuroprotection by solid fetal telencephalic graft in middle cerebral artery occlusion: a preventive approach

In the present study, embryonic rat neocortex was implanted into the parietal subcortical area of adult naive animals. On the 7th day, the middle cerebral artery was permanently occluded ipsilateral to the graft. Twenty-four hours after middle cerebral artery occlusion, the extent of infarct was visualized by means of 2,3,5-triphenyltetrazolium chloride histochemistry and quantified in four different standardized coronal plains. Subsequently, the effects of fetal tissue grafting and those of transplantation were identified by using glial fibrillary acidic protein and nerve growth factor immunocytochemistry. The grafts integrated well into their new environment and significantly reduced the size of infarct in middle cerebral artery-occluded animals compared with both sham-operated and control rats 24 h postoperation. The underlying mechanism of this phenomenon might be an increased neurotrophic, particularly nerve growth factor, release by the grafted fetal tissue. Moreover, reactive astroglial cells may also trigger the neuroprotection by additional ischemia-induced nerve growth factor release. The present data demonstrate the potential neurotrophin-mediated protective effects of fetal brain tissue implanted into the adult rat brain before unilateral middle cerebral artery occlusion and the beneficial effects of astrocyte activation.

NADPH-d positive neurons in the developing somatosensory cortex of the rat: effects of early and late environmental enrichment

The effects of environmental enrichment upon the topographic arrangement of NADPH diaphorase-positive neurons (NADPH-d+ neurons) was studied in the somatosensory cortex of 56 Sprague-Dawley albino rats during early stages of development (18th, 24th, 30th and 60th postnatal days). This diaphorase is easily demonstrable, providing a convenient marker for quantitative studies. Environmental enrichment diminished the number of NADPH-d+ neurons and exerted its maximal influence during lactation, a time of exceptional cortical susceptibility. This implies that the magnitude of such effects on the density of NADPH-d+ neurons is age-dependent. Furthermore, it was found that the experience-dependent cortical changes persisted after a subsequent period without environmental stimulation. The effects of early environmental enrichment did not occur uniformly throughout the cerebral hemispheres but, instead, such effects were maximal in the latero-ventral sector of the cerebral cortex where a dramatic reduction in the number of NADPH-d+ neurons was observed. Particularly striking was the existence of a latero-medial sequence of NADPH-d+ neurons in the infragranular layer and a reversed distribution of labeled cells, in the supragranular layer. Both ontogenetic sequences of NADPH-d+ neurons remained unchanged during postnatal development in controls and enriched subjects (18th-60th postnatal days).

Thrombosis and cerebrovascular disease

Strokes are heterogeneous not only with respect to their presentation, but more importantly in terms of the underlying pathology. There are now a number of choices available for the treatment of ischemic stroke, and the causative mechanisms responsible for each individual stroke must be considered in choosing an appropriate form of treatment. This article explores the underlying pathophysiological mechanisms responsible for the major categories of stroke and also examines the reasons why strokes worsen or evolve.