Intraventricular Grafts Research Articles

615: A study on stem cell function in the ischemia-damaged area after stroke

Studies in neonatal mice show that if neural stem cells (NSCs) are seeded on synthetic extracellular matrix and implanted into an ischemia-damaged area, then new parenchyma composed of neurons and glia is formed and becomes vascularized. Findings by Eriksson et al indicated neurogenesis from precursors in the subventricular zone (SVZ) in vivo in humans, and precursors capable of forming neurons in human subcortical white matter. For efficient repair after stroke it may be necessary to provide NSCs with a platform so that they can reform appropriate brain structure and connections. However, NSCs are concentrated along the subventricular zone, and their migration to the zone of infarction is limited by a long migratory pathway. Bone marrow cells, being distributed throughout all tissues by the bloodstream, have easy access to the zone of infarction. Brain injury, specifically cerebral ischemia, enhances bone marrow plasticity and provides an environment that supports the differentiation of bone marrow-derived cells into endothelial cells and neurons. Neovascularization of the peripheral and coronary vasculature can be enhanced by the exogenous delivery of bone marrow-derived endothelial progenitor cells (EPCs). Some animal studies indicate intrastriatal and intravenous delivery of marrow stromal cells results in a small percentage of these cells expressing neuronal markers in ischemic brain. Considering the differentiation of bone marrow-derived progenitor cells into endothelial cells and NeuN-expressing cells , the utility of bone marrow–derived cells offers a novel potential treatment for stroke. The type of functional recovery after stroke depends on the site of implantation. Some studies report no recovery of sensorimotor function in rats with intraventricular grafts, whereas animals with intraparenchymal grafts either ipsilateral or contralateral to the lesion have shown reduced sensorimotor asymmetry.

Primordial Hematopoietic Stem Cells Generate Microglia But Not Myelin-Forming Cells in a Neural Environment

Finding ways to enhance remyelination is a major challenge in treating demyelinating diseases. Recent studies have suggested that circulating bone marrow cells can home in brain and transdifferentiate into neural cells. To ask whether hematopoietic precursors can form myelinating cells, we investigated the neuropoietic potential of embryonic precursors sorted from the mouse aorta-gonads-mesonephros (AGM) region. This cell fraction is capable of long-term hematopoietic reconstitution and generates colonies containing multipotential precursors and lymphoid or erythro-myeloid progenies. When cultured in hematopoietic growth conditions, a fraction of CD45-positive AGM cells coexpress neural markers such as nestin, the polysialylated form of neural cell adhesion molecule, the betaIII tubulin isoform, and glial fibrillary acidic protein. However, when hematopoietic precursors containing green fluorescent protein were cocultured with embryonic striatal precursors into neurospheres, they maintained their hematopoietic phenotype without undergoing differentiation into neurons, astrocytes, or oligodendrocytes. After intraventricular grafting, hematopoietic precursors integrated into the brain of wild-type or hypomyelinated newborn shiverer mice and gave rise to microglia but not neurons or glia. In contrast, when wild-type embryonic striatal neurospheres were grafted in shiverer, they formed numerous myelin internode patches. Even when neural and hematopoietic precursors were grafted together into shiverer mice, only neural precursors generated myelin-forming cells and synthesized myelin. Thus, embryonic neurospheres have myelin repair properties not shown by embryonic hematopoietic precursors. This suggests that the use of multipotential neural precursors to generate myelin-forming cells remains one of the most promising avenues toward remyelination therapies.

Transplantation of neural stem cells modulates apolipoprotein E expression in a rat model of stroke

The expression of apolipoprotein E (apoE) after ischemic brain damage has been associated with plasticity involved in promoting functional recovery. We therefore examined the expression and distribution of apoE in rats that received intraparenchymal grafts of the conditionally immortal stem cell line MHP36 either ipsilateral or contralateral to the lesion or intraventricular grafts 4 months after transplantation. ApoE immunoreactivity was highly expressed in the striatum, somatosensory cortex, and thalamus of the lesioned hemisphere in all rats subjected to middle cerebral artery occlusion. Only in rats with intraparenchymal grafts, apoE was significantly upregulated in the contralateral hemisphere, whereas levels and distribution in rats with intraventricular grafts resembled those of ischemic controls. In ischemic rats, apoE was seen in both astrocytes and neurons on the lesioned side, and in grafted rats, apoE was present in host and transplanted neurons and astrocytes. Previously we have shown that intraparenchymal grafts reduced sensorimotor asymmetry, whereas intraventricular grafts improved cognitive dysfunction, with transplanted cells being widely distributed in cortex, striatum, and corpus callosum on both sides of the brain in all grafted groups. Thus, stem cells grafted in the parenchyma are not only capable of limited expression of apoE in the host brain but also trigger a robust increase on the side contralateral to stroke damage where this does not normally occur. Findings that parenchymal, but not ventricular, grafts facilitated sensorimotor recovery suggests that apoE might contribute to plastic changes in relevant pathways, possibly on both sides of the brain. In contrast, no evidence was found for an association between apoE and recovery of cognitive function in rats with intraventricular grafts.

Effects of implantation site of stem cell grafts on behavioral recovery from stroke damage.

Findings that MHP36 stem cells grafted into intact parenchyma contralateral to the lesion induced by middle cerebral artery occlusion promoted recovery from stroke deficits led us to investigate whether implantation site of stem cells affects the functional efficacy of MHP36 grafts. MHP36 cells (200 000/8 microL) were implanted in the left (n=8) or right (n=9) parenchyma or infused into the right ventricle (intraventricular; n=7) 2 to 3 weeks after stroke induced by 60 minutes of intraluminal right middle cerebral artery occlusion. Additionally, intact (n=11) and stroke (n=7) control groups were tested for 14 weeks in bilateral asymmetry, rotation bias, and spatial learning tasks before histological investigation of cell distribution and differentiation. Rats with left and right parenchymal grafts showed reduced bilateral asymmetry but no improvement in spatial learning. Conversely, spatial learning improved in rats with intraventricular grafts, but marked asymmetry persisted. No grafted group showed reduced amphetamine-induced rotation bias or reduced lesion volume relative to stroke controls. In all grafted groups, cells occupied both sides of the brain. A third of cells grafted in the striatum crossed the midline to occupy homologous regions in intact and lesioned hemispheres and differentiated into site-appropriate phenotypes. After stroke, both the intact and lesioned hemispheres attract grafted stem cells, suggesting repair processes that utilize cells both for local repair and to augment plastic changes in contralateral motor pathways. However, differential effects of parenchymal and intraventricular grafts suggest that different mechanisms are implicated in recovery from cognitive and sensorimotor deficits induced by stroke.

Evidence for Target-Specific Nerve Fiber Outgrowth from Subpopulations of Grafted Dopaminergic Neurons: A Retrograde Tracing Study Using in Oculo and Intracranial Grafting

Efforts have been made to counteract the symptoms of Parkinson's disease by substituting the loss of dopaminergic neurons with fetal ventral mesencephalic grafts. One of the postulated limiting factors in this treatment is the relatively poor cell survival and limited graft-derived fiber outgrowth. Recent results documenting enhanced survival of grafted dopaminergic neurons showed no positive correlation to enhanced innervation of the striatal target. Therefore this study was undertaken to investigate whether all surviving grafted dopaminergic neurons projected to the striatal target. Hence, fetal ventral mesencephalic tissue was implanted adjacent to mature versus immature striatal tissue using in oculo and intraventricular grafting techniques. In in oculo grafting, fetal ventral mesencephalon was implanted simultaneously with fetal lateral ganglionic eminence (immature striatal target) or to already matured striatal in oculo grafts (mature striatal target). Furthermore, fetal ventral mesencephalon was implanted into the lateral ventricle adjacent to mature dopamine-depleted striatum. The retrograde tracer fluorogold was injected into the striatal portion of the in oculo cografts and into reinnervated areas of the adult brain. Immunohistochemistry revealed that a significantly larger proportion of tyrosine hydroxylase-positive neurons in the ventral mesencephalic graft was innervating in oculo immature striatal tissue, and hence was fluorogold-positive, in comparison with the number of tyrosine hydroxylase-positive neurons innervating mature striatal tissue. Moreover, intracranial transplantations showed that tyrosine hydroxylase-positive neurons were distributed within the grafts in dense clusters of cells. In most clusters tyrosine hydroxylase-positive cells were fluorogold-negative but calbindin-positive. In a few tyrosine hydroxylase-positive cell clusters, neurons were coexpressing fluorogold but were calbindin-negative. In conclusion, significantly more dopamine neurons projected to immature than to mature striatal tissue and thus, a subpopulation of grafted dopaminergic neurons was not projecting into adult striatum. Thus, the results from this study show that further attempts to enhance survival of grafted dopamine neurons in purpose to enhance graft-derived fiber outgrowth and efficacy should also consider different subtypes of dopamine neurons.

Seizure Suppression in Kindled Rats by Intraventricular Grafting of an Adenosine Releasing Synthetic Polymer

Adenosine, an endogenous inhibitory neuromodulator in the central nervous system, exerts anticonvulsant activity that is largely based on the inhibition of the release of excitatory amino acids. As a novel approach to treat pharmacoresistant partial epilepsies, the grafting of adenosine-releasing cells is foreseen to provide a local and sustained source of adenosine. The feasibility of this cell-based therapy was investigated in the present study by the intraventricular implantation of synthetic polymers that release adenosine. Kindled rats with a ventricular implant of an adenosine-releasing polymer showed a profound reduction of seizure activity. This was demonstrated not only by a 75% reduction of grade 5 seizures but also by a reduction of the amplitude and duration of afterdischarges in electroencephalographic (EEG) recordings. Kindled control rats that were implanted with bovine serum albumin (BSA)-containing polymers or were sham operated, continued to show their presurgery seizure pattern. Adenosine displayed antiepileptic activity when released in an amount of 20–50 ng per day. This finding sets the target for the required amount of adenosine to be released from future adenosine-releasing cells for antiepileptic therapy. The present results clearly support the feasibility of a novel therapy for epilepsy based on adenosine-releasing cells.

Unilateral fetal mesencephalic grafts in intact rats reduce amphetamine-induced dopamine release in both striata. An in vivo voltammetric study

This study investigated amphetamine-induced striatal dopamine release after intraventricular unilateral fetal mesencephalic grafts in otherwise intact rats. Dopamine was monitored in vivo by differential pulse voltammetry. In grafted animals, amphetamine-induced dopamine release was decreased compared to sham-grafted, age-matched controls. This decrease was observed in the grafted as well as in the contralateral striatum five months after intraventricular grafting. There was no measurable effect of the grafts on the amphetamine-induced rotational behaviour. Our results exceed former observations reporting decreased amphetamine-induced dopamine release in the contralateral striatum of 6-hydroxydopamine-lesioned and unilaterally-grafted rats which had been attributed to a reduction of dopamine transporters. Furthermore, it was shown that concerning this effect ventral mesencephalic grafts are independent of a previous 6-hydroxydopamine lesion.

Developmental Expression of Neuron-Specific Enolase Immunoreactivity and Cytochrome Oxidase Activity in Neocortical Transplants

The present study has examined certain metabolic markers in fetal neocortical tissue transplanted to the cortex, hippocampus, striatum, or ventricle. Particularly, the immunocytochemical expression of neuron-specific enolase (NSE) was studied in a series of host rats ranging between 10 days and 15 months postoperative. NSE is a major glycolytic pathway enzyme found in all neurons. The antibody to NSE is a very reliable marker for neuronal functional metabolic activity and developmental status and its onset has been shown to coincide with synaptic connections. In some grafts oxidative metabolic status was investigated using cytochrome oxidase (CO) histochemistry. In addition, the normal development of NSE expression in rat neocortex was also examined. In normal development, NSE was weakly expressed in fetal brain, but by 1-2 weeks postnatal the enzyme was strongly expressed in all neurons. Typical cortical laminar patterns were evident at 30 days with neurons in layer V and scattered interneurons the most strongly stained. In cortex-cortex transplants NSE expression was very weak; at 1-3 weeks postoperative, it was practically nonexistent; and at all later times only a minority of neurons had normal expression when compared to that in normal development even though by Nissl staining standards in adjacent sections they appeared "normal." Labeling indices ranged between 30 and 49%. Intraventricular grafts had consistently low NSE expression with labeling indices ranging between 18 and 46%. However, when the neocortical tissue was placed in other regions, neuronal NSE appeared only slightly below normal. CO histochemistry corroborated the NSE activity with regards to graft placement. Several possibilities that may account for reduced NSE profile in transplanted neurons include incomplete migration patterns, reduced synaptic connectivity, and potential ischemia causing lowered protein synthesis during reestablishment of vascular connections. If neuronal glycolysis is weakened, it is possible that neurotransmitter production or axonal transport are reduced. Since most energy capacity in brain is dependent on the glycolytic sequence for oxidative metabolism, reduced glycolytic capacity, as depicted by NSE expression, may suggest the presence of transplanted neurons that have adapted to their new environment with a relatively immature profile.

Adrenal medulla grafts in the hemiparkinsonian rat: profile of behavioral recovery predicts restoration of the symmetry between the two striata in measures of pre- and postsynaptic dopamine function

Following unilateral striatal dopamine depletion, the hemiparkinsonian rat exhibits rotational behavior in response to amphetamine and apomorphine. The rotational behaviors induced by these drugs are thought to reflect an asymmetry in presynaptic striatal dopamine release and an asymmetry in postsynaptic striatal dopamine receptor function, respectively. Grafts of adrenal medulla cells in the lateral ventricle of hemiparkinsonian rats have been reported to reduce behavioral asymmetry. More than one profile of behavioral recovery, however, is observed. Some animals show a graft-induced decrease only in the response to apomorphine, but others show a decrease in the response to amphetamine, and still others show a decrease in the behavioral responses to amphetamine and apomorphine. In this report, amphetamine- and apomorphine-induced turning behaviors were determined in hemiparkinsonian rats prior to and following intraventricular grafts of adrenal medulla or control tissue. Both bilateral intrastriatal microdialysis in freely moving animals and quantitative dopamine receptor autoradiography procedures were conducted in each animal so as to determine the relations between pre- and postsynaptic dopaminergic measures as well as the association between these measures and the different profiles of behavioral recovery after adrenal medulla grafts. We report here that in animals with an adrenal medulla graft-induced decrease in the behavioral response to amphetamine, the balance between the two striata in extracellular striatal dopamine concentrations and D2 dopamine receptor binding was restored. Furthermore, enhanced extracellular striatal dopamine concentrations were highly correlated with the graft-induced symmetry in striatal D2 dopamine receptor binding. In contrast to animals with decreased amphetamine-induced turning, in animals with a graft-induced decrease exclusively in response to apomorphine, the presynaptic symmetry was not restored and there was a significantly smaller effect on D2 receptor binding. We conclude that those animals that show decreased amphetamine-induced turning after adrenal medulla grafts had the most effective grafts, and suggest that methods designed to optimize this behavioral profile are most likely to lead to enhanced clinical efficacy with this procedure.

The Development of Hypertension in Rats with Intraventricular Grafts of Fetal SHR or WKY Hypothalamus

To evaluate the role of the hypothalamus in hypertension, we compared the. development of blood pressure (BP) in normotensive host rats grafted at weaning with fetal hypothalamus from genetically hypertensive or normotensive donors. The anteroventral region of the third ventricle (AV3V) has been implicated in the control of BP, such that lesions of AV3V prevent or attenuate hypertension in a number of animal models. Recent studies have shown that BP is elevated after grafting SHR hypothalamus into the AV3V region of genetically normotensive hosts. WKY hosts grafted with fetal SHR hypothalamus (E15) exhibited increased BP for over 5 months after implantation, while hosts receiving WKY hypothalamus experienced only a transient rise in BP at 1 month post-implant /1/. Normal Wistar hosts grafted with older (E19-20) SHR hypothalamus exhibited increased BP at 1 month post-implant, and not at subsequent ages, while E19-20 WKY hypothalamus did not influence BP at any age /2/. The following experiments were designed to determine how the pressor effects of grafting SHR hypothalamus may vary as a function of the embryonic age and specific anatomical origin of grafted cells. Two normotensive rat strains were used as hosts: outbred Wistar and inbred Wistar-Kyoto (WKY) rats. At 25 days of age, hosts were grafted in the AV3V region with E15-16 fetal SHR hypothalamus, SHR cortex or WKY hypothalamus. Sham-operated controls received infusions of 0.9% saline. Systolic blood pressure was measured at 30, 60, 90 and 120 days of age. Based on evidence that the AV3V region also mediates behavioral control of fluid/electrolyte homeostasis, daily consumption of water and 1.5% saline was also measured at 60 and at 120 days of age.

Effects of adrenal medulla and sciatic nerve co-grafts in rats with unilateral substantia nigra lesions.

Major limitations of adrenal medulla transplantation in animal models of Parkinson's disease have been the relatively small behavioral effects and the poor or inconsistent graft survival. Transplantation of fragments of sural nerve in combination with adrenal medulla has been reported to increase the survival of chromaffin cells in adrenal medulla grafts in primates. In the present study, the possibility was tested that peripheral nerve co-grafts would increase the functional effects of adrenal medulla grafts in a 6-hydroxydopamine-lesioned rat model. Animals received unilateral substantia nigra lesions, and subsequently received intraventricular grafts of adrenal medulla, sciatic nerve, adrenal medulla plus sciatic nerve, or sham grafts consisting of medium only. Functional effects of the grafts were tested using apomorphine-induced rotational behavior. The sciatic nerve co-grafts did not increase the survival of TH-immunoreactive chromaffin cells. The co-grafting treatment also did not augment the overall effect of adrenal medulla grafts on rotational behavior. In the animals with substantial numbers of surviving chromaffin cells, however, the animals with sciatic nerve co-grafts showed greater decreases in rotational behavior as compared to the animals with adrenal medulla grafts alone, even though the number of surviving cells was not increased.

Permeability to blood‐borne protein and 3HGABA in CNS tissue grafts. I. Intraventricular grafts

In the present study, solid grafts of fetal CNS tissue from the rat neocortex, cerebellum, or ventral mesencephalon were placed into the lateral, III or IV ventricles of young adult hosts. Survival periods ranged from 2 days to 20 months. To study the permeability to protein and potential changes in the blood-brain barrier (BBB), macromolecules such as HRP, HRP-human serum albumin, and HRP-human IgG were administered intravascularly and circulated for periods between 3 minutes and 1 hour. Younger grafts were completely filled with the protein, even at 2 days, when the graft vasculature already contained host macrophages, whereas all older grafts showed variability in permeation with protein ingress initiating at the graft-host interface and subsequently diffusing through the extracellular spaces. Permeation was from several sources: permeable vessels of the circumventricular organs and the choroid plexus which grew into the grafts, the perivascular spaces surrounding these vessels, or from the normally impermeable vessels of the pia mater, which, because of their engulfment by the graft and subsequent angiogenesis, may have been rendered permanently leaky. Invading vessels were often "cuffed" by lymphocytic cells. Many grafts were only partially filled by the glycoprotein conjugates; ventral mesencephalic grafts allowed the least diffusion even when vascularized by choroidal vessels. Fenestrated vessels were not directly observed even though petechial leaks were evident and vessels indigenous to the CNS grafts retained BBB properties. To determine endogenous protein exudation, noninjected animals were immunocytochemically examined for rat serum albumin (RSA). The distribution of RSA mimicked that of the injected proteins at interface regions, although in most instances the entire graft was filled by a light, diffuse labeling suggesting a steady-state protein leakage over the life of the graft. When HRP was delivered intraventricularly, the intraventricular grafts were nearly filled with reaction product by 20 minutes. The depth of penetration in the grafts from the CSF interface was generally threefold greater than in normal brain. The increase in permeation suggests that solutes may flow through these grafts (out of or into the CSF) at an increased rate. Lastly the neurotransmitter tritiated gamma-aminobutyric acid (3HGABA) which does not cross the BBB was vascularly administered to hosts bearing neocortical grafts. These experiments not only confirmed the permeability in these grafts but showed that the blood-borne amino acid could be directly sequestered by grafted neurons or glia.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of intraventricular substantia nigra allografts as a function of donor age

Transplantation of fetal substantia nigra into the brain can alleviate some of the manifestations of animal models of Parkinson's disease. The purpose of the present experiment was to determine the optimal embryonic donor age for solid tissue substantia nigra grafts. Rats with unilateral substantia nigra lesions were tested for rotational behavior in response to apomorphine. Animals then received intraventricular grafts of ventral mesencephalon from fetal donors of 11, 13, 15, 17, or 19 days gestational age, and were tested for rotational behavior 6 and 12 weeks after transplantation. After 12 weeks, animals receiving grafts from donors of 11 through 17 days gestation showed similar decreases (means= 42−58%) in rotation. All 4 groups showed greater decreases in rotation than the 19 day group (17%). In both the 11 and 13 day groups, however, there were substantial decreases in rotational behavior from the 6th to the 12th week testing periods. This study confirms that during a critical period of rat fetal development, between 17 and 19 days gestational age, the substantia nigra loses much of its ability to produce functional effects after transplantation. Grafts from very immature donors did not, however, produce markedly greater effects, and the youngest grafts required more time for the development of maximal effects.

The fine structure of vascular-astroglial relations in transplanted fetal neocortex

The vascular development within allografts of rat fetal neocortex was examined ultrastructurally with particular attention to astroglial-endothelial relationships. Grafts placed in the fourth ventricle exhibited a progressive astrogliosis around the host pial or choroidal vessels incorporated within the transplant which was evident by 1 month postoperative. Immunostaining with antisera to laminin showed intense reactivity around such neovessels at the light microscopic level. Transplants located intraparenchymally within the host parietal cortex also developed reactive astroglial “cuffs” around their marginal vessels by 1 week post-operative, although the degree and location of this reaction varied considerably with time. The origin of the reactive astroglia could not be directly determined from this study, but it is possible that they were stimulated by the collagen and fibroblasts present around vascularizing host pial and choroidal vessels in intraventricular grafts and by meningeal elements that entered the wound created for the intraparenchymal grafts. The marked astroglial reactivity within the grafts raises issues concerning their metabolic activity and their intimate relationship with brain endothelium. The close proximity of reactive astroglia to the graft vasculature would not appear to enhance the blood-brain barrier capabilities of transplant neovasculature, especially in intraventricular transplants, as might be suggested by many in vitro studies.

A comparison of intraventricular and intraparenchymal cerebellar allografts in rat brain: evidence for normal phosphorylation of neurofilaments

Allografts of embryonic (E14-E15) rat cerebellum in adult brain were compared using the intraparenchymal and intraventricular transplantation techniques. We studied the expression and distribution of phosphorylated neurofilament (PNF) epitopes, nonphosphorylated neurofilament (nPNF) epitopes, synapse-associated antigens, glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP). Both intraventricular and intraparenchymal grafts developed a clear trilaminar organization. Intraparenchymal grafts were much smaller and showed a large GFAP-positive glial scar and demyelination of host tissue. Nevertheless, myelinated fibers were present more often crossing the host-transplant border in intraparenchymal grafts. PNF and nPNF epitopes were present in both types of grafts. Staining patterns characteristic of normal rat cerebellum were seen. nPNF epitopes were present in Purkinje cell bodies and dendrites and PNF epitopes in basket cell axons surrounding Purkinje neurons. The appearance and distribution of PNF epitopes resembled that seen in normal postnatal cerebellar development and both PNF and nPNF epitopes were present at the same times in early development in both intraventricular and intraparenchymal grafts. In contrast to the situation in trauma and disease, PNF epitopes never appeared in perikarya of transplanted cerebellar neurons. The expression of synapse-associated antigens in grafted tissue was also similar to that seen in normal cerebellum.

Development of hypothalamic neurons in intraventricular grafts: Expression of specific transmitter phenotypes

The anlages of the medial-basal hypothalamus (MBH), septopreoptic area (POA), Rathke's pouch, and the parietal cortex (CC) of rats (at 12.5, 14.5 and 16.5 days of gestation) were transplanted singly or in combination into the third ventricle of adult female rats, and the development of neurons in the grafts was investigated immunohistochemically with the use of antisera to tyrosine hydroxylase (TH), somatostatin (SRIH), ACTH, methionine enkephalin-Arg 6-Gly 7-Leu 8 (Enk-8), rat corticotropin-releasing factor (rCRF), rat hypothalamic growth hormone-releasing factor (rhGRF), and luteinizing hormone-releasing hormone (LHRH). TH and all the peptides examined except LHRH were detected in distinct neurons in MBH grafts and in cografts of MBH plus Rathke's pouch from 12.5-day-old embryos. SRIH, rCRF, Enk-8, and TH were found in POA grafts from embryos of the same age. Although immunoreactive LHRH was first detected in neurons in POA grafts from 16.5-day-old embryos, it appeared in cografts of POA and MBH from 12.5-day-old embryos. The immunoreactive fibers developed in the grafts expressed the same characteristic behaviors as in intact brain; the fibers containing hormonal substances formed complexes with the vasculature like in the organum vasculosum laminae terminalis (OVLT) or in the median eminence, while the fibers containing neurotropic signals formed fiber networks surrounding other nerve cell bodies as if they synaptically associate. In CC grafts, the neurons contained TH, SRIH, rCRF, or Enk-8, and their axonal processes formed fiber networks. These findings suggest that all the hypothalamic neurons examined are committed by 12.5 days of gestation to develop maintaining transmitter phenotype and target recognition capacity.

Chapter 68 Neurochemical correlates of behavioral changes following intraventricular adrenal medulla grafts: intraventricular microdialysis in freely moving rats

Publisher Summary This chapter describes the neurochemical correlates of behavioral changes by measuring concentrations of monoamine metabolites in cerebral spinal fluid (CSF) using microdialysis in freely moving rats before and after intraventricular grafts of adrenal medulla or control tissue. The data indicates that adrenal medulla grafts in the lateral ventricle induce a change in dopaminergic activity in vivo. Dopamine (DA) turnover is increased in animals with adrenal medulla grafts indicated by: (1) an increase in CSF concentrations of dihydroxyphenylacetic acid (DOPAC), (2) a greater response to amphetamine sulfate (AMPH), and (3) a greater rate of DA metabolite accumulation following probenecid. If an adrenal medulla graft is effective in reducing AMPH-stimulated rotational behavior, then the concentrations of DA in the striatum adjacent to the graft are significantly elevated compared to control animals and relative to the graft. This increase in striatal DA concentrations reflects an increase in the functional capacity of striatal DA neurons is supported by preliminary findings that AMPH stimulates DA release from the striatum of animals with adrenal medulla grafts, but not in animals with adrenal cortex grafts.

Chapter 52 Central nervous system grafts of nerve growth factor-rich tissue as an alternative source of trophic support for axotomized cholinergic neurons

Publisher Summary Nerve growth factor (NGF) promotes survival of sympathetic and some neural crest-derived sensory neurons of the peripheral nervous system. This chapter explores the possibility that transplantation of this NGF-rich tissue into the lateral ventricle of the rat may provide a constant source of NGF to axotomized septa1 neurons. The chapter focuses on the grafting of tissue, which synthesizes a trophic factor known to influence the survival of a population of cholinergic neurons in the host brain. The results demonstrate that intraventricular grafts of male mouse submaxillary gland, a rich source of NGF, can increase the survival and regeneration of axotomized medial septum and vertical limb of the diagonal band nuclei (MS/VDB) neurons in the basal forebrain of the rat. The chapter indicates that transplants of male mouse submaxillary gland can (1) survive for extended periods in the host rat CNS, (2) influence the survival and regeneration of axotomized cholinergic cells in the MS/VDB, and (3) possibly influence the expression of behaviors associated with normal cholinergic function. However, further behavioral studies are necessary to determine whether these animals are using extra maze cues or some other non-spatial strategy to locate the platform.

Local blood flow and vascular permeability of autonomic ganglion-transplants in the brain

The purpose of this study was to determine whether the blood vessels of transplanted neural tissue retain their functional characteristics Quantitative autoradiography was used to measure local blood flow (F) with iodoantipyrine and the blood-to-tissue transfer constant (K) with α-aminoisobutyric acid in superior cervical ganglion (SCG) allografted to the surface of ventricle IV and into the cerebellum of the same rat. The F of the intraparenchymal grafts was slightly lower than that of the intraventricular grafts; F decreased between 1 and 4 weeks in SCG grafts at both sites. The permeability-surface area (PS) product of the microvessels and extraction fraction of AIB were calculated from these results and indicated restricted transvacular passage of the amino acid in both the in situ and grafted SCG. Surface area (S) and average length (L) of the microvessels were determined morphometrically and their permeability (P) was calculated from these data. Although K and PS decreased in the grafts compared to in situ SCG, a comparable decrease in S indicated that P was similar for the microvessels of both in situ and 1-week-old SCG transplants: 3.5–4.3 × 10 −6 cm/s. Between 1 and 4 weeks after transplantation, the P of the microvessels decreased to approximately 1.6–2.3 × 10 −6 cm/s without any change in S. Thus, the blood vessels of SCG grafts within or upon the brain initially retain the functional attributes of in situ SCG microvessels, but the average permeability of the graft microvessels decreases to approximately one half of the initial value by 4 weeks after transplantation.

Survival and growth of fetal catecholamine neurons transplanted into primate brain

Dopamine and norepinephrine neuroblasts of the ventral mesencephalon, hypothalamus, and dorsolateral pons were transplanted from fetal African green monkeys into multiple brain sites in adult (host) African green monkeys. Tissue was grafted from both early and late gestational age fetuses. Immunohistochemical analysis, with antibodies to tyrosine hydroxylase, a marker of catecholamine-containing neurons, showed large numbers of transplanted catecholamine neurons in host cerebral cortex, corpus striatum and lateral ventricles up to 69 days after transplantation. Serial reconstructions revealed extensive outgrowth of neuronal processes from large numbers of transplanted neurons as well as expansion of the size of transplanted (solid) grafts of fetal brain tissue in the host brain. Some grafts extended from the caudate nucleus into the adjacent lateral ventricles or from the cerebral cortex into the underlying corpus callosum and ventricle. There were dense networks of varicose fibers emanating from the tyrosine hydroxylase positive neurons within intraparenchymal and intraventricular grafts. The size and shape of transplanted neurons retained characteristics common to catecholaminergic neurons from the dissected regions of fetal brain. Thus, a variety of fetal, catecholamine-containing neurons survive transplantation to primate brain and produce extensive neuritic outgrowths. Moreover, rejection of transplanted tissue was not apparent. These findings provide essential information on nerve cell grafting in a species closely related to humans as a prerequisite in the consideration of neural transplants as therapeutic measures in neurological disease.