Beneficial effects of antioxidant-enriched diet for tyrosine hydroxylase-positive neurons in ventral mesencephalic tissue in oculo grafts.

Supplementation of antioxidants to the diet has been proved to be beneficial in aging and after brain injury. Furthermore, it has been postulated that the locus coeruleus promotes survival of dopamine neurons. Thus, this study was performed to elucidate the effects of a blueberry-enriched diet on fetal ventral mesencephalic tissue in the presence or absence of locus coeruleus utilizing the in oculo grafting method. Sprague-Dawley rats were given control diet or diet supplemented with 2% blueberries, and solid tissue pieces of fetal locus coeruleus and ventral mesencephalon were implanted as single and co-grafts. The results revealed that the presence of locus coeruleus tissue or the addition of blueberries enhanced the survival of ventral mesencephalic tyrosine hydroxylase (TH)-positive neurons, whereas no additive effects were observed for the two treatments. The density of TH-positive nerve fibers in ventral mesencephalic tissue was significantly elevated when it was attached to the locus coeruleus or by blueberry treatment, whereas the innervation of dopamine-beta-hydroxylase-positive nerve fibers was not altered. The presence of locus coeruleus tissue or bluberry supplementation reduced the number of Iba-1-positive microglia in the ventral mesencephalic portion of single and co-grafts, respectively, whereas almost no OX6 immunoreactivity was found. Furthermore, neither the attachment of ventral mesencephalic tissue nor the addition of blueberries improved the survival of TH-positive neurons in the locus coerulean grafts. To conclude, locus coeruleus and blueberries are beneficial for the survival of fetal ventral mesencephalic tissue, findings that could be useful when grafting tissue in Parkinson's disease.

[Neurosurgical methods in treatment of Parkinson disease. Current status]. / Neurochirurgische Verfahren zur Behandlund des Morbus Parkinson. Eine Bestandsaufnahme.

There is a world-wide renaissance of neurosurgical treatments of Parkinson's disease (PD), based on substantial progress in basic sciences. A model of parallel motor circuitry has identified potential targets for lesioning by clarifying the pathophysiological role of the basal ganglia in PD. The internal globus pallidus (Gpi) is an essential player as it connects to thalamocortical projections and can be disinhibited by overactivity of the nucleus subthalamicus (Nst). Lesioning of these targets has been successful in MPTP damaged primates. There is clinical use of destructive as well as restorative and stimulative technics. Pallidotomy and thalamatomy have evolved by the use of better neuroradiological and electrophysiological targeting. The first technic is used for treatment of rigidity, hypokinesia and dyskinesias, the latter one has proven to be efficient for tremor. Dopaminergic reinnervation and increased dopaminergic output of the striatum has only been seen after transplantation of fetal cells; this method however carries immunological and ethical problems. The continuous high frequency stimulation of basal ganglia is the newest technic; it is highly adaptable to the patient's need and carries a low morbidity profile. Thalamic stimulation is used for the treatment of tremor. The stimulation of Nst and Gpi are proposed for dyskinesias and on/off phenomena. Animal research further focuses on xenotransplantation and implantation of genetically transformed cells or pluripotent precursor cells.--In summary neurosurgical procedures seem to be very promising; however longterm comparison studies are needed to define the best (combination) treatment(s) for the future.

Ontogenesis of embryonic porcine ventral mesencephalon in the perspective of its potential use as a xenograft in Parkinson's disease.

Human fetal neural dopaminergic tissue can be transplanted and can ameliorate neurological deficiencies in patients with Parkinson's disease (PD). Donor tissue from other species has been used experimentally for several years in animal experiments and is now being considered an attractive alternative, particularly from a donor species that breeds in large litters, e.g., the pig. We have studied the early ontogenetic development of the mesencephalic dopaminergic system in the pig, utilising an anti-tyrosine hydroxylase (TH) immunocytochemical technique, and demonstrated the earliest appearance of its cell bodies at embryonic day 20 (E20). We compared the porcine data with those of human fetal development, as revealed by the same technique. Embryonic dopaminergic cell groups resembling the A8, A9, and A10 of the rat are present in the pig and differentiate into the homologous cell groups of human, although interesting quantitative differences are apparent. In the pig, prolonged presence of immature characteristics of TH-immunoreactive (TH-i.r.) cell bodies was observed, notwithstanding the early outgrowth of TH-i.r. axons into the ganglionic eminence. In the human, on the other hand, cell divisions and maturation of dendrites have progressed to a further degree than in the pig, before such distinct outgrowth of axons takes place. In pig embryos of 28 days, cells in the ventral mesencephalon had differentiated into TH containing neurons, which indicates their potential to synthesize dopamine. In spite of their differentiation, these cells still showed immature morphological features (rounded cell bodies with undifferentiated, short processes). Dopamine synthesis by these cells was demonstrated in previous studies by the high performance liquid chromatographic technique (HogenEsch et al. [1993] Can. J. Neurol. Sci. 20(suppl. 4):P.S. 235). In a separate paper, we have described that these porcine 28-day dopaminergic cells retain their potential for development and outgrowth in culture (van Roon et al. [1995] Res. Neurol. Neurosci. 7:199-205). We conclude that the ventral mesencephalon in pig embryos of 28 days is a potential source of dopaminergic neurons to be used as a xenograft in PD.

Further observations on the susceptibility of diencephalic prosomeres to En-2 induction and on the resulting histogenetic capabilities.

It has been previously shown by chick/quail heterotopic grafts that En-2 expression and a mesencephalic phenotype can be induced within the avian primordial prosencephalic vesicle, although the induction appeared restricted to the caudal forebrain. The present experiments were aimed at further analyzing the competence of the prosencephalic neuroepithelium. Different types of grafts were performed between chick and quail embryos: (i) caudal forebrain grafts positioned in the midbrain/hindbrain junction (the En-2-positive domain); (ii) En-2-positive grafts integrated at different levels of the forebrain. In both cases, the grafts were transplanted either with a normal orientation or after inversion of their rostro-caudal axis. The chimeric embryos were analyzed at stages HH19-24 for expression of En-2 and Pax-6 homeobox-containing genes, normally expressed in the meso-isthmo-cerebellar and prosencephalic domains, respectively. A cytoarchitectonic analysis of grafted and surrounding host tissue was also performed at later developmental stages in chimeric embryos with caudal forebrain grafts. Our results show that the caudal diencephalon, including the prospective territories for prosomeres 1 and 2, is competent to express En-2 when in close contact to the En-2 polarizing region, whereas the more rostral neuroepithelium, including the prospective territories for the third prosomere and telencephalon, does not change its fate under similar conditions. The ectopic-induced neuroepithelium can develop mesencephalon, but also isthmus and cerebellum according to its site of integration rostrally or caudally to the mesencephalic/isthmo-cerebellar boundary. Our data also show that within the competent diencephalon, the induced En-2 expression can be arrested at the P1/P2 interneuromeric boundary. This arrest appears to be directionally oriented as it only takes place when the induction is produced within prosomere 1 but not when it comes from prosomere 2. These data can be considered as resulting from either a possible oriented permissiveness of cells which form the boundary separating prosomeres 1 and 2, or of a different permissiveness of the cells composing these two caudal prosomeres.

Transmitter release from transplants of fetal ventral mesencephalon or locus coeruleus in the rat frontal cortex and nucleus accumbens: effects of pharmacological and behaviorally activating stimuli.

The present study was performed in order to establish whether dopamine (DA) release from behaviorally functional intracerebral DA transplants is dependent on changes in neuronal impulse flow, and is under control of the host brain. Rats were subjected to combined intraventricular and ventral tegmental injections of 6-hydroxydopamine (6-OHDA) in order to obtain a severe bilateral lesion of the ascending mesocorticolimbic DA projections. Cell suspension grafts of fetal ventral mesencephalic neurons were thereafter implanted into the medial frontal cortex (MFC) and the nucleus accumbens (NAc). Since the neurotoxin injections removed also the ascending noradrenergic systems, fetal locus coeruleus neurons were added to the graft suspension in one group of animals. Age-matched lesion-only and normal animals served as controls. The lesion-induced alterations in spontaneous, amphetamine- and apomorphine-induced locomotor activity and in a skilled paw reaching task were evaluated before transplantation, and at 3 and 6 months post-grafting. Microdialysis probes were finally implanted in the MFC and NAc in order to monitor extracellular DA and noradrenaline (NA) levels (i) during administration of pharmacological agents which augment or depress catecholamine release in the intact brain; (ii) during exposure of the rats to stressful manipulations (handling and immobilization) or appetitive stimuli (eating) known to enhance cortical and limbic DA or NA release in intact animals. The lesion-induced reduction in amphetamine-induced locomotor activity was reversed in all grafted animals, which also showed a higher than normal spontaneous overnight activity. Daytime spontaneous locomotor activity (which was reduced in the lesion-only rats) as well as apomorphine-induced hyperactivity was reversed by the grafts of DA neurons only. By contrast, the lesion-induced impairment in skilled forelimb use was not alleviated by the grafts. The grafted DA neurons restored normal steady-state DA overflow in the NAc, whereas they enhanced cortical DA overflow to significantly higher than normal levels. Restoration of both cortical and striatal NA overflow was observed in the group that received mixed DA and NA grafts, whereas animals that received DA grafts only did not differ from the lesioned controls. The changes in extracellular DA and NA levels measured in the grafted MFC and NAc under potassium depolarization (100 mM KCl), inhibition of terminal catecholamine reuptake (10 microM nomifensine), and sodium channel blockade (1 microM TTX) indicated that graft-derived DA or NA release had normal neuronal properties, and was dependent on an intact axonal impulse flow.(ABSTRACT TRUNCATED AT 400 WORDS)

Neurosurgical horizons in Parkinson's disease.

Based on recent neuroanatomic and physiologic discoveries, neurosurgical therapies may increasingly complement and extend pharmacologic management of Parkinson's disease. Procedures showing promise include subthalamotomy and pallidotomy; thalamic electrical stimulation may also offer application for tremor control. Transplantation of adrenal chromaffin cells has not been associated with consistent long-term improvement in most patients, and fetal mesencephalic transplantation remains controversial. Trophic factors that may be pivotal to cellular repair and survival of transplanted tissue have potential therapeutic roles when purified and perfused centrally or when the cells that produce the factors are transplanted.

Embryonic dopaminergic neuron transplants in MPTP lesioned mouse striatum.

The aim of this work is to study CNS development and plasticity, and to study the mechanisms that allow exogenous embryonic dopaminergic neurons to restore transmitter function in the experimental parkinsonism. Recently, we have developed a new method that produces a selective degeneration of the dopaminergic nigrostriatal system in mice by a combined acetaldehyde/MPTP treatment. This procedure results in a selective and irreversible loss of substantia nigra dopaminergic neurons in C57BL mice, while other dopaminergic areas of the brain are spared. MPTP alone results instead only in a temporary, reversible damage of nigro- striatal dopaminergic functions. Embryonic dopaminergic neurons from ventral mesencephalon or hypothalamus are implanted in lesioned or normal right striata or lateral ventricles. The mesencephalic neurons implanted in a lesioned host form a dense network of fibers which establish functional reinnervation of the striatum (or caudate-putamen complex). After several months about the entire striatal parenchyma appears reinnervated; on average, 20% of the grafted mesencephalic dopaminergic cells survive. Implants of embryonic HYP neurons instead, show little or no survival. Moreover, dopaminergic mesencephalic neurons in control non-lesioned animals show a poor development with little fiber outgrowth. These data indicate that interactions between embryonic dopaminergic neurons and adult striatal neurons is specific. They also suggest that this specificity is sustained by trophic and/or tropic factors possibly produced by the lesioned striatum and by putative inhibitory mechanisms of cell migration and neuritic outgrowth.

Development of intracerebral dopaminergic grafts: a combined immunohistochemical and autoradiographic study of its time course and environmental influences.

The aim of the study was to obtain a description of some aspects of the development of intracerebral dopaminergic grafts, namely, the time course of the glial reaction and its relation to cell division on one hand, and the development of graft-originated innervation and its dependence on adequate matching of the implanted neurons and target site on the other hand. Cell suspensions obtained from the mesencephalon or hypothalamus of embryonic day (ED) 14 rat embryos were implanted into the striatum or lateral hypothalamus of adult rats following the destruction of the nigrostriatal system of the hosts. Animals were sacrificed at different postimplantation times, and the development of the graft was followed by immunohistochemistry by using antisera directed against tyrosine hydroxylase (TH) or glial fibrillary acidic protein (GFA). Furthermore, the existence of cell division at various times following implantation was examined by performing autoradiography on immunostained sections after prior intraventricular administration of 3H-thymidine to the host. The first stage of the development of intracerebral grafts was characterized by the existence of intense cell division within the grafted tissue, lasting about 2 weeks, and also in the host tissue surrounding the graft, lasting only about 6 days. The cell division in the host tissue was paralleled by the existence of a strong glial reaction which, however, did not extend into the graft itself. Glial reaction in the host tissue gradually decreased at later times and disappeared by 4 weeks postimplantation without leaving behind a noticeable glial scar. The graft itself was, however, transiently filled with a population of reactive astroglial cells between 3 and 6 weeks postimplantation. Within grafts of mesencephalic tissue located in the striatum TH-positive neurons were distributed evenly at short times postimplantation (2-6 days). At later time a compartmentation could be observed, with TH-positive neurons being aligned along the graft-host interface or clustered within the graft itself. Innervation of the host tissue by TH-positive fibers increased between 1 and 6 weeks postimplantation. On the other hand, no compartmentation and reinnervation of surrounding host tissue was observed for intrahypothalamic grafts of mesencephalic tissue or intrastriatal grafts of hypothalamic tissue. This last observation indicates that adequate matching of implanted neurons and target tissue plays an important role in the development of intracerebral dopaminergic grafts.

[Immunocytochemical study of catecholaminergic neurons in grafted mesencephalon transplanted into the hypothalamus of the rat]. / Etude immunocytochimique des neurones catécholaminergiques dans des greffons mésencéphaliques transplantés dans l'hypothalamus du rat.

Mesencephalic fragments from 14 day old embryonic rat brain were transplanted into the third ventricle of adult rats neonatally treated with monosodium glutamate. From two to twelve months after grafting, the implanted tissue was still present in the ventricle and contained TH immunoreactive neurons which displayed a normal appearance at ultrastructural level. While endogenous TH containing neurons were still present in dopaminergic regions of the recipient hypothalamus, grafted mesencephalic fragments could survive and develop. They contained TH immunopositive most probably dopaminergic neurons which are able, in some cases, to innervate the host brain. This model should be of interest in the study of neuroendocrine functions of dopaminergic neurons.