mystery of yawning
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La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
 
Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal
Le bâillement, du réflexe à la pathologie
Le bâillement : de l'éthologie à la médecine clinique
Le bâillement : phylogenèse, éthologie, nosogénie
 Le bâillement : un comportement universel
La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
 
Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal
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19 janvier 2012
Exp Brain Res.
1991;85(2):335-348.

 

Grafting of fetal substantia nigra to striatum reverses behavioral deficits induced by MPTP in primates:
a comparison with other types of grafts as controls
Taylor JR, Elsworth JD, Roth RH,
Sladek JR Jr, Collier TJ, Redmond DE Jr.
 
Neurobehavior Laboratory, Yale University School of Medicine, New Haven

Chat-logomini

Abstract
 
Fetal substantia nigra (SN) cells were transplanted into the caudate nucleus (CN) of four vervet monkeys (Cercopithecus aethiops sabaeus) that had been treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPTP treatment appears to produce a syndrome similar to that observed in patients with idiopathic Parkinson's disease. Normal and parkinsonian behaviors were quantitated by trained observers 5 days/week. Twenty-eight behaviors based on previous factor analyses were individually scored and rated. Parkinsonian signs included freezing, head and limb tremor, difficulty in eating, delayed initiation of movement, poverty of movement, tremor that stopped with intention, decreased response to threats, and lying immobile in the cage.
 
These signs were combined to give an overall rating of parkinsonism. A summary measure of 'normal' healthy behavior was also examined, including such behaviors as yawning, scratching, self-grooming, shifting, and eating. Overall ratings of parkinsonism increased and those of healthy behavior decreased after MPTP. In the 4 monkeys grafted with fetal SN cells into the CN, behavior returned to pre-treatment levels by the time of sacrifice (2, 5, or 7.5 months after grafting). Three control subjects were transplanted with either SN cells into an inappropriate brain site (cortex) or inappropriate, non-dopaminergic, cells (cerebellar) into the CN. Subjects were also compared with three control animals that did not receive MPTP but received cryopreserved or fresh SN and other cells into the CN. Only MPTP-treated subjects that received SN cells into the CN showed evidence of a reversal of the MPTP syndrome after transplantation. In addition, grafting in animals that were not MPTP-treated did not appear to affect behavior. This paper reports the specific behavioral effects of severe MPTP toxicity that were or were not reversed after transplantation and suggests that only fetal SN cells grafted into the CN may be able to reverse behavioral deficits in MPTP-treated monkeys.

Introduction
 
Transplantation of fetal neural tissue to rodents and to non-human primates has been reported to alter behavior, biochemistry, and morphology of the host brain (Bj6rklund and Stenevi 1979, 1984; Bj6rklund et al. 1981; Lund and Hauschka 1976; Perlow et al. 1979; Gash et al. 1980; Sladek et al. 1986, 1987a,b). The specific destruction of dopamine systems by the neurotoxin 1-methyl-4-phenyl- 1,2,3,6-tetrahydropyridine (MPTP) in human (Langston et al. 1983; Stern et al. 1985) and non-human primates (Bankiewicz et al. 1986; Burns et al. 1983, 1985; Chiueh et al. 1984, 1985; Degryse and Colpaert 1986; Elsworth et al. 1987a,b, 1989; Kitt et al. 1986; Jenner and Marsden 1986; Langston et al. 1984; Mitchel et al. 1986) and the similarities with the neuropathology of Parkinson's disease have provided a valuable model for studying the ability of transplanted dopamine-containing fetal tissue to modify behavior.
 
Few reports have quantitatively assessed the behavioral deficits after MPTP-induced parkinsonism in monkeys although motor deficits akin to those observed in patients with idiopathic Parkinson's disease and after accidental MPTP ingestion (Langston et al. 1983) have been documented. MPTP has effects on motor performance that vary within and between species (Eidelberg et al. 1986; Di Paolo et al. 1986; Jenner and Marsden 1986; Elsworth et aL 1987a, 1989). In fact in mildly affected subjects, there may be some behavioral recovery over time after initial impairments (Eidelberg et al. 1986; Nomoto et al. 1986; Schneider et al. 1987), even though striatal dopamine levels are markedly decreased (Elsworth et al. 1989). Moreover residual behavioral deficits may be hard to detect in these mildly affected animals even when detailed observational analyses are used. It is necessary therefore to be able to quantitate and compare the MPTPimpairments with other subjects before and after intervention aimed at ameliorating parkinsonism such as transplantation.
 
We examined the behavioral consequences of transplanting fetal substantia nigra (SN) cells into the caudate nucleus (CN) of monkeys that become moderately to severely affected by MPTP treatment and compared these subjects with control subjects. Because the behavioral effects of MPTP administration can vary between animals and some improvements may occur spontaneously, we used sensitive observational analyses and compared transplanted monkeys with control grafted subjects. Two types of control grafted MPTP-treated subjects were studied. Those with inappropriate grafts of SN tissue into cortex and with inappropriate cerebellar donor tissue into CN were used to examine the 1) non-specific effects of surgery and dopaminergic tissue implantation, and 2) the effects of surgical damage to the CN and non-dopaminergic tissue implantation. In addition, subjects that were not given MPTP were also given transplants of SN and other cells into CN to determine whether or not dopaminergic and other grafted tissue could modify normal behavior or generate abnormal behavior.
 
Discussion
 
Fetal SN neurons grafted into the CN that survived at least 7.5 months appeared to be associated with amelioration of the moderate to severe behavioral impairments induced by MPTP treatment. Examination of these subjects using parkinsonian summary scores and healthy behavior scores allowed us to quantify and compare the incidence of abnormal behaviors and the changes in the normal repertoire of behavior for this primate species following the administration of MPTP. Subjects given MPTP that received inappropriate fetal cells or placements did not show evidence of either an increase in normal healthy behaviors or a decrease in overall parkinsonian symptoms. In non MPTP-treated subjects, there was no evidence of adverse effects of the grafting procedure on normal behavior.
 
These results suggest that transplantation of fetal dopaminergic SN cells into the CN may reverse experimental parkinsonism in monkeys treated with M PTP. Although surgical intervention itself does not appear to be responsible for behavioral changes (since inappropriately grafted subjects that were severely affected by the toxin did not show signs of improvement) we cannot determine whether less severely affected subjects grafted inappropriately would also have shown some behavioral improvements. Nevertheless, three of the four SN-CN subjects were severely affected by MPTP administration as classified by parkinsonian summary score, and all subjects showed sustained recovery after grafting for their respective periods studied before sacrifice.
 
Previous studies have demonstrated a behavioral deficit induced by MPTP treatment that is characterized by decreased motor activity as measured by activity counts or decreased movement (Bankiewicz et al. 1986; Burns et al. 1983, 1985; Chiueh et al. 1984, 1985; Degryse and Colpaert 1986; Jenner and Marsden 1986; Langston et al. 1984). More quantitative assessment of motor function during arm movements or simple reaching tasks has also been examined in MPTP-treated monkeys (Doudet et al. 1985, 1986; Schultz et al. 1985; Schneider et al. 1988). This study confirms the presence of motor impairments and extends this characterization to include specific parkinsonian-like motor deficits that were observed after MPTP, such as poverty of movement, immobility, freezing, delayed initiation of movement, tremor, and tremor that decreases with intentional movement. Several of these impairments may correspond to akinesia, bradykinesia, resting tremor and other motor deficits that are clinically used to describe aspects of idiopathic Parkinson's disease. The behavioral rating and scoring methodology employed here quantified these behavioral impairments and allowed us to determine discrete changes in abnormal and normal behavior over time. Overall changes in behavior also could be assessed and measured by parkinsonian summary scores and healthy behavior scores. The precise behavioral consequences of MPTP toxicity as well as the overall condition of the subjects provide valuable data that support the similarity of the MPTP syndrome to Parkinson's disease. In addition, by detailed analysis of the effects of MPTP administration on normal and parkinsonian behavior it is possible to determine whether either fetal SN cells grafted into the CN or control grafting can reverse or even subtly alter the MPTP-induced behavioral deficits.
 
The present results suggest that MPTP-induced deficits can be gradually reversed in the months after grafting of SN cells into the CN. Overall ratings of parkinsonism, which provide assessment of behavior similar to that used to determine impariments in patients with Parkinson's disease, indicated that these subjects were not behaviorally different from non MPTP-treated subjects at the time of their sacrifice (up to 2, 6 or 7.5 months). MPTP-induced impairments such as freezing, immobility, and poverty and delayed initiation of movement were abolished following grafts of SN-CN by the time of sacrifice. However, analyses of individual behavior indicated that head and limb tremor, although reduced, was still present in the two animals sacrificed at 7.5 months after SN-CN grafting: Of course, we could not determine whether or not tremor would have eventually disappeared if these subjects had not been sacrificed. In addition, healthy behavior scores in the SN-CN group remained slightly below baseline values at sacrifice. Although categories of behavior associated with anxiety (yawn, chew, scratch, and self-groom) returned to normal, behavior associated with arousal (shift, tail flag, bipedal lookout and vertical climb) remained decreased after placement of appropriate grafts in MPTPtreated subjects.
 
Behavioral recovery may have been due to presence of dopamine neurons within the graft. Monkeys that showed sustained behavioral recovery from MPTP possessed welldefined grafts of fetal tissue that contained cells that stained positively for TH, indicating the presence of dopamine neurons. These neurons often appeared in dense clusters at various locations in the grafts, generally at the interface with the host brain. Although the grafts appeared to survive without precavitation surgery and the cells chronologically were still relatively immature, some possessed extensive neuritic ramifications that coursed throughout the neuropil of the graft and occasionally traversed relatively large distances into the host brain surrounding the grafted tissue. Grafts (e.g. S089) that were located within bridges of tissue that connected the corpus callosum to the CN showed fiber growth that was directed at the appropriate target site (i.e., the CN). These fibers that reached the appropriate target site then exited the graft to begin to ramify throughout the host brain. There was also some evidence suggesting that graft-induced host dopaminergic systems could be involved after grafts of SN into CN. For example, relatively dense TH fiber patterns were observed in the CN and putamen of subject S147 possibly reflecting some regenerative capacity of the partially damaged nigrostriatal system in this mildly affected subject. However, nigral cell losses were in the range of more severely symptomatic subjects, and thus we cannot account for why this subject showed this stronger TH staining than other subjects such as S089. In two of the subjects ($147 and $207) small bipolar cells that stained for TH were seen in the striatum indicating that recovery could also have been due to induction of host dopamine cells in the CN, or these could have been cells that migrated from the grafts. However, we have no clear evidence that host cells were involved in functional dopamine release.
 
Subjects that were also severely affected by MPTP that received inappropriate grafts or placements did not show evidence of behavioral recovery and also had substantial losses of TH positive cells in the SN. In one of the subjects that received SN tissue into cortex relatively large numbers of TH positive cells were observed, yet no behavioral recovery was found in these inappropriately grafted subjects. Grafts of cerebellar tissue, while of comparable size and placement to those of nigral tissue into the CN, revealed no TH positive cells as expected. No evidence of graft or host induced regeneration was observed in these subjects. These results suggest that behavioral recovery does not result from, 1). grafts of mesencephalic tissue placed into cortex and surgical trauma to the cortex overlying the CN, or from 2). grafts of non-dopaminergic cerebellar tissue and surgical trauma to the CN. Subjects not treated with MPTP that received various types of grafted tissue in various sites continued to show healthy/ normal behaviors, were found to have grafts that showed no signs of rejection, and in several cases had TH positive neurons with fiber networks.
 
Some evidence for the involvement of central dopamine activity (graft or host) in the sustained behavioral recovery observed in two of the SN-CN subjects (S089, S147) reported here is suggested by increased dopamine levels and altered dopamine metabolite/dopamine ratios in regions of the CN close to the graft but not in regions distant from the graft (Elsworth et al. 1990). These subjects were found to have an approximately 10 fold increase, compared with severely impaired MPTP-treated subjects, in dopamine concentration proximal, but not distal, to the graft, up to 7.5 months after transplantation. However, behavioral deficits after MPTP were accompanied by a reduction in (i) dopamine metabolite concentration assayed from CSF (Taylor et al. 1990c), (ii) dopamine concentration in cell body regions of the mesostriatal system (Elsworth et al. 1990), and (iii) approximately a 70% loss of TH positive neurons in the SN in these subjects, confirming the presence of a large MPTPinduced dopamine lesion in the MPTP-treated compared to control subjects.
 
Two of the subjects in the SN-CN group, two in the inappropriate group and all control subjects reported here were also investigated using a task that has been used to examine cognitive and subtle motor impairments (Diamond 1989; Taylor et al. 1990a, b). Only MPTP-treated subjects that received SN cells into the CN showed improvements in cognitive and motor performance (Taylor et al. 1990d). We had previously found both cognitive and subtle motor deficits on the acquisition (or learning) of this object retrieval/detour task in primates mildly affected by MPTP treatment (Taylor et al. 1990a), and on the stability of these deficits during long-term performance on this task (Taylor et al. 1990b). In addition to the characteristic motor deficits, which are thought to be due mainly to loss of striatal dopaminergic function, cognitive impairments are also a part of the behavioral sequelae of Parkinson's disease (Benecke et al. 1987; Reitan and Boll 1971; Loranger et al. 1972; Lees and Smith 1983; Stern et al. 1983; Weingartner et al. 1984). We therefore have used a multifaceted approach in studying MPTP-induced deficits and the ability of fetal neural grafts to alter behavior. A major advantage of this cognitive and motor procedure is that it detects subtle deficits that are not easily observed or rated. Its disadvantage is that an animal can become too impaired to perform at all. In the case of very impaired animals, observational methods are required for behavioral assessments.
 
The results of this study provide evidence to support the hypotheses that MPTP produces behavioral signs and symptoms that are strikingly similar to those observed in patients with idiopathic Parkinson's disease and that behavioral recovery can be sustained for up to 7.5 months in severely debilitated subjects after only fetal-SN cells were grafted into the CN. Similar grafts in non-MPTPtreated subjects did not generate abnormal behavior or affect normal behavioral responses as assessed by the methods described. MPTP-treated subjects grafted with inappropriate fetal tissue or at inappropriate implantation sites became so impaired that they were immobile and thus few behaviors could be documented, resulting in high ratings of parkinsonism and low ratings of healthy behavior, which remained stable until sacrifice or death. Further studies in larger numbers of subjects will be necessary to determine the duration of behavioral recovery, the effects sham surgery, and the possible graftinduced and host-derived mechanisms responsible for recovery after fetal SN transplantation into the striatum in MPTP-treated monkeys.