Analysis of microRNA-203 function in CREB/MITF/RAB27a pathway: comparison between canine and human melanoma cells

MicroRNA (miR)-203 is downregulated and acts as an anti-oncomir in melanoma cells. Here, using human and canine melanoma cells, we elucidated the effects of miR-203 on cyclic adenosine monophosphate response element binding protein (CREB)/microphthalmia-associated transcription factor (MITF)/RAB27a pathway, which is known to be important for the development and progression of human melanoma. In this study, we showed that miR-203 directly targeted CREB1 and regulated its downstream targets, MITF and RAB27a. miR-203 significantly suppressed the growth of human and canine melanoma cells and inhibited melanosome transport through the suppression of the signalling pathway. In conclusion, miR-203 was shown to be a common tumour-suppressive miRNA in human and canine melanoma and thus to play a crucial role in the biological mechanisms of melanoma development.

Melatonin-secreting pineal gland: a novel tissue source for neural transplantation therapy in stroke

Chronic systemic melatonin treatment attenuates abnormalities produced by occlusion of middle cerebral artery (MCA) in adult rats. Because the pineal gland secretes high levels of melatonin, we examined in the present study whether transplantation of pineal gland exerted similar protective effects in MCA-occluded adult rats. Animals underwent same-day MCA occlusion and either intrastriatal transplantation of pineal gland (harvested from 2-month-old rats) or vehicle infusion. Behavioral tests (from day of surgery to 3 days posttransplantation) revealed that transplanted stroke rats displayed significantly less motor asymmetrical behaviors than vehicle-infused stroke rats. Histological analysis at 3 days posttransplantation revealed that transplanted stroke rats had significantly smaller cerebral infarction than vehicle-infused rats. Additional experiments showed that pinealectomy affected transplantation outcome, in that transplantation of pineal gland only protected against stroke-induced deficits in stroke animals with intact pineal gland, but not in pinealectomized stroke rats. Interestingly, nonpinealectomized vehicle-infused stroke rats, as well as pinealectomized transplanted stroke rats, had significantly lower melatonin levels in the cerebrospinal fluid than nonpinealectomized transplanted stroke rats. We conclude that intracerebral transplantation of pineal gland, in the presence of host intact pineal gland, protected against stroke, possibly through secretion of melatonin.

GDNF is a major component of trophic activity in DA-depleted striatum for survival and neurite extension of DAergic neurons

Extracts from dopamine (DA)-depleted striatal tissue (lesion extract) and from intact striatal tissue (intact extract) were prepared, and trophic activities in these extracts were evaluated using survival and neurite extension of DAergic neurons as indices. Levels of brain-derived neurotrophic factor (BDNF), basic fibroblast growth factor (bFGF), glial cell-line derived neurotrophic factor (GDNF) and neurotrophin-3 (NT-3) in extracts were measured using enzyme-linked immunosorbent assay (ELISA). The lesion extract exhibited a stronger trophic activity on survival and neurite extension of DAergic neurons than intact extract. In lesion extract, bFGF was slightly and GDNF was significantly increased, while BDNF and NT-3 were the same level in each extract. The peak increase of bFGF and GDNF was during 2 to 3 weeks after DA depletion. Trophic activity of extract was strongly attenuated after immunoprecipitation of GDNF and partly attenuated after immunoprecipitation of bFGF. In parallel immunohistological study, no significant variations were found for striatal microtubule-associated protein-2 (MAP-2)- nor OX-41-immunoreactive cells, while the number of strongly labeled glial fibrillary acidic protein (GFAP)-immunoreactive cells were increased in DA-depleted striatum, suggesting reactive gliosis. Data suggest that bFGF is a minor, while GDNF is a major component of trophic activity for DAergic neurons in DA-depleted striatum, and increased bFGF and GDNF levels may be mediated partly by reactive gliosis.

Glial cell survival is enhanced during melatonin-induced neuroprotection against cerebral ischemia

The role of glial cells in neuronal death has become a major research interest. Glial cell activation has been demonstrated to accompany cerebral ischemia. However, there is disagreement whether such gliosis is a cell death or a neuroprotective response. In the present study, we examined alterations in glial cell responses to the reported neuroprotective action of the free radical scavenger, melatonin, against cerebral ischemia. Adult male Wistar rats were given oral injections of either melatonin (26 micromol/rat) or saline just prior to 1 h occlusion of the middle cerebral artery (MCA), then once daily for 11 or 19 consecutive days. At 11 and 19 days after reperfusion of the MCA, randomly selected animals were killed and their brains removed for immunohistochemical assays. Melatonin significantly enhanced survival of glial cells (as revealed by glial cell specific markers, glial fibrillary acidic protein and aquaporin-4 immunostaining) at both time periods postischemia, and the preservation of these glial cells in the ischemic penumbra corresponded with a markedly reduced area of infarction (detected by immunoglobulin G and hematoxylin-eosin staining), as well as increased neuronal survival. The ischemia-induced locomotor deficits were partially ameliorated in melatonin-treated animals. In vitro replications of ischemia by serum deprivation or by exposure to free radical-producing toxins (sodium nitroprusside and 3-nitropropionic acid) revealed that melatonin (10 microg/ml or 100 microM) treatment of pure astrocytic cultures significantly reduced astrocytic cell death. These results suggest a potential strategy directed at enhancing glial cell survival as an alternative protective approach against ischemic damage.

Mesencephalic neural stem (progenitor) cells develop to dopaminergic neurons more strongly in dopamine-depleted striatum than in intact striatum

Epidermal growth factor (EGF)/fibroblast growth factor (FGF)-responsive stem (progenitor) cells from embryonic brain have self-renewing and multipotent properties and thus are good candidates for donor cells in neural transplantation. However, the survival and differentiation to mature neurons after grafting of stem cells into adult brain are rather poor. We hypothesize that the differentiation of stem cells to mature neurons, such as dopaminergic (DAergic) neurons, is dependent on environmental cues that control the ontogenic development. We compared the survival and differentiation between mesencephalic (MS) and cortical (CTx) stem (progenitor) cells, following grafting into bilateral striata of hemiparkinsonian model rats. MS and CTx stem cells were prepared from E12 rats and proliferated in serum-free medium with EGF or basic FGF for 2 weeks. One day after being primed to differentiate, the cell suspensions of both origins were grafted into the bilateral striata of adult rats that had unilateral 6-OHDA lesions in the substantia nigra. MS cells differentiated to tyrosine hydroxylase (TH)-positive neurons more strongly in DA-depleted striatum than in intact striatum, and methamphetamine-induced rotation was ameliorated in half of the grafted animals. Rosette-like cell aggregation and dysfunction of the blood-brain barrier (BBB) were less in and around the grafts in DA-depleted striatum, suggesting less proliferation and more differentiation of MS stem cells in DA-depleted striatum. Neither TH-positive neurons nor behavioral amelioration were detected following CTx stem (progenitor) cell transplantation in the striata. Data suggest that the DA-depleted striatum offers a suitable environment for MS stem (progenitor) cells to differentiate into mature DAergic neurons.

The striatum is the most vulnerable region in the brain to mitochondrial energy compromise: a hypothesis to explain its specific vulnerability

The striatum, together with the hippocampus, is one of the most vulnerable regions in the brain. Recently, genetic abnormalities or mutations have been linked to various neurodegenerative diseases, that is, Huntington's disease, Alzheimer's disease, amyotrophic lateral sclerosis (ALS), etc., but the processes from genetic abnormality to the final phenotypic expression are not well understood. Disturbances in energy metabolism especially in mitochondrial energy compromise could facilitate genetic abnormalities and enhance neuronal cell death. Here, we report that the striatum is the most vulnerable brain region to systemic intoxication with 3-nitropropionic acid (3-NPA), an inhibitor of succinate dehydrogenase inducing energy compromise. We hypothesize that the striatum-specific lesion by 3-NPA is due to cummulative insults characteristic to the striatum including glutamatergic excitotoxicity, dopaminergic toxicity, vulnerability of the lateral striatal artery and high activity in the glutamate-transporter. The former two are extravascular in origin while the latter two are intra-/perivascular. We also discuss the possibility that a high turnover rate in metabolism of nitric oxide (NO) might underlie the vulnerability of the lateral striatal artery. We posit that systemic intoxication with 3-NPA offers a good animal model to investigate the pathophysiology of neuronal/glial cell death, neurodegenerative disease, dysfunction of the blood-brain barrier (BBB), neuroimmune disorders, and stroke.

Elucidation of intestinal absorption of D,L-amino acid enantiomers and aging in rats

At the present time, the origin of protein bound D-amino acid (AA) has been fairly well elucidated, but that of free D-AA is still not well understood. To gain greater understanding of this, intestinal absorption in rats of free D,L-AA enantiomers (arginine, alanine and aspartic acid as models for basic, neutral and acidic AAs, respectively, in this study) and the relationship between age and absorption were investigated. The degree of rat intestinal absorption of free D,L-AAs was evaluated using apparent membrane permeability coefficients (Papp) which were obtained from an in situ intestinal single-pass perfusion method with Krebs-Ringer bicarbonate buffer (pH 7.4) solution containing D,L-AA enantiomers. Determinations of D,L-AA enantiomers in perfusion (in- and outflow) solutions were carried out by the in-capillary derivatization high-performance capillary electrophoretic methods (ICD-HPCE methods) that were previously developed by our group. Collectively, our observations suggest: (1) that the Papp of L-AA is higher than that of the D-isomer; (2) that D-AA can be absorbed as well as L-AA using a sodium ion-dependent transporter that is located on the brush border membrane of rat intestinal epithelial cells; (3) that Papp reached a maximum at 8 weeks of age, but were measured at decreased amounts at 52 and 104 weeks of age. These results suggest that free D-AA in a mammalian body originates from 'exogenous sources'.

Estrogen protects against while testosterone exacerbates vulnerability of the lateral striatal artery to chemical hypoxia by 3-nitropropionic acid

Gender differences in the vulnerability of the lateral striatal artery (1STR artery) to systemic intoxication with 3-nitropropionic acid (3-NPA, succinate dehydrogenase inhibitor) were studied. Subcutaneous injection of 3-NPA (20 mg/kg once a day for 2 days) induced striatal selective lesions in half of male rats associated with motor symptoms (rolling, paddling, recumbency, etc) while female rats were resistant. Lesions were located in the lateral striata and characterized by astroglial necrotic cell death, enhanced immunoreaction to factor VIII-related antigen, edema, extravasation of IgG and sometimes bleeding. The motor and histological disturbances were highly sex-dependent and modulated by changes in hormonal levels. Males were more susceptible than females. Castration had little effect but ovariectomy enhanced the vulnerability. Replacement therapy with testosterone increased while estradiol or tamoxifen suppressed the vulnerability in ovariectomized females. Investigation of the arterial architecture of the brain often revealed rectangular and acute angled branchings in the centrolateral striatum where the ISTR artery feeds. A parallel in vitro toxicity study demonstrated that an extreme Ca++ overload and a strong cellular swelling resulted in astrocytic cell death. Data suggest that 1STR artery and astrocytes are highly vulnerable to 3-NPA intoxication in males. The greater vulnerability of the ISTR artery may contribute to the pathogenesis of neurodegenerative diseases, striatal bleeding, etc. Protective effects of estrogen and tamoxifen may mediate gender differences often observed in these disorders and suggest their potential use as therapeutic agents for these disorders.

Dopamine metabolism in the striatum of hemiparkinsonian model rats with dopaminergic grafts

To investigate dopamine (DA) levels as well as DA metabolism by which the striatal DAergic grafts may bring the functional recovery to hemiparkinsonian model rats, a microdialysis study was performed in the striatum, and an autoradiographic analysis for DA transporter was made. In hemiparkinsonian model rats, the concentrations of DA, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in striatal perfusates, decreased considerably (less than 5%, of control levels). In grafted rats that showed motor recovery, the concentration of DA recovered to almost control level, and DOPAC and HVA to about 20% of controls' suggesting that the rate of DA metabolism is low. L-DOPA loading to grafted rats induced a big release of DOPAC and HVA, thus the DOPAC/DA ratio was close to that of the controls'. Methamphetamine loading increased the concentration of DA but did not change the level of DOPAC and HVA. Haloperidol loading increased DA, DOPAC and HVA. [3H]mazindol binding that reflects the activity of the DA transporter decreased considerably in hemiparkinsonian model rats, but it reappeared more or less in grafted rats. Data indicated that in grafted striatum, the extracellular DA level is almost normal level while the rate of DA metabolism is low. By L-DOPA loading, the grafts show the capacity to synthesize, release and metabolize DA and then the DOPAC/DA ratio is normalized. Responses to methamphetamine and haloperidol, as well as the results of the autoradiographic study suggest that the grafts are under a good feedback regulation of DA metabolism.

Acute 3-nitropropionic acid intoxication induces striatal astrocytic cell death and dysfunction of the blood-brain barrier: involvement of dopamine toxicity

Mechanisms underlying the selective vulnerability of the lateral striatal area to the toxic effects of 3-nitropropionic acid (3-NPA) were investigated in rats. A single exposure to 3-NPA (20 mg/kg, s.c.) induced no deficits in behavior and histology, but subsequent injection produced motor symptoms, catalepsy, lip smacking, abnormal gait, paddling, rolling, opisthotonos, tremor, recombence, somnolence and so on, in 30% of the animals within a few hours. Diffusion-weighted magnetic resonance imaging of the brains revealed an area of high signal intensity in the bilateral striata. By this stage (within a few hours), striatal astrocytes had become swollen and disintegrated. Extravasation of immunoglobulin G was detected, indicating blood-brain barrier (BBB) dysfunction. Electron microscopy revealed edema and disorganization of structures inside the astrocytic end-feet around the branches of the lateral striatal artery. Neurons were less vulnerable than astrocytes to the 3-NPA injury. Treatment of the rats with D2 receptor agonist prior to exposure to 3-NPA attenuated the behavioral abnormalities and histological damage whereas pretreatment with D2 antagonist exacerbated these changes. The concentrations of extracellular dopamine (DA) and dihydroxyphenyl acetic acid (DOPAC) were both increased in rats exposed to 3-NPA. In vitro imaging of astrocytes revealed a progressive increase in [Ca2+]i after superfusion with 3-NPA, and the 'ceiling' level was maintained even after extensive washing. DA superfusion also increased the astrocytic [Ca2+]i and this increase was reversible. Data indicate that 3-NPA-induced striatal damage was associated with astrocytic cell death and dysfunction of the BBB. Intracellular edema and extreme Ca2+ overload induced by the toxin were further aggravated by an increase in the level of DA activity. These factors acting either singly or in combination may trigger astrocyte destruction.

Expression of dopamine transporter mRNA and its binding site in fetal nigral cells transplanted into the striatum of 6-OHDA lesioned rat

Neurological disorders in rat model of hemi-Parkinson's disease can be compensated by the transplantation of fetal nigral cells. However, the role of the dopamine transporter (DAT) in this recovery has not been clarified. To clarify this mechanism, we examined the expression of DAT in the caudate putamen (CPu) by in situ hybridization histochemistry (mRNA) and autoradiography (using the ligand [125I] beta-CIT, which labels DAT) and compared them with the recovery of motor disturbance revealed with methamphetamine-induced rotation. Models were made with the stereotaxic injection of 6-hydroxydopamine into the left side of the substantia nigra pars compacta. Cell suspensions from rat fetus (embryonic day 14-15) were transplanted into the lesioned side of CPu. Methamphetamine-induced rotation, expression of DAT mRNA, and [125I] beta-CIT binding were evaluated 2, 4 and 12 weeks after the transplantation. Methamphetamine-induced rotation recovered partly in the 2nd week and significantly in the 4th week. [125I] beta-CIT binding increased with time and the dense binding was detected 4 and 12 weeks after the transplantation. In all transplanted rats, cells expressing DAT mRNA were found in CPu. These results indicated that transplanted fetal dopaminergic cells maturated in CPu of host animals and extended nerve terminals where high density of DAT binding sites were found.

3-Nitropropionic acid produces striatum selective lesions accompanied by iNOS expression

Systemically administered 3-nitropropionic acid (3-NPA) that inhibits the mitochondrial oxidative phosphorylation induces selective lesions in the striatum. To investigate the nature of these selective lesions, we administered 3-NPA (20 mg/kg, s.c. daily for 2 or 3 days) to Wistar rats and investigated the behavioral disturbance, striatal lesions and their variations after modulating the activity of nitric oxide synthase (NOS). On the second or third day of 3-NPA administration, half the animals manifested behavioral disturbances (paddling, rolling, tremor, abnormal gait, and recumbence). A strong extravasation of immunoglobulin G (IgG) and a decrease in immunoreaction for glial fibrillary acidic protein (GFAP) were detected, and iNOS-like (iNOS-L) immunoreactive small cells appeared in the lateral and central striatum especially around the vessels. A week later, lesions lacking GFAP-immunoreaction were detected in the striatum in survived animals. Pretreatment with N-nitro-L-arginine methyl ester (L-NAME) along with each injection of 3-NPA did not improve the behavioral disturbances nor the survival rate, but attenuated the extravasation of IgG and iNOS-L immunoreaction. Pretreatment with aminoguanidine or FK506 improved the behavioral symptoms and survival rate. Extravasation of IgG and expression of iNOS-L immunoreactivity were attenuated, and the striatal lesion was reduced. Data indicate the involvement of NO in the high vulnerability of the striatum, and that iNOS, one of inflammatory markers, is induced following exposure to 3-NPA.

Labeling and identification of living donor cells in brain slices of recipient hemiparkinsonian model rats for physiological recordings: methods for physiological assessments of neural transplantation

Physiological properties of grafted neurons, such as membrane and intr acellular properties, have not been reported. To fill this lack in knowledge, physiological recordings from the identified grafted cells are required. Fluorescent latex microspheres (FLM) are non-toxic and stable, and thus seem suitable for long-term labeling of donor cells. Therefore, we tested the feasibility of labeling with FLM to identify living donor cells in the recipients' brain slices. We also tested if physiological recordings from the identified cells are possible or not. Cell suspensions were prepared from the substantia nigra (SN) of Embryonic Days 15 or 16 rats with enzymatic and mechanical trituration. Cell suspensions were then incubated with 0.5% FLM for 30 min to 2 h. The longer cells were incubated, the more FLM were taken up. The FLM-labeled SN cell suspensions were injected in the striatum of the hemiparkinsonian model rats. Eight to 13 weeks later, 150-mu m thick coronal brain slices including the graft track were prepared from the recipients. Slices were kept in vitro for several hours. Grafted cells could be clearly identified in the slice preparations by the uptake of FLM under a fluorescence microscope. Voltage-dependent currents and intracellular Ca2+ transcients were successfully recorded from the identified grafted neurons. It is suggested that labeling and identification of living donor cells with FLM is feasible and thus can provide a powerful tool to study the mechanisms underlying graft-induced amelioration of neurological deficits in parkinsonism by enabling physiological assessments of grafted cells.

Early cytopathic features in rat ischemia model and reconstruction by neural graft

Using a silver impregnation (argyrophil III) and immunohistochemistry, acute cytopathic features after cerebral ischemia were investigated. Additionally, functional recovery and interconnection between the host and graft was also explored after neural graft. Animals were embolized in unilateral middle cerebral artery for 1 h. Argyrophil III method demonstrated "collapsed" dark neurons in the striatum, cortex, reticular thalamus, amygdala, and hypothalamus on ischemic side. These neurons exhibited characteristic shrunken somata with corkscrew-like dendrites, suggesting changes in cytoskeletal protein. In the above mentioned areas, the loss of immunoreactivity for mu-calpain proenzyme and microtubule-associated protein 2 was also detected. Neural graft into the ischemic striatum was made 2 weeks after the ischemia paradign. The grafted striatal cells were prepared from E15 fetuses to make cell suspension marked by rhodamine-labeled latex microspheres. Methamphetamine-evoked rotations were detected after ischemia. These motor alterations were reduced gradually but significantly at 8 weeks after the graft. Interconnecton between the host and grafted cells was then studied in a brain slice preparation after loading fura-2 AM. About 10% of grafted cells tested from rats that showed motor amelioration exhibited [Ca2+]i increase to the electrical stimulation applied to the neighboring host tissue. Data indicate that, in the very early stage after ischemia, cytoskeletal damages, especially on microtubules, started and this would lead to later infarct. The graft survived in the ischemic striatum having connections with the host, and this might be partly involved in the amelioration of motor function.

Chronically administered 3-nitropropionic acid produces selective lesions in the striatum and reduces muscle tonus

Systemically administered 3-nitropropionic acid (3- NPA), irreversible inhibitor of succinate dehydrogenase, produced characteristic bilateral lesions in the striatum (STR) in the rat. Inside the lesion, neutrophils invaded and strong immunoreaction for IgG as well as complement factor C3b/C4b receptor (C3b/C4br) were observed. The core of the lesion lost the immunoreaction for glial fibrillary acidic protein (GFAP) while the marginal area had abundant GFAP-labeled astrocytes around the vessels. Intoxicated rats often became somnolent and were awkward in cooperative movement on a pole climbing test, but they had a quite good memory retention in a passive avoidance learning. Muscle tonus in some of the intoxicated rats became hypotonic with low voltage electromyogram (EMG) activity, especially in lower limbs. In summary, 3-NPA intoxicated rats had selective bilateral lesions in the STR and exhibited disturbances in a cooperative movement owing to the impairment in muscle tonus, thus it would be a useful animal model to deduce the central pathogenesis of Huntington's disease.

Chronically administered 3-nitropropionic acid induces striatal lesions attributed to dysfunction of the blood-brain barrier

3-Nitropropionic acid (3-NPA), an irreversible inhibitor of succinate dehydrogenase, was administered to rats and the characteristics of the neuronal damage were investigated. Injections of 3-NPA (15 mg/kg s.c.) every 2 or 3 days for 1-2 weeks induced a mild neuronal loss and neutrophil invasions in the striatum (STR). The same administration for 4 weeks induced specific symmetric lesions in the lateral STR although the size was variable in each animal. Inside the lesions, strong neutrophil invasions and a strong immunoreaction for IgG, C3 as well as complement factor C3b/C4b receptor (C3b/C4br) were detected. Lesioned sites lost the immunoreaction for GFAP while the marginal areas contained abundant GFAP-labeled astrocytes around the vessels. In intoxicated animals, there was a weak but stout immunoreaction for IgG and C3b/C4br localizing around vessels in the STR even when there were no lesions or neuronal loss. The data suggest that the blood-brain barrier dysfunction is responsible for the specific vulnerability of the STR for the toxin.

Striatal grafts in the ischemic striatum improve pallidal GABA release and passive avoidance

Fetal striatal cells were grafted into the ischemic striatum of rats and pallidal GABA release, and behavioral improvement were investigated. Intraluminal occlusion of the middle cerebral artery (MCA) for 1 h induced ischemic infarcts in the lateral striatum and the adjacent cortex. In ischemic rats, the performance of a passive avoidance task was disturbed, and the pallidal GABA level detected by microdialysis decreased to about a half of control. After the graft, the deficit in the passive avoidance was partially alleviated and the GABA level recovered moderately and increased further by the infusion of an uptake blocker. The data indicate that fetal striatal cell grafts in the ischemic striatum partially restored both chemical and behavioral deficits.

Sialyl cholesterol enhances the development of grafted neurons and motor recovery

Trophic actions of alpha-sialyl cholesterol (SC) and its sialidase-tolerant derivative, alpha-(3 beta-hydroxysialyl) cholesterol (SCt), were carried out on the development of midbrain neurons both in vitro and in vivo transplantation studies. Low to moderate concentrations of SC (0.01 to 0.05 micrograms/ml) facilitated neurite extension but had no effects on cell survival of primary cultured midbrain neurons. However, high concentration of SC (0.1 micrograms/ml) disturbed both neurite genesis and cell survival. SCt had a similar effect on midbrain neurons. At higher concentrations, SC and SCt induced concentration-dependent morphological changes in astrocytes from flat to fibrous. The effect on astrocytes was stronger in SCt than SC. At highest concentration tested (20 micrograms/ml), the proliferation of astrocytes was completely blocked, cells became detached and finally died. This effect of SC and SCt was partially blocked by simultaneous application of aFGF. Following dopaminergic cell grafting in vivo, SC and SCt had biphasic effects: a low dose (0.2 mg/kg, SC) enhanced motor recovery at 4 and 6 weeks after transplantation, while the highest dose (20 mg/kg, SC) disturbed motor recovery at all periods tested. These effects on motor recovery were paralleled by an effect on neurite genesis as studied by tyrosine hydroxylase immunostaining. Thus, at low concentrations, SC and SCt are neurotrophic agents that stimulate the development and differentiation of dopaminergic neurons.

Overshoot and high equilibrium in body temperature responses of rats to ambient heat: relation to thermoregulatory ability and improvement in estimation of survival time in a hot environment

Physiological significance of body temperature responses to ambient heat (BTRAH) with high overshoot or a high equilibrium phase was studied in relation to thermoregulatory ability. Subsequently, an attempt was made to predict survival time (ST) by measuring the period required to attain a colonic temperature (Tco) of 42.0 degrees C (t42.0), whereas ST hitherto having been calculated on the basis of a period until Tco attains 42.5 degrees C (t42.5). Tco of rat was monitored continuously with a Cu-Co thermocouple during exposure to an ambient temperature (Ta) of 42.5 degrees C. The lower the overshoot temperature (Tos) or the equilibrium temperature (Teq), the longer the rats survived in a hot environment. The present findings further suggest that these two types of BTRAH are immature variations of the typical triphasic BTRAH which is characteristic of heat resistant individuals. A new regression line of ST (Y) as a function of the t42.0 (X) was obtained for most rats as follows: Y = 0.963X + 43.85 (male); and Y = 0.973X + 39.10 (female). This equation enabled to calculate ST without thermal death. However, the former approach based on t42.5 must be applied yet in small number of rats which showed the irregular BTRAHs with Tos or Teq higher than 42.0 degrees C. Delayed influence on survival and fecundity at a Ta of 24 degrees C were not found during one year following this hyperthermia up to 42.5 degrees C.

Long-term survival of grafted cells, dopamine synthesis/release, synaptic connections, and functional recovery after transplantation of fetal nigral cells in rats with unilateral 6-OHDA lesions in the nigrostriatal dopamine pathway

In animal models of hemi-Parkinson's disease, survival of grafted nigral cells, their synaptic connections, dopamine (DA) synthesis/release, and recovery from motor disturbances were investigated, and these were compared among 3 groups of animals raised for 3 months, 1 year and 2 years after the transplantation. Fetal nigral DAergic cell suspensions were transplanted in the ipsilateral caudate nucleus of rats with unilateral 6-OHDA lesions in the nigrostriatal DA pathway. Motor disturbances, assessed by methamphetamine-induced rotation, recovered partly in the 2nd week, significantly in the 4th week after the grafting, and remained stable thereafter. Many tyrosine hydroxylase (TH)-positive cells were detected along the grafting tracks. The number of TH-positive cells was similar in the 3 groups of animals. These TH-positive cells made synaptic connections in the host caudate. By in vivo microdialysis measurement, extracellular DA, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) around the grafted sites recovered to 30-100% of those of controls. No significant differences were observed in the concentration of DA, DOPAC and HVA among 3 groups of animals. They also responded to methamphetamine loading though the magnitudes were smaller. Using a TH cDNA probe, TH-positive cells were found to express TH mRNA in in situ hybridization-autoradiographic analysis. Data indicate that grafted fetal DAergic cells survive, synthesize and release DA, make synaptic connections in the host brain and ameliorate motor disturbances for over 2 years. There were no differences in these parameters among the 3 groups of animals, and no untoward side effects were observed even at 2 years after the grafting. Thus it was confirmed that the grafting of neuronal cells into the brain is a promising approach to restore disturbed function.

tGS ganglioside induces peculiar morphological features in grafted dopaminergic cells and promotes motor recovery in rats with unilateral lesions in the nigrostriatal dopamine pathway

A cell suspension of substantia nigra from fetal rats was introduced into the ipsilateral caudate nucleus of rats with unilateral lesions in the nigrostriatal dopamine pathway, and effects of bovine total ganglioside (tGS) and monosialoganglioside (GM1) treatment on the morphological features of the transplanted cells and recovery from motor imbalance (rotation induced by methamphetamine) were investigated. Gangliosides (30 mg/kg) were administered intraperitoneally once a day for 2 weeks after transplantation to test animals while control animals received saline alone. tGS animals showed definite motor recovery in the 2nd week (P less than 0.05) while control and GM1 animals exhibited slight recovery only. At 6 weeks after transplantation, motor imbalance disappeared in all 3 groups. Tyrosine hydroxylase (TH) immunocytochemical staining revealed that in the 2nd week TH-positive cells in tGS animals had more primary dendrites and more large neurites (meganeurites) than did controls. TH-positive cells of all 3 groups often had spiny processes at that time. In the 20th week, TH-positive cells became more multigonal and had wider dendritic fields in all groups, and had less meganeurites and spines. Motor recovery of each animal was dependent on the number of TH-positive cells and no significant difference was observed in the number of TH-positive cells among the three groups. tGS treatment for 2 weeks without grafting induced immunohistologically no axonal sprouting in the substantia nigra, medial forebrain bundle, accumbens and caudate nucleus when the chemical lesions were complete. Data suggest that tGS induces hypertrophy but not hyperplasia of the transplanted nigral cells, and increases the morphological plasticity. This might be the basis for promotion of recovery in motor function after transplantation.

Behavioral and biochemical effects of intra-accumbens dopaminergic grafts

6-Hydroxydopamine (6-OHDA) lesions in the ventral tegmental area (VTA) in rats prevented the hyperactivity response to methamphetamine in an open field. Transplantation of mesencephalic dopaminergic cells, obtained from rat embryos, into the nucleus accumbens (NAC) of 6-OHDA-lesioned animals restored the hyperactivity 4 weeks after grafting. By microdialysis of the NAC in freely moving rats no significant differences in baseline concentration of dopamine (DA) among the 3 groups (control, lesioned, grafted) were observed. However, after methamphetamine administration, DA increased significantly during the first 80 min in control animals, during the first 40 min in grafted animals, but did not increase in lesioned animals. On the other hand baseline concentrations of dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) decreased to one sixth to one third of those of controls in 6-OHDA-lesioned animals, and they did not respond to methamphetamine. After grafting, however, DOPAC and HVA restored to control levels and responded to methamphetamine with decreases as was observed in control animals. Data suggest that grafts not only restore the ability to release DA but also improve DA metabolism in the NAC. This might be a reason for recovery of locomotor activity.

Phenotypic plasticity of grafted catecholaminergic cells in the dopamine-depleted caudate nucleus in the rat

Catecholamine-producing cells were grafted in the caudate nucleus of model rats with hemi-Parkinson's disease--animals with unilateral 6-hydroxydopamine (6-OHDA) lesions in the nigrostriatal dopaminergic pathway. Survival of the grafted cells, dopamine synthesis/release, and recovery from motor imbalance were investigated. Motor imbalance (methamphetamine rotations) recovered in more than 90% of animals by grafting of nigral dopaminergic (DAergic) cells, in 40-60% of animals by grafting of locus coeruleus noradrenergic (LC-NAergic) cells, and in 0-30% of animals by grafting of adrenal medullary cells. Many tyrosine hydroxylase (TH)-positive cells survived in the host caudate after grafting of DAergic cells. A moderate number of TH-positive but dopamine-beta-hydroxylase (DBH)-negative cells survived after grafting of NAergic cells. A few TH-positive neuron-like cells survived after grafting of adrenal medullary cells. In vivo microdialysis revealed that extracellular DA recovered up to 50-80% of that of control level, and dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) up to 25-50% of those of controls in animals that showed motor recovery after grafting. Using a TH cDNA probe, TH-positive cells were found to express TH mRNA in an in-situ hybridization-autoradiographic study. Animals that received 6-OHDA lesion only or animals that received grafting but had no surviving cells showed neither behavioral nor chemical recovery. The data suggest that grafted catecholaminergic cells survive, make phenotypic plasticity, synthesize/release dopamine, and ameliorate motor function.