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R J Mandel

Publications and source records attributed to R J Mandel.

At least 37 records · Page 2Linked to original sources
PubMed1998

Self-inactivating lentivirus vector for safe and efficient in vivo gene delivery.

In vivo transduction of nondividing cells by human immunodeficiency virus type 1 (HIV-1)-based vectors results in transgene expression that is stable over several months. However, the use of HIV-1 vectors raises concerns about their safety. Here we describe a self-inactivating HIV-1 vector with a 400-nucleotide deletion in the 3' long terminal repeat (LTR). The deletion, which includes the TATA box, abolished the LTR promoter activity but did not affect vector titers or transgene expression in vitro. The self-inactivating vector transduced neurons in vivo as efficiently as a vector with full-length LTRs. The inactivation design achieved in this work improves significantly the biosafety of HIV-derived vectors, as it reduces the likelihood that replication-competent retroviruses will originate in the vector producer and target cells, and hampers recombination with wild-type HIV in an infected host. Moreover, it improves the potential performance of the vector by removing LTR sequences previously associated with transcriptional interference and suppression in vivo and by allowing the construction of more-stringent tissue-specific or regulatable vectors.

3T3 Cells↗
PubMed1997

Midbrain injection of recombinant adeno-associated virus encoding rat glial cell line-derived neurotrophic factor protects nigral neurons in a progressive 6-hydroxydopamine-induced degeneration model of Parkinson's disease in rats.

A recombinant adeno-associated virus (rAAV) vector capable of infecting cells and expressing rat glial cell line-derived neurotrophic factor (rGDNF), a putative central nervous system dopaminergic survival factor, under the control of a potent cytomegalovirus (CMV) immediate/early promoter (AAV-MD-rGDNF) was constructed. Two experiments were performed to evaluate the time course of expression of rAAV-mediated GDNF protein expression and to test the vector in an animal model of Parkinson's disease. To evaluate the ability of rAAV-rGDNF to protect nigral dopaminergic neurons in the progressive Sauer and Oertel 6-hydroxydopamine (6-OHDA) lesion model, rats received perinigral injections of either rAAV-rGDNF virus or rAAV-lacZ control virus 3 weeks prior to a striatal 6-OHDA lesion and were sacrificed 4 weeks after 6-OHDA. Cell counts of back-labeled fluorogold-positive neurons in the substantia nigra revealed that rAAV-MD-rGDNF protected a significant number of cells when compared with cell counts of rAAV-CMV-lacZ-injected rats (94% vs. 51%, respectively). In close agreement, 85% of tyrosine hydroxylase-positive cells remained in the nigral rAAV-MD-rGDNF group vs. only 49% in the lacZ group. A separate group of rats were given identical perinigral virus injections and were sacrificed at 3 and 10 weeks after surgery. Nigral GDNF protein expression remained relatively stable over the 10 weeks investigated. These data indicate that the use of rAAV, a noncytopathic viral vector, can promote delivery of functional levels of GDNF in a degenerative model of Parkinson's disease.

Animals↗
PubMed1997

Practical aspects of the development of ex vivo and in vivo gene therapy for Parkinson's disease.

Current approaches to gene therapy of CNS disorders include grafting genetically modified autologous cells or introducing genetic material into cells in situ using a variety of viral or synthetic vectors to produce and deliver therapeutic substances to specific sites within the brain. Here we discuss issues related to the application of ex-vivo and in-vivo gene therapies as possible treatments for Parkinson's disease. Autologous monkey fibroblasts engineered ex-vivo to express tyrosine hydroxylase were grafted into MPTP-treated monkeys and found to express for up to 4 months. Adeno-associated (AAV) viral vectors expressing beta-galactosidase or tyrosine hydroxylase were introduced into monkey brains to determine the extent of infection and the types of cells infected by the vector at 21 days and 3 months. Gene expression was detected at both time points and was restricted to neurons in the striatum. These experiments demonstrate that two different approaches can be used to deliver proteins into the CNS. However, further technological advances are required to optimize gene delivery, regulation of gene expression, and testing in appropriate functional models before gene therapy can be considered for treating human disease.

Animals↗
PubMed1997

Multiply attenuated lentiviral vector achieves efficient gene delivery in vivo.

Retroviral vectors derived from lentiviruses such as HIV-1 are promising tools for human gene therapy because they mediate the in vivo delivery and long-term expression of transgenes in nondividing tissues. We describe an HIV vector system in which the virulence genes env, vif, vpr, vpu, and nef have been deleted. This multiply attenuated vector conserved the ability to transduce growth-arrested cells and monocyte-derived macrophages in culture, and could efficiently deliver genes in vivo into adult neurons. These data demonstrate the potential of lentiviral vectors in human gene therapy.

Animals↗
PubMed1995

Amphetamine sensitivity in open-field activity vs. the prepulse inhibition paradigm.

Amphetamine-induced mesolimbic dopamine release has been reported to reduce prepulse inhibition of the acoustic startle response. In addition, it is well known that mesolimbic dopamine stimulation leads to hyperactivity. The present study was undertaken to explore the possibility that one or the other measure may be a more sensitive in vivo indicator of dopamine release in the nucleus accumbens by determining if the amphetamine dose-response curves for these two behavioral measures were different. The data indicate that the dose-response curves obtained for the different behavioral measures are identical. These data are consistent with the idea that the same dopamine terminal field supports both prepulse inhibiton of the acoustic startle response and dopamine-stimulated hyperactivity.

Acoustic Stimulation↗
PubMed1994

Amphetamine induces excess release of striatal acetylcholine in vivo that is independent of nigrostriatal dopamine.

The effect of amphetamine on striatal acetylcholine (ACh) release was studied by an in vivo intrastriatal microdialysis technique. Although we expected systemic amphetamine to inhibit baseline striatal ACh release, the opposite was found. In addition, we found that the amphetamine-induced striatal ACh release did not depend on nigrostriatal DA since 6-hydroxydopamine (6-OHDA) lesions had no effect on amphetamine-induced ACh release. Local intrastriatal injection of amphetamine via the microdialysis probe had no effect on striatal ACh release even when the probe was located more laterally in striatum to take advantage of the medial to lateral gradient of striatal ACh and D2 receptors. The hypothesis that amphetamine increased extracellular striatal ACh by increasing the release of biogenic amines besides dopamine was tested by pharmacological manipulations designed to specifically increase local striatal norepinephrine or serotonin levels. The serotonergic and noradrenergic manipulations had no effect on striatal ACh levels. These results indicate that amphetamine-induced release of ACh in striatum is mediated via distal brain regions that are functionally connected with the striatum.

Acetylcholine↗
PubMed1993

A quantitative estimate of the role of striatal D-2 receptor proliferation in dopaminergic behavioral supersensitivity: the contribution of mesolimbic dopamine to the magnitude of 6-OHDA lesion-induced agonist sensitivity in the rat.

Rats with unilateral depletions of neostriatal dopamine display increased sensitivity to dopamine agonists estimated to be 30 to 100 x in the 6-hydroxydopamine (6-OHDA) rotational model. Given that mild striatal dopamine D-2 receptor proliferation occurs (20-40%), it is difficult to explain the extent of behavioral supersensitivity by a simple increase in receptor density. This study was designed to investigate the quantitative aspects of the rotational behavior model utilizing constrained non-linear curve fitting routines. A dose-response curve for the rotational response arising from apomorphine stimulation of the normosensitive striatum was obtained in animals bearing unilateral lesions of striatal efferents (predominantly the striato-nigral pathway as previously described). After the control dose-response experiment, rats received a dopamine- (DA) depleting lesion in the contralateral hemisphere. In one group, 6-OHDA was infused into the medial forebrain bundle (MFB), a placement which is common in the literature and is known to deplete DA in both the striatum and nucleus accumbens. In a second group of rats, 6-OHDA was infused into the globus pallidus at a site which depletes caudate DA, but leaves n. accumbens DA relatively intact. The two experimental groups were tested in identical apomorphine-induced rotation dose-response experiments. The ED50's of the MFB- and caudate-lesioned rats were reduced by 36 and 5.8 fold, respectively, as compared to the control dose-response curve. The MFB and caudate lesions depleted striatal DA and produced a 30 and 36% increase in striatal D-2 binding sites, respectively. Modeling the behavioral and biochemical data with the null model for receptor occlusion indicated that increased striatal D-2 receptor density could account for the magnitude of behavioral supersensitivity in neither the MFB-lesioned group, nor even in the caudate-lesioned group. Thus simple up-regulation or D-2 receptors is unlikely to account for supersensitization as measured in the rotational model. Further, we suggest that quantitative modeling of such hypotheses is a valuable experimental technique for assessing relationships between biochemical and behavioral variables.

Animals↗
PubMed1993

Characterization of GABA release from intrastriatal striatal transplants: dependence on host-derived afferents.

Extracellular levels of GABA, derived from cell suspension transplants of embryonic day 14-15 rat striatal primordia implanted into the previously excitotoxically lesioned striatum, were measured using intracerebral microdialysis in halothane-anaesthetized rats. GABA overflow was monitored using loop type dialysis probes implanted into grafted, age-matched ibotenic acid-lesioned and intact striata, under baseline conditions and after different pharmacological manipulations. Basal and evoked GABA release, which was reduced by 58 and 96%, respectively, in the excitotoxin-lesioned striatum, was restored by the striatal grafts to levels close to or above those observed in normal striata. The graft-derived release of GABA was most likely of neuronal origin, since the K(+)-evoked (100 mM) GABA overflow was reduced by almost 80% when Ca++ was replaced by 20 mM Mg++ in the perfusion medium, and blockade of GABA uptake by nipecotic acid (0.5 mM), induced a greater than six-fold increase in GABA overflow. However, perfusion of the graft with 1 microM tetrodotoxin in combination with K+ (100 mM) resulted in little if any reduction in the K(+)-evoked overflow. Histological analysis demonstrated a dense tyrosine hydroxylase-positive fibre network in the grafts, which was removed after a 6-hydroxydopamine lesion of the ipsilateral nigrostriatal pathway. The dopamine denervating lesion resulted in an increased K(+)-evoked GABA overflow both in the intact (+76%) and the grafted striata (+181%), suggesting that the tonic dopaminergic inhibitory control of GABA release, seen in the intact striatum, is also present in the grafted striata. The glutamate analogue, kainic acid (1 mM added to the perfusion fluid), evoked a 60-74% increase in GABA overflow both in intact striata (with or without dopaminergic denervation) and in the striatal grafts. This effect seemed to be dependent on an intact corticostriatal projection, since knife-cut transections of the frontal cortex at the level of the forceps minor, abolished the response in both the intact and grafted striata. These results demonstrate that grafts of fetal striatal tissue implanted into the excitotoxically lesioned striatum restore striatal GABA overflow in a neuron-dependent manner, close to or above that seen in the normal intact striatum. Furthermore, the graft-derived GABA release appears to be under normal regulatory control from the host dopaminergic and glutamatergic systems. Since the GABAergic striatal output system is critical for the expression of striatum-related behaviours, it is proposed that the graft-induced behavioural recovery in the striatal lesion model, at least in part, may depend on the restoration of striatal GABAergic neurotransmission.

Animals↗
PubMed1992

Fos expression in intrastriatal striatal grafts: regulation by host dopaminergic afferents.

Previous studies have shown that transplants of fetal striatum, implanted into the ibotenic acid-lesioned striatum of adult rats, become innervated from the host nigrostriatal dopamine (DA) pathway. In the present study we have used DA-receptor-mediated expression of the Fos protein (i.e. the product of the immediate-early c-fos gene) as a cellular marker for functional dopaminergic host-graft interactions in the striatal grafts. Amphetamine (5 mg/kg; 2 h) induced Fos-like immunoreactivity in clusters of cells located mainly within the DARPP-32-positive areas within the transplants, i.e. within the striatum-like graft compartment which is preferentially innervated by the host DA afferents. As in the normal striatum, this effect was largely, although not completely, abolished by a 6-hydroxydopamine lesion of the ipsilateral nigrostriatal DA pathway. Apomorphine (0.25 mg/kg; 2 h) had no detectable effect in grafts with an intact host DA system. Two to 3 weeks after a 6-OHDA lesion of the host DA pathway (i.e. a time sufficient for DA receptor supersensitivity to develop), apomorphine-induced extensive Fos-activation selectively within the DARPP-32-positive areas of the graft. The magnitude of the response was similar to that seen in the DA-denervated host striatum. Dual Fos/DARPP-32 immunostaining revealed that the activated graft neurons were, at least in part, DARPP-32-positive. In intrastriatal grafts of fetal neocortical tissue, which were studied for comparison, the amphetamine- and apomorphine-induced effects on Fos expression were much smaller and similar to that seen in the DARPP-32-negative, non-striatal compartment within the striatal grafts.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1992

Diencephalic lesions, learning impairments, and intact retrograde memory following acute thiamine deficiency in the rat.

Previous studies have shown that following an acute bout of pyrithiamine-induced thiamine deficiency (PTD) rats are impaired in learning appetitively and aversively motivated T-maze tasks. The present study examined if PTD-treated rats exhibit both anterograde and retrograde memory loss of an aversively motivated spatial navigation task. Histological examination revealed two consistent lesions in the PTD treated rats: a bilateral, symmetrical destruction of medial thalamus centered on the internal medullary lamina (IML), and a lesion of the medial nucleus of the mammillary body. In Experiment 1, control and recovered PTD rats were trained to find a hidden platform in a Morris water maze. PTD rats with the IML lesion were impaired in learning the water maze task but were eventually able to perform as well as controls and PTD animals without the IML lesion. In Experiment 2, half of the pretrained CT animals underwent thiamine deficiency (PTD2), were recovered, and subsequently were tested for retention of the platform location. The remaining CT animals and the PTD1 group were also tested for retention. No significant group differences were observed on any of the four postretention trials. When compared to their performance on the last four preretention trials, the performance of PTD1 and PTD2 animals with IML lesions were similar to those of the controls. These results demonstrate that acute thiamine deficiency in rats produces damage of medial thalamic and mammillary body nuclei, a mild anterograde learning deficit, but no loss of retrograde memory of the Morris water maze task.

Animals↗
PubMed1992

Regional differences in the regulation of dopamine and noradrenaline release in medial frontal cortex, nucleus accumbens and caudate-putamen: a microdialysis study in the rat.

Dopamine (DA) and noradrenaline (NA) extracellular levels have been measured by microdialysis in the medial frontal cortex (MFC), nucleus accumbens (NAc) and caudate-putamen (CP) under baseline conditions in awake and halothane-anaesthetized rats, and after application of three types of stimuli which are likely to activate the brainstem catecholaminergic systems: mild stressors (handling and tail pinch), rewarded behavior (eating palatable food without prior food deprivation) and electrical stimulation of the lateral habenular nucleus. Changes were studied with and without uptake blockade (10 microM nomifensine in the perfusion fluid). The influence of calcium concentration (1.2 or 2.3 mM in the perfusion fluid) on DA and NA overflow was tested in some cases. Handling and tail pinch stimulated both DA and NA overflow in MFC, and enhanced NA overflow in NAc. By contrast, these mildly stressful stimuli had only marginal effects on DA overflow in NAc and no effects on either DA or NA overflow in CP. Eating behavior was accompanied by increased DA and NA overflow in MFC but had no effect in NAc. These regional differences were similar also when the manipulations were applied under uptake blockade, which indicates that the more pronounced changes seen in MFC did not simply reflect a more sparse innervation (i.e. lower density of uptake sites) in the MFC compared to the more densely innervated NAc and CP areas. Stimulation of the lateral habenula induced a 2-3-fold increase in NA overflow in both MFC, NAc and CP but had no consistent effect on DA overflow in any region. The effect on NA release was abolished by a transection of the ipsilateral fasciculus retroflexus (which carries the efferent output of the lateral habenula). The results show that the forebrain DA and NA projections to cortical and striatal targets are differentially regulated during ongoing behavior, that the mesocortical and mesostriatal DA systems respond quite differently to stressful and rewarding stimuli; and that the NA projection to MFC (like the dopaminergic one) is more responsive to stressful and rewarding stimuli than the ones innervating the striatum (NAc and CP). The results support the view that environmental stimuli evoking emotional arousal (whether aversive or non-aversive) are accompanied by increased DA and NA release above all in the MFC and only to a minor extent in limbic and striatal areas.

Animals↗
PubMed1992

Behavioral quantification of striatal dopaminergic supersensitivity after bilateral 6-hydroxydopamine lesions in the mouse.

Quantitative studies using dopamine (DA) agonist-induced rotational behavior after denervation have found that the behavioral sensitivity is much greater than would be predicted on the basis of striatal DA receptor upregulation alone. The sensitivity to DA agonists after chronic treatment with neuroleptics, which elicits striatal receptor alterations equal to denervation, displays increases more consistent with alterations in striatal receptor density. Since the behavioral paradigms used to assess agonist supersensitivity after denervation are different than that for chronic neuroleptic treatment (rotational vs. stereotypic behavior), we measured the behavioral supersensitivity after bilateral denervation using stereotypic behavior. The increase in sensitivity to apomorphine after bilateral nigrostriatal 6-hydroxydopamine lesions was consistent with the increases measured previously with rotational behavior. These data suggest that the quantitative difference observed in behavioral supersensitivity resulting from the different preparations lies with the biological consequences of denervation rather than with the behavioral paradigm.

Animals↗
PubMed1992

Dopaminergic transplants normalize amphetamine- and apomorphine-induced Fos expression in the 6-hydroxydopamine-lesioned striatum.

Dopamine receptor-mediated Fos protein expression in the striatum has been used to monitor dopamine receptor activation at the cellular level after dopaminergic denervation and reinnervation by fetal nigral transplants. The pattern of striatal Fos expression after systemic administration of either the dopamine receptor agonist, apomorphine, or the dopamine-releasing agent, amphetamine, was studied in rats which had received cell suspension grafts of fetal ventral mesencephalic neurons into the striatum after a complete 6-hydroxydopamine lesion of mesostriatal dopaminergic projection. Grafted animals, and normal and lesioned controls were killed 2 h after administration of either D-amphetamine (5 mg/kg, i.p.) or apomorphine (0.25 mg/kg, s.c.). Fos protein was detected immunohistochemically, and the density of Fos-immunoreactive cell nuclei was measured in 12 selected areas of caudate-putamen, nucleus accumbens and globus pallidus by computerized image analysis. Consistent with previous studies, amphetamine induced high Fos expression in the medial and dorsal parts of the intact caudate-putamen and significantly lower expression in the denervated caudate-putamen. A significant difference between lesioned and intact striata was present also in globus pallidus, but not in nucleus accumbens. In grafted rats, amphetamine-induced Fos activation was restored to normal or supranormal levels in the anterior and central caudate-putamen (i.e. close to the graft deposits), whereas in the tail of caudate-putamen Fos expression was significantly lower than normal. The side-to-side difference in globus pallidus seen in lesioned rats was no longer present in the grafted animals. Apomorphine led to high Fos activation throughout the dopamine-depleted caudate-putamen, whereas only very few immunopositive cells were observed in the intact caudate-putamen. Also in globus pallidus and nucleus accumbens, a significantly higher number of Fos-immunoreactive cells was detected on the denervated side. In the grafted rats, apomorphine-induced Fos activation was similar to normal in all striatal areas sampled, as well as in the globus pallidus. The graft-induced effect extended over a considerably larger area than that covered by the graft-derived tyrosine hydroxylase-immunoreactive innervation. These findings indicate that fetal ventral mesencephalic transplants normalize dopamine receptor-mediated function in the 6-hydroxydopamine-lesioned caudate-putamen and nucleus accumbens, as well as in a primary target of the striatal output neurons, the globus pallidus. The results support the idea that dopamine released from the grafted neurons, both under baseline conditions and after amphetamine administration, exerts functional effects over a larger volume of the striatum than that reached by the graft-derived fibers.

Animals↗
PubMed1992

Independent effects of age and nucleus basalis magnocellularis lesion: maze learning, cortical neurochemistry, and morphometry.

The effects of age and lesion of the cholinergic nucleus basalis magnocellularis (NBm) were assessed behaviorally, morphologically, and biochemically. Groups consisted of rats lesioned 1 month before testing, rats lesioned 13 months before testing, and their respective age-matched controls. Both age and lesion independently induced behavioral deficits in performance on two water maze tasks. The combined effect of these two factors produced behavioral deficits equal to the sum of the individual impairments. NBm lesion produced a 28% decrease in anterior cortical choline acetyltransferase activity and a 20% decrease in synaptophysin immunoreactivity in the neocortex that was stable over a 12-month period. Neither neuritic plaque nor neurofibrillary-tanglelike structures were found in the brains of 18-month-old control rats, nor were they found in NBm-lesioned rats examined 15 months postlesion. There was an age-related decrease in homovanillic acid levels in both control and NBm groups, which suggests a decrease in dopamine turnover. These results show a lack of biochemical and behavioral recovery after NBm lesion and suggest that the effects of age on behavior are independent of NBm-cortical dysfunction.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1990

Nucleus basalis lesions fail to induce senile plaques in the rat.

Fourteen months after receiving bilateral ibotenic acid lesions of the nucleus basalis magnocellaris (NBM), male rats demonstrated impairment in spatial learning in a water maze task, increased incidence of high voltage spindles, and significant depletion of cortical choline acetyltransferase (ChAT) activity. Histological evaluation revealed decreased acetylcholinesterase (AChE) staining but no plaque-like structures in the cortex.

Acetylcholinesterase↗
PubMed1990

Behavioral demonstration of a reciprocal interaction between dopamine receptor subtypes in the mouse striatum: possible involvement of the striato-nigral pathway.

It is well known that stimulation of the D-2 dopamine receptor in vitro inhibits the increased efflux of cyclic adenosine monophosphate caused by D-1 receptor agonists. Furthermore, behavioral data suggest that the striato-nigral pathway is more involved with the dopamine agonist-induced expression of oral behaviors, which are, in turn, mediated by stimulation of the D-1 receptor. We examined an in vivo model to determine whether this D-1/D-2 reciprocal interaction is detectable at a behavioral level. First, mice were pretreated with wide range of doses of the D-2 antagonist, spiperone, and then injected with a behaviorally active dose of apomorphine (a nonspecific direct dopamine agonist) and were observed for incidence of oral behavior and rated for stereotypic behavior. A biphasic effect of spiperone pretreatment was observed, at some low doses both stereotypy and oral behavior were enhanced, while at high doses, both agonist-induced behaviors were progressively inhibited. To test the specificity of this effect for the striato-nigral pathway, mice were administered discrete electrolytic lesions in the ventral portion of the internal capsule in one hemisphere. The animals that responded to apomorphine by rotating ipsilaterally to the lesion were used in two, five-point apomorphine dose-response curves, one with, and one without, pretreatment with the dose of spiperone which most enhanced stereotypic behavior and incidence of oral behavior. The spiperone pretreatment caused a clear increase in the maximum rotational response to apomorphine without affecting the ED50. These data suggest that behavior associated with the striato-nigral efferent from striatum is marked by the opposition of D-1 and D-2 receptors.

Animals↗