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A R Schonfeld

Publications and source records attributed to A R Schonfeld.

13 recordsLinked to original sources
PubMed1986

Hippocampal neurotrophic factor: characterization and response to denervation.

The rat hippocampus contains an acidic macromolecular neurotrophic factor (NTF) which supports the survival of cultured chick ciliary ganglion cells. Hippocampal NTF increases approximately 2-fold from birth to adulthood with no further change with aging. Disruption of extrinsic inputs to the hippocampus from the entorhinal cortex, locus coeruleus or contralateral hippocampus, but not from the septum, results in an increase in the concentration of NTF in the hippocampus. Destruction of intrinsic hippocampal neurons by kainic acid treatment is accompanied by a large increase in hippocampal NTF, a result consistent with a glial origin for the factor. This conclusion is supported by the finding that a lesion-induced rise in NTF can be suppressed by administration of methotrexate, an inhibitor of gliosis.

Adrenergic Fibers↗
PubMed1985

Neuronotrophic factors: effects on central cholinergic regeneration in vivo.

To determine if neurotrophic factors (NTFs) which either support the survival (CNTF) or promote neuritic outgrowth (PNPF) of peripheral cholinergic neurons in vitro affect central cholinergic regeneration in vivo, NTFs were administered intracerebrally to rats after injury to septohippocampal fibers. Choline acetyltransferase activity within intrahippocampal iris implants was used as an index of cholinergic innervation. CNTF stimulated cholinergic sprouting while PNPF was ineffective under our experimental conditions, suggesting that the effects of other NTFs in vivo may be mediated by enhanced neuronal survival after injury rather than increased axonal sprouting.

Animals↗
PubMed1984

Enhancement of central cholinergic sprouting by prior injury: correlation with endogenous trophic content of hippocampus.

Injury to neural tissue elicits the release of neurotrophic substances which support the survival of cultured cholinergic neurons. The aim of the present report was to determine the effect of prior hippocampal injury on the sprouting of mature intrinsic cholinergic septal afferents in vivo. Levels of choline acetyltransferase (CAT) in intrahippocampal iris implants were used as an index of cholinergic regeneration. The results show that prelesioning the hippocampus 1 week prior to insertion of the iris increased CAT levels of implants left for 8 days in situ. Levels of iris CAT were correlated with the trophic content of the surrounding hippocampal tissue. These observations suggest that endogenous trophic factors released as a consequence of neural injury facilitate cholinergic sprouting in vivo.

Animals↗
PubMed1984

Iopamidol and Conray 60: comparison in superselective angiography.

Iopamidol (280 mgI/ml) was compared with Conray 60 (iothalmate meglumine, 282 mgI/ml) during selective and superselective cerebral arteriography. Twelve patients were examined, and a total of 51 selective injections were compared. Iopamidol produced significantly less pain and burning than Conray 60 and caused no patient motion.

Adult↗
PubMed1983

Heart conditioned medium elicits post-lesion muscarinic receptor recovery in vivo.

Intraseptal administration of heart conditioned medium (HCM) stimulates the growth of injured cholinergic fibers into iris implants placed in the anterodorsal hippocampus. The aims of the present report were to monitor muscarinic cholinergic receptor concentrations during denervation and central innervation of the peripheral tissue targets, and to evaluate the effect of HCM on these changes. For 0, 4, 8, 16 and 28 days after mechanical injury to septohippocampal axons, animals received either intraseptal injections of HCM or control vehicle. Binding of [3H]quinuclidinylbenzilate ([3H]QNB) within iris implants was used as an index of cholinergic muscarinic receptor concentration. The results indicate that within the iris implants: (1) a dramatic drop in the number of muscarinic receptors is observed 4 days after denervation; (2) under control conditions, central cholinergic innervation is not associated with muscarinic receptor recovery; and (3) after administration of HCM, muscarinic receptor levels begin to increase within two weeks and approach the pre-lesion endogenous concentration following 28 days of treatment. These results support the hypothesis that trophic factors may facilitate the restoration of effective, appropriate connections between nerve fibers and their targets.

Animals↗
PubMed1982

An electron microscope autoradiographic study of regenerating locus coeruleus fibers into iris tissue implants in the rat mesencephalon.

Following interruption, fibers from the locus coeruleus have been shown to undergo axonal regeneration and invade peripheral tissue implants in the rat brain. The aim of the present study was to analyze the ultrastructural features of this phenomenon using electron microscope autoradiography. For this, iris tissue implants were inserted in the region of the dorsal tegmental bundle (DTB) in the mesencephalon of unilaterally sympathectomized rats. Approximately 2 weeks later, rats were injected with [3H]-leucine in the ipsilateral locus coeruleus and sacrificed 2 days later. The tissue was prepared for EM autoradiography and studied after an incubation period of at least 12 weeks. The results showed that regenerating fibers from the locus coeruleus were most dense in regions of implant proximal to the DTB. Within the implants, less than one-half of regenerating axons present were labeled and, hence, of locus coeruleus origin. The labeled fibers were characteristically thin and unmyelinated. At this relatively short survival time, there was no evidence that the regenerating locus coeruleus axons formed synaptic specializations or contacts with the surrounding iris neuropil. Thus, while these observations confirm previous reports describing the regenerative capacity of central monoaminergic axons, they fail to provide anatomical evidence of the establishment of functional interactions between incoming fibers and the target tissue.

Afferent Pathways↗
PubMed1981

Heart conditioned medium promotes central cholinergic regeneration in vivo.

The aim of the present study was to evaluate the effect of a proposed cholinergic growth factor, heart conditioned medium (HCM), on the regeneration of the cholinergic septo-hippocampal pathway in rats. At 0, 4, 8 and 16 days after mechanical injury to septo-hippocampal axons, animals received either repeated intraseptal injections of HCM or control vehicles. Recovery of choline acetyltransferase (CAT) activity in iris implants placed in the hippocampus was used as an index of cholinergic regeneration. The results indicate that CAT activity in iris implants from animals receiving HCM was significantly greater than in control implants. Thus, this is the first report of the in vivo activity of heart conditioned medium as a cholinergic growth factor.

Animals↗
PubMed1981

Handling-induced seizures and rotational behavior in th Mongolian gerbil.

The aim of this report was to examine the relationship between sensory-induced seizures, cerebral laterality (as measured by rotation) and nigrostriatal asymmetry in Mongolian gerbils. Seizure resistant gerbils made proportionally more spontaneous turns to be preferred direction than sensitive animals. Three prototypical antiepileptic drugs strongly elicited rotational behavior (carbamazepine (10-20 mg/kg), diazepam (16 mg/kg) and pentobarbital (40 mg/kg)) and two others (phenobarbital 20-40 mg/kg) and ethosuximide (500 mg/kg)) also appeared to potentiate rotation; only diphenylhydantoin and trimethadione were effective. Two dopaminergic agonists, amphetamine (4 mg/kg) and apomorphine (16 mg/kg) enhanced rotation at anticonvulsant doses while the dopaminergic antagonist haloperidol reduced rotational behavior at a dose (1 mg/kg) which exacerbate seizure severity. Finally, surgical induction of nigrostriatal asymmetry by means of unilateral electrolytic striatal lesions reduced seizure severity; sham and bilateral striatal lesions had no significant effects on seizures. These results suggest that seizure activity and rotational behavior are inversely related and, furthermore, that the link between these two behaviors may be the asymmetry between nigrostriatal dopaminergic systems.

Amphetamine↗
PubMed1980

Autoradiographic demonstration of the central origin of regenerating fibers into iris tissue implants in the rat mesencephalon.

One model useful for demonstrating axonal regeneration in the central nervous system is that in which peripheral tissue, particularly the iris, is implanted into the brain or spinal cord. The aim of the present study was to establish the origin of some of the regenerating fibers by the use of an autoradiograhic tracing technique. Briefly, iris implants were inserted in the caudal mesencephalon in the region of the dorsal tegmental bundle in unilaterally sympathectomized rats. Approximately two weeks later, subjects were injected with [3H]leucine in the region of the ipsilateral locus coeruleus and sacrificed two days later. Numerous labeled fibers were observed within the implants and traversing between brain and implant. Fibers formed loose plexuses, coursed along smooth muscle and grew toward blood vessels within the implants. These results may be added to fluorescent histochemical, biochemical and ultrastructural evidence supporting the regenerative capacity of central noradrenergic fibers.

Animals↗