Biomedical subjects

F S Silverstein

Publications and source records attributed to F S Silverstein.

At least 37 records · Page 2Linked to original sources

PubMed1996

Adenovirus-mediated over-expression of interleukin-1 receptor antagonist reduces susceptibility to excitotoxic brain injury in perinatal rats.

In seven-day-old rats, intracerebral injection of N-methyl-D-aspartate transiently stimulates expression of Interleukin-1 beta messenger RNA. To evaluate the role of Interleukin-1 beta in the pathogenesis of excitotoxic injury, we sought to determine if Interleukin-1 receptor antagonist, an endogenous competitive inhibitor of Interleukin-1 beta, could attenuate N-methyl-D-aspartate-induced injury. To induce sustained over-expression of Interleukin-1 receptor antagonist in the brain, a recombinant adenovirus encoding Interleukin-1 receptor antagonist was administered by intracerebroventricular injection into three-day-old rats. Increased brain concentrations of Interleukin-1 receptor antagonist two to six days later were documented by assays of tissue homogenates and by immunocytochemistry. To evaluate the impact of Interleukin-1 receptor antagonist on N-methyl-D-aspartate neurotoxicity, three-day-old animals received intracerebroventricular injections of either adenovirus encoding Interleukin-1 receptor antagonist or a control adenovirus encoding beta-galactosidase, followed four days later by right intrastriatal injections of N-methyl-D-aspartate (10 nmol/0.5 microliter), a dose that typically elicits excitotoxic injury in the ipsilateral striatum and adjacent hippocampus, or saline. Animals were killed five days later, and brain damage was quantitated by measurement of bilateral cross-sectional areas of the striatum and anterior hippocampus. In three independent experiments, in N-methyl-D-aspartate-lesioned animals, both striatal and hippocampal injuries were reduced in animals that had been infected with adenovirus that encoded Interleukin-1 receptor antagonist, in comparison with littermates infected with the control adenovirus (right striatal volume loss ranged from 16 to 24%, compared with 54-65% volume loss in control). There was no striatal atrophy in adenovirus-infected saline-injected animals. These results provide strong support for the hypothesis that Interleukin-1 beta is a mediator of excitotoxic brain injury in perinatal rats.

Adenoviruses, Human↗

PubMed1996

Intracerebral NMDA injection stimulates production of interleukin-1 beta in perinatal rat brain.

Susceptibility to NMDA neurotoxicity peaks in the early postnatal period in rats. Although indirect evidence suggests that interleukin-1 beta is a mediator of NMDA neurotoxicity in perinatal rats, direct confirmation of NMDA-induced interleukin-1 beta production in the brain has not been reported previously. The primary goal of this study was to determine if intracerebral injection of a neurotoxic dose of NMDA stimulates interleukin-1 beta production acutely. We used a rat-specific interleukin-1 beta ELISA to quantify brain tissue homogenate interleukin-1 beta content, and an immunocytochemical assay with a monoclonal antirat interleukin-1 beta antibody to visualize its distribution. NMDA (10 nmol) was injected stereotaxically into 7-day-old rats, using coordinates that targeted the striatum and overlying dorsal hippocampus. Interleukin-1 beta concentrations were measured in samples from the injected and contralateral cerebral hemispheres 0-12 h later; In addition, the impact of treatment with the noncompetitive NMDA antagonist MK-801 on interleukin-1 beta production was assessed. We found marked increases in tissue content of interleukin-1 beta in the lesioned hemisphere; values peaked at 6 h post injection. Treatment with MK-801 (1 mg/kg) blocked NMDA-induced increases in interleukin-1 beta. Preliminary immunocytochemical analysis demonstrated high concentrations of interleukin-1 beta-immunoreactive cells in the lesioned hippocampus, and concurrent increases in interleukin-1 beta immunoreactivity diffusely in the ependyma at 6 h after NMDA administration. Our data provide the first direct evidence that NMDA-induced excitotoxic injury stimulates interleukin-1 beta production in vivo.

Animals↗

PubMed1996

Hypoxic-ischemic injury acutely disrupts microtubule-associated protein 2 immunostaining in neonatal rat brain.

We evaluated the influence of an acute hypoxic-ischemic insult on the neuronal dendritic cytoskeletal protein microtubule-associated protein 2 (MAP2) in the immature rat brain. Studies were performed using a well-characterized perinatal rodent stroke model, in which unilateral ischemic forebrain injury was induced in 7-day-old rats by right carotid artery ligation, followed by 3 h exposure to 8% oxygen. Changes in the neuroanatomic distribution of MAP2 in the first 48 h after injury were evaluated by immunocytochemistry with a monoclonal mouse anti-MAP2 antibody. The distribution of MAP2 immunoreactivity was markedly disrupted in the lesioned hippocampus; prominent reductions in MAP2 immunostaining evolved concurrently in lesioned cortex, caudate and thalamus. These data demonstrate that at this developmental stage, MAP2 immunocytochemistry provides a sensitive indicator of the distribution and severity of hypoxic-ischemic neuronal injury.

Animals↗

PubMed1996

Hypoxic-ischemic brain injury induces an acute microglial reaction in perinatal rats.

Activated microglia may contribute to the progression of neuronal injury after a wide range of CNS insults. In this study, we used two complementary methods to evaluate acute changes in the morphology and regional distribution of microglia induced by a focal hypoxic-ischemic insult in 7-d-old (P7) rats. To elicit injury, P7 rats underwent right carotid ligation followed by 3 h of 8% O2 exposure; rats were killed 10 min to 5 d later (n > or = 3/group). A histochemical assay using Griffonia simplicifolia B4-isolectin enabled detection of both resting and activated microglia in tissue sections; vascular cells were also reactive. Activated microglia were also identified immunocytochemically using a macrophage-specific MAb, ED-1. In normal P7-12 brain, lectin, and ED-1 immunoreactive-activated microglia were concentrated in white matter; lectin-positive resting, ramified microglia were also detected throughout the gray and white matter. Subtle morphologic evidence of microglial activation was noted 10 min posthypoxia-ischemia in the lesioned right cerebral hemisphere; activated microglia began to accumulate within the next 4 h. Accumulation of lectin-positive activated microglia peaked at 2-4 d posthypoxia-ischemia. ED-1 immunoreactive-microglia were first noted 4 h after hypoxic-ischemic injury in the lesioned right hemisphere, and there was a corresponding increase in accumulation over the first 48 h posthypoxia-ischemia. In the left hemisphere, contralateral to the ligation, no increase in activated microglia were detected with either method. In brain sections where no neuronal injury was evident, activated microglia did not accumulate. These data demonstrate that perinatal hypoxic-ischemic brain injury induced rapid accumulation of activated microglia in hypoxic-ischemic forebrain.

Animals↗

PubMed1996

The platelet-activating factor antagonist BN 52021 attenuates hypoxic-ischemic brain injury in the immature rat.

Platelet-activating factor (PAF) is overproduced in ischemic brain. Although postischemic PAF antagonist administration protects the mature brain in some models, little is known about the effects of PAF antagonists in the immature brain. We hypothesized that the PAF antagonist BN 52021 would attenuate perinatal cerebral hypoxic-ischemic injury. To elicit focal hypoxic-ischemic brain injury, 7-d-old (P7) rats (n = 111) underwent right carotid ligation, followed by 2.5-3.25 h of hypoxia (fractional concentration of inspired O2 = 0.08). BN 52021 neuroprotection was evaluated in three groups of experiments: 1) 25 mg/kg/dose, 0 and 2 h posthypoxia; 2), 25 mg/kg/dose immediately before and 1 h after hypoxia; and 3) posthypoxia-ischemia treatment with BN 52021 12.5, 25, or 50 mg/kg/dose in 2 doses 0 and 2 h after hypoxia. All experiments included concurrent vehicle-injected controls. To quantitate severity of injury, bilateral regional cross-sectional areas (groups 1 and 2) or hemisphere weights (group 3) were evaluated on P12. Both pre- and posthypoxic treatment with BN 52021 (25 mg/kg/dose, two serial doses) decreased the incidence of cerebral infarction from 90% to about 30% (p < 0.02, Fisher's exact test). Measurement of cross-sectional areas confirmed neuroprotection and indicated some benefit of pre- over posthypoxic-ischemic treatment in hippocampus and cortex. Over the dose range tested, the neuroprotective effect of BN 52021 administration was not dose-dependent. In contrast, BN 52021 did not attenuate N-methyl-D-aspartate-induced hippocampal excitotoxic injury in P7 rats. Either prophylactic or "rescue" administration of PAF antagonists decreases the incidence and severity of brain injury associated with an episode of perinatal cerebral hypoxia-ischemia.

Animals↗

PubMed1995

The mitochondrial inhibitor malonate enhances NMDA toxicity in the neonatal rat striatum.

Intra-striatal injections of the mitochondrial inhibitor malonate elicit age-dependent neuronal damage in rat brain; injury is more extensive in older animals than in young adults. We investigated the neurotoxic potential of malonate in the immature rat brain. We found that 7-day-old (P7) rats were highly resistant to malonate neurotoxicity. Yet, although intra-striatal injections of 1 mumol malonate did not elicit overt tissue injury in P7 rats, co-administration of this dose of malonate with a dose of NMDA close to its toxicity threshold (2.5 nmol) doubled the severity of resulting excitotoxic injury.

Animals↗

PubMed1995

gp120, an HIV-1 protein, increases susceptibility to hypoglycemic and ischemic brain injury in perinatal rats.

Recent data suggest that gp120, a glycoprotein secreted by HIV-1-infected macrophages, is neurotoxic, and that toxicity is mediated, at least in part, by overactivation of NMDA-type excitatory amino acid receptors. In experimental animals, considerable evidence indicates that hypoglycemic and ischemic neuronal injury are mediated by endogenous excitatory amino acids. We hypothesized that in the presence of gp120 the severity of brain injury resulting from hypoglycemia and cerebral ischemia would increase. To test this hypothesis in vivo, we evaluated the influence of gp120 on the extent of brain injury resulting from these two clinically relevant pathophysiological insults in 7-day-old (P7) rats, the developmental stage of peak susceptibility to NMDA neurotoxicity. We compared the severity of hippocampal injury resulting from right intrahippocampal injections of gp120 (50 ng) in P7 rats rendered markedly hypoglycemic (n = 10) and in controls (n = 12). We also determined the influence of gp120 administration on the severity of hypoxic-ischemic injury, using a perinatal rat stroke model. P7 rats received intrahippocampal injections of gp120 (50 ng) (n = 23) or saline (n = 18) and then underwent right carotid ligation, followed by 2 h exposure to 8% oxygen. Brain injury was evaluated 5 days later, based on neuropathology evaluation and measurements of bilateral regional cross-sectional areas. The severity of hippocampal injury, based on cross-sectional area measurements, was considerably greater in animals from the hypoglycemic group than in litter-mate gp120-injected controls. Among the animals that underwent hypoxic-ischemic lesioning, the severity of injury, based on histopathology scoring and regional volume measurements, was considerably greater in animals that received gp120 than in those that received saline. These results provide support for the hypothesis that locally secreted HIV peptides, such as gp120, may potentiate the neurotoxicity of endogenous excitatory amino acid neurotransmitters in HIV-infected brain.

Animals↗

PubMed1995

gp120 and neurotoxicity in vivo.

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Animals↗

PubMed1995

Inhibition of nitric oxide synthase activity attenuates striatal malonate lesions in rats.

Mitochondrial inhibitors such as malonate are potent neurotoxins in vivo. Intrastriatal injections of malonate result in neuronal damage reminiscent of "excitotoxic" lesions produced by compounds that activate NMDA receptors. Although the mechanism of cell death produced by malonate is uncertain, overactivation of NMDA receptors may be involved; pretreatment of animals with NMDA antagonists provides neuroprotection against malonate lesions. NMDA receptor activation stimulates the enzyme nitric oxide (NO) synthase (NOS). Elevated tissue levels of NO may generate highly reactive intermediates that impair mitochondrial function. We hypothesized that NO may be a mediator of malonate toxicity. We investigated whether in vivo inhibition of NO production by the NOS inhibitor N omega-nitro-L-arginine (NLA) would attenuate lesions produced by intrastriatal injections of malonate. We found that systemic injections of 3 mg/kg of NLA significantly reduced the extent of histologic damage elicited by intrastriatal injections of 1.5 mumol of malonate in adult rats.

Amino Acid Oxidoreductases↗

PubMed1995

Cerebral hypoxia-ischemia stimulates cytokine gene expression in perinatal rats.

BACKGROUND AND PURPOSE: We tested the hypothesis that cerebral hypoxia-ischemia selectively stimulates interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) gene expression in brain regions susceptible to irreversible injury in perinatal rats. METHODS: To elicit focal hypoxic-ischemic brain injury, 7-day-old perinatal (P7) rats were subjected to right carotid artery ligation followed by 3 hours of 8% O2 exposure and were killed 0 to 48 hours after hypoxia. Regional tissue IL-1 beta and TNF-alpha mRNA content were measured by reverse transcription followed by polymerase chain reaction amplification (RT-PCR) in samples prepared from cortex and hippocampus of the lesioned and contralateral hemispheres. cDNAs were amplified with primers specific for IL-1 beta, TNF-alpha, and the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which served as an internal control. The RT-PCR products were subjected to Southern blot analysis and hybridized with 32P-labeled gene-specific probes. Radioactivity was measured in excised bands, and results were normalized on the basis of levels of GAPDH expression. RESULTS: In unlesioned P7 brain, IL-1 beta mRNA was barely detectable. In lesioned forebrain, there was a marked, transient stimulation of IL-1 beta mRNA expression, peaking at 4 hours after hypoxia. Hybridization signal was increased 16- to 30-fold over values from contralateral hemisphere samples in three independent assays (P < .05 comparing values in left and right cortex and in left and right hippocampus with the Kruskal-Wallis ranking test); by 24 hours after hypoxia, levels returned to normal. Similar transient increases in TNF-alpha mRNA expression were detected. In a closely related model of perinatal brain injury elicited by focal intracerebral N-methyl-D-aspartate injection, there was a corresponding acute stimulation of IL-1 beta and TNF-alpha mRNA expression at 4 hours after injection. CONCLUSIONS: These results suggest that IL-1 beta and TNF-alpha may play important roles in the response of the developing brain to acute hypoxic-ischemic injury.

Animals↗

PubMed1995

Postvaricella basal ganglia infarction in children.

Two patients presented with acute neurologic deficits attributable to contralateral basal ganglia infarction 1 to 3 months after episodes of chickenpox. Both presented with hemiparesis with one patient also demonstrating ipsilateral choreoathetosis. In both patients MR revealed unilateral basal ganglia infarction. Cerebral angiography findings in one patient were normal; in the second, there was unilateral narrowing of the common carotid artery and of proximal branches of the anterior and middle cerebral artery.

Adrenal Cortex Hormones↗

PubMed1994

Resistance to nitroprusside neurotoxicity in perinatal rat brain.

Nitric oxide (NO) may mediate some of the toxic effects of the excitatory amino acid (EAA) glutamate when there is overactivation of the N-methyl-D-aspartate (NMDA) receptor. In the developing rodent nervous system, NMDA neurotoxicity peaks at postnatal day 7. To assess whether NO toxicity exhibits a similar developmental profile, we injected the NO generator sodium nitroprusside into the immature and adult rodent hippocampal formation and striatum, using a dose known to damage the adult nervous system. Contrary to our expectations, we found the immature brain highly resistant to the toxic effects of sodium nitroprusside.

Aging↗

PubMed1994

Hypoxic-ischemic brain injury stimulates glial fibrillary acidic protein mRNA and protein expression in neonatal rats.

Accumulation of glial fibrillary acidic protein xk(G-FAP) in reactive astrocytes is a characteristic neuropathologic feature of ischemic brain injury. We examined injury-induced changes in GFAP mRNA and protein in a well-characterized model of focal hypoxic-ischemic injury in perinatal rodent brain. Postnatal Day (PND) 7 rats underwent right carotid artery ligation followed by 2.5 h exposure to 8% oxygen, which results in injury to ipsilateral cortex, hippocampus, and striatum in the majority of animals. Using Northern analysis, we assayed GFAP mRNA in samples from the lesioned and contralateral hemispheres of animals killed 1 h to 14 days later, and from animals treated with the neuroprotective glutamate antagonist MK-801. GFAP immunoreactivity in tissue homogenates from the lesioned and contralateral hemispheres was also compared with an immunoblot assay. One and 4 h posthypoxia GFAP mRNA expression was barely detectable. In the lesioned cortex, increased GFAP mRNA was detected at 24 h postinjury; over the next 2 weeks GFAP mRNA was consistently higher (at least 2-fold) in lesioned than in contralateral cortex. In contrast, in lesioned hippocampus and striatum, consistent increases in GFAP mRNA were first detected on PND 12. Immunoassays of GFAP demonstrated early (PND 8) and sustained (to PND 21) up to 10-fold increases in lesioned cortex, hippocampus, and striatum. In this perinatal stroke model regionally specific increases in GFAP mRNA expression and GFAP immunoreactivity are detected in the first 2 weeks after hypoxic-ischemic injury; intrinsic properties of glia and/or neurons in different brain regions may influence the timing and magnitude of stimulation of this response.

Aging↗

PubMed1994

Acute disruption of cytochrome oxidase activity in brain in a perinatal rat stroke model.

Cytochrome oxidase histochemistry in frozen brain sections provides an estimate of mitochondrial respiratory function and neuronal metabolic activity. We hypothesized that in a perinatal rodent stroke model acute selective disruption of cytochrome oxidase activity could identify neuronal populations susceptible to irreversible ischemic injury. In 7-d-old rats, focal ischemic injury was induced by right carotid ligation followed by 8% O2 exposure (2.75 h); this procedure elicits ipsilateral forebrain injury with prominent hippocampal lesions, often including dentate gyrus. Cytochrome oxidase activity was quantitated by densitometry in brain sections prepared from animals killed 1 h (n = 8), 24 h (n = 11), or 5 d (n = 3) posthypoxia. At 1 h posthypoxia, in six of eight there was diffuse ipsilateral suppression of cytochrome oxidase activity (p = 0.0001, two-way analysis of variance, compared with values in contralateral hemisphere), which was most marked in periventricular regions including dentate gyrus (-29%), medial habenula (-38%), and posterolateral thalamic nucleus (-42%). Nissl staining of adjacent sections was completely intact in four of eight, and four of eight had subtle focal reductions in staining. At 24 h and 5 d posthypoxia, heterogeneous suppression of cytochrome oxidase activity persisted in the lesioned hemisphere, with close anatomic correspondence between loss of cytochrome oxidase activity and loss of Nissl staining. Additional studies indicated that the threshold duration of 8% O2 exposure (after carotid ligation) for suppression of cytochrome oxidase activity was 1-2 h. Disruption of cytochrome oxidase activity represents one of the earliest detectable indicators of neuronal injury in this perinatal stroke model.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1993

Excitotoxic injury stimulates glial fibrillary acidic protein mRNA expression in perinatal rat brain.

To study the molecular mechanisms contributing to glial fibrillary acidic protein (GFAP) accumulation after neuronal injury in the developing brain, we used a reproducible and pharmacologically modifiable model of excitotoxic injury, intracerebral injection of N-methyl-D-aspartate (NMDA) in Postnatal Day 7 rats. Injection of NMDA into the posterior striatum elicits dose-dependent ipsilateral injury to striatum, hippocampus, and overlying cortex; treatment with the non-competitive NMDA antagonist MK-801 is neuroprotective. To examine regionally specific changes in GFAP mRNA expression after lesioning, GFAP mRNA content was assayed, by Northern analysis, in pooled tissue samples of striatum, hippocampus, and cortex, derived from the injected and contralateral hemispheres of animals killed 1-16 days after lesioning with NMDA (12.5 nmol), and in samples derived from lesioned animals and littermates treated with MK-801. In addition, in situ hybridization assays were done to visualize the anatomic distribution of GFAP mRNA expression in NMDA-lesioned (n = 5) and lesioned/MK-801-treated animals (n = 3) 5 days postinjection. There was a marked rise in GFAP mRNA in lesioned cortex within 24 h, and increases were sustained over the next 2 weeks. In contrast, in striatum and hippocampus, in which severe histologic damage evolves, at 24 h postlesioning there was little stimulation of GFAP mRNA expression. Subsequently, 5-16 days postinjury increases in GFAP mRNA were detected in both brain regions. In animals examined 5 days postlesioning, MK-801 treatment markedly attenuated stimulation of GFAP mRNA expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Potentiation of N-methyl-D-aspartate-mediated brain injury by a human immunodeficiency virus-1-derived peptide in perinatal rodents.

In this study, we tested the hypothesis that human immunodeficiency virus (HIV)-1-derived peptides augment the neurotoxicity of excitatory amino acid agonists in vivo in postnatal day (PND) 7 rats. Stereotaxic intracerebral injections of the excitatory amino acid agonist N-methyl-D-aspartate (NMDA), alone or coinjected with an HIV-derived recombinant fusion peptide envelope gag (env-gag) were performed in PND-7 rats [group I: 5 nmol NMDA, n = 20; group II: 5 nmol NMDA + low-dose (1 or 50 ng) env-gag, n = 27; group III: 5 nmol NMDA + high-dose (100 ng) env-gag, n = 20], and brain injury was evaluated on PND 12. Based on histopathology scoring and measurements of hippocampal cross-sectional areas in the injected and contralateral hemispheres, coinjection of 100 ng of env-gag with 5 nmol of NMDA markedly increased the severity of resulting injury (p < 0.002, comparing histopathology scores; p < 0.003, comparing interhemispheric differences in hippocampal areas). These data suggest that in the developing nervous system HIV neurotoxicity may result, at least in part, from overactivation of excitatory amino acid receptors, and that perinatal rodent models may provide clinically relevant insights about the pathophysiology of HIV-mediated brain injury.

AIDS Dementia Complex↗

PubMed1992

The microsomal calcium-ATPase inhibitor thapsigargin is a neurotoxin in perinatal rodent brain.

Thapsigargin is a potent inhibitor of the microsomal calcium-ATPase. We hypothesized that thapsigargin-induced liberation of calcium from sequestered intracellular sites could result in irreversible brain injury. To assess neurotoxicity, intracerebral injections of 0.1-100 nmol thapsigargin were performed in 7-day-old rats, and the severity of injury was assessed 5 days later by microscopy and measurements of lesioned areas. We found that thapsigargin elicited dose-dependent tissue injury in perinatal rodent brain.

Animals↗

PubMed1992

N-methyl-D-aspartate-mediated injury enhances quisqualic acid-stimulated phosphoinositide turnover in perinatal rats.

Previous work in our laboratory demonstrated that ischemic-hypoxic brain injury in postnatal day 7 rats causes a substantial increase in phosphoinositide (PPI) turnover stimulated by the glutamate analogue quisqualic acid (QUIS) in the hippocampus and striatum. To examine this phenomenon in more detail, we performed similar experiments after producing injury by unilateral intracerebral injections of the glutamate analogue N-methyl-D-aspartate (NMDA). The 7-day-old rodent brain is hypersensitive to NMDA neurotoxicity and NMDA injection causes histopathology that closely resembles that produced by ischemia-hypoxia. NMDA, 17 nmol in 0.5 microliter, was injected into the right posterior striatum of 7-day-old rat pups and they were killed 3 days later. Hippocampal or striatal tissue slices were prepared from ipsilateral and contralateral hemispheres from vehicle-injected control and from noninjected control rat pups. Slices were then incubated with myo-[3H]inositol plus glutamate agonists or antagonists in the presence of lithium ions and [3H]inositol monophosphate ([3H]IP1) accumulation was measured. The glutamate agonists, QUIS, L-glutamic acid, and (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, stimulated greater [3H]IP1 release in tissue ipsilateral to the NMDA injection compared with that in the contralateral side and in control pups. The glutamate antagonists, D,L-2-amino-7-phosphonoheptanoic acid, 3-[(+)-2-carboxypiperazin-4-yl]-propyl-1-phosphoric acid, kynurenic acid, and 6,7-dinitroquinoxaline-2,3-dione did not inhibit QUIS-stimulated [3H]IP1 release. The enhanced PPI turnover in the lesioned tissue was specific to glutamate receptors because carbachol (CARB) failed to elicit preferential enhanced stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗