bluuebunny/crossref_metadata_2025 huggingface dataset:
Matrix Remodeling after Stroke: De Novo Expression of Matrix Proteins and Integrin Receptors
Authors: ELLISON JULIE A. , BARONE FRANK C. , FEUERSTEIN GIORA Z.
Published: February 2006

ABSTRACT: Following an ischemic insult to the central nervous system a reorganization of cells and tissue takes place as the sorrounding cells attempt to limit the injury, repair the damage, and restore normal architecture of the brain. This tissue remodeling requires de novo synthesis of genes and proteins which enables cells to actively change their relationship with the existing extracellular matrix and with other cells to recognized the damage tissue. We have identified two key molecular components of the matrix remodeling process after focal ischemia: osteopontin (OPN) and its integrin receptor αvβ3 (αvβ3). OPN is initially expressed by activated macrophages and microglia in the periinfarct region (24–48 hr) and at later times (5–15 days) in the core infarct. After focal stroke the αvβ3 was upregulated by astrocytes in the periinfarct region. Spatial and temporal analyses demonstrated that at 5 days after injury the αvβ3‐positive astrocytes were at a distance from the osteopontin‐expressing macrophages; by 15 days the αvβ3‐expressing astrocytes were localized within an osteopontin‐rich matrix. In vitro OPN was shown to induce migration of astrocytes in a Boyden chamber system. These data suggest that OPN derived from microglia at the infarct border zone (and possible macrophages in the infarct core) may serve as an “astrokine” (suggested term for astrocyte chemoattractant) to organize the astrocyte scar after focal stroke. Our data demonstrate profound changes in brain matrix remodeling after focal ischemic stroke, including the systhesis and release of matrix proteins alien to the normal brain, the expresion of integrin receptors that ligate these proteins, and possibly a novel function for microglial‐derived OPN in astrocyte migration after focal ischemia that may drive glial activation, organization, and repair functions.
Metallothioneins Attenuate Methylmercury‐Induced Neurotoxicity in Cultured Astrocytes and Astrocytoma Cells
Authors: YAO CHANG PING , ALLEN JEFFREY W. , ASCHNER MICHAEL
Published: February 2006

ABSTRACT: Metallothionein‐I (MT‐I) was expressed in neonatal rat primary astrocyte cultures and an astrocytoma cell line by pGFAP‐MT‐I plasmid transfection under the control of the astrocyte‐specific glial fibrillary acidic protein (GFAP) promoter. Following transient transfection of the pGFAP‐MT‐I plasmid, MT‐I mRNA and MT‐I protein levels were determined by Northern blot and immunoprecipitation analyses, respectively. The ability of cells overexpressing MT‐I to withstand acute methylmercury (MeHg) treatment was measured by the release of preloaded Na251CrO4, an indicator of membrane integrity. Transfection with the pGFAP‐MT‐I plasmid led to increased mRNA (2.5‐fold in astrocytes and 7.4‐fold in astrocytomas) and MT‐I protein (2.4‐fold in astrocytes and 4.0‐fold in astrocytomas) levels compared with their respective controls. Increased expression of MT‐I was associated with attenuated release of Na251CrO4 upon MeHg (5 μM) treatment. These results demonstrate that MT‐I can be highly expressed both in primary astrocyte cultures and astrocytomas by pGFAP‐MT‐I plasmid transfection, and lend credence to the hypothesis that increased expression of MT‐I affords protection against the cytotoxic effects of MeHg. Taken together, the data suggest that MTs offer effective cellular adaptation to MeHg cytotoxicity.
Implication of Poly(ADP‐Ribose) Polymerase (PARP) in Neurodegeneration and Brain Energy Metabolism: Decreases in Mouse Brain NAD+ and ATP Caused by MPTP Are Prevented by the PARP Inhibitor Benzamide
Authors: COSI CRISTINA , MARIEN MARC
Published: February 2006

ABSTRACT: Poly(ADP‐ribose) polymerase (PARP) is a DNA binding protein that uses nicotinamide adenine dinucleotide (NAD+) as a substrate. Evidence from in vitro studies on nonneuronal cells in culture have shown that when fully activated by free radical‐induced DNA damage, PARP depletes cellular NAD+ and consequently adenosine triphosphate (ATP) levels within a matter of minutes, and that this depletion is associated with a cell death that can be prevented by PARP inhibitors. The present in vivo study utilized the 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP)‐treated mouse, a model of central nigrostriatal dopamine neurotoxicity that recapitulates certain features of Parkinson's disease (PD), and one in which we have previously shown PARP inhibitors to be protective, 6 to examine whether MPTP acutely caused region‐ and time‐dependent changes in levels of NAD+ and ATP in the brain in vivo and whether such effects were modified by treatments with neuroprotective doses of the PARP inhibitor benzamide. The results confirm that MPTP reduces striatal ATP levels, as previously reported by Chan et al., 4 show that MPTP causes a regionally‐selective (striatal and midbrain) loss of NAD+, and indicate that the PARP inhibitor benzamide can prevent these losses without interfering with MPTP‐induced striatal dopamine release. These findings suggest an involvement of PARP in the control of brain energy metabolism during neurotoxic insult, provide further evidence in support of the participation of PARP in MPTP‐induced neurotoxicity in vivo and suggest that PARP inhibitors might be beneficial in the treatment of PD.
Neuroprotection against Ischemia by Metabolic Inhibition Revisited: A Comparison of Hypothermia, a Pharmacologic Cocktail and Magnesium Plus Mexiletine
Authors: MAYNARD KENNETH I. , QUIÑONES‐HINOJOSA ALFREDO , MALEK JUNAID Y.
Published: February 2006

ABSTRACT: Previous studies have suggested that metabolic inhibition is neuroprotective, but little evidence has been provided to support this proposal. Using the in vitro rabbit retina preparation as an established model of the central nervous system (CNS), we measured the rate of glucose utilization and lactate production, and the light‐evoked compound action potentials (CAPs) as indices of neuronal energy metabolism and electrophysiologic function, respectively. We examined the effect of three (3) treatments options: hypothermia (i.e., 33°C and 30°C), a six‐member pharmacologic “cocktail” (tetrodotoxin (0.1 μM), 2‐amino‐4‐phosphonobutyric acid (20 μM), 2‐amino‐5‐phosphonovaleric acid (1 mM), amiloride (1 mM), magnesium (10 mM) and lithium (10 mM)) and the combination of magnesium (Mg2+ 1 mM) and mexiletine (Mex, 300 μM) on in vitro rabbit retinas, to see if there is a correlation between neuronal energy metabolism during ischemia (simulated by the reduction of oxygen from 95% to 15% and glucose from 6 mM to 1 mM), and the subsequent recovery of function. Hypothermia and the “cocktail” significantly inhibited both the rate of glucose utilization and lactate production, whereas Mg2+ and/or Mex showed only a nonsignificant tendency toward a reduction, compared to control retinas. Recovery of light‐evoked CAPs was significantly improved in hypothermia‐ and cocktail‐treated retinas, as well as with retinas exposed to the combination of Mg2+ plus Mex, but not with Mg2+ or Mex alone, relative to control retinas. A linear regression analysis of the % recovery of function versus the % reduction in the rate of glucose utilization during ischemia showed a significant correlation (
r2= 0.80

,
correlation coefficient = 0.9

,
p < 0.05
) between these two parameters. This and other data discussed provide convincing evidence that there is a correlation between metabolic inhibition, achieved during ischemia, and neuroprotection.
Calpeptin and Methylprednisolone Inhibit Apoptosis in Rat Spinal Cord Injury
Authors: RAY SWAPAN K. , WILFORD GLORIA G. , MATZELLE DENISE C. , HOGAN EDWARD L. , BANIK NAREN L.
Published: February 2006

ABSTRACT: Intracellular free Ca2+ and free radicals are increased following spinal cord injury (SCI). These can activate calpain to degrade cytoskeletal proteins leading to apoptotic and necrotic cell death. Primary injury triggers a cascade of secondary injury, which spreads to rostral and caudal areas. We tested calpain involvement in apoptosis in five 1‐cm segments of rat spinal cord with injury (40 g‐cm) induced at T12 by weight‐drop. Animals were immediately treated with calpeptin (250 μg/kg) and methylprednisolone (165 mg/kg) and sacrificed at 48 hr. Untreated SCI rats manifested 68‐kD neurofilament protein (NFP) degradation (indicating calpain activity), and internucleosomal DNA fragmentation (indicating apoptosis). Both calpain activity and apoptosis were highest in the lesion, and decreased with increasing distance from the lesion. Treatment decreased 68‐kD NFP degradation with reduction in apoptosis in all five areas. Thus, calpeptin and methylprednisolone are found to be neuroprotective in SCI.
High Extracellular Glutamate and Neuronal Death in Neurological Disorders: Cause, Contribution or Consequence?
Authors: OBRENOVITCH TIHOMIR P.
Published: February 2006

ABSTRACT: In models of neurological disorders, increased extracellular glutamate and beneficial effects produced by glutamate‐receptor antagonists are consistently taken as supporting evidence of excitotoxicity. This systematic interpretation is over‐simplified and potentially misleading.

High extracellular glutamate is not a reliable indicator of endogenous excitotoxixity, i.e., the intrinsic, potential neurotoxicity of endogenous glutamate whenever it accumulates extracellularly. Firstly, because the extracellular levels of glutamate necessary to produce depolarization and death in vivo, are far above those measured in models of neurological disorders. Secondly, because changes in the concentration of glutamate in the synaptic cleft (i.e., the relevant compartment for endogenous excitotoxicity) are not reflected extracellularly.

Protection by glutamate‐receptor antagonists does not necessarily imply inhibition of excitotoxic abnormalities. Indeed, neuronal death initiated by insults such as ischemia results from multifactorial processes that may be interrelated. Therefore, beneficial effects resulting from an interaction with glutamate‐mediated transmission may actually render the cell more resistant to other deleterious mechanisms (e.g., mitochondrial injury, oxidative stress).
Evidence Disputing the Importance of Excitotoxicity in Hippocampal Neuron Death after Experimental Traumatic Brain Injury
Authors: CARBONELL W. SHAWN , GRADY M. SEAN
Published: February 2006

ABSTRACT: The hippocampus is selectively vulnerable to experimental traumatic brain injury (TBI). Beneficial effects of glutamate receptor antagonists and increased extracellular levels of glutamate have suggested that glutamate‐mediated excitotoxicity may be responsible for this selective damage. In order to clarify this important issue, we applied a severe parasagittal fluid percussion injury (FPI) to strains of mice shown to be susceptible and resistant to kainic acid (KA)‐induced excitotoxic hippocampal damage. Dystrophic neurons were present by 10 min after FPI in the hippocampi of both strains. Damaged hippocampal neurons were absent at 4 days and 7 days. Additionally, there was no significant difference (
p= 1.00

) in CA3 Neuron survival between KA‐susceptible and ‐resistant mice at 4 days. In conclusion, excitotoxicity does not significantly contribute to hippocampal neuron loss after FPI and, in contrast to classic studies of excitotoxicity in vivo, the pattern of hippocampal cell death after TBI is extremely acute.
Neuroprotective Properties of Nitric Oxide
Authors: CHIUEH CHUANG C.
Published: February 2006

ABSTRACT: The discoveries of physiological roles of nitric oxide (·NO) as the mediator of endothelium‐derived relaxing factor (EDRF) action and the activator of guanylyl cyclase to increase cyclic guanosine monophosphate (cGMP), which lead to vasorelaxation in the cardiovascular system, have been awarded with the 1998 Nobel Prize of Medicine. The present review discusses putative beneficial effects of ·NO in the central nervous system (CNS). In addition to its prominent roles of the regulation of cerebral blood flow and the modulation of cell to cell communication in the brain, recent in vitro and in vivo results indicated that ·NO is a potent antioxidative agent. ·NO terminates oxidant stress in the brain by (i) suppressing iron‐induced generation of hydroxyl radicals (·OH) via the Fenton reaction, (ii) interrupting the chain reaction of lipid peroxidation, (iii) augmenting the antioxidative potency of reduced glutathione (GSH) and (iv) inhibiting cysteine proteases.

It is apparent that ·NO‐a relative long half‐life nitrogen‐centered weak radical‐scavenges those short‐lived, highly reactive free radicals such as superoxide anion (O2·−), ·OH, peroxyl lipid radicals (LOO·) and thiyl radicals (i.e., GS·), yielding reactive nitrogen species including nitrites, nitrates, S‐nitrosoglutathione (GSNO) and peroxynitrite (ONOO−). GSNO is 100‐fold more potent than GSH; it completely inhibits the weak peroxidative effect of ONOO−. Moreover, CO2 and ·NO neutralize prooxidative effects of ONOO−. CO2 prevents protein oxidation but not 3‐nitrotyrosine formation caused by ONOO−. Finally, neuroprotective effects of GSNO and ·NO have been demonstrated in brain preparations in vivo.

These novel neuroprotective properties of ·NO and GSNO may have their physiological significance, since oxidative stress depletes GSH while increasing GS· and ·NO formation in astroglial and endothelial cells, resulting in the generation of a more potent antioxidant GSNO and providing additional neuroprotection at μM concentrations. This putative GSNO pathway (GSH → GS·→ GSNO →·NO + GSSG → GSH) may be an important part of endogenous antioxidative defense system, which could protect neurons and other brain cells against oxidative stress caused by oxidants, iron complexes, proteases and cytokines. In conclusion, ·NO is a potent antioxidant against oxidative damage caused by reactive oxygen species, which are generated by Fenton reaction or other mechanisms in the brain via redox cycling of iron complexes.
The Antioxidative Effect of Carboxyfullerenes (C3/D3) on Iron‐Induced Oxidative Injury in CNS
Authors: LIN ANYA M. Y. , LUH T.‐Y. , CHOU C. K. , HO L. T.
Published: February 2006

ABSTRACT: Carboxyfullerenes, including two regioisomers C3 and D3, were investigated as antioxidants against iron‐induced oxidative stress in vivo and in vitro. Both C3 and D3 dose‐dependently inhibited autoxidation and iron‐elevated lipid peroxidation in cortical homogenates. The antioxidative property of C3 was compared to Trolox (a water‐soluble analogue of vitamin E) and glutathione. C3 was more effective than glutathione but was less effective than Trolox in inhibiting iron‐induced elevation in lipid peroxidation. In urethane‐anesthetized rats, intranigral infusion of iron degenerated the nigrostriatal dopaminergic system, including as elevation in lipid peroxidation in the infused substantia nigra (SN) and reductions in K+‐evoked dopamine overflow and dopamine content in the ipsilateral striatum 7 days after the infusion. Local application of iron with C3 or D3 prevented iron‐induced oxidative injuries. Our data suggest that carboxyfullerenes have a neuroprotective effect in preventing iron‐induced oxidative injury in CNS.
Protective and Rescuing Abilities of IGF‐I and Some Putative Free Radical Scavengers against β‐Amyloid‐Inducing Toxicity in Neurons
Authors: DORÉ SYLVAIN , BASTIANETTO STÉPHANE , KAR SATYABRATA , QUIRION RÉMI
Published: February 2006

ABSTRACT: β‐Amyloid (AB) peptides are most likely involved in the neurodegenerative process occurring in Alzheimer's disease (AD) and are enriched in senile plaques. The mechanisms of Aβ toxicity are not clear but likely involve free radicals and apoptosis. Much interest is currently aiming at developing effective approaches to block Aβ toxicity in order to slow down disease progression. In that context, we are particularly interested in studying the role of insulin‐like growth factors, particularly IGF‐I and purported free radical scavengers including a Gingko biloba extract (EGB761) as blocker of Aβ toxicity in a simple in vitro model of hippocampal primary cultures. We observed that both IGF‐I and EGB761 are unique in that they are able not only to protect but even to rescue neurons against Aβ toxicity. These results are summarized here and possible mechanisms of action are discussed to explain the protective properties of these two classes of agents.
The Unique Histopathological Responses of the Injured Spinal Cord: Implications for Neuroprotective Therapy
Authors: GUTH LLOYD , ZHANG ZIYIN , STEWARD OSWALD
Published: February 2006

ABSTRACT: Tissue destruction at the primary site of a spinal cord injury leads to persistent necrosis that progressively enlarges the lesion. Steroids attenuate this necrotizing process and promote tissue repair even though such anti‐inflammatory drugs interfere with wound healing in non‐CNS organs. To address this paradox, the spinal cord of rats and mice was crushed extradurally and the effects of the following anti‐inflammatory agents studied by light microscopical image analysis: allopurinol, aminoguanidine, indomethacin, a bacterial lipopolysaccharide, naproxen, and pregnenolone. The contribution of Wallerian degeneration to progressive necrosis was studied in a mutant mouse strain (WldS) that is characterized by delayed Wallerian degeneration.

In rats, the anti‐inflammatory agents selectively attenuated progressive necrosis and encouraged wound healing. In mice, considerable tissue repair occurred without pharmacological intervention; this wound‐healing process was delayed in the mutant WldS strain. Since spinal cord injury results in concomitant tissue necrosis and wound healing, a goal of neuroprotective therapy is to regulate the dynamic balance between these destructive and reparative processes.
Blockade of NAALADase: A Novel Neuroprotective Strategy Based on Limiting Glutamate and Elevating NAAG
Authors: VORNOV JAMES J. , WOZNIAK KRYSTYNA , LU MAY , JACKSON PAUL , TSUKAMOTO TAKASHI , WANG ERIC , SLUSHER BARBARA
Published: February 2006

ABSTRACT: Excessive glutamate receptor activation is thought to be involved in the neuronal injury caused by stroke. Based on the hypothesis that N‐acetyl‐Aspartyl‐glutamate (NAAG) is a modulatory neurotransmitter or storage form of glutamate, we have pursued a novel strategy of therapeutic intervention, blockade of N‐acetylated alpha‐linked acidic dipeptidase (NAALADase), the enzyme that hydrolyzes NAAG to liberate glutamate. Using the suture model of transient middle cerebral artery occlusion (MCAO) in rats, the prototype NAALADase inhibitor 2‐(phosphonomethyl)pentanedioic acid (2‐PMPA) dramatically reduced extracellular glutamate accumulation measured by microdialysis both during a 2‐hour occlusion and during reperfusion, consistent with an effect on glutamate supply. During reperfusion, the decrease in glutamate was accompanied by an equimolar, Reciprocal rise in extracellular NAAG. NAALADase inhibition may prove to be a well tolerated therapy for cerebral ischemia. In addition, NAALADase inhibitors should prove to be important tools in understanding the physiological role of NAAG in the brain.
Intracellular Survival Pathways against Glutamate Receptor Agonist Excitotoxicity in Cultured Neurons: Intracellular Calcium Responsesa
Authors: MARINI ANN M. , UEDA YUJI , JUNE CARL H.
Published: February 2006

ABSTRACT: Cultured rat cerebellar granule cells are resistant to the excitotoxic effects of N‐methyl‐d‐aspartate (NMDA) and non‐NMDA receptor agonists under three conditions: 1) prior to day seven in vitro when cultured in depolarizing concentrations of potassium [25 mM]; 2) at any time in vitro when cultured in non‐depolarizing concentrations of potassium [5 mM]; and 3) when neurons, cultured in depolarizing concentrations of potassium [25 mM] for eight days in vitro, are pretreated with a subtoxic concentration of NMDA. The focus of this paper is to determine: a) whether the resistance to excitotoxicity by NMDA and non‐NMDA receptor agonists is due to a decreased intracellular calcium [Ca++]i response to glutamate receptor agonists in cultured rat cerebellar granule cells; or b) whether [Ca++]i levels induced by the agonists are similar to those observed under excitotoxic conditions.

Granule cells, matured in non‐depolarizing growth medium, treated with glutamate resulted in an increase in [Ca++]i followed by a plateau that remained above baseline in virtually all neurons that responded to glutamate. The response was rapid in onset (<10 sec) and the pattern of response heterogeneous in that cells responsive to glutamate increased their [Ca++]i to different extents; some cells did not respond to glutamate. Kainate also produced significant elevations in [Ca++]i.

The [Ca++]i response to glutamate in neurons matured in depolarizing (25 mM K+) growth medium for three days was rapid, transient and heterogeneous, which reached a plateau that was elevated above baseline levels; removing the glutamate markedly reduced the [Ca++]i concentration. Activation of the α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA)/kainate receptors by kainic acid produced similar changes in [Ca++]i responses. At a time when cultured cerebellar granule cells become susceptible to the excitotoxic effects of glutamate acting at NMDA receptors (day in vitro (DIV) 8) in depolarizing growth medium, glutamate elicited [Ca++]i responses similar to those observed at a culture time when the neurons are not susceptible to the excitotoxic effects of glutamate (DIV 3). Pretreatment of the cultured neurons with a subtoxic concentration of NMDA, which protects all neurons against the excitotoxic effects of glutamate, did not alter the maximal [Ca++]i elicited by an excitotoxic concentration of glutamate.
Neuroprotective Actions of Novel and Potent Ligands of Group I and Group II Metabotropic Glutamate Receptors
Authors: KINGSTON A. E. , O'NEILL M. J. , BOND A. , BRUNO V. , BATTAGLIA G. , NICOLETTI F. , HARRIS J. R. , CLARK B. P. , MONN J. A. , LODGE D. , SCHOEPP D. D.
Published: February 2006

ABSTRACT: The role of group I metabotropic glutamate (mGlu) receptors in neurodegeneration is controversial because of the contradictory effects of mGlu1/5 agonists in in vitro models of neuronal cell death. In this study, novel and selective antagonists of mGlu1 and mGlu5: LY367385 and LY367366 were found to show consistent neuroprotective effects against N‐methyl‐d‐aspartate (NMDA)‐induced excitotoxicity in vitro and in vivo. Furthermore, intraventricular administration of LY367385 reduced hippocampal cell death in gerbils subjected to transient global ischemia.

Previous studies have also shown that activation of group II mGlu receptors may contribute to neuroprotective mechanisms in vitro and in vivo. Three potent group II mGlu agonists‐LY354740, LY379268 and LY389795‐were found to attenuate both NMDA excitotoxicity and staurosporine‐induced neuronal cell death. LY354740 and LY379268 were protective against transient global ischemia in gerbils when dosed intraperitoneally.

These results support the view that antagonists of mGlu1 and mGlu5 and agonists of group II mGlu receptors may be useful agents in the therapeutic treatment of neurodegenerative disease.
NPS 1506, A Novel NMDA Receptor Antagonist and Neuroprotectant: Review of Preclinical and Clinical Studies
Authors: MUELLER ALAN L. , ARTMAN LINDA D. , BALANDRIN MANUEL F. , BRADY ELLEN , CHIEN YONGWEI (ERIC) , DELMAR ERIC G. , GEORGE KAREN , KIERSTEAD ALLISON , MARRIOTT THOMAS B. , MOE SCOTT T. , NEWMAN MICHAEL K. , RASZKIEWICZ JOANNA L. , SANGUINETTI ELIZABETH L. , VAN WAGENEN BRADFORD C. , WELLS DAVID
Published: February 2006

ABSTRACT: NPS 1506 is a moderate affinity, uncompetitive N‐methyl‐d‐aspartate (NMDA) receptor antagonist. NPS 1506 is neuroprotective in rodent models of ischemic stroke, hemorrhagic stroke, and head trauma, with a 2‐hr window of opportunity. Neuroprotectant doses of NPS 1506 ranged from approximately 0.1–1.0 mg/kg, with peak plasma concentrations ranging from 8–80 ng/mL. Even at doses producing behavioral toxicity, NPS 1506 did not elicit MK‐801‐like behaviors, did not generalize to phencyclidine (PCP), and did not elicit neuronal vacuolization.

In a Phase I study, intravenous (i.v.) doses of NPS 1506 from 5–100 mg were well tolerated and provided plasma concentrations in excess of those required for neuroprotection in rodents. Adverse events at the 100‐mg dose included mild dizziness and lightheadedness, and mild to moderate ataxia. Neither PCP‐like psychotomimetic effects nor cardiovascular effects were noted. The long plasma half‐life of NPS 1506 (∼60 hr) suggests that a single i.v. dose will provide prolonged neuroprotection in humans.
Peroxynitrite Scavengers for the Acute Treatment of Traumatic Brain Injury
Authors: HALL EDWARD D. , KUPINA NANCY C. , ALTHAUS JOHN S.
Published: February 2006

ABSTRACT: Recent evidence has suggested that the superoxide and nitric oxide‐derived reactive oxygen species peroxynitrite (ONOO−) may play a significant role in the acute pathophysiology of brain injury. One pharmacological mechanism by which ONOO−‐mediated damage might be interrupted is by the administration of scavenging compounds such as the thiol‐containing compound penicillamine. In the present study, we examined the ability of either penicillamine (Pen) or the more brain penetrable penicillamine methyl ester (PenME) (0.01, 0.1, 1.0 or 10.0 mg/kg i.v. 5 min post‐injury) to improve the early (1 hr) neurological recovery (grip score) of male CF‐1 mice after a severe (900 g‐cm; 50 g × 18 cm) injury. Pen produced a dose‐related improvement in grip score. At 1.0 mg/kg, a +112% improvement was observed compared to vehicle‐treated mice, and at 10.0 mg/kg, the increase was +168% (both,
p < 0.05

). PenME more potently improved the 1‐hr grip score, but the magnitude of the optimal effect (+96% at 0.1 mg/kg;
p < 0.02

) was no greater than that observed with Pen, which largely remains in the cerebral microvasculature. These results are consistent with a role of ONOO− in acute head injury, but suggest that microvascular scavenging may be of primary therapeutic importance during the early post‐traumatic period.
Melatonin as a Pharmacological Agent against Neuronal Loss in Experimental Models of Huntington's Disease, Alzheimer's Disease and Parkinsonism
Authors: REITER RUSSEL J. , CABRERA JAVIER , SAINZ ROSA M. , MAYO JUAN CARLOS , MANCHESTER LUCIEN C. , TAN DUN‐XIAN
Published: February 2006

ABSTRACT: This review summarizes the experimental findings related to the neuroprotective role of melatonin. In particular, it focuses on research directed at models of Huntington's disease, Alzheimer's disease and Parkinsonism. Melatonin has been shown to be highly effective in reducing oxidative damage in the central nervous system; this efficacy derives from its ability to directly scavenge a number of free radicals and to function as an indirect antioxidant. In particular, melatonin detoxifies the highly toxic hydroxyl radical as well as the peroxyl radical, peroxynitrite anion, nitric oxide, and singlet oxygen, all of which can damage macromolecules in brain cells. Additionally, melatonin stimulates a variety of antioxidative enzymes including superoxide dismutase, glutathione peroxidase and glutathione reductase. One additional advantage melatonin has in reducing oxidative damage in the central nervous system is the ease with which to crosses the blood‐brain barrier. This combination of actions makes melatonin a highly effective pharmacological agent against free radical damage. The role of physiological levels of melatonin in forestalling oxidative damage in the brain is currently being tested.
The Regulation of Cerebral Blood Flow during Intravenous Cocaine Administration in Cocaine Abusers
Authors: HERNING RONALD I. , BETTER WARREN , NELSON RICHARD , GORELICK DAVID , CADET JEAN L.
Published: February 2006

ABSTRACT: Cocaine abuse is associated with heightened risk of life‐threatening neurological complications such as strokes, seizures, and transient ischemic attacks. We used transcranial Doppler (TCD) sonography, a continuous measure of cerebral blood flow velocity, to better understand the changes in cerebral hemodynamics produced by cocaine administration, which may lead to an increased risk for stroke in cocaine abusers. Heart rate and blood pressure were also measured. Blood flow velocity of seven cocaine abusers was studied during placebo, 10‐, 25‐, and 50‐mg intravenous (i.v.) injections of cocaine. A significant increase in mean and systolic velocity which lasted for about two minutes was observed with all doses of cocaine, with no change in the placebo condition. This increase in systolic velocity indicates that cocaine produces an immediate and brief period of vasoconstriction in large arteries of the brain. The present results elucidate the time course of cocaine's acute cerebrovascular effects and provide a better understanding of etiology of cocaine‐related stroke and transient ischemic attacks.
Time Course of Brain Temperature and Caudate/Putamen Microdialysate Levels of Amphetamine and Dopamine in Rats after Multiple Doses ofd‐Amphetamine
Authors: CLAUSING PETER , BOWYER JOHN F.
Published: February 2006

ABSTRACT:Brain temperature monitoring and microdialysis were performed simultaneously in the caudate/putamen (CPu) of conscious, freely moving rats dosed withd‐amphetamine (AMPH). The brain temperature was determined via a thermistor inserted through a microdialysis guide cannula located in the left CPu, while the microdialysis probe was positioned in the right CPu. The peak AMPH and dopamine (DA) levels were reached 40 to 60 min after dosing, while peak brain temperature was not achieved until 20 to 40 min thereafter in rats becoming moderately hyperthermic. Those rats becoming severely hyperthermic (temperatures above 41.0°C) had microdialysate concentrations of AMPH and DA almost 2‐fold higher than those with moderate hyperthermia after the second dose of 5 mg/kg AMPH. However, these peaks were not reached until 60 to 80 min after dosing. This was probably due, in part, to the longer half‐life of AMPH in the severely hyperthermic group. The changes in brain temperature observed after exposure to neurotoxic doses of AMPH closely paralleled core body temperature changes previously reported during AMPH exposure. Temperature plays an important role in many types of neurotoxicity, and monitoring brain temperature during microdialysis studies can be done continuously, and with less chance of damage to the microdialysis equipment than most of the traditional methods used to measure core body temperature.
Biological Warfare Training: Infectious Disease Outbreak Differentiation Criteriaa
Authors: NOAH DONALD L. , SOBEL ANNETTE L. , OSTROFF STEPHEN M. , KILDEW JOHN A.
Published: February 2006

Abstract: The threat of biological terrorism and warfare may increase as the availability of weaponizable agents increase, the relative production costs of these agents decrease, and, most importantly, there exist terrorist groups willing to use them. Therefore, an important consideration during the current emphasis of heightened surveillance for emerging infectious diseases is the capability to differentiate between natural and intentional outbreaks. Certain attributes of a disease outbreak, while perhaps not pathognomic for a biological attack when considered singly, may in combination with other attributes provide convincing evidence for intentional causation. These potentially differentiating criteria include proportion of combatants at risk, temporal patterns of illness onset, number of cases, clinical presentation, strain/variant, economic impact, geographic location, morbidity/mortality, antimicrobial resistance patterns, seasonal distribution, zoonotic potential, residual infectivity/toxicity, prevention/therapeutic potential, route of exposure, weather/climate conditions, incubation period, and concurrence with belligerent activities of potential adversaries.
Safeguarding Production Agriculture and Natural Ecosystems against Biological Terrorism: A U.S. Department of Agriculture Emergency Response Framework
Authors: SEQUEIRA RON
Published: February 2006

Abstract: Foreign pest introductions and outbreaks represent threats to agricultural productivity and ecosystems, and, thus, to the health and national security of the United States. It is advisable to identify relevant techniques and bring all appropriate strategies to bear on the problem of controlling accidentally and intentionally introduced pest outbreaks. Recent political shifts indicate that the U.S. may be at increased risk for biological terrorism. The existing emergency‐response strategies of the Animal and Plant Health Inspection Services (APHIS) will evolve to expand activities in coordination with other emergency management agencies. APHIS will evolve its information superstructure to include extensive application of simulation models for forecasting, meteorological databases and analysis, systems analysis, geographic information systems, satellite image analysis, remote sensing, and the training of specialized cadres within the emergency‐response framework capable of managing the necessary information processing and analysis. Finally, the threat of key pests ranked according to perceived risk will be assessed with mathematical models and “what‐if” scenarios analyzed to determine impact and mitigation practices. An infrastructure will be maintained that periodically surveys ports and inland regions for the presence of exotic pest threats and will identify trend abnormalities. This survey and monitoring effort will include cooperation from industry groups, federal and state organizations, and academic institutions.
The Cost of Disease Eradication: Smallpox and Bovine Tuberculosis
Authors: NELSON ANN MARIE
Published: February 2006

Abstract: Although eradication is the ideal approach to reduce the economic and human health costs of disease, there may be both short‐ and long‐term consequences. A $300 million effort succeeded in completely eradicating smallpox in less than ten years. The campaign was effective because variola virus produced acute illness, had no carrier stage or non‐human reservoirs, and had an effective vaccine that was used in combination with international surveillance and public education. Bovine tuberculosis was completely eradicated in many U.S. herds at a cost of $450 million over 50 years using a “test and slaughter” program combined with meat inspection. Mycobacterium bovisM often does not produce acute disease, persists in the carrier stage, has multiple non‐human reservoirs, and easily crosses species. No effective vaccine or centralized global surveillance or eradication programs currently exist. Control measures result in significant economic losses. Smallpox eradication had limited economic consequences but has left much of world's population highly susceptible to zoonotic orthopoxviruses and to the use of smallpox as a biologic weapon. The primary threat of M. bovis exists in wildlife that share watering holes or pasture land with domestic stock. In the developed world, surveillance can minimize risks, but one‐third of the world's population lacks effective agricultural and food safety programs, leaving them at substantial risk for zoonotic infection by M. bovis.
Agroterrorism: Agricultural Infrastructure Vulnerability
Authors: VON BREDOW JURGEN , MYERS MICHAEL , WAGNER DAVID , VALDES JAMES J. , LOOMIS LARRY , ZAMANI KAVEH
Published: February 2006

Abstract: The intentional contamination of animal feed to reduce the availability of animal‐derived human food or to infect human populations is seldom mentioned, but animal feed could be an easy target for bioterrorists. The period of delay between the contamination of the animal feed and adulteration of the human food product provides an additional degree of uncertainty about the source of the contamination and minimizes the possibility of apprehending the terrorist. The less obvious and more natural the source of biological contamination, the greater the likelihood that the animal feed contamination will be mistaken as a natural phenomenon. However, the problems related to managing natural food contamination and intentional food contamination remain the same. Rapid testing and separation of contaminated feed are important steps, followed by the more specific identification of the contaminant to determine the source of adulteration and/or the possibility of decontamination. At this time identification of the bioagents is dependent on the availability of antibody‐specific test systems. The rapid development of specific antibodies for the development of sensitive and specific test kits is the key to identifying contamination and dealing effectively with the disposal or decontamination of the animal feed and, ultimately, preventing the contamination of animal‐derived human food products.
Long‐Term Chemical Carcinogenesis Bioassays Predict Human Cancer Hazards: Issues, Controversies, and Uncertainties
Authors: HUFF JAMES
Published: February 2006

Abstract: Long‐term carcinogenesis bioassays are the most valued and predictive means for identifying potential carcinogenic hazards of various agents to humans. Agents may be chemicals, chemical mixtures, multiple chemicals, combinations of chemicals, residues and contaminants, commercial products and formulations, and various exposure circumstances. Life‐styles, dietary factors, and occupational exposure circumstances are very difficult, but not totally impossible, to evaluate experimentally. Historically, the first chemical bioassay took place in the early part of this century: Yamagiwa and Ichikawa 1 in 1915, showed that coal tar applied experimentally to rabbit ears caused skin carcinomas. Since then, nearly 1500–2000 bioassays of one sort or another have been carried out. Importantly, however, some of these bioassays must be considered inadequate for judging the absence of carcinogenicity, since there were various limitations on the way they were performed: too few animals, too short a duration, too low exposure concentrations, too limited pathology, as examples. Thus, each bioassay must be critically evaluated, especially those reported to be negative, because “false negatives” are certainly more hazardous to human health than are “false positives”. Likewise, one must be careful not to discount bioassay results simply because a target organ in rodents may not have a direct counterpart in humans (e.g., Zymbal glands 2), or because an organ site in rodents may not be a major site of cancers in humans (e.g., mouse liver). The design and conduct of a bioassay is not simple, however, and one must be fully aware of possible pitfalls as well as viable and often necessary alternatives. Similarly, evaluating results and interpreting findings must be approached with the utmost objectivity and consistency. These and other select issues, controversies, and uncertainties possibly encountered in long‐term bioassays are covered in this paper. One fact remains abundantly clear: for every known human carcinogen that has been tested adequately in laboratory animals, the findings of carcinogenicity are concordant.
Using Molecular Epidemiology in Assessing Exposure for Risk Assessment
Authors: SCHULTE P. A. , WATERS M.
Published: February 2006

ABSTRACT: Quantitative estimation of health risks depends on exposure characterization, the nature of the dose response relationships, and the toxicity of the agents involved. The greatest uncertainties in risk assessment almost always arise from sparse or inadequate exposure data, inadequate understanding of exposure mechanisms, and insufficient understanding of the exposure‐dose‐response pathway. Additional sources of uncertainty arise when mixed or multiple exposures are implicated in the disease pathway, and as a result of variability in both exposures and responses within and between individuals. Here we consider the role of exposure assessment in the risk assessment process, the use of biological markers or molecular epidemiology to contribute to improvements in exposure assessment for risk assessment, and uncertainties associated with the use of biological markers.
Kaplan‐Meier Tumor Probability as a Starting Point for Dose‐Response Modeling Provides Accurate Lifetime Risk Estimates from Rodent Carcinogenicity Studies
Authors: TEN BERGE WIL F.
Published: February 2006

Abstract: In rodent carcinogenicity studies the linearized multistage model for modelling the dose‐response for specific tumor incidence has limitations in accuracy. This note provides an alternative basic method for analyzing the dose‐response relationship. It is based on an actuarial analysis of mortality and specific tumor incidence. The survival and the Kaplan‐Meier specific tumor probability are fitted to a Weibull model, in which exposure level, exposure period, and observation period are independent variables. The mortality from specific cancers at a certain time is simulated by means of the product of survival and specific tumor rate (derivative of Kaplan‐Meier tumor probability) as function of exposure level, exposure duration, and observation period, integrated over the observation period. The model is demonstrated by means of fitting the mortality and tumor incidence data from the second NTP mice study on butadiene to a Weibull model and to the linear, so‐called, one‐hit model. It will be shown that, in the experimental exposure range, the Weibull model is far superior to the one‐hit model and predicts the specific tumor incidence with a high accuracy over the total dose range. The Kaplan‐Meier probability model for a specific tumor is also useful for regulatory risk estimation. It is proposed that to develop a specific tumor a risk level of 1 in 1,000 over a lifetime is about equal to 5 in 10,000 at 50% survival of the population. The Kaplan‐Meier probability may be estimated at the time of 50% survival of the exposed population, which can be deduced from the all mortality data. This estimation method provides meaningful data, using exposure level, exposure duration, and observation period properly. The advantage of the actuarial analysis method for interpreting rodent studies is that allowance is made for competition between death causes, which is essential in case of considerable difference in mortality and specific mortality between dose groups. Integrating the product of survival and specific tumor rate is the proper way to predict, comparatively, mortality and specific mortality in exposed and unexposed rodent populations.
Measures of Exposure to Environmental Tobacco Smoke: Validity, Precision, and Relevance
Authors: WOODWARD ALISTAIR , AL‐DELAIMY WAEL
Published: February 2006

Abstract: It is often not clear what the best measures of exposure are for a risk assessment, or even how one should answer this question. Environmental tobacco smoke (ETS) provides a good example for an exploration of uncertainty. There are a variety of methods for estimating exposure and each has shortcomings. In this paper we summarize the physical characteristics of ETS and the principal methods for assessing exposure. We review the accuracy and applicability of these methods, and explore major sources of uncertainty in the assessment of ETS.
Combining Uncertainty Factors in Deriving Human Exposure Levels of Noncarcinogenic Toxicants
Authors: KODELL RALPH L. , GAYLOR DAVID W.
Published: February 2006

Abstract: Acceptable levels of human exposure to noncarcinogenic toxicants in environmental and occupational settings generally are derived by reducing experimental no‐observed‐adverse‐effect levels (NOAELs) or benchmark doses (BDs) by a product of uncertainty factors (Barnes and Dourson, Ref. 1). These factors are presumed to ensure safety by accounting for uncertainty in dose extrapolation, uncertainty in duration extrapolation, differential sensitivity between humans and animals, and differential sensitivity among humans. The common default value for each uncertainty factor is 10. This paper shows how estimates of means and standard deviations of the approximately log‐normal distributions of individual uncertainty factors can be used to estimate percentiles of the distribution of the product of uncertainty factors. An appropriately selected upper percentile, for example, 95th or 99th, of the distribution of the product can be used as a combined uncertainty factor to replace the conventional product of default factors.
Nonparametric Analysis of Dose‐Response Relationships
Authors: ULM K.
Published: February 2006

Abstract: A nonparametric method, isotonic regression, is proposed for analyzing a dose‐response relationship and for assessing a threshold value. There are several advantages of this method compared to parametric models. No specific form of the relationship (type of model and use of the covariates) is required, the only assumption is monotonicity. Rejection of specific hypothesis can be based on the result of a permutation test. Several applications (para‐aramid, crystalline silica, and PNOC) are presented. In these examples the dose‐response relationships are analyzed. Where a relationship is present the existence of a threshold is investigated.
Estimates of the Proportions of Carcinogens and Anticarcinogens in Bioassays Conducted by the U.S. National Toxicology Program: Application of a New Meta‐analytic Approach
Authors: CRUMP KENNY S. , KREWSKI DANIEL , VAN LANDINGHAM CYNTHIA
Published: February 2006

Abstract: A meta‐analysis was performed in order to estimate the proportion of liver carcinogens, the proportion of chemicals carcinogenic at any site, and the corresponding proportion of anticarcinogens among chemicals tested in 397 long‐term cancer bioassays conducted by the U.S. National Toxicology Program (NTP). Although the estimator used was negatively biased, the study provided persuasive evidence for a larger proportion of liver carcinogens (0.43, 90% CI: 0.35, 0.51) than was identified by the NTP (0.28). A larger proportion of chemicals carcinogenic at any site was also estimated (0.59, 90% CI: 0.49, 0.69) than was identified by the NTP (0.51), although this excess was not statistically significant. A larger proportion of anticarcinogens (0.66) was estimated than carcinogens (0.59). Despite the negative bias, it was estimated that 85% of the chemicals were either carcinogenic or anticarcinogenic at some site in some sex‐species group. This suggests that most chemicals tested at high enough doses will cause some sort of perturbation in tumor rates.