Biomedical subjects

Robert J Dempsey

Publications and source records attributed to Robert J Dempsey.

8 recordsLinked to original sources

PubMed2003

Inhibition of Na(+)-K(+)-Cl(-) cotransporter during focal cerebral ischemia decreases edema and neuronal damage.

Our previous study demonstrated that pharmacological inhibition of the Na(+)-K(+)-Cl(-) cotransporter isoform 1 (NKCC1) during ischemia and reperfusion attenuated neuronal damage and edema. In this study, we further investigated whether NKCC1 activity contributes to ischemic damage during either ischemia or reperfusion. Immunoblotting revealed that expression of NKCC1 protein was increased following 2-h focal ischemia in cerebral cortex. A sustained up-regulation of NKCC1 in cortex was detected at 4, 8, 12, and 24 h of reperfusion. An increase in the phosphorylated NKCC1 (NKCC1-p) was found at 4 and 8 h of reperfusion. In striatum, a significant increase in NKCC1 expression occurred between 4 and 24 h of reperfusion and no elevation of NKCC1-p signal was observed. Artificial cerebral spinal fluid (aCSF) or 100 microM bumetanide in aCSF were continuously microdialyzed into left cortices either 1 h prior to ischemia plus 2-h ischemia, or only during 24-h reperfusion. Infarction volume was significantly decreased in the pre-ischemic bumetanide-treated group (P<0.05) but not in the post-ischemic treatment group (P>0.05). In addition, pre-ischemic bumetanide treatment reduced the ipsilateral water content increase by 70% (P<0.05). Inhibition of NKCC1 did not attenuate poly (ADP-ribose) polymerase cleavage or the number of TUNEL-labeled apoptotic cells in ischemic brains. These results suggest that inhibition of NKCC1 attenuates cytotoxic edema and necrotic neuronal death during focal ischemia. Activation of NKCC1 activity plays a role in the early stage of ischemic damage.

Animals↗

PubMed2003

Traumatic brain injury-induced acute gene expression changes in rat cerebral cortex identified by GeneChip analysis.

Proper CNS function depends on concerted expression of thousands of genes in a controlled and timely manner. Traumatic brain injury (TBI) in mammals results in neuronal death and neurological dysfunction, which might be mediated by altered expression of several genes. By employing a CNS-specific GeneChip and real-time polymerase chain reaction (PCR), the present study analyzed the gene expression changes in adult rat cerebral cortex in the first 24 hr after a controlled cortical impact injury. Many functional families of genes not previously implicated in TBI-induced brain damage are altered in the injured cortex. These include up-regulated transcription factors (SOCS-3, JAK-2, STAT-3, CREM, IRF-1, SMN, silencer factor-B, ANIA-3, ANIA-4, and HES-1) and signal transduction pathways (cpg21, Narp, and CRBP) and down-regulated transmitter release mechanisms (CITRON, synaptojanin II, ras-related rab3, neurexin-1beta, and SNAP25A and -B), kinases (IP-3-kinase, Pak1, Ca(2+)/CaM-dependent protein kinases), and ion channels (K(+) channels TWIK, RK5, X62839, and Na(+) channel I). In addition, several genes previously shown to play a role in TBI pathophysiology, including proinflammatory genes, proapoptotic genes, heat shock proteins, immediate early genes, neuropeptides, and glutamate receptor subunits, were also observed to be altered in the injured cortex. Real-time PCR analysis confirmed the GeneChip data for many of these transcripts. The novel physiologically relevant gene expression changes observed here might explain some of the molecular mechanisms of TBI-induced neuronal damage.

Animals↗

PubMed2003

L-arginine in focal cerebral ischemia.

Nitric oxide and its precursor, L-arginine, have a great importance in cerebrovascular studies. In this study, we elucidate the dose dependent L-arginine effects on cerebral ischemia. The study involved 96 New Zealand albino rabbits, which were randomly allocated into four groups. The middle cerebral artery was occluded after a modified transorbital approach. Before the occlusion of MCA, each group was intravenously administered three doses of L-arginine i.e. 2.5 mg kg-1 for Group 1, 7.5 mg kg-1 for Group 2, and 12.5 mg kg-1 for Group 3. Thus, each group consisting of 24 animals was listed as 2.5 mg kg-1 (Group 1), 7.5 mg kg-1 (Group 2), 12.5 mg kg-1 (Group 3), and control group (receiving no intervention). Cerebral tissue oxygenazation was measured in parietal area by near infrared spectroscopy in all animals prior to and at 5, 30, and 60 min after MCA occlusion. Six hours after MCA occlusion, all the animals were studied for the area of ischemia (n = 40), edema formation (n = 32), and blood nitrite-nitrate levels (n = 24). At the dose of 2.5 mg kg-1 of L-arginine no differences were detected on ischemic tissue volume, brain edema, cerebral tissue oxygenazation, blood nitrite-nitrate levels when compared to the values of control group. However, with the dose of 7.5 mg kg-1, there were significant improvements in the levels of ischemic tissue volume, brain edema, and nitrite-nitrate levels compared to those of the control group and the 2.5 mg kg-1 group. At a dose of 12.5 mg kg-1, there were further improvements in the levels of ischemic tissue volume, brain edema, penumbral zone nitrite-nitrate levels. After 30 min of occlusion, cerebral tissue oxygenazation values increased in a dose dependent fashion. L-arginine's protective effect on cerebrovascular ischemia shows a dose dependent effect on infract size and tissue water content that may prove beneficial in the treatment of ischemia. However, further dose-dependent studies are needed.

Animals↗

PubMed2003

Cytidinediphosphocholine treatment to decrease traumatic brain injury-induced hippocampal neuronal death, cortical contusion volume, and neurological dysfunction in rats.

OBJECT: In previous studies at their laboratory the authors showed that cytidinediphosphocholine (CDP-choline), an intermediate of phosphatidylcholine synthesis, decreases edema formation and blood-brain barrier disruption following traumatic brain injury (TBI). In the present study the authors investigate whether CDP-choline protects hippocampal neurons after controlled cortical impact (CCI)-induced TBI in adult rats. METHODS: After adult male Sprague-Dawley rats had been anesthetized with halothane, a moderate-grade TBI was induced with the aid of a CCI device set at a velocity of 3 m/second, creating a 2-mm deformation. Sham-operated rats, which underwent craniectomy without impact served as controls. The CDP-choline (100, 200, and 400 mg/kg body weight) or saline was injected into the animals twice (once immediately postinjury and once 6 hours postinjury). Seven days after the injury, the rats were neurologically evaluated and killed, and the number of hippocampal neurons was estimated by examining thionine-stained brain sections. By 7 days postinjury, there was a significant amount of neuronal death in the ipsilateral hippocampus in the CA2 (by 53 +/- 7%, p < 0.05) and CA3 (by 59 +/- 9%, p < 0.05) regions and a contusion (volume 34 +/- 8 mm3) in the ipsilateral cortex compared with sham-operated control animals. Rats subjected to TBI also displayed severe neurological deficit at 7 days postinjury. Treating rats with CDP-choline (200 and 400 mg/kg, intraperitoneally) significantly prevented TBI-induced neuronal loss in the hippocampus, decreased cortical contusion volume, and improved neurological recovery. CONCLUSIONS: Treatment with CDP-choline decreased brain damage following TBI.

Animals↗

PubMed2002

GeneChip analysis shows altered mRNA expression of transcripts of neurotransmitter and signal transduction pathways in the cerebral cortex of portacaval shunted rats.

Identifying the gene expression changes induced by hepatic encephalopathy (HE) leads to a better understanding of the molecular mechanisms of HE-induced neurological dysfunction. Using GeneChip and real-time PCR, the present study evaluated the gene expression profile of rat cerebral cortex at 4 weeks after portacaval shunting. Among 1,263 transcripts represented on the chip, mRNA levels of 31 transcripts were altered (greater than twofold; 16 increased and 15 decreased) in the portacaval shunted (PCS) rat compared to sham control. Changes observed by GeneChip analysis were confirmed for 20 transcripts (8 increased, 7 decreased, and 5 unchanged in PCS rat brain) by real-time PCR. Neurotransmitter receptors, transporters, and members of the second messenger signal transduction are the major groups of genes altered in PCS rat brain. Of importance was that the increased heme oxygenase-1 and decreased Cu,Zn-superoxide dismutase expression observed raise the possibility of oxidative stress playing a pathogenic role in chronic HE.

Animals↗

PubMed2002

Polyamines and central nervous system injury: spermine and spermidine decrease following transient focal cerebral ischemia in spontaneously hypertensive rats.

Polyamines (putrescine, spermidine and spermine) are ubiquitous cellular components, but their specific role in central nervous system (CNS) injury has yet to be characterized. CNS injury results in increased activities of ornithine decarboxylase and spermidine/spermine-N(1)-acetyltransferase, and accumulation of putrescine. The present study determined the polyamine profile in three models of CNS injury, in two different species (gerbil and rat) and two strains of rats (Sprague-Dawley and spontaneously hypertensive): (1) transient focal cerebral ischemia in spontaneously hypertensive rats (SHR); (2) traumatic brain injury in Sprague-Dawley rats; and (3) transient forebrain ischemia in gerbils. While there was a significant increase in putrescine in all three models, spermine and spermidine levels were unaltered in forebrain ischemia and traumatic brain injury. However, transient focal cerebral ischemia shows depletion of spermine and spermidine levels in injured hemisphere compared to contralateral region. Exogenous spermine significantly restored the spermine as well as spermidine levels in the ipsilateral hemisphere after transient focal cerebral ischemia, but did not alter putrescine levels or the ratio of spermidine to spermine. The loss of spermine in particular, may have several consequences that contribute to ischemic injury, including destabilization of chromatin, decreased mitochondrial Ca(2+) buffering capacity, and increased susceptibility to oxidative stress. Based on our and other studies, we propose a tentative antioxidant mechanism of spermine neuroprotection.

Animals↗

PubMed2002

Gene expression analysis of spontaneously hypertensive rat cerebral cortex following transient focal cerebral ischemia.

Identification of novel modulators of ischemic neuronal death helps in developing new strategies to prevent the stroke-induced neurological dysfunction. Hence, the present study evaluated the gene expression changes in rat cerebral cortex at 6 and 24 h of reperfusion following transient middle cerebral artery occlusion (MCAO) by GeneChip analysis. Transient MCAO resulted in selective increased mRNA levels of genes involved in stress, inflammation, transcription and plasticity, and decreased mRNA levels of genes which control neurotransmitter function and ionic balance. In addition to a number of established ischemia-related genes, many genes not previously implicated in transient focal ischemia-induced brain damage [suppressor of cytokine signaling (SOCS)-3, cAMP responsive element modulator (CREM), cytosolic retinol binding protein (CRBP), silencer factor-B, survival motor neuron (SMN), interferon-gamma regulatory factor-1 (IRF-1), galanin, neurotrimin, proteasome subunit RC8, synaptosomal-associated protein (SNAP)-25 A and B, synapsin 1a, neurexin 1-beta, ras-related rab3, vesicular GABA transporter (VGAT), digoxin carrier protein, neuronal calcium sensor-1 and neurodap] were observed to be altered in the ischemic cortex. Real-time PCR confirmed the GeneChip results for several of these transcripts. SOCS-3 is a gene up-regulated after ischemia which modulates inflammation by controlling cytokine levels. Antisense knockdown of ischemia-induced SOCS-3 protein expression exacerbated transient MCAO-induced infarct volume assigning a neuroprotective role to SOCS-3, a gene not heretofore implicated in ischemic neuronal damage.

Animals↗

PubMed2002

Diffusion tensor MR imaging in diffuse axonal injury.

BACKGROUND AND PURPOSE: Disruption of the cytoskeletal network and axonal membranes characterizes diffuse axonal injury (DAI) in the first few hours after traumatic brain injury. Histologic abnormalities seen in DAI hypothetically decrease the diffusion along axons and increase the diffusion in directions perpendicular to them. DAI therefore is hypothetically associated in the short term with decreased diffusion anisotropy. We tested this hypothesis by measuring the diffusion characteristics of traumatized brain tissue with use of diffusion tensor MR imaging. METHODS: Five patients with mild traumatic brain injuries and 10 control subjects were studied with CT, conventional MR imaging, and diffusion tensor imaging. All patients were examined within 24 hours of injury. In each participant, diffusion tensor indices from homologous normal-appearing white matter regions of both hemispheres were compared. These indices were also compared between homologous regions of each patient and the control group. In two patients, diffusion tensor images from the immediate post-trauma period were compared with those at 1 month follow-up. RESULTS: Patients displayed significant reduction of diffusion anisotropy in several regions compared with the homologous ones in the contralateral hemisphere. Such differences were not observed in the control subjects. Significant reduction of diffusion anisotropy was also detected when diffusion tensor results from the patients were compared with those of the controls. This reduction was often less evident 1 month after injury. CONCLUSION: White matter regions with reduced anisotropy are detected in the first 24 hours after traumatic brain injury. Therefore, diffusion tensor imaging may be a powerful technique for in vivo detection of DAI.

Adult↗