Biomedical subjects

J A Clemens

Publications and source records attributed to J A Clemens.

At least 19 recordsLinked to original sources

PubMed2000

Cerebral ischemia: gene activation, neuronal injury, and the protective role of antioxidants.

A large number of gene products appear after an ischemic insult making it difficult to decipher which genes are involved in tissue injury. Reactive oxygen species (ROS) can influence gene expression and have a role in the events that lead to neuronal death. In global cerebral ischemia the oxidative responsive transcription factor, NF-kappa B, is persistently activated in neurons that are destined to die. There are several potential routes through which NF-kappa B can act to induce neuronal death, including production of death proteins and an aborted attempt to reenter the cell cycle. NF-kappa B is only transiently activated in neurons that survive. Persistent NF-kappa B activation can be blocked by antioxidants, which suggests that the neuroprotective effect of antioxidants may be due to inhibiting activation of NF-kappa B.

Animals↗

PubMed2000

Neuroprotection by LY341122, a novel inhibitor of lipid peroxidation, against focal ischemic brain damage in rats.

LY341122 (2-(3, 5-di-t-butyl-4-hydroxyphenyl)-4-(2-(4-methylethylaminomethyl-ph enylox y)ethyl)oxazole) is a potent inhibitor of lipid peroxidation which has been shown to protect against global ischemia and traumatic brain injury in rats. The purpose of this study was to examine the effect of LY341122 on ischemic injury in a highly reproducible model of focal cerebral ischemia in rats. Male Sprague-Dawley rats were anesthetized with halothane and subjected to 120 min of temporary middle cerebral artery occlusion by retrograde insertion of an intraluminal nylon suture coated with poly-L-lysine. The drug (LY341122, n=19) or vehicle (phosphate-buffered saline (PBS), n=10) was administered i.v. (as a 5 or 10 mg/kg bolus followed by a 5 or 10 mg/kg/h infusion for 20 h, respectively, starting 1 or 2 h after the onset of middle cerebral artery occlusion). Neurological status was evaluated during middle cerebral artery occlusion (60 min) and daily for 3 days thereafter. Three days after ischemia, brains were perfusion-fixed and infarct volumes and brain edema were determined. LY341122 significantly improved the neurological score compared to vehicle at 24, 48 and 72 h after middle cerebral artery occlusion. Treatment with LY341122 significantly reduced total infarct volume in all treated groups compared to vehicle rats. Cortical infarct volume was significantly reduced by LY341122 treatment in the 10 mg/kg (1 h) and LY341122 10 mg/kg (2 h) groups compared to vehicle rats (14.7+/-9.5 vs. 106.8+/-20.9 mm(3), and 36.9+/-20.1 vs. 106. 8+/-20.9 mm(3), respectively (mean+/-S.E.M.)). Striatal infarct volume was also significantly reduced by treatment with LY341122 in the 10 mg/kg (1 h) group compared to vehicle (23.7+/-3.4 vs. 68. 2+/-6.7 mm(3)). These results demonstrate the neuroprotective efficacy of LY341122 in focal cerebral ischemia.

Animals↗

PubMed1999

Rat B(2) sequences are induced in the hippocampal CA1 region after transient global cerebral ischemia.

Global brain ischemia causes cell death in the CA1 region of the hippocampus 3-5 days after reperfusion. The biological pathway leading to such delayed neuronal damage has not been established. By using differential display analysis, we examined expression levels of poly(A) RNAs isolated from hippocampal extracts prepared from rats exposed to global ischemia and found an up-regulated transcript, clone 17a. Northern blot analysis of clone 17a showed an approximately 35-fold increase in the ischemic brain at 24 h after four-vessel occlusion. Rapid amplification of cDNA ends of clone 17a revealed a family of genes (160-540 base pairs) that had the characteristics of rodent B(2) sequences. In situ hybridization demonstrated that the elevated expression of this gene was localized predominantly in the CA1 pyramidal neurons. The level of expression in the CA1 region decreased dramatically between 24 and 72 h after ischemia. The elevated expression of clone 17a was not observed in four-vessel occlusion rats treated with the compound LY231617, an antioxidant known to exert neuroprotection in rats subjected to global ischemia. Since delayed neuronal death has the characteristics of apoptosis, we speculate that clone 17a may be involved in apoptosis. We examined the expression level of clone 17a in in vitro models of apoptosis using cerebellar granule neurons that were subjected to potassium removal, glutamate toxicity, or 6-hydroxydopamine treatment and found that clone 17a transcripts were induced in cerebellar granule neurons by glutamate or 6-hydroxydopamine stimulation but not potassium withdrawal.

Amino Acid Sequence↗

PubMed1999

Fatigue behavior of calcium phosphate coatings with different stability under dry and wet conditions.

To obtain stable plasma sprayed calcium phosphate coatings, coatings with a high crystallinity and low solubility were developed. However, stability of ceramic coatings is also influenced by their fatigue resistance. Recently, fatigue failure was proposed to explain coating detachment from implants under loaded conditions. Therefore, plasma-sprayed calcium phosphate coatings with different crystallinity were investigated in vitro for fatigue failure. An amorphous and a crystalline hydroxylapatite coating (AHA and CHA) and a highly crystalline fluorapatite coating (FA) were subjected to cyclic load tests, both in dry conditions and in simulated body fluid (SBF). The results in SBF revealed that the crystalline CHA and FA coating detached completely at the highest stressed middle section of the bar. The FA coating delaminated earlier than the CHA coating. The amorphous AHA coating showed only partial coating loss at the completion of the test. Tests in dry conditions did not reveal any change in the coatings tested. These results suggest a relation between crystallinity of apatite coatings and their failure due to fatigue: high crystallinity coatings demonstrate earlier and more complete fatigue failure than the amorphous apatite coatings. It can be concluded that coating stability is not determined solely by static dissolution, but by fatigue failure as well.

Biocompatible Materials↗

PubMed1999

Early treatment with a novel inhibitor of lipid peroxidation (LY341122) improves histopathological outcome after moderate fluid percussion brain injury in rats.

OBJECTIVE: Reactive oxygen species are thought to participate in the pathobiology of traumatic brain injury (TBI). This study determined whether treatment with LY341122, a potent inhibitor of lipid peroxidation and an antioxidant, would provide neuroprotection in a rat model of TBI. METHODS: To investigate the efficacy of LY341122 in this parasagittal fluid percussion model (1.8-2.1 atm), the rats received oral administration of LY341122 (100 mg/kg) or vehicle 2 hours before and 4 hours after TBI (each group, n = 7). To investigate the therapeutic window for treatment, rats were treated with LY341122 or vehicle for 20 hours by femoral vein infusion starting at 5 minutes, 30 minutes, or 3 hours after TBI (each group, n = 5). Three days after injury, analysis of contusion volumes and the frequency of damaged cortical neurons was conducted. RESULTS: Oral administration of LY341122 before and after TBI led to a significant reduction in overall contusion volume (3.28 mm3+/-0.75 mm3 [mean +/- standard error of the mean] versus 1.32 mm3 +/- 0.33 mm3; P < 0.05) and also reduced the frequency of damaged cortical neurons (1191.7 +/- 267.1 versus 474.6 +/- 80.2; P < 0.05). In the second experiment, rats treated with LY341122 at 5 minutes or 30 minutes after TBI also demonstrated a significant reduction (P < 0.05) in contusion volume (1.92 mm3 +/- 0.64 mm3 or 1.59 mm3 +/- 0.50 mm3, respectively) compared with vehicle-treated rats (4.32 mm3 +/- 1.15 mm3). A significant reduction in total cortical necrotic neuron counts was also demonstrated in the 5-minute group (2243.8 +/- 265.3 versus 1457.8 +/- 265.3; P < 0.05). In contrast, histopathological outcome was not significantly improved when treatment was delayed until 3 hours after TBI. CONCLUSION: These data reinforce the hypothesis that lipid peroxidation and reactive oxygen species participate in the acute pathogenesis of TBI. Treatment delayed until 3 hours after TBI did not provide significant histopathological protection.

Administration, Oral↗

PubMed1999

Continuing postischemic neuronal death in CA1: influence of ischemia duration and cytoprotective doses of NBQX and SNX-111 in rats.

BACKGROUND AND PURPOSE: Transient forebrain ischemia results in a 24- to 72-hour delayed loss of CA1 neurons. Previous work has not assessed whether insult durations can vary the degree and maturation rate of CA1 injury and whether there are different ultrastructural features of death after brief or severe ischemia. We also tested whether known cytoprotective drugs achieve permanent or transient neuroprotection. METHODS: In the first experiment, ischemia was induced for 5, 15, or 30 minutes with the use of the 4-vessel occlusion rat model with 1- to 28-day survival. Others subjected to 5 or 15 minutes of ischemia and allowed to survive for 14 or 7 days, respectively, were examined with electron microscopy. Finally, we determined whether NBQX (30 mg/kg x3 at 0 or 6 hours after ischemia), an AMPA antagonist, and SNX-111 (5 mg/kg at 6 hours after ischemia), an N-type Ca2+ channel antagonist, provided enduring CA1 protection against 10 minutes of ischemia. RESULTS: CA1 damage was not detected at 24 hours. Thirty minutes of ischemia produced 47% and 84% CA1 damage at 2 and 3 days, respectively. A 15-minute occlusion yielded 11%, 74%, and 86% loss at 2, 3, and 7 days, respectively. Five minutes of ischemia produced an even slower progression with 24%, 52%, and 59% loss at 3, 7, and 14 days, respectively. Ultrastructural examination after 5 and 15 minutes of ischemia revealed necrosis with no morphological evidence of apoptosis. Both NBQX (P<0.021) and SNX-111 (P<0.001) significantly reduced CA1 death at 7 days (</=35%) but not at 28 days (>/=80%) compared with saline treatment ( approximately 79%). CONCLUSIONS: Brief forebrain ischemia results in a slower progression of CA1 loss than more severe insults. Nonetheless, neuronal injury had necrotic, not apoptotic, morphology. NBQX and SNX-111 only postponed CA1 injury.

Animals↗

PubMed1998

Healing of large (2 mm) gaps around calcium phosphate-coated bone implants: a study in goats with a follow-up of 6 months.

Plasma-sprayed hydroxylapatite (HA) coatings are known for their ability to demonstrate osseointegration with bone. Recently it was found that the amount of bone apposition was strongly reduced 6 weeks after implantation in a goat model if gaps of two millimeters between bone and apatite coating existed. Stability of the apatite coatings examined did not influence the gap-healing ability. This study investigated whether a longer follow-up period of 24 weeks would be sufficient for the restoration of bone apposition on apatite coatings in an identical surgical model with 2 mm gaps, and whether bone apposition on the apatite coatings is influenced by the coating stability. Three coatings were investigated: 25-30% crystalline HA (aHA), 60-63% crystalline HA (cHA), and 85-90% crystalline fluorapatite (FA). Uncoated Ti-6A1-4V implants were used as controls. Implants were inserted in the femoral condyles of both femora of eight goats. Each goat received four implants. Histology revealed that bone formation on each of the apatite coatings remained low and did not increase with an extended follow-up period of 24 weeks. The coatings showed significantly (P < 0.01) more bone contact than the uncoated control implants. The three different coatings did not show significant differences in bone apposition. The aHA coating in most cases had disappeared completely after 24 weeks. Despite the disappearance of the aHA coating, bone contact was seen on the substrate surface without fibrous tissue interposition. The cHA coating showed minor signs of degradation while the FA coatings showed no visible degradation. It is concluded that non-press-fit implantation of apatite-coated implants leads to more bone apposition as compared to uncoated Ti-6A1-4V implants. However, it is suggested by these results that the upper limit of gaps around apatite implants is 2 millimeters in a non-weight-bearing model in goats. Bone apposition will not increase by extending the follow-up period more than six weeks, nor will it be altering the stability of the apatite coatings used.

Animals↗

PubMed1998

Metabotropic glutamate receptor activation in vivo induces intraneuronal amyloid immunoreactivity in guinea pig hippocampus.

Stimulation of metabotropic glutamate receptors in vitro has been shown to accelerate the breakdown of amyloid precursor protein (APP) to form increased production of non-amyloidogenic secreted APP (sAPP). The mechanism whereby this occurs is not entirely clear but it is presumed to be linked to generation of diacylglycerol and activation of protein kinase C because other neurotransmitter receptors such as m1 and m3 muscarinic receptors, known to be coupled to this second messenger cascade, likewise increase sAPP production. Although it is presumed that a reciprocal relationship exists between the formation of amyloid beta protein (Abeta) and the production of sAPP, recent evidence suggests alternative processing can occur. Given the fact that much of the observations on APP metabolism have been made in vitro we sought to investigate the effect of metabotropic receptor activation on Abeta in vivo in a species known to contain the same amino acid sequence of Abeta as found in humans. Intrahippocampal injection of the mGluR agonist 1S,3R-ACPD in guinea pigs produced neurodegeneration of CA1 hippocampal pyramidal neurons at 12 h postinjection. Immunocytochemistry of sections from ACPD injected animals using selective antibodies to Abeta revealed the presence of punctate intraneuronal granules in pyramidal neurons of the hippocampus. These structures appeared to be localized within the nucleus and were particularly prominent in neurons within the region of neurodegeneration. Immunoreactivity was not observed in vehicle injected controls nor in sections from ACPD injected animals stained with preadsorbed antiserum. Abeta immunodetection was correlated with the onset of neurodegeneration since animals evaluated at 1 h and 4 h postinjection lacked both Abeta immunoreactivity as well as neurodegeneration. Evaluation of animals injected with NMDA revealed neurodegeneration but no Abeta immunoreactivity suggesting Abeta formation did not appear to be due to non-selective excitotoxicity. Staining of sections with antibodies directed to various regions of APP demonstrated increased C-terminal APP immunoreactivity in pyramidal neurons in the vicinity of degeneration. These data support recent in vitro studies illustrating that Abeta can be found intracellularly within neurons.

Amyloid↗

PubMed1998

Drug-induced neuroprotection from global ischemia is associated with prevention of persistent but not transient activation of nuclear factor-kappaB in rats.

BACKGROUND AND PURPOSE: Nuclear factor-kappaB (NF-kappaB) is an oxidative stress responsive transcription factor that is transiently activated in most forebrain neurons in response to transient global ischemia. However, in hippocampal CA1 neurons destined to die, NF-kappaB remains persistently activated. The present study was performed to determine whether an antioxidant (LY231617) that afforded neuroprotection in previous studies had any effect on NF-kappaB activation in hippocampal CA1 neurons after global ischemia. METHODS: Rats were subjected to 30 minutes of forebrain ischemia by 4-vessel occlusion (4-VO) and killed at 24 and 72 hours after ischemia. LY231617 was administered orally at a dose of 50 mg/kg 30 minutes before 4-VO and again 4 hours after 4-VO. Neuronal damage was evaluated in sections stained with cresyl violet. Other sections were immunostained with antibodies to NF-kappaB p50 to assess nuclear localization. An electrophoretic mobility shift assay was performed on nuclear extracts from sham- and LY231617-treated rats at 24 and 72 hours after ischemia. RESULTS: The administration of LY231617 had a significant protective effect on hippocampal CA1 neurons at 72 hours after ischemia (control group, 16 +/- 7 neurons/mm; treated group, 294 +/- 35 neurons/mm, P<.02) and prevented nuclear translocation of activated NF-kappaB as normally seen at 72 hours after ischemia in untreated controls. In contrast, the untreated controls showed activated NF-kappaB at 72 hours after ischemia. At 24 hours after ischemia, both the control group and the LY231617 group showed intense nuclear localization of NF-kappaB. CONCLUSIONS: Activation of NF-kappaB in vitro has been reported to promote proapoptotic as well as antiapoptotic mechanisms, depending on the cell type being investigated. In the present in vivo study, the role of the transient activation of NF-kappaB observed at 24 hours may be responsible for the induction of protective factors in neurons that survive the ischemic insult, whereas the persistent activation of NF-kappaB in hippocampal neurons could be responsible for the induction of proteins that result in CA1 neuronal death.

Animals↗

PubMed1997

Bcl-Xshort is elevated following severe global ischemia in rat brains.

Hippocampal CA1 neurons are highly susceptible to short periods of transient global ischemia. We have previously reported in a rat model of transient forebrain global ischemia that activation and nuclear localization of NF-kB occurs in the CA1 neurons at 24 and 72 h post reperfusion. Events following NF-kB activation would ultimately determine whether damaged cells will undergo programmed cell death. We have selected bcl-x gene expression for study because there is increasing evidence that proteins encoded by the bcl-2 gene family (bcl-2, bcl-x, bax etc) play a role in the regulation of programmed cell death. We have observed that the bcl-x gene promoter contains a putative consensus sequence for NF-kB/CS4 responsive activation. We also can show that other members of the bcl-2 multigene family contain the NF-kB/CS4 sequence in their five prime regulatory regions. In this study, we show that NF-kB p50 and NF-kB p65 act in synergy to transactivate the bcl-x promoter in co-transfected 293 cells. We also report that following ischemia and NF-kB activation, bcl-x messenger RNA levels increase in the CA1 hippocampal region. As a result of this transcriptional increase, surprisingly, it is bcl-xs, the apoptotic form of bcl-x, that is elevated. These results suggest that activation of NF-kB can lead to increased expression of bcl-x as manifested by the increase in the short form of bcl-x.

Animals↗

PubMed1997

Healing of gaps around calcium phosphate-coated implants in trabecular bone of the goat.

Hydroxylapatite coatings are under clinical investigation in orthopaedics and dentistry. Bone formation on apatite coatings in the presence of gaps is important for clinical applications. The importance of the stability of the coating is not known at present. By varying the plasma-spray parameters, and by the addition of fluoride, the crystallinity and stability of calcium phosphates can be changed. It is suggested that bone formation is enhanced by dissolution of the apatite coating. We studied apatite coatings of varying stability with regard to their gap-healing characteristics, and we examined what the maximum gap would be that can be bridged if a coating is applied. Ti-6A1-4V implants coated with 62% crystalline hydroxylapatite, 30% crystalline hydroxylapatite or fluorapatite, or noncoated Ti-6A1-4V were implanted in 16 goats. The implants were surrounded by gaps of 1 or 2 mm, and the follow-up period was 6 weeks. Histological examination and histometry revealed that gaps of 1 mm can be bridged by bone if an apatite coating is applied. However, only a minimal amount of bone contact was seen on the apatite coatings with 2 mm gaps. Uncoated implants demonstrated no bone contact at all. Among the three different coatings there were no differences in gap healing. It can be concluded that in the goat, gaps of 2 or more mm between coated implants and host bone tissue inhibit bone deposition on the coating (p < 0.05), but the stability of the coating does not influence gap-healing characteristics.

Alloys↗

PubMed1997

Global cerebral ischemia activates nuclear factor-kappa B prior to evidence of DNA fragmentation.

The oxidative stress responsive transcription factor nuclear factor-kappa B (NF-kappa B) consists of a p50 (50 kDa) and p65/RelA (65 kDa) component and can be activated in vitro by TNF alpha, IL1 beta, hydrogen peroxide and oxygen radicals. All of the above factors are also known to be elevated at certain times after transient global ischemia. The present study was performed to determine if NF-kappa B was activated in vivo by transient global forebrain ischemia. Adult male rats were subjected to 30 min of 4-vessel occlusion (4-VO) and sacrificed at selected post-ischemic time points. Levels of NF-kappa B p50 and p65 subunits were determined by immunocytochemistry, Western blot and electrophoretic mobility-shift analysis. The enhancer complex was also confirmed by immuno-gel-shift analysis. Specific labeling of DNA strand breaks and DNA fragmentation was examined in situ by means of the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method. Western blot analysis of hippocampus showed induction of p50 and p65. A time course of NF-kappa B induction in hippocampus showed a p50-specific band at 6 h that increased in intensity over 12, 48 h and then decreased by 96 h post-ischemia. Immunocytochemistry revealed at 24 h post-ischemia that p65 and p50 immunoreactivity was present in neuronal nuclei of hippocampal CA1 neurons as well as all other hippocampal regions and several other forebrain regions which were not vulnerable to transient forebrain ischemia. At 72 h post-ischemia, nuclear NF-kappa B immunoreactivity had disappeared in all brain areas except in hippocampal CA1 neurons which were degenerating. No evidence for DNA fragmentation as revealed by TUNEL staining could be observed at 24 h. However, at 72 h, hippocampal CA1 neurons were heavily labeled. The results of this study demonstrate that global forebrain ischemia causes a transient activation of NF-kappa B in many forebrain regions. NF-kappa B remains persistently activated in the vulnerable hippocampal CA1 sector. Because of the persistent activation of NF-kappa B in these neurons, the possibility exists that NF-kappa B has a role in programmed cell death in hippocampal CA1 neurons.

Animals↗

PubMed1997

Increased expression of peripheral benzodiazepine receptors in the facial nucleus following motor neuron axotomy.

Peripheral benzodiazepine receptors (PBRs) are expressed in a variety of tissues but are normally found at low levels in the brain. Following various types of nerve injury, a reactive gliosis results that exhibits a high expression of this receptor. To further characterize the expression of PBRs following neuronal injury, we evaluated PBR expression in the facial nucleus following facial nerve axotomy (FNA). Injury to a peripheral nerve results in a complex series of metabolic and morphological changes around the injured neuron. Transections of the facial nerve results in a rapid activation of both astrocytes and microglia around axotomized motor neurons. FNA resulted in an increase in the staining for both astrocytes (glial fibrillary acidic protein) and activated microglia (OX42). There was also a reduction in synaptic contacts with the motor nucleus as evidenced by reduced staining for the synaptic marker, synaptophysin. In sections labeled with [3H]-PK11195, the subsequent autoradiograms displayed marked increases in the labeling for PBRs. This increase was observed at 5, 7 and 10 days after nerve transection. The increase was primarily in the level of expression (Bmax), with no change in the affinity of the ligand (Kd). The increase in PBR expression after FNA supports the hypothesis that PBRs can be used as a sensitive marker for CNS injury.

Animals↗

PubMed1997

Global ischemia activates nuclear factor-kappa B in forebrain neurons of rats.

BACKGROUND AND PURPOSE: After global ischemia, brain levels of hydrogen peroxide, oxygen radicals, and the cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) are increased. Oxygen radicals, TNF-alpha, and IL-1 beta are known to activate nuclear factor-kappa B (NF-kappa B) in vitro. The present study was performed to determine whether NF-kappa B was activated in vivo by global ischemia in hippocampal CA1 neurons. METHODS: Adult male rats were subjected to 30 minutes of four-vessel occlusion and killed 72 hours later. Levels of NF-kappa B p50 and p65 subunits in hippocampus were determined by immunocytochemistry, Western blot, and gel-shift analysis. Specific labeling of DNA strand breaks was demonstrated by means of an Apoptag apoptosis detection kit. RESULTS: Labeling of DNA strand breaks was present at 72 hours. Chromatin compaction and segregation, a characteristic of apoptosis, was observed in sections stained with hematoxylin and eosin. NF-kappa B p50 and p65 immunoreactivity localized only to nuclei of CA1 neurons at 72 hours after reperfusion. Induction of the activated p50 and p65 subunits was confirmed by Western blot and electromobility shift analysis. The results demonstrate that NF-kappa B is activated selectively in hippocampal CA1 neurons at 72 hours after four-vessel occlusion, which is at the approximate time of CA1 neuronal cell death. CONCLUSIONS: Transient forebrain ischemia resulted in a marked activation of nuclear NF-kappa B in the highly vulnerable CA1 sector. Intense nuclear localization of NF-kappa B was associated only with dying neurons; regions of the hippocampus that were not vulnerable to four-vessel occlusion did not exhibit nuclear NF-kappa B localization. The elevation of NF-kappa B in degenerating CA1 neurons may be associated mechanistically with apoptotic or necrotic cell death.

Animals↗

PubMed1997

Effect of delayed albumin hemodilution on infarction volume and brain edema after transient middle cerebral artery occlusion in rats.

The authors examined the effect of delayed high-concentration albumin therapy on ischemic injury in a highly reproducible model of middle cerebral artery (MCA) occlusion in rats. Male Sprague-Dawley rats weighing 270 to 320 g were anesthetized with halothane and subjected to 120 minutes of temporary MCA occlusion induced by means of a poly-L-lysine-coated intraluminal nylon suture inserted retrograde via the external carotid artery into the internal carotid artery and MCA. The agent (20% human serum albumin [HSA]) or control solution (sodium chloride 0.9%) was administered intravenously at a dosage of 1% of body weight immediately after suture removal following a 2-hour period of MCA occlusion. The animals' neurological status was evaluated during MCA occlusion (at 60 minutes) and daily for 3 days thereafter. The brains were perfusion-fixed, and infarct volumes and brain edema were determined. The HSA significantly improved the neurological score compared with saline at 24 hours after MCA occlusion. The rats treated with HSA also had significantly reduced total infarct volume (by 34%) and brain edema (by 81%) compared with saline-treated rats. There was a strong correlation between hematocrit level and brain edema (p < 0.01), and between total infarct volume or brain edema and neurological score at 24, 48, and 72 hours postinjury (p < 0.0002). These results strongly support the beneficial effect of delayed albumin therapy in transient focal ischemia and indicate its possible usefulness in treating patients with acute ischemic stroke.

Anesthetics, Inhalation↗

PubMed1996

Effects of LY231617 and angiotensin IV on ischemia-induced deficits in circular water maze and passive avoidance performance in rats.

The antioxidant LY231617 has previously been shown to offer significant protection against postischemic cell death in the hippocampus and corpus striatum of rats. The present results extend this observation by demonstrating a concomitant protection against the spatial memory deficits that accompany damage to the hippocampus, as measured by the circular water maze task. These animals were further tested for changes in associative memory by employing a passive avoidance conditioning task. No deficits in passive avoidance conditioning were measured among the 4-vessel occlusion animals treated with LY231617 or vehicle. However, the intracerebroventricular injection of angiotensin IV (Ang IV) immediately prior to foot-shock conditioning improved retention of the conditioned response during the subsequent 2-day period. These results suggest that LY231617 can offer considerable protection against global ischemia-induced cell death in the hippocampus with resulting preservation of spatial memory abilities. In addition, untreated animals that suffered cell losses in the hippocampus remained capable of responding to the facilitory effect of centrally administered Ang IV on a non-spatial memory task. The hypothesized mechanisms of the protection characteristics of LY231617, and the nootropic effect of Ang IV, are discussed.

Angiotensin II↗

PubMed1996

Nuclear and cytoplasmic localization of the beta-amyloid peptide (1-43) in transfected 293 cells.

Cultures of transformed human embryonic kidney 293 cells were transiently transfected with minigene constructs coding for the Abeta peptide (1-43). The Abeta minigene used in this study consisted of exons 16 and 17 of the amyloid precursor protein gene, including the 6000+ bp intronic region. Two of the constructs used in this study, human amyloid precursor protein (APP) promoter-driven Abeta minigene and BK virus enhancer/adenovirus major late promoter-driven Abeta minigene, did not contain a signal peptide sequence, whereas the third, human APP promoter-signal peptide Abeta minigene did not contain the human APP signal sequence. The resulting Abeta products were detected by immune precipitation, using 10D5 antibody and Western blot analysis, using R1280 antisera, as SDS stable oligomers in cell lysates of cells containing all three constructs or in culture media when produced by the signal peptide construct. Evaluation of the cells by immunocytochemistry using conventional and transmission electron microscopy indicated that the cells transfected with constructs without the signal peptide accumulated immunoreactive Abeta primarily in the nucleus.

Amyloid beta-Peptides↗

PubMed1996

Cytosolic phospholipase A2 (cPLA2) immunoreactivity is elevated in Alzheimer's disease brain.

Phospholipase A2 (PLA2) is the key enzyme that initiates the arachidonic acid cascade, which leads to the generation of multiple eicosanoid products. Many of these products are believed to play an important role in the inflammatory process. Activation of PLA2 is observed under pathological conditions where inflammation is present. Cytosolic PLA2 (cPLA2) is activated by very low levels of calcium and is thought to control receptor-mediated eicosanoid production and to participate in intracellular signal transduction processes. In view of the presence of numerous inflammatory mediators and acute phase proteins in the Alzheimer's disease (AD) brain, localization of cPLA2 in AD brain was evaluated and compared to that observed in nonneurologically diseased controls. In this study, a monoclonal antibody raised against cPLA2 was used to immunostain tissue sections of human cerebral cortex. Five AD cases and six neurologically normal cases were evaluated in the occipital cortex and the cerebellum. Two of the AD cases were also examined in other cortical regions. Granular-like staining with anti-cPLA2 was found to be associated with astrocytes in the cortex of both control and AD cases. Colocalization with GFAP confirmed that cPLA2 immunoreactivity is associated almost exclusively with protoplasmic astrocytes. Staining was abolished when sections were labeled with antibody that had been preadsorbed with purified cPLA2. In AD brain, cPLA2 immunoreactive astrocytes were greater in number and more intensely stained than those in control cases. cPLA2 immunoreactivity was virtually absent in the cerebelium of AD and control cases, despite the presence in this region of diffuse amyloid in two AD cases and amyloid angiopathy in a third case. In the cortex, cPLA2 immunoreactive astrocytes were detected in regions that contained numerous A beta deposits. The finding of elevated levels of cPLA2 immunoreactivity in AD brain supports the hypothesis that there is an active inflammatory process occurring in AD.

Adult↗