摘要:

ABSTRACTPathological activation of the intracellular Ca2+-dependent proteases calpains may be responsible for the neuronal pathology associated with neurodegenerative diseases and acute traumas to the central nervous system. Though calpain activation has been shown definitively in traumatic brain injury (TBI), no studies have investigated calpastatin (CAST), the calpains' endogenous and specific inhibitor, after TBI. The present study examined temporal changes in CAST protein following controlled cortical impact injury in the rat. Western blot analyses of CAST in cortex and hippocampus detected two bands corresponding to molecular weights of 130 kDa [high-molecular-weight (HMW)] and 80 kDa [low-molecular-weight (LMW)]. A modest decrease in the HMW band in conjunction with a significant increase in the LMW band was observed in cortex ipsilateral to the site of impact following TBI. Examination of ipsilateral hippocampus revealed an increasing trend in the LMW band after injury, while no changes were observed in the HMW band. Thus, observable changes in CAST levels appear to occur several hours after reported calpain activation and cleavage of other substrates. In addition, a new analysis was performed on previously published data examining calpain activity in the same tissue samples used in the present study. These data suggest an association between decreases in calpain activity and accumulation of LMW CAST in the ipsilateral cortex following TBI. The present study cannot exclude proteolytic processing of CAST to LMW forms. However, the absence of reciprocity between changes in LMW and HMW bands in consistent with other data suggesting that rat brain could contain different CAST isoforms.

ISSN:0897-7151    

DOI:10.1089/neu.1999.16.1

年代:1999

数据来源: MAL

摘要:

ABSTRACTTraumatic brain injury (TBI) can cause polymorphonuclear leukocyte (PMN) migration into brain parenchyma, mediating various cytodestructive mechanisms. We examined the effect of blocking leukocyte/endothelial cell adhesion molecules (CAMs) on the anatomic and behavioral sequelae in lateral fluid-percussion injury in rats. Monoclonal antibodies (MAb) directed against a functional (PB1.3) or nonfunctional (PNB1.6) epitope on endothelial P-selectin were used as treatments. Subjects were tested in the Morris water maze (MWM) at 7 and 14 days postinjury then immunohistochemistry was performed using antibodies that recognize ChAT, GFAP and OX-42. A second set of animals underwent myeloperoxidase (MPO) assay in the brain parenchyma and a third set was used to examine neutrophil migration using the MAb RP-3. Time in quadrant, but not escape latency or proximity improved with PB1.3 (p<0.05). Similarly, PB1.3 reduced MPO levels after injury (p<0.05), in the ipsilateral cortex. No significant difference occurred in neutrophil counts in cortex, corpus callosum, hippocampus, and thalamus between injured only rats and injured rats treated with PB1.3. Quantitative analysis of cholinergic cells in the medial septum showed a protective effect by PB1.3. Densitometry readings of GFAP and OX-42 immunolabeling revealed no discernible differences between the treated and untreated injured rats. Qualitatively, there was no difference in microglia or astrocyte response to treatment. Treatment with P-selectin blockade in brain-injured rats may reduce PMN migration into brain, help preserve cholinergic immunolabeling of medial septal nucleus neurons, and may alleviate mnemonic deficits.

ISSN:0897-7151    

DOI:10.1089/neu.1999.16.13

年代:1999

数据来源: MAL

摘要:

ABSTRACTBlood-brain barrier breakdown and edema, indicative of cerebrovascular injury, are characteristic pathophysiologic outcomes following head trauma. These injuries result from both primary mechanical damage and from secondary events initiated by the traumatic insult. Free radicals are recognized as mediators of secondary injury in a number of trauma models. In this study, we used a novelin vitromodel of traumatic microvascular injury to test the hypothesis that endogenous glutathione protects cerebral endothelial cells from secondary autooxidative injury following mechanical trauma. Porcine brain cerebral endothelial cells were grown in tissue culture wells with Silastic membrane bottoms, and cellular injury was induced by displacing the membrane different distances with user-defined pressure pulses from a customized device. The resultant endothelial cell injury 2 h following stretch was determined by measuring lactate dehydrogenase in the culture media. Significant stretch-dependent increases in endothelial injury were elicited that depended in a nonlinear fashion on the degree of membrane displacement. Depletion of intracellular glutathione with buthionine sulfoximine (1 mM) increased the extent of traumatic endothelial cell injury by 17–56%, particularly at low to moderate levels of traumatic injury (30–40% of total endothelial cell LDH release). Conversely, traumatic injury was reduced by 22–45% when endothelial cell glutathione levels were augmented threefold (to 140 ± 8 nmol/mg protein) by preincubating cells with 2 mM glutathione; the extent of protection was inversely proportional to the extent of the traumatic stretch. Traumatic endothelial cell injury was also significantly and dose-dependently attenuated (up to 40%) by treatment with the xanthine oxidase inhibitor oxypurinol (50 and 100 μM). These results demonstrate that cerebral endothelial cells are the targets of hydrogen peroxide–mediated injury secondary to trauma-induced superoxide radical formation via the xanthine oxidase pathway. The neutralization of peroxides by the endogenous glutathione redox cycle provides endothelial cells a finite capacity to reduce free radical–mediated traumatic injury; this cycle may be amenable to therapeutic manipulation to mitigate posttraumatic edema and other manifestations of vascular

ISSN:0897-7151    

DOI:10.1089/neu.1999.16.27

年代:1999

数据来源: MAL

摘要:

ABSTRACTVasospasm after traumatic or aneurysmal subarachnoid hemorrhage is associated with smooth muscle contraction, a process that results in part from increased intracellular calcium in smooth muscle cells. These experiments tested the hypothesis that chelation of intracellular calcium with the cell-permeant calcium chelator, l,2-bis-(2-aminophenoxy)ethane-N,N,N′,N′-tetracetic acid acetoxymethyl ester (BAPTA-AM), decreases smooth muscle contraction in response to agents that cause contraction by increasing intracellular calcium. Effects of BAPTA-AM on vasoconstriction induced by KCl, prostaglandin F2α(PGF2α), caffeine, and erythrocyte hemolysate were tested on monkey basilar artery under isometric tension. BAPTA-AM, 30 and 100 μmol/L, caused a significant decrease in resting tension in rings with and without endothelium (30 μmol/L; 8 ± 6% [n.s.] and 14 ± 5%, 100 (μmol/L; 19 ± 3% and 32 ± 6%,p<0.05, pairedttest). Contractions to caffeine were significantly decreased by 30 μmol/L BAPTA-AM and were abolished at 100 μmol/L in rings with and without endothelium (p<0.05). BAPTA-AM, 100 μmol/L, competitively inhibited contractions to PGF2α. BAPTA-AM, 100 μmol/L, significantly decreased the maximum contractions to KCl in rings with and without endothelium (p<0.05). There were no significant effects of BAPTA-AM on contractions induced by hemolysate in rings with endothelium but in rings without endothelium, BAPTA-AM, 100 μmol/L, significantly inhibited contractions. In rings with endothelium contractions to hemolysate could be significantly reduced by BAPTA-AM plus indomethacin or indomethacin alone, suggesting that hemolysate releases an eicosanoid from the endothelium by a pathway that is not inhibited by BAPTA. These results suggest that the ability of BAPTA-AM to inhibit smooth muscle contractions will depend on the agonists mediating the contraction. In response to erythrocyte hemolysate, loading of endothelial cells with BAPTA-AM increases the release of a vasoconstricting eicosanoid from these cells that counteracts the decreased contraction caused by loading of smooth muscle c

ISSN:0897-7151    

DOI:10.1089/neu.1999.16.37

年代:1999

数据来源: MAL

摘要:

ABSTRACTNoninvasive transcranial magnetic stimulation (TMS) of the motor cortex was used to evoke electromyographic (EMG) responses in persons with spinal cord injury (n= 97) and able-bodied subjects (n= 20, for comparative data). Our goal was to evaluate, for different levels and severity of spinal cord injury, potential differences in the distribution and latency of motor responses in a large sample of muscles affected by the injury. The spinal cord injury (SCI) population was divided into subgroups based upon injury location (cervical, thoracic, and thoracolumbar) and clinical status (motor-complete versus motor-incomplete). Cortical stimuli were delivered while subjects attempted to contract individual muscles, in order to both maximize the probability of a response to TMS and minimize the response latency. Subjects with motor-incomplete injuries to the cervical or thoracic spinal cord were more likely to demonstrate volitional and TMS-evoked contractions in muscles controlling their foot and ankle (i.e., distal lower limb muscles) compared to muscles of the thigh (i.e., proximal lower limb muscles). When TMS did evoke responses in muscles innervated at levels caudal to the spinal cord lesion, response latencies of muscles in the lower limbs were delayed equally for persons with injury to the cervical or thoracic spinal cord, suggesting normal central motor conduction velocity in motor axons caudal to the lesion. In fact, motor response distribution and latencies were essentially indistinguishable for injuries to the cervical or thoracic (at or rostral to T10) levels of the spine. In contrast, motor-incomplete SCI subjects with injuries at the thoracolumbar level showed a higher probability of preserved volitional movements and TMS-evoked contractions in proximal muscles of the lower limb, and absent responses in distal muscles. When responses to TMS were seen in this group, the latencies were not significantly longer than those of able-bodied (AB) subjects, strongly suggestive of "root sparing" as a basis for motor function in subjects with injury at or caudal to the T11 vertebral body. Both the distribution and latency of TMS-evoked responses are consistent with highly focal lesions to the spinal cord in the subjects examined. The pattern of preserved responsiveness predominating in the distal leg muscles is consistent with a greater role of corticospinal tract innervation of these muscles compared to more proximal muscles of the thigh and hip.

ISSN:0897-7151    

DOI:10.1089/neu.1999.16.49

年代:1999

数据来源: MAL

摘要:

ABSTRACTWe have investigated sacral spinal cord lesions in rats with the goal of developing a rat model of muscular spasticity that is minimally disruptive, not interfering with bladder, bowel, or hindlimb locomotor function. Spinal transections were made at the S2 sacral level and, thus, only affected the tail musculature. After spinal transection, the muscles of the tail were inactive for 2 weeks. Following this initial period, hypertonia, hyperreflexia, and clonus developed in the tail, and grew more pronounced with time. These changes were assessed in the awake rat, since the tail is readily accessible and easy to manipulate. Muscle stretch or cutaneous stimulation of the tail produced muscle spasms and marked increases in muscle tone, as measured with force and electromyographic recordings. When the tail was unconstrained, spontaneous or reflex induced flexor and extensor spasms coiled the tail. Movement during the spasms often triggered clonus in the end of the tail. The tail hair and skin were extremely hyperreflexive to light touch, withdrawing quickly at contact, and at times clonus could be entrained by repeated contact of the tail on a surface. Segmental tail muscle reflexes, e.g., Hoffman reflexes (H-reflexes), were measured before and after spinalization, and increased significantly 2 weeks after transection. These results suggest that sacral spinal rats develop symptoms of spasticity in tail muscles with similar characteristics to those seen in limb muscles of humans with spinal cord injury, and thus provide a convenient preparation for studying this condition.

ISSN:0897-7151    

DOI:10.1089/neu.1999.16.69

年代:1999

数据来源: MAL

摘要:

ABSTRACTThe pharmacological effects of nitric oxide synthase (NOS) inhibitors, NO donor, and NOS substrate on dynorphin(Dyn) A(1–17) spinal neurotoxicity were studied. Intrathecal (i.t.) pretreatment with both 7-nitroindazole 1 μmol, a selective neuronal constitutive NOS (ncNOS) inhibitor, and aminoguanidine 1 μmol, a selective inducible NOS (iNOS) inhibitor, 10 min prior to i.t. Dyn A(1–17) 20 nmol significantly ameliorated Dyn-induced neurological outcome. Both 7-nitroindazole and aminoguanidine significantly antagonized the increases of cNOS and iNOS activities measured by conversion of3H-l-arginine to3H-l-citrulline in the ventral spinal cord, and blocked the Dyn-induced increases of ncNOS-immunoreactivity in the ventral horn cells 4 h after i.t. Dyn A(1–17) 20 nmol. Pretreatment withNω-nitro-l-arginine methyl ester (l-NAME) 1 μmol, a cNOS inhibitor nonselective to both ncNOS and endothelial NOS (ecNOS), did not antagonize Dyn A(1–17) 20 nmol-induced permanent paraplegia but aggravated Dyn A(1–17) 10 nmol-induced transient paralysis and caused permanent paraplegia. Pretreatment withl-NAME 1 μmol 10 min before i.t. Dyn A(1–17) 1.25 and 2.5 nmol, which produced no significant motor dysfunction alone, induced transient paralysis in seven out of 12 and five out of seven rats, respectively.l-NAME 1 μmol plus Dyn A(1–17) 10 nmol induced ncNOS-immunoreactivity expression in ventral horn cells. Both low and high doses of aminoguanidine (0.2–30 μmol) did not affect spinal motor function, but high doses ofl-NAME (5–20 μmol) induced dose-dependent hindlimb and tail paralysis associated with spinal cord injury in normal rats. Pretreatment with low-dose Spermine NONOate, a controlled NO releaser, 0.1 and 0.5 μmol 10 min before i.t. Dyn A(1–17) 20 nmol, significantly prevented Dyn spinal neurotoxicity, and high-dose Spermine NONOate 2 μmol i.t.per seinduced transient and incomplete paraplegia. But pretreatment withl-Arg 10 μmol 10 min before Dyn A(1–17) 20 nmol produced only partial blockade of Dyn-induced paraplegia. These results demonstrated that relatively specific inhibition of ncNOS and iNOS block Dyn-induced increases in cNOS and iNOS activities and ncNOS-immunoreactivity in ventral spinal cord, but nonspecific inhibition of ncNOS and ecNOS aggravated Dyn spinal neurotoxicity. It suggested that both ncNOS and iNOS play an important role, but ecNOS might be beneficial in Dyn spinal neurotoxicity. Moderate production of NO (at vascular level) has an apparently neuroprotective effect, and overproduction of NO (at cellu

ISSN:0897-7151    

DOI:10.1089/neu.1999.16.85

年代:1999

数据来源: MAL

摘要:

ABSTRACTAntiemetics are widely used drugs, frequently administered to alleviate postoperative and postchemotherapeutic nausea and vomiting. While antiemetics do not induce peripheral neurotoxicity when administered systemically, it is not known whether peripheral nerve injury can occur as a result of inadvertent intraneural injection during intramuscular administration. The purpose of this study was to characterize the neurotoxic effect of three commonly used antiemetic agents (promethazine, dimenhydrinate, and prochlorperazine) as compared to saline in the rat sciatic nerve model. Intrafascicular and extrafascicular injection as well as direct application of the antiemetic drugs were performed. Nerves were harvested at 2 weeks postoperatively for histology and morphometry, with an additional sacrifice point at 8 weeks for the intrafascicular injection group.Injection injuries caused by antiemetic drugs differed depending on the agent injected and the location of injection. Extrafascicular injection and direct application caused no damage. Intrafascicular injection caused diffuse axonal injury in the promethazine and dimenhydrinate groups, while prochlorperazine caused only focal injury. Regeneration was prominent at 8 weeks in all intrafascicular injection groups in this rat model. Prochlorperazine thus appears to be less neurotoxic when injected intraneurally and should preferentially be used for intramuscular injections.

ISSN:0897-7151    

DOI:10.1089/neu.1999.16.99

年代:1999

数据来源: MAL