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L B Pearce

Publications and source records attributed to L B Pearce.

At least 19 recordsLinked to original sources
PubMed2006

Bovine polymerized hemoglobin (hemoglobin-based oxygen carrier-201) resuscitation in three swine models of hemorrhagic shock with militarily relevant delayed evacuation--effects on histopathology and organ function.

OBJECTIVE: To test our hypothesis that hemoglobin-based oxygen carrier (HBOC)-201 resuscitation in hemorrhagic shock (HS) will not lead to increased organ injury and dysfunction. DESIGN: Three swine HS models simulating military-relevant delayed evacuation: a) moderate controlled HS, b) severe controlled HS, and c) severe uncontrolled HS. SETTING: Military research laboratory. SUBJECTS: Swine. INTERVENTIONS: Swine were anesthetized/intubated and instrumented. To induce HS, in two controlled hemorrhage experiments, 40% (moderate controlled HS) or 55% (severe controlled HS) of blood volume was withdrawn; in an uncontrolled HS experiment, the liver was crushed/lacerated. During a 4-hr "prehospital phase," pigs were resuscitated with HBOC-201 (HBOC) or Hextend (HEX) or were nonresuscitated (NON). Upon "hospital arrival," liver injury was repaired (severe uncontrolled HS), blood or saline was infused, hemodynamics were monitored, and blood was collected. Upon animal death and/or 72 hrs, necropsy was followed by histopathologic evaluation of organ injury (hematoxylin and eosin, electron microscopy) and immunohistochemistry of oxidative potential (3-nitrotyrosine). Significance (p < .05) was assessed by Kruskal-Wallis, analysis of variance/Bonferroni, and mixed procedure tests. MEASUREMENTS AND MAIN RESULTS: Survival was significantly higher with HBOC than HEX only with severe uncontrolled HS (p = .002). Myocardial necrosis/fibroplasia, fluid requirements, cardiac output, and cardiac enzymes were generally similar or lower in HBOC than HEX pigs, but creatine kinase-MB (but not creatine kinase-MB/creatine kinase ratio) was higher with HBOC in moderate controlled HS. Alveolar/interstitial pulmonary edema was similar with HBOC and HEX, but Po2 was higher with HBOC in severe uncontrolled HS. Jejunal villar epithelial and hepatocellular necrosis were similarly minimal to moderate in all groups. Minimal biliary changes occurred exclusively with HBOC. Aspartate aminotransferase, lactate dehydrogenase, and alkaline phosphatase were generally higher with HBOC than HEX. Mild renal papillary injury occurred more frequently with HBOC, but consistent patterns for urine output, blood urea nitrogen, and creatinine, were not seen. The 3-nitrotyrosine staining intensity was not different. CONCLUSIONS: In comparison with hetastarch, HBOC-201 resuscitation of swine with HS increased survival (with severe HS), did not increase evidence of oxidative potential, and had histopathologic and/or functional effects on organs that were clinically equivocal (myocardium, lungs, hepatic parenchyma, jejunum, and renal cortex/medulla) and potentially adverse (hepatobiliary and renal papilla). The effects of HBOC-201-resuscitation in HS should be corroborated in controlled clinical trials.

Analysis of Variance↗
PubMed2006

Vasoactivity of bovine polymerized hemoglobin (HBOC-201) in swine with traumatic hemorrhagic shock with and without brain injury.

BACKGROUND: We previously reported that bovine polymerized hemoglobin (HBOC- 201) improved outcome in swine with hemorrhagic shock (HS) with and without traumatic brain injury (TBI). Herein, we add analyses of blood pressure (BP) responses, associated physiologic data, and HS fluid infusion guidelines. METHODS: HBOC-201 versus standard fluid resuscitation was compared in four anesthetized invasively monitored swine models: moderate controlled HS, severe controlled HS, severe uncontrolled HS (liver injury), and severe uncontrolled HS/TBI (liver/parietal brain injuries). Pigs received fluid for hypotension and tachycardia, and were followed up to 6 (HS alone) or 72 hours (HS/TBI). The change in mean arterial pressure (DeltaMAP) response severity was stratified and analyzed based on infusion number and HS severity, using Student's t and Fisher's exact tests. RESULTS: HBOC-201 vasoactivity resulted in higher MAP in all studies. Among HBOC-201 pigs, DeltaMAP responses were significant for the first two infusions and inversely related to HS severity. Among controls, DeltaMAP responses remained significant through the fourth infusion in controlled HS models, and through the first in severe uncontrolled HS/TBI; none were significant in severe uncontrolled HS. DeltaMAP was higher with HBOC-201 through the first infusion in moderate controlled HS, the fifth in severe uncontrolled HS, and the second in severe uncontrolled HS/TBI; there were no group differences in severe controlled HS. No severe MAP responses occurred. Higher DeltaMAP severity did not impact outcome. Hypotension satisfied fluid reinfusion criteria less consistently than tachycardia. Overall, HBOC-201 improved physiologic parameters and survival without causing hypoperfusion; in severe HS, perfusion improved. CONCLUSIONS: In swine with HS +/- TBI, HBOC-201 had mild to moderate vasoactivity, resulting in significant DeltaMAP responses mainly after initial infusions, no severe/adverse responses, and improved outcome. Our data suggest that use of physiologic parameters (e.g., tachycardia), in addition to hypotension to guide fluid reinfusion during HS resuscitation with HBOC-201, will minimize hypoperfusion risk and maximize potential benefit.

Animals↗
PubMed2006

Coagulation patterns following haemoglobin-based oxygen carrier resuscitation in severe uncontrolled haemorrhagic shock in swine.

Massive blood loss due to penetrating trauma and internal organ damage can cause severe haemorrhagic shock (HS), leading to a severely compromised haemostatic balance. This study evaluated the effect of bovine polymerized haemoglobin (Hb) (Hb-based oxygen carrier, HBOC) resuscitation on haemostasis in a swine model of uncontrolled HS. Following liver injury/HS, swine received HBOC (n= 8), Hextend (HEX) (n= 8) or no resuscitation (NON) (n= 8). Fluids were infused to increase mean arterial pressure above 60 mmHg and to reduce heart rate to baseline. At 4 h, the animals were eligible for blood transfusions. Prothrombin time (PT), activated partial thromboplastin time, fibrinogen, thromboelastography (TEG) and platelet function analyser closure time (PFA-CT) were compared by using mixed statistical model. At 4 h, blood loss (% estimated blood volume) was comparable for HBOC (65.5 +/- 18.5%) and HEX (80.8 +/- 14.4%) and less for NON (58.7 +/- 10.1%; P < 0.05). Resuscitation-induced dilutional coagulopathy was observed with HBOC and HEX, as indicated by reduced haematocrit, platelets and fibrinogen (P < 0.05). At 4 h, PT was higher in HEX than in HBOC groups (P < 0.01). In the early hospital phase, a trend to increased TEG reaction time and PFA-CT indicates that dilutional effects persist in HBOC and HEX groups. PFA-CT returned to baseline later with HBOC than with HEX (48 vs. 24 h) following blood transfusion. At 4 h, all surviving HEX animals (n= 3) required transfusion, in contrast to no HBOC (n= 7) or NON (n= 1) animals. In this severe uncontrolled HS model, successful resuscitation with HBOC produced haemodilutional coagulopathy less than or similar to that produced by resuscitation with HEX.

Abdominal Injuries↗
PubMed2001

Selective aortic arch perfusion with hemoglobin-based oxygen carrier-201 for resuscitation from exsanguinating cardiac arrest in swine.

OBJECTIVE: The prospects for resuscitation after blunt traumatic cardiac arrest are dismal. Selective aortic arch perfusion (SAAP) with a hemoglobin-based oxygen carrier (HBOC-201) offers a potentially effective therapy. This study evaluated the acute cardiovascular and metabolic effects of SAAP with HBOC-201 in an exsanguination model of cardiac arrest. DESIGN: Randomized, controlled, laboratory investigation. SETTING: University research laboratory. SUBJECTS: Domestic swine, 25-39 kg. INTERVENTIONS: Partial resection of four liver lobes rapidly led to profound hemorrhagic shock and subsequent cardiac arrest at 10-13 mins. At 15 mins, swine were randomized to receive either SAAP with oxygenated lactated Ringer's (LR) solution (n = 6) or SAAP with oxygenated HBOC-201 (n = 6) at a rate of 10 mL x kg(-1) x min(-1) until return of spontaneous circulation with a mean aortic pressure of 60 mm Hg (8.0 kPa) was achieved. Epinephrine (0.005 mg/kg) was given via intra-aortic route every 30 secs as needed to promote return of spontaneous circulation beginning at 18 mins after onset of liver injury (3 mins after beginning SAAP). MEASUREMENTS AND MAIN RESULTS: Mean aortic pressure, cardiac output, total blood loss, and time of arrest were similar for both groups before SAAP therapy. In the SAAP-HBOC group, return of spontaneous circulation with a sustained mean aortic pressure of 60 mm Hg (8.0 kPa) was achieved in six of six swine at 1.9 +/- 0.3 mins of SAAP, and none of these swine required epinephrine. In the SAAP-LR group, no swine (from a total of six) achieved return of spontaneous circulation before intra-aortic epinephrine administration, and only two of six swine had brief return of spontaneous circulation with an mean aortic pressure of 60 mm Hg (8.0 kPa) after intra-aortic epinephrine that was sustained for <10 mins. One-hour survival was five of six in the SAAP-HBOC group and none of six in the SAAP-LR group (p <.05, Fisher's exact test). CONCLUSION: SAAP with oxygenated HBOC-201 rapidly restored viable cardiovascular function after exsanguinating cardiac arrest in this swine model of liver injury with profound hemorrhagic shock.

Animals↗
PubMed2000

Bovine hemoglobin-based oxygen carrier (HBOC-201) for resuscitation of uncontrolled, exsanguinating liver injury in swine. Carolina Resuscitation Research Group.

In the setting of rapidly exsanguinating hemorrhage, resuscitation with intravenous (i.v.) crystalloid solution may not sustain survival before availability of allogenic blood transfusion and surgery. This study tested the hypothesis that bovine hemoglobin-based oxygen carrier, HBOC-201, would improve resuscitation and extend early survival from exsanguinating hemorrhage. This study simulated the prehospital scenario of rapidly exsanguinating hemorrhage with prolonged prehospital time and lack of blood availability. Severe hemorrhagic shock was induced in swine by using multiple liver lacerations. At 9 min after the onset of bleeding, swine were randomized to receive approximately 10 mL/kg/min of i.v. lactated Ringer's solution (n = 10) or HBOC-201 (n = 7) to achieve a mean aortic pressure (MAP) of 60 mmHg. Thereafter, infusion rate was adjusted to maintain MAP at 60 mmHg for up to 2 h. All animals were initially successfully resuscitated. The results showed 2-h survival was 1 of 10 with lactated Ringer's and 7 of 7 with HBOC-201 (P = 0.0004). Nine lactated Ringer's swine had cardiovascular collapse at 36 +/- 10 min. Lactate at 30 min was 18 +/- 3 mmol/L with lactated Ringer's and 12 +/- 2 mmol/L with HBOC-201 (P < 0.05). Hematocrit was <1% in 9 of 10 lactated Ringer's and 6 of 7 HBOC-201 animals. These data indicate that HBOC-201 improved early survival and stabilized hemodynamic and metabolic parameters vs. lactated Ringer's in this swine model of liver injury with uncontrolled, lethal hemorrhage that simulates the prehospital care environment where allogenic blood is unavailable.

Animals↗
PubMed1997

Pharmacologic characterization of botulinum toxin for basic science and medicine.

The use of Botulinum neurotoxin (BoNT) is increasing in both clinical and basic science. Clinically, intramuscular injection of nanogram quantities of BoNT is fast becoming the treatment of choice for a spectrum of disorders including movement disorders such as torticollis, blepharospasm, Meige Disease, and hemifacial spasm (Borodic et al., 1991, 1994a; Jankovic and Brin, 1991; Clarke, 1992). Neuroscientists are using BoNTs as tools to develop a better understanding of the mechanisms underlying the neurotransmitter release process. Consequently, our ability to accurately and reliably quantify the biologic activity of botulinum toxin has become more important than ever. The accurate measurement of the pharmacologic activity of BoNTs has become somewhat problematic with the most significant problems occurring with the clinical use of the toxins. The biologic activity of BoNTs has been measured using a variety of techniques including assessment of whole animal responses to in vitro effects on neurotransmitter release. The purpose of this review is to examine the approaches employed to characterize, quantify and investigate the actions of the BoNTs and to provide a guide to aid investigators in determining which of these methods is most appropriate for their particular application or use.

Animals↗
PubMed1995

The effect of MK-801 and SCH23390 on the expression and sensitization of morphine-induced oral stereotypy.

Repeated high doses of morphine sulfate, administered in a 24-36 h period, stimulates the expression of oral stereotypy in rats. Sensitization to this effect of morphine is demonstrated by the reexpression of the stereotypy by the administration of 4.0 mg/kg of morphine one week following the original exposure. To investigate the role of N-methyl-D-aspartic acid (NMDA) and D1 dopamine (DA) receptors in the acute expression and sensitization of morphine-induced oral stereotypy, rats were administered four injections of morphine (10.0 mg/kg) one injection every 12 h and observed for the expression of stereotypic behaviors following pretreatment with selective antagonists. Pretreatment with the NMDA antagonist, MK-801 (0.7 mg/kg), before each of the four morphine injections antagonized both the initial expression of oral stereotypy and the development of sensitization. In contrast, the DA D1 receptor antagonist SCH23390 (40.0 micrograms/kg) administered during the four high-dose treatments with morphine antagonized the initial expression of oral stereotypy and not the development of sensitization. These findings implicate glutamate's action at the NMDA receptor in both the acute expression of morphine-induced oral stereotypy, and the development of sensitization of this morphine effect, whereas DA D1 receptors may only be involved in the acute expression of the stereotypy.

Animals↗
PubMed1995

The median paralysis unit: a more pharmacologically relevant unit of biologic activity for botulinum toxin.

Although the LD50 has been used to quantify the biologically active toxin in clinical preparations of botulinum A toxin (Botox and Dysport), a discrepancy exists between the clinical potency of equivalent international units of different formulations of botulinum A toxin for multiple clinical indications. Our laboratory previously reported that a regional chemodenervation assay in the mouse could be utilized to detect the difference in the potencies of the clinical preparations of toxin [Pearce et al. (1994) Toxic. appl. Pharmac. 128, 69-77]. The purpose of this study was to quantify the regional paralysis produced by botulinum toxin and define a new pharmacologic/biologic unit of activity that more accurately reflects the mechanism of action of botulinum toxin in the clinical setting. Quantal analysis of regional paralysis revealed that the ED50, defined as the median paralysis unit (MPU) for Botox and Dysport, was 0.41 +/- 0.01 and 1.00 +/- 0.02 LD50 units, respectively. Differences in the potencies found in retrospective clinical studies comparing Botox and Dysport were accurately reflected, for the first time, by the dose of toxin expressed in terms of the MPU (median paralysis unit). The data suggested that the MPU may be a more appropriate measure of the biologic activity in therapeutic formulations of botulinum toxin.

Animals↗
PubMed1994

Histologic assessment of dose-related diffusion and muscle fiber response after therapeutic botulinum A toxin injections.

Fiber diameter variability, acetylcholinesterase staining properties, and average fiber diameter were determined 5 weeks after varying doses of botulinum A toxin were administered into albino rabbit longissimus dorsi muscle. The average fiber diameter within the muscle appeared to be a function of the dose of botulinum toxin injected. Fiber diameter variability correlated with the dose of botulinum toxin administered. Both fiber diameter variability and acetylcholinesterase spread characteristics showed a distinct diffusion gradient over a defined field within a muscle. At lower doses (1 IU), collapse of the diffusion gradient occurred over a 15-30-mm segment of muscle. At higher doses (5-10 IU), diffusion of botulinum A toxin effect occurred throughout the entire muscle with no apparent end point. This study demonstrated that botulinum A toxin produces a gradient of denervation in a given muscle and that both the magnitude of denervation and the extent of the gradient are dose dependent. Furthermore, both muscle fiber diameter variability and acetylcholinesterase staining were useful as measures of chemodenervation.

Acetylcholinesterase↗
PubMed1994

Measurement of botulinum toxin activity: evaluation of the lethality assay.

The use of the mouse lethality assay for the estimation of the biologic activity of botulinum toxin was evaluated. The relationship between the number of animals, number of doses, and duration of the assay used to estimate the LD50 and the precision of the assay was investigated. The results of these studies demonstrated that the LD50 for botulinum toxin can be estimated with a high degree of precision (+/- 5%). The precision of the assay is not increased by using more than a 5-dose 50-animal assay or extending the duration of the assay beyond 72 hr. Estimates of the LD50 obtained at 48 hr were only slightly less precise but underestimated the LD50 by 15%. Analysis of the commercially available preparations of botulinum toxin with the mouse LD50 assay revealed significant discrepancies between the units of toxin in these preparations. In addition, a 2.67-fold difference in the relative potency of the two preparations of botulinum A toxin was observed using a regional chemodenervation assay that measures paralysis. The mouse LD50 assay could not detect this large difference in the potency of the two approved clinical preparations of botulinum toxin. The results of these studies demonstrate that although the mouse LD50 assay can be used to estimate the number of units of botulinum toxin with a high degree of precision this assay alone is not an adequate method for assessing the preclinical biological potency of botulinum toxin.

Animals↗
PubMed1993

Botulinum B toxin as an alternative to botulinum A toxin: a histologic study.

Histochemical effects of botulinum B toxin were studied on fibers from longissimus dorsi muscle in Albino rabbits and compared to effects produced by botulinum A toxin. Acetylcholinesterase staining, muscle fiber size analysis, and ATPase staining indicated botulinum B toxin produced a denervation gradient and field similar to that produced by botulinum A toxin. At 5 weeks postinjection with botulinum B toxin, analysis showed muscle fiber size variability, and diffuse acetylcholinesterase fiber staining comparable to botulinum A toxin at the injection site. Muscle sections taken at 4.0 cm for analysis showed statistically significant decreased fiber size variability and contraction of acetylcholinesterase staining pattern for both immunotypes. In addition, the denervation reflected by histochemical staining and fiber size analysis appeared transient and lasted for approximately 3 months for both immunotypes. These findings suggest botulinum B toxin produces pharmacologic effects on innervation of striated muscle similar to botulinum A toxin. Because immunologic tolerance has been demonstrated after therapeutic botulinum A toxin injections, further clinical studies need to be conducted with other immunotypes of toxin with no cross-reactivity to type A.

Acetylcholinesterase↗
PubMed1993

Botulinum A toxin for treatment of aberrant facial nerve regeneration.

Twelve patients with involuntary synkinetic eyelid closure were given 40 injections of botulinum A toxin. Temporary improvement in involuntary eyelid closure was observed in all 12 patients. Eleven of the 12 patients desired repeated injections. Dose requirements for this indication were compared with doses used in 697 injections in 112 patients with essential blepharospasm and Meige syndrome. Additionally, dose comparisons were made with 269 injections in 71 patients with hemifacial spasm. Dose requirements needed to treat aberrant regeneration of the facial nerve were substantially less than needed to treat blepharospasm and Meige syndrome. The dose requirement was similar to that in hemifacial spasm treatment. The reason for the differences probably relates to existing muscular denervation associated with hemifacial spasm and aberrant facial nerve regeneration.

Blepharospasm↗
PubMed1991

Rapid kinetics of potassium-evoked release of acetylcholine from rat brain synaptosomes: analysis by rapid superfusion.

The rapid kinetics of spontaneous and evoked [3H]acetylcholine efflux from synaptosomes was investigated using the technique of rapid superfusion. Synaptosomes were isolated from whole rat brain and the intraterminal pool of acetylcholine was radiolabeled by preincubation with [3H]choline. Synaptosomes were retained within the superfusion system on filter disks and superfused with Krebs-bicarbonate buffer, pH 7.4, at flow rates of 0.3-0.5 ml/s. These experimental conditions provided a mixing half-life of 119 ms and efficiency of superfusion of greater than 85%. The kinetics of tritium efflux was followed on the second and subsecond time scales by collection of serial 4.8-s and 50-ms samples for a total of 67.2 and 1.0 s, respectively. Superfusion for 48 s with isoosmotic Krebs buffer containing 10, 20, 30, 50, 75, and 100 mM potassium ion stimulated concentration-dependent tritium release. All of potassium-evoked release, but only 17% of spontaneous release, was calcium-dependent. Kinetic analysis of net (total minus spontaneous) potassium-stimulated release revealed a single calcium-dependent component of release that fit a single exponential function with a half-life of 12.7 s. Analysis of the area under the tritium efflux curves observed on the millisecond time scale revealed that 0.111, 0.550, and 0.614% net tritium release was evoked by superfusion for 750 ms with isoosmotic buffer containing 20, 50, and 100 mM KCl, respectively. Consistent with the results observed on the second time scale, a small fraction of spontaneous release and all of potassium-evoked release observed on the millisecond time scale were calcium-dependent. These data indicate that the technique of rapid superfusion can be utilized for the direct investigation of spontaneous and evoked [3H]acetylcholine release, as well as the factors that regulate this release from brain synaptosomes on the second and millisecond time scales.

Acetylcholine↗