Comparison of Direct and Indirect Methods of Measuring Arterial Blood Pressure in Healthy, Anesthetized African Green Monkeys (Chlorocebus aethiops).

Quantitative blood pressure measurement is a critical parameter for assessing cardiovascular health, monitoring physiologic status under anesthesia, and making clinical decisions. The placement of an arterial catheter is the most accurate way to measure blood pressure, but is invasive and perhaps uncomfortable for the patient, requires sedation or anesthesia, and is technically challenging for staff. Noninvasive devices and methods, including oscillometry, high-definition oscillometry, and Doppler flow can be used to measure blood pressure. However, the American College of Veterinary Internal Medicine guidelines state that blood pressure should be measured using devices that have been validated in the species of interest and under the circumstances in which the measurement is being made. The alternatives listed above have not been validated in this manner. The objective of this study was to compare indirect ultrasonic Doppler flow detection and oscillometric blood pressure measures with direct arterial measurement in 8 healthy, anesthetized African green monkeys using the methods of Bland-Altman to assess agreement. Our results indicated that neither Doppler flow nor oscillometry consistently estimates direct blood pressure measurements in anesthetized African green monkeys. In 6 female monkeys, which weighed less than the 2 male subjects, the indirect Doppler measurement more closely predicted direct mean arterial pressure, indicating Dop- pler flow may be useful for monitoring mean arterial pressure in small patients.

Impairment of wound healing by reactive skin decontamination lotion (RSDL®) in a Göttingen minipig® model.

Reactive Skin Decontamination Lotion (RSDL®) is an FDA-approved skin decontamination kit carried by service members for removal and neutralisation of vesicants and nerve agents. The RSDL kit, comprised of a lotion-impregnated sponge, was shown to be the superior medical decontamination device for chemical warfare agent (CWA) exposure on intact skin. In the event of a chemical exposure situation (i.e. terrorism, battlefield) physical injuries are probable, and preservation of life will outweigh the risk associated with application of RSDL to compromised skin. The purpose of this study was to quantify the rate and quality of wound healing in epidermal skin wounds treated with RSDL in a porcine model. Degree of wound healing was assessed using bioengineering methods to include ballistometry, colorimetry, evaporimetry, and high-frequency ultrasonography. Clinical observation, histopathology and immunohistochemistry were also utilised. All pigs received four bilateral superficial abdominal wounds via a pneumatic dermatome on their ventral abdomen, then were treated with the following dressings over a seven-day period: RSDL sponge, petroleum based Xeroform® gauze, 3 M™ Tegaderm™ Film, and 3 M™ Tegaderm™ Foam. Two additional non-wounded sites on the flank were used as controls. Two groups of pigs were then evaluated for a 21- or 56-day time period, representing short- and long-term wound-healing progression. Our findings indicated RSDL had a negative impact on wound-healing progression at both 21 and 56 days post-injury. Wounds receiving RSDL demonstrated a decreased skin elasticity, significant transepidermal water loss, and altered skin colouration and thickness. In addition, the rate of wound healing was delayed, and return to a functional skin barrier was altered when compared to non-RSDL-treated wounds. In conclusion, wound management care and clinical therapeutic intervention plans should be established to account for a prolonged duration of healing in patients with RSDL-contaminated wounds.

Evaluation of fosphenytoin, levetiracetam, and propofol as treatments for nerve agent-induced seizures in pediatric and adult rats.

Multiple recent instances of nerve agent (NA) exposure in civilian populations have occurred, resulting in a variety of negative effects and lethality in both adult and pediatric populations. Seizures are a prominent effect of NAs that can result in neurological damage and contribute to their lethality. Current anticonvulsant treatments for NAs are approved for adults, but no approved pediatric treatments exist. Further, the vast majority of NA-related research in animals has been conducted in adult male subjects. There is a need for research that includes female and pediatric populations in testing. In this project, adult and pediatric male and female rats were challenged with sarin or VX and then treated with fosphenytoin, levetiracetam, or propofol. In this study, fosphenytoin and levetiracetam failed to terminate seizure activity when animals were treated 5 min after seizure onset. Propofol was effective, exhibiting high efficacy and potency for terminating seizure activity quickly in pediatric and adult animals, suggesting it may be an effective anticonvulsant for NA-induced seizures in pediatric populations.

Delayed midazolam dose effects against soman in male and female plasma carboxylesterase knockout mice.

Chemical warfare nerve agent exposure leads to status epilepticus that may progress to epileptogenesis and severe brain pathology when benzodiazepine treatment is delayed. We evaluated the dose-response effects of delayed midazolam (MDZ) on toxicity induced by soman (GD) in the plasma carboxylesterase knockout (Es1-/- ) mouse, which, similar to humans, lacks plasma carboxylesterase. Initially, we compared the median lethal dose (LD50 ) of GD exposure in female Es1-/- mice across estrous with male mice and observed a greater LD50 during estrus compared with proestrus or with males. Subsequently, male and female GD-exposed Es1-/- mice treated with a dose range of MDZ 40 min after seizure onset were evaluated for survivability, seizure activity, and epileptogenesis. GD-induced neuronal loss and microglial activation were evaluated 2 weeks after exposure. Similar to our previous observations in rats, delayed treatment with MDZ dose-dependently increased survival and reduced seizure severity in GD-exposed mice, but was unable to prevent epileptogenesis, neuronal loss, or gliosis. These results suggest that MDZ is beneficial against GD exposure, even when treatment is delayed, but that adjunct therapies to enhance protection need to be identified. The Es1-/- mouse GD exposure model may be useful to screen for improved medical countermeasures against nerve agent exposure.

Butyrylcholinesterase, a stereospecific in vivo bioscavenger against nerve agent intoxication.

Human butyrylcholinesterase (E.C. 3.1.1.8) purified from blood plasma has previously been shown to provide protection against up to five and a half times the median lethal dose of an organophosphorus nerve agent in several animal models. In this study the stoichiometric nature of the protection afforded by human butyrylcholinesterase against organophosphorus nerve agents was investigated in guinea pigs. Animals were administered human butyrylcholinesterase (26.15 mg/kg ≡ 308 nmol/kg) by the intravascular or intramuscular route. Animals were subsequently dosed with either soman or VX in accordance with a stage-wise adaptive dose design to estimate the modified median lethal dose in treated animals. Human butyrylcholinesterase (308 nmol/kg) increased the median lethal dose of soman from 154 nmol/kg to 770 nmol/kg. Comparing the molar ratio of agent molecules to enzyme active sites yielded a stoichiometric protective ratio of 2:1 for soman, likely related to the similar stereoselectivity the enzyme has compared to the toxic target, acetylcholinesterase. In contrast, human butyrylcholinesterase (308 nmol/kg) increased the median lethal dose of VX from 30 nmol/kg to 312 nmol/kg, resulting in a stoichiometric protective ratio of only 1:1, suggesting a lack of stereoselectivity for this agent.

Evaluation of a Synthetic Bedding Substrate for Mice (Mus musculus).

This study compared a synthetic bedding substrate (SBS), which has the potential to be a particulate-free animal bedding system, with the standard woodchip bedding. The objective was to demonstrate that the SBS is habitable for mice and reduces particulates to levels that would not contaminate the eye or potentially induce ocular (corneal) injury. Newly weaned mice were placed in either standard woodchip bedding or SBS. All mice were monitored regarding overall health (appearance, food and water intake, natural behavior, clinical signs, and provoked behavior) to verify their ability to adjust to the bedding. At 8 to 10 wk of age, the mice underwent slit-lamp evaluation for ocular (corneal) abnormalities. Results showed significant differences in body weight and overall health between bedding groups. The incidence of ocular abnormalities did not differ significantly between groups. We conclude that, without modifications and more testing, SBS is not a favorable bedding for mice, and results were inconclusive regarding its use as a bedding to preclude ocular contamination.

Assessment of mouse strain differences in baseline esterase activities and toxic response to sarin.

Genetics likely play a role in various responses to nerve agent (NA) exposure, as genetic background plays an important role in behavioral, neurological, and physiological responses. This study uses different mouse strains to identify if mouse strain differences in sarin exposure exist. In Experiment 1, basal levels of acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and carboxylesterase (CE) were measured in different strains of naïve mice to account for potential pharmacokinetic determinants of individual differences. In Experiment 2, median lethal dose (MLD) levels were estimated in 8 inbred mouse strains following subcutaneous (s.c.) administration of sarin. Few strain or sex differences in esterase activity levels were observed, with the exception of erythrocyte AChE activity in the C57BL/6J strain. Both sex and strain differences in toxicity were observed, with the most resistant strains being the BALB/cByJ and FVB/NJ strains and the most sensitive strain being the DBA/2J strain. These findings can be expanded to explore pathways involved in NA response, which may provide an avenue to develop therapeutics for preventing and treating the damaging effects of NA exposure.