Journal of the American Association for Laboratory Animal Science : JAALAS最新文献

Facial expressions have increasingly been used to assess emotional states in mammals. The recognition of pain in research animals is essential for their well-being and leads to more reliable research outcomes. Automating this process could contribute to early pain diagnosis and treatment. Artificial neural networks have become a popular option for image classification tasks in recent years due to the development of deep learning. In this study, we investigated the ability of a deep learning model to detect pain in Japanese macaques based on their facial expression. Thirty to 60 min of video footage from Japanese macaques undergoing laparotomy was used in the study. Macaques were recorded undisturbed in their cages before surgery (No Pain) and one day after the surgery before scheduled analgesia (Pain). Videos were processed for facial detection and image extraction with the algorithms RetinaFace (adding a bounding box around the face for image extraction) or Mask R-CNN (contouring the face for extraction). ResNet50 used 75% of the images to train systems; the other 25% were used for testing. Test accuracy varied from 48 to 54% after box extraction. The low accuracy of classification after box extraction was likely due to the incorporation of features that were not relevant for pain (for example, background, illumination, skin color, or objects in the enclosure). However, using contour extraction, preprocessing the images, and fine-tuning, the network resulted in 64% appropriate generalization. These results suggest that Mask R-CNN can be used for facial feature extractions and that the performance of the classifying model is relatively accurate for nonannotated single-frame images.

Despite the major use of mice in biomedical research, little information is available with regard to identifying their postmortem changes and using that information to determine the postmortem interval (PMI), defined as the time after death. Both PMI and environmental conditions influence decomposition (autolysis and putrefaction) and other postmortem changes. Severe decomposition compromises lesion interpretation and disease detection and wastes limited pathology resources. The goal of this study was to assess postmortem changes in mice in room temperature cage conditions and under refrigeration at 4 °C to develop gross criteria for the potential value of further gross and histologic evaluation. We used 108 experimentally naïve C57BL/6 mice that were humanely euthanized and then allocated them into 2 experimental groups for evaluation of postmortem change: room temperature (20 to 22 °C) or refrigeration (4 °C). PMI assessments, including gross changes and histologic scoring, were performed at hours 0, 4, 8, and 12 and on days 1 to 14. Factors such as temperature, humidity, ammonia in the cage, and weight change were also documented. Our data indicates that carcasses held at room temperature decomposed faster than refrigerated carcasses. For most tissues, decomposition was evident by 12 h at room temperature as compared with 5 d under refrigeration. At room temperature, gross changes were present by day 2 as compared with day 7 under refrigeration. Mice at room temperature lost 0.78% of their baseline body weight per day as compared with 0.06% for refrigerated mice (95% CI for difference 0.67% to 0.76%, P < 0.0005). This study supports the consideration of temperature and PMI as important factors affecting the suitability of postmortem tissues for gross and histologic evaluation and indicates that storage of carcasses under refrigeration will significantly slow autolysis.

Extended-release (ER) local anesthetics are often incorporated in multi-modal analgesia or as an alternative when the effect of systemic analgesics may confound research. In this study, we compared the analgesic efficacy of 2 ER bupivacaine anesthetics with different ER mechanisms, a slow-release bupivacaine-meloxicam polymer (BMP) and a sucrose acetate isobutyrate bupivacaine (SABER-B) system. We used a full-thickness unilateral skin incision porcine model to evaluate the efficacy of these 2 ER bupivacaine analgesics. Eighteen male swine were randomized into 3 groups: control (saline; n = 6), bupivacaine:meloxicam (10 mg/kg, 0.3 mg/kg; n = 6), and SABER-B (10 mg/kg; n = 6). After surgery, pigs were assessed for changes in body weight, salivary cortisol level, and response to von Frey testing at 1, 3, 6, 24, 48, 72, 96, 120, and 168 h. Body weight and salivary cortisol levels were not significantly different between groups. Based on the von Frey testing, the pigs that received analgesics showed a significantly higher withdrawal threshold of nociceptive stimulus than those that received saline at 1, 3, 6, and 24 h after the surgery. At 48 h after surgery, the SABER-B group had a significantly higher withdrawal threshold than the saline group. The withdrawal threshold was not significantly different from the baseline measurement on intact skin at 3 and 6 h after surgery in the BMP group or 1 and 3 h for the SABERB group. The analgesic effects of BMP were greatest at 3 and 6 h after surgery and that of SABER-B as 1 and 3 h SABER-B provided an earlier onset of analgesia and longer analgesia duration than did BMP. This study demonstrates that ER bupivacaine can provide pigs with 24 to 48 h of analgesia for incisional pain.

Sterilization of rodent feed is recommended to eliminate potential murine pathogens and minimize microbial variability between batches. Most research institutions sterilize feed using steam/pressure (autoclave) or irradiation. Both methods have advantages and disadvantages that contribute to their suitability, including cost, maintenance, availability, and alterations to the exposed product. Dry heat sterilization, which has been in use for over 75 y, uses higher temperatures and longer sterilization times than steam autoclave and is most often used for delicate instruments or products that would be damaged by water such as powders or oil-based liquids. Dry heat sterilization in vivaria has been limited to date but is gaining popularity due to lower initial purchase and ongoing operational costs as compared with steam autoclaves. Little published information exists on the effects of dry heat sterilization on animal feed. We evaluated the sterility and chemical alterations of a natural ingredient, pelleted, rodent diet (NIH-31) after exposure to dry heat. Feed sterility was achieved using a dry heat exposure temperature of 160 °C (320 °F) for 4 h. This exposure resulted in a significant loss of heat-labile vitamins and significantly more acrylamide production as compared with the nonsterile, irradiated, and autoclaved feed.

Validated glass bead sterilization protocols to effectively sterilize rodent surgical instruments after bacterial exposure (for example, cecal contamination) are lacking. To refine current approaches, we added either a multienzyme detergent, neutral pH detergent, or chlorhexidine scrub step before glass bead sterilization of forceps or needle drivers exposed to cecal contents. We exposed sets of forceps and needle drivers to cecal contents, which were then air dried for 3 min. Immediately after, the instruments were wiped several times with a clean, dry paper towel. The contaminated tips were soaked in either a multienzyme or neutral pH detergent (t = 5 min), chlorhexidine scrub (t = 2 min), or no pretreatment solution. To further increase debris removal, instruments (from all groups) were brushed using a clean toothbrush. The nonpretreatment instruments were briefly soaked in saline before brushing. After being rinsed with sterile water, all instruments were exposed to a glass bead sterilizer for 60 s at 500 °F (260 °C). Sets were then swabbed for bacterial culturing. Swabs were plated onto either sheep blood agar (n = 23) or chocolate agar (n = 20) for aerobic culturing or Brucella agar (n = 20) for anaerobic culturing. A subset of instruments was sampled to determine organic material presence after treatment using an ATP luminometer (n = 21). Multiple agar types and bioluminescence were used to more deeply evaluate tool sterility and to differentiate the relative effectiveness of each protocol. From the saline group, only one pair of forceps yielded growth on Brucella agar, and 2 pairs yielded growth on chocolate agar. No other bacterial growth was observed. The use of a pretreatment agent also lowered overall organic contamination levels in needle drivers compared with using only saline. These results indicate that brushing instruments to mechanically remove debris from instruments is paramount to ensure sterility. However, a best practice would be to also use one of the pretreatment options used in this study.

Demodex mites are a common ectoparasite in nonlaboratory Mus musculus (mouse) populations. While infrequently reported in laboratory research mice, the prevalence is thought to be as high as 35% of all colonies. Here, we discuss an outbreak of Demodex within an SPF high-barrier vivarium housing laboratory mice first identified through commercial sentinel-free PCR testing. Consequently, in-house PCR-mediated identification of individually infected cages was conducted, and a successful method for eradication of secondary reemergent infection was generated via recurrent testing and empirical 12-wk treatment with 3 mg/kg moxidectin and 13 mg/kg imidacloprid. While we were unable to determine the source of our primary outbreak, the secondary outbreak was traced to nongenetically modified C57B6/J immunocompetent mice, which were capable of harboring subclinical infection below our PCR threshold. Our eventual successful eradication of Demodex confirmed, first, that in-house PCR detection is a cost-effective means of monitoring an outbreak; second, that treatment with 3 mg/kg moxidectin and 13 mg/kg imidacloprid does kill Demodex mites in laboratory mice; and third, that treatment of only PCR-positive mice is an insufficient way to control an outbreak. Taken together, our methodological approach for infestations such as Demodex suggests it is possible to eradicate them but that it requires a thorough, systematic, and aggressive treatment regimen. Moreover, we recommend that all cages derived from infected animals be treated as positive, regardless of PCR positivity, to prevent recurrent and/or persistent infections within an animal colony.

Mice often undergo painful procedures and surgeries as part of biomedical research protocols. Buprenorphine, a partial μ-opioid receptor agonist and κ receptor antagonist, is commonly used to alleviate the pain associated with such procedures. Due to its pharmacokinetic profile, buprenorphine requires frequent dosing, resulting in handling stress that can impact animal welfare and study data. A long-acting transdermal buprenorphine formulation (LA-bup) was recently approved for use in cats to provide up to 4 d of postoperative analgesia. In this study, we characterized the pharmacokinetics of a single topical dosing of LA-bup in male and female CD-1 mice administered a 0.36-mg or 18-μL topical dose at select time points. Plasma buprenorphine concentrations were evaluated at 0.25, 0.5, 1, 1.5, 2, 4, 8, 24, 48, and 72 h (n = 3 mice/time point) and remained above the purported therapeutic threshold (1 ng/mL) from 1 to 24 h postadministration. Repeated daily dosing at 24 and 48 h demonstrated plasma levels above 1 ng/mL for up to 72 h with minimal accumulation or changes in maximal concentrations over time. Inadvertent transfer of the topical drug to nondosed mice in the same cage was evaluated by measuring plasma buprenorphine concentrations in nondosed mice cohoused with a single-dosed mouse. Male mice did not demonstrate transfer of drug via grooming or interactions, yet 2 out of 26 nondosed female mice had detectable buprenorphine plasma levels indicating a relatively low incidence of cross-ingestion in cohoused female mice. This study demonstrates that LA-bup is a promising analgesic in mice that could be used for tailored analgesia strategies, depending on the surgical model or duration of analgesic therapy.