Carbon dioxide for euthanasia: concerns regarding pain and distress, with special reference to mice and rats

Mass spectrometry imaging protocol for spatial mapping of lipids, N-glycans and peptides in murine lung tissue

RATIONALE

The application of matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to murine lungs is challenging due to the spongy nature of the tissue. Lungs consist of interconnected air sacs (alveoli) lined by a single layer of flattened epithelial cells, which requires inflation to maintain its natural structure. Therefore, a protocol that is compatible with both lung instillation and high spatial resolution is essential to enable multi-omic studies on murine lung disease models using MALDI-MSI.

METHODS AND RESULTS

To maintain the structural integrity of the tissue, murine lungs were inflated with 8% (w/v) gelatin for lipid MSI of fresh frozen tissues or 4% (v/v) paraformaldehyde neutral buffer for N-glycan and peptide MSI of FFPE tissues. Tissues were sectioned and prepared for enzymatic digestion and/or matrix deposition. Glycerol-free PNGase F was applied for N-glycan MSI, while Trypsin Gold was applied for peptide MSI using the iMatrixSpray and ImagePrep Station, respectively. For lipid, N-glycan and peptide MSI, α-cyano-4-hydroxycinnamic acid matrix was deposited using the iMatrixSpray. MS data were acquired with 20 μm spatial resolution using a timsTOF fleX MS instrument followed by MS fragmentation of lipids, N-glycans and peptides. For lipid MSI, trapped ion mobility spectrometry was used to separate isomeric/isobaric lipid species. SCiLS™ Lab was used to visualize all MSI data. For analyte identification, MetaboScape®, GlycoMod and Mascot were used to annotate MS fragmentation spectra of lipids, N-glycans and tryptic peptides, respectively.

CONCLUSIONS

Our protocol provides instructions on sample preparation for high spatial resolution MALDI-MSI, MS/MS data acquisition and lipid, N-glycan and peptide annotation and identification from murine lungs. This protocol will allow non-biased analyses of diseased lungs from preclinical murine models and provide further insight into disease models.

Forensic investigation of carcass decomposition and dipteran fly composition over the summer and winter: a comparative analysis of indoor versus outdoor at a multi-story building

This study aimed to explore the rate of decomposition of rabbit carcasses and the succession pattern of the associated dipteran flies outdoor, indoor, and on the roof of a 4-story building during the summer and winter. A total of 6,069 flies were recorded, with 30.91% reported as 2 waves outdoor and on the roof in the summer and 69.09% as 4 waves outdoor in the winter. The roof showed the most flies in the summer but the least in the winter, whereas the outdoor showed the most in the winter but the least in the summer. The ground and first floors showed the most indoor flies, while the second and third floors showed the least in both seasons. Indoor carcasses decomposed slower than those outdoor, and those on the second and third floors decomposed slower than those on the ground and first floors. Ten fly species from 8 families were identified in the winter, compared to 6 from 5 families in the summer. The most abundant species was Musca domestica Linnaeus (Muscidae) on the roof in the summer, while it was Chrysomya albiceps (Wiedemannn) (Calliphoridae) outdoor in the winter. The rare species (singletons) were Musca sp. (Muscidae) and Megaselia scalaris (Loew) (Phoridae) on the first floor in both seasons, Scaptomyza pallida (Zetterstedt) (Drosophilidae) on the ground floor in the summer, and Atherigona orientalis Schiner (Muscidae) outdoor in the winter. These data highlight the variance in carcass decomposition and fly composition across outdoor, indoor, and the roof of human dwellings, which could be of forensic importance.

A preliminary investigation of rabbit carcass decomposition and attracted ants (Hymenoptera: Formicidae) on the seaward coastal beach of Al-Jubail City, Saudi Arabia

The current study was carried out in the seaward coastal beach environment of Al-Jubail City, Saudi Arabia, to analyze the rabbit carcass decomposition process, the succession pattern of associated ants, and their potential utility in forensic investigation. Experiments were conducted over a 4-season course (from autumn 2018 to summer 2019). A total of 9 species belonging to the 2 subfamilies, Myrmicinae and Formicinae, were recorded. The myrmicine species were Crematogaster aegyptiaca Mayr, 1862; Messor ebeninus Santschi, 1927; Messor foreli Santschi, 1923; and Monomorium abeillei Andre, 1881. The formicine species were Camponotus xerxes Forel, 1904; Cataglyphis albicans (Roger, 1859); Cataglyphis hologerseniCollingwood & Agosti, 1996; Cataglyphis viaticoides (André, 1881); and Nylanderia jaegerskioeldi (Mayr, 1904). M. abeillei was the only species recorded in all 4 seasons, while M. abeillei and C. albicans were the dominant species in summer and C. aegyptiaca and C. albicans in spring. Diversity was lowest in the autumn, with only 4 species recorded. The COI gene sequences of 5 species have been successfully deposited in the GenBank database for the first time. In total, 4 carcass decomposition stages were observed, with the longest duration in winter (13 days), the shortest in summer (11 days), and in between for both autumn and spring. Most ant species were present during both decay and dry stages, while M. abeillei, C. aegyptiaca, M. ebeninus, and C. albicans were observed in all decomposition stages. These data may indicate that ants on this coastal beach showed seasonal and geographical succession patterns that could be taken into consideration in forensic investigations.

Preclinical Mouse Metastatic Model Established Through Induced Lung Metastases

Metastatic disease is the major cause of cancer death, and the lung is one of the most common sites of cancer metastases. To investigate systemic antitumor effects or protective potential of local therapies, mouse models with induced metastases are indispensable in preclinical cancer research. Here, we describe the protocol for the metastatic mouse model established through induced 4T1 mammary carcinoma metastases. With minor prior optimization, it can be applied to other tumor cell lines of interest.

Differential in vivo labeling with barcoded antibodies allows for simultaneous transcriptomic profiling of airway, lung tissue and intravascular immune cells

Single-cell RNA sequencing (scRNA-seq) is the state-of-the-art approach to study transcriptomic signatures in individual cells in respiratory health and disease. However, classical scRNA-seq approaches provide no spatial information and are performed using either bronchoalveolar lavage fluid (BAL) or lung single cell suspensions to assess transcript levels in airway and tissue immune cells, respectively. Herein we describe a simple method to simultaneously characterize transcriptomic features of airway, lung parenchymal and intravascular immune cells based on differential in vivo labeling with barcoded antibodies. In addition to gaining basic spatial information, this approach allows for direct comparison of cells within different anatomical compartments. Furthermore, this method provides a time- and cost-effective alternative to classical scRNA-seq where lung and BAL samples are processed individually, reducing animal and reagent use. We demonstrate the feasibility of this approach in a preclinical mouse model of bacterial lung infection comparing airway, parenchymal and vasculature neutrophils early after infection.

Rat Grimace Scale as a Method to Evaluate Animal Welfare, Nociception, and Quality of the Euthanasia Method of Wistar Rats

Refinement of experimental procedures in animal research has the objective of preventing and minimizing pain/distress in animals, including the euthanasia period. This study aimed to evaluate pain associated with six methods of euthanasia in Wistar rats (injectable, inhalational, and physical), by applying the Rat Grimace Scale (RGS), comparing the scores, and determining the method with the highest score that might indicate pain for laboratory rodents. Sixty adult male and female Wistar rats were used and assigned to six treatments: pentobarbital, CO2, decapitation, isoflurane, ketamine + xylazine, and ketamine + CO2. Video recording to assess the RGS scores was performed in four events: basal: 24 h before the procedure; Ti1: three minutes before the procedure; Ti2: during the application of the euthanasia method; and Ti3: immediately after the application until LORR. The main findings of this study showed that, during Ti2, decapitation and ketamine + xylazine had the highest scores (0.6 ± 0.26 and 0.6 ± 0.16, respectively) (p < 0.0001), while at Ti3, CO2 (0.9 ± 0.18) and isoflurane (1.2 ± 0.20) recorded the highest scores (p < 0.0001). According to the present results, decapitation and ketamine + xylazine elicited short-term acute pain, possibly due to tissue damage caused by both methods (injection and guillotine). In contrast, isoflurane's RGS scores recorded during Ti3 might be associated with nociception/pain due to the pungency of the drug or to the pharmacological muscle relaxant effect of isoflurane. Further research is needed to establish a comprehensive study of pain during euthanasia, where RGS could be used minding the limitations that anesthetics might have on facial expression.

Protective Effect of Galantamine against Doxorubicin-Induced Neurotoxicity

BACKGROUND AND AIMS

Doxorubicin (DOX) causes cognitive impairment (chemobrain) in patients with cancer. While DOX damages the cholinergic system, few studies have focused on the protective effects of cholinergic function on chemobrain. The acetylcholinesterase inhibitor galantamine (GAL) demonstrates neuroprotective properties. We investigated the mechanisms associated with DOX-induced cognitive impairments and the potential protective role of GAL in preventing chemobrain.

MAIN METHODS

Female Wistar rats were divided into control, DOX, GAL, and DOX + GAL groups. The rats in the DOX group were administered DOX (5 mg/kg intraperitoneally twice weekly for two weeks), while those in the GAL group were orally administered GAL (2.5 mg/kg) via oral gavage once daily for 15 days. The combination group (DOX + GAL) received GAL (once daily) and DOX (two times per week) concurrently. The body weights and survival rates were monitored daily. The animals were subjected to behavioral tests to assess the memory function followed by the biochemical estimation of inflammatory markers, including tumor necrosis factor-α (TNF-α), interleukine-1β (IL-1β), and interleukine-6 (IL-6) in rat brain tissue and RT-qPCR.

KEY FINDINGS

DOX caused a reduction in the body weight and survival rate, which was alleviated by GAL concomitant treatment with DOX (DOX + GAL). These groups had reduced body weights and survival rates. DOX-treated animals exhibited an impairment of short-term spatial working memory, manifested as a behavioral alteration in the Y-maze test, the novel object recognition (NOR) test, and the elevated plus-maze (EPM) test. Concurrent treatment with GAL (DOX + GAL) showed improved memory function, as evidenced by an increase in the number of entries and time spent in the novel arm, the time spent exploring the novel object, and the transfer latency in the Y-maze, NOR test, and EPM test, respectively. These findings were also supported by biochemical observations showing the reversal of DOX-induced changes in IL-1β, IL-6, and TNF-α, as well as their relative expression of mRNA in brain tissue following concurrent GAL treatment.

CONCLUSION

GAL appeared to be a neuroprotective agent against neuroinflammation caused by DOX by reducing inflammatory markers in the brain.

Extreme Physiology Extreme Tolerance to Hypoxia, Hypercapnia, and Pain in the Naked Mole-Rat

Challenging environmental conditions can drive the evolution of extreme physiological traits. The naked mole-rat has evolved to survive and thrive in a low oxygen, high carbon dioxide environment that would be deadly to humans and most other mammals. The naked mole-rat's lifestyle is unusual in that this species combines subterranean living and living in large, social groups of up to 300 + individuals. Many respiring animals in a closed environment can lead to depletion of oxygen (hypoxia) and accumulation of carbon dioxide (hypercapnia). Naked mole-rats display a variety of physiological traits that negate the adverse effects of living in this atmosphere. For hypoxia tolerance, naked mole-rats have a low resting metabolism, high affinity hemoglobin, intrinsic brain tolerance, the ability to use fructose for anaerobic glycolysis, and the ability to enter a low energy, suspended animation-like state. For hypercapnia tolerance, these animals have a mutation in a voltage gated sodium channel that effectively eliminates neuronal responses to tissue acidosis. In other mammals, acidosis from exposure to high concentrations of carbon dioxide induces pain and pulmonary edema. Understanding these mechanisms of extreme physiology is not only inherently interesting, but it may lead to biomedical breakthroughs in research on heart attacks, strokes, and pain pathologies.

The perspectives of UK personnel towards current killing practices for laboratory rodents

Rodents are the predominant species used for scientific research and must be humanely killed upon completion of the work. In the UK this is regulated by Schedule 1 of the Animals Scientific Procedures Act 1986, which lists permitted methodologies considered capable of humane killing, including overdose of an anaesthetic, exposure to carbon dioxide (CO₂) gas, dislocation of the neck and concussion of the brain by striking the cranium. Although all are permitted, operator motivations behind method selection and individual operator preference remain unknown. The views of 219 laboratory animal personnel on institutional availability and use of Schedule 1 killing methods for laboratory rodents were obtained. Only 10% of participants reported that all four methods were available at their institution with 57.5% of respondents preferring cervical dislocation. For CO₂, only 18.6% of participants reported using the recommended flow rate, while 45.5% did not know the flow rate employed. We highlight the urgent requirement for the development of quality-controlled training programmes, to improve knowledge and confidence in the selection and application of killing methods. We advocate for continuous review of killing practices to ensure best practice is reflected in legislation and achieve optimal protection of the welfare of laboratory rodents during killing.

Naked Mole-Rats Demonstrate Profound Tolerance to Low Oxygen, High Carbon Dioxide, and Chemical Pain

Naked mole-rats (Heterocephalus glaber) are very unusual among subterranean mammals in that they live in large colonies and are extremely social, spending large amounts of time gathered together in underground nests more than a meter below the surface. Many respiring individuals resting in deep, poorly ventilated nests deplete the oxygen supply and increase the concentration of carbon dioxide. Consistent with living in that atmosphere, naked mole-rats tolerate levels of low oxygen and high carbon dioxide that are deadly to most surface-dwelling mammals. Naked mole-rats appear to have evolved a number of remarkable adaptations to be able to thrive in this harsh atmosphere. In order to successfully survive low oxygen atmospheres, they conserve energy utilization by reducing the physiological activity of all organs, manifest by reduced heart rate and brain activity. Amazingly, they resort to the anaerobic metabolism of fructose rather than glucose as a fuel to generate energy when challenged by anoxia. Similarly, high carbon dioxide atmospheres normally cause tissue acidosis, while naked mole-rats have a genetic mutation preventing both acid-induced pain and pulmonary edema. Together, these putative adaptations and the tolerances they provide make the naked mole-rat an important model for studying a host of biomedical challenges.

Halofuginone ameliorates systemic lupus erythematosus by targeting Blk in myeloid-derived suppressor cells

Systemic lupus erythematosus (SLE) is a multisystemic, inflammatory autoimmune disease. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells participated in the pathogenesis of SLE. MDSCs has been considered a potential therapeutic target for lupus. As traditional Chinese medicine, Halofuginone (HF) has the extensive immunomodulatory effects on some autoimmune disorders. Our research was dedicated to discovering therapeutic efficacy of HF for lupus to explore novel mechanisms on MDSCs. We found that HF prominently alleviated the systemic symptoms especially nephritis in Imiquimod-induced lupus mice, and simultaneously repaired the immune system, reflected in the alteration of autoantibodies. HF diminished the quantity of MDSCs in lupus mice, and induced apoptosis of MDSCs. Through RNA sequencing performed on the sorted MDSC from lupus mice and HF-treated lupus mice, B lymphoid tyrosine kinase (Blk, a non-receptor cytoplasmic tyrosine kinase) was screened as the target molecule of HF. It's proven that HF had two independent effects on Blk. On the one hand, HF increased the mRNA expression of Blk in MDSCs by inhibiting the nuclear translocation of p65/p50 heterodimer. On the other hand, HF enhanced the kinase activity of Blk in MDSCs through direct molecular binding. We further investigated that Blk suppressed the phosphorylation of downstream ERK signaling pathway to increase the apoptosis of MDSCs. In conclusion, our study illustrated that HF alleviated the disease progression of lupus mice by targeting Blk to promote the apoptosis of MDSCs, which indicated the immunotherapeutic potential of HF to treat lupus.

Adipocyte signaling affects thyroid-specific gene expression via down-regulation of TTF-2/FOXE1

Obesity affects thyroid gland function. Hypothyroidism, thyroid nodules, goiter, and thyroid cancer are more frequent in patients with higher BMI values. Although these data are supported by many clinical and epidemiological studies, our knowledge is very scarce at the molecular level. In this study, we present the first experimental evidence that adipocyte signaling downregulates the expression of thyroid-specific transcription factor 2 (TTF-2/FoxE1). It plays a crucial role in thyroid development and thyroid homeostasis and it is strictly connected to thyroid cancer as well. We provide in vivo and in vitro evidence that inhibition of TTF-2/FoxE1 gene expression is mediated by adipocyte signaling.

Effect of Different Gas-Stunning Conditions on Heme Pigment Solutions and on the Color of Blood, Meat, and Small Intestine of Rabbits

The objectives of this study were to elucidate the effect of different high-concentration levels of inert gases (Ar and N2) on heme-pigment solutions and on the color of the blood, meat, and small intestine of rabbits; and to figure out the proper concentration level of inert gas (Ar or N2) for the complete stunning of the rabbit. To observe the changing of color attributes, a research study was conducted in the abattoir of the National Institute of Animal Science (NIAS), RDA, Republic of Korea. This experiment had 2 parts, (i) A trial on heme-pigment solutions (hemoglobin and myoglobin solution) was conducted in a gas chamber with different high-concentration levels of carbon dioxide, argon, nitrogen, and normal air; and (ii) a rabbit experiment was conducted—stunning with different high-concentration levels of carbon dioxide, argon, nitrogen, and the Halal method (non-stunning). A small-size digital gas chamber was used for this experiment (size: width 850 mm × depth 1350 mm). Artificial hemoglobin (Hb) and myoglobin (Mb) solutions were created from “porcine hemoglobin lyophilized powder” and “equine skeletal muscle myoglobin lyophilized powder”, respectively. In the heme-pigment solutions trial, 10 treatments were used: (i) 80% carbon dioxide (T1), (ii) 85% carbon dioxide (T2), (iii) 90% carbon dioxide (T3), (iv) 80% argon (T4), (v) 85% argon (T5), (vi) 90% argon (T6), (vii) 80% nitogen (T7), (viii) 85% nitogen (T8), (ix) 90% nitogen (T9), and (x) normal air (T10). Heme-pigment solutions (both Hb and Mb) were exposed with each treatment for four separate durations of time (30 s, 1 min, 2 min, and 4 min); and every sample (Hb and Mb) was exposed during each duration of time for 10 times (n = 10). In the rabbit experiment, seven treatments were used (i) 85% carbon dioxide (T1), (ii) 90% carbon dioxide (T2), (iii) 85% argon (T3), (iv) 90% argon (T4), (v) 96% nitrogen (T5), (vi) 98% nitogen (T6), and (vii) the Halal method (non-stunning) (T7). Forty-two rabbits (mixed-breed) were collected from the nearest commercial farm and randomly selected for a treatment group (n = 6). The average body weight was 2.3 kg. For stunning, each individual rabbit was separately kept in a gas chamber, after which each specific gas was used to fulfill the desired level in the pit. After reaching the desired level of concentration, rabbits were stunned within a very short time. It was observed that the time required for stunning in the T1, T2, T3, T4, T5 and T6 treatment was 79−82, 68−73, 97−103, 88−91, 164−173, and 108−115 s, respectively. In the case of the Halal method (non-stunning), as per the rules of Islam, rabbits were slaughtered without stunning. After slaughtering, in all treatments, the blood, meat, and small intestine of each animal were collected carefully and kept in a cool room in which the temperature was −2 °C, and after 24 h, the color attributes—lightness (L*), redness (a*), and yellowness (b*)—were measured via a Chroma Meter. It was found that in both experiments (trial on heme-pigment solutions and rabbit stunning), the color values (L*, a* and b*) showed a significant difference (p < 0.05) among the treatment groups. The CO2-treated groups showed high redness (a*) and low lightness (L*) and yellowness (b*), which indicated a dark-red color, and N2-treated groups showed high lightness (L*) and yellowness (b*) and low redness (a*), which implied a bright-red color. The effect of the Ar was in between the CO2- and N2-treated groups. These phenomena were observed both in the heme-pigment solutions (Hb and Mb) and in the blood, meat, and small intestine of the rabbits. N2-stunned animals fulfill the fundamental desire of consumers to purchase bright red-colored fresh meat. Therefore, in view of color attributes, consumer satisfaction, and animal welfare, N2 gas can be thought of as a valuable alternative to stunning. Considering the time required for complete stunning and desirable color attributes, a 98% concentration of N2 is best for rabbit stunning. As such, it could be used as a better option for the gas stunning of animals.

Carbon dioxide tolerability and toxicity in rat and man: A translational study

Background: Due the increasing need for storage of carbon dioxide (CO₂) more individuals are prone to be exposed to high concentrations of CO₂ accidentally released into atmosphere, with deleterious consequences.

Methods: We tested the effect of increasing CO₂ concentrations in humans (6–12%) and rats (10–50%) at varying inhalation times (10–60 min). In humans, a continuous positive airway pressure helmet was used to deliver the gas mixture to the participants. Unrestrained rats were exposed to CO₂ in a transparent chamber. In both species regular arterial blood gas samples were obtained. After the studies, the lungs of the animals were examined for macroscopic and microscopic abnormalities.

Results: In humans, CO₂ concentrations of 9% inhaled for >10 min, and higher concentrations inhaled for <10 min were poorly or not tolerated due to exhaustion, anxiety, dissociation or acidosis (pH < 7.2), despite intact oxygenation. In rats, concentrations of 30% and higher were associated with CO₂ narcosis, epilepsy, poor oxygenation and, at 50% CO₂, spontaneous death. Lung hemorrhage and edema were observed in the rats at inhaled concentrations of 30% and higher.

Conclusion: This study provides essential insight into the occurrence of physiological changes in humans and fatalities in rats after acute exposure to high levels of CO₂. Humans tolerate 9% CO₂ and retain their ability to function coherently for up to 10 min. These data support reconsideration of the current CO₂ levels (<7.5%) that pose a risk to exposed individuals (<7.5%) as determined by governmental agencies to ≤9%.

Hydroxychloroquine induces apoptosis of myeloid-derived suppressor cells via up-regulation of CD81 contributing to alleviate lupus symptoms

Background

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder that results from widespread immune complex deposition and secondary tissue injury. Hydroxychloroquine (HCQ) has been used clinically to treat SLE, while its exact mechanism has still remained elusive. Some studies have shown that myeloid-derived suppressor cells (MDSCs) play a vital role in the regulation of SLE. In this study, we aimed to explore the effects of HCQ on the apoptosis of MDSCs in lupus mice and its possible molecular regulatory mechanism.

Methods

We constructed the imiquimod (IMQ)-induced lupus model in mice. The proportion and apoptosis of MDSCs were measured by flow cytometry. CD81-overexpressed adeno-associated virus was intraperitoneally injected into the lupus mice. We also transfected the CD81 siRNA into bone marrow-derived MDSCs, and employed qRT-PCR and Western blotting to quantify the level of CD81.

Results

The results showed that HCQ ameliorated IMQ-induced lupus symptoms, and simultaneously inhibited the expansion of MDSCs. In particular, HCQ induced the apoptosis of MDSCs, and also up-regulated the expression level of CD81 in MDSCs, which might indicate the relationship between the expression level of CD81 and the apoptosis of MDSCs. CD81 was further confirmed to participate in the apoptosis of MDSCs and lupus disease progression by overexpressing CD81 in vivo. Molecular docking experiment further proved the targeting effect of HCQ on CD81. And then we interfered CD81 in bone marrow derived MDSCs in vitro, and it was revealed that HCQ rescued the decreased expression level of CD81 and relieved the immune imbalance of Th17/Treg cells.

Conclusion

In summary, HCQ promoted the apoptosis of MDSCs by up-regulating the expression level of CD81 in MDSCs, and ultimately alleviated lupus symptoms. Our results may assist scholars to develop further effective therapies for SLE.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00493-6.

A review of methods used to kill laboratory rodents: issues and opportunities

Rodents are the most widely used species for scientific purposes. A critical pre-requisite of their use, based on utilitarian ethical reasoning, is the provision of a humane death when necessary for scientific or welfare grounds. Focussing on the welfare challenges presented by current methods, we critically evaluate the literature, consider emerging methodologies that may have potential for refinement and highlight knowledge gaps for future research. The evidence supports the conclusion that scientists and laboratory personnel should seek to avoid killing laboratory rodents by exposing them to carbon dioxide (CO₂), unless exploiting its high-throughput advantage. We suggest that stakeholders and policymakers should advocate for the removal of CO₂ from existing guidelines, instead making its use conditionally acceptable with justification for additional rationale for its application. With regards to physical methods such as cervical dislocation, decapitation and concussion, major welfare concerns are based on potential inaccuracy in application and their susceptibility to high failure rates. There is a need for independent quality-controlled training programmes to facilitate optimal success rates and the development of specialist tools to improve outcomes and reliability. Furthermore, we highlight questions surrounding the inconsistent inclusion criteria and acceptability of physical methods in international regulation and/or guidance, demonstrating a lack of cohesion across countries and lack of a comprehensive 'gold standard' methodology. We encourage better review of new data and championing of open access scientific resources to advocate for best practice and enable significant changes to policy and legislation to improve the welfare of laboratory rodents at killing.

Determining Candidate Hypobaric Hypoxia Profiles for Humane Killing of Laboratory Mice

Millions of mice are used annually in scientific research and must be humanely killed. Despite significant welfare concerns, carbon dioxide exposure remains the most common killing method, primarily because there is no practical and humane alternative. We explored whether hypobaric hypoxia via gradual decompression could induce a non-recovery state in anesthetized male C57BL/6 and Balb/c laboratory mice. We aimed to determine if this was possible in a feasible timescale with minimal pathological consequences, as a proof-of-principle step. Systematic evaluation of two decompression rates (75, 150 ms−1) and three profile shapes (accelerated, linear, gradual) in a factorial design revealed that hypobaric hypoxia effectively induced a non-recovery state in anesthetized laboratory mice, irrespective of decompression rate and shape. Mice took longer to reach a non-recovery state with the 75 ms−1 decompression rate (75 ms−1: 257 ± 8.96 vs. 150 ms−1: 214 ± 7.26 s), with longer latencies in gradual and linear shaped profiles. Accelerated shaped profiles were least susceptible to meaningful refinement via rate. The only pathological changes of concern were moderate middle ear congestion and hemorrhage. These findings suggest that hypobaric hypoxia has potential, and subsequent work will evaluate the welfare consequences of gradual decompression in conscious mice, to identify decompression profiles that minimize welfare harms associated with ear barotrauma.

Comparative Study of the Aftereffect of CO2 Inhalation or Tiletamine–Zolazepam–Xylazine Anesthesia on Laboratory Outbred Rats and Mice

CO2 inhalation is currently the most common method of euthanasia for laboratory rats and mice, and it is often used for further terminal blood sampling for clinical biochemical assays. Lately, this method has been criticized due to animal welfare issues associated with some processes that develop after CO2 inhalation. The stress reaction and the value of the clinical laboratory parameters significantly depend on the used anesthetics, method, and the site of blood sampling. Especially in small rodents, an acute terminal state followed by a cascade of metabolic reactions that can affect the studied biochemical profile may develop and cause unnecessary suffering of animals. The aim of this study was to compare the stability of biochemical parameters of outbred Sprague Dawley rats and CD-1 mice serum collected after CO2 inhalation or the intramuscular injection of tiletamine–zolazepam–xylazine (TZX). The serum content of total protein and albumin, cholesterol, triglycerides, aspartate aminotransferase (AST), alanine aminotr ansferase (ALT), alkaline phosphatase (ALP), total bilirubin, and creatinine was decreased by the injection of TZX in comparison with CO2 inhalation. In addition, the levels of calcium, phosphates, chlorides and potassium were lowered by TZX vs. CO2 administration, while the level of sodium increased. Finally, the level of the majority of serum clinical biochemical parameters in rats and mice tend to be overestimated after CO2 inhalation, which may lead to masking the possible effect of anti-inflammatory drugs in animal tests. Injection anesthesia for small rodents with TZX is a more feasible method for terminal blood sampling, which also reduces the suffering of animals.

Curcumin Oxidation Is Required for Inhibition of Helicobacter pylori Growth, Translocation and Phosphorylation of Cag A

Curcumin is a potential natural remedy for preventing Helicobacter pylori-associated gastric inflammation and cancer. Here, we analyzed the effect of a phospholipid formulation of curcumin on H. pylori growth, translocation and phosphorylation of the virulence factor CagA and host protein kinase Src in vitro and in an in vivo mouse model of H. pylori infection. Growth of H. pylori was inhibited dose-dependently by curcumin in vitro. H. pylori was unable to metabolically reduce curcumin, whereas two enterobacteria, E. coli and Citrobacter rodentium, which efficiently reduced curcumin to the tetra- and hexahydro metabolites, evaded growth inhibition. Oxidative metabolism of curcumin was required for the growth inhibition of H. pylori and the translocation and phosphorylation of CagA and cSrc, since acetal- and diacetal-curcumin that do not undergo oxidative transformation were ineffective. Curcumin attenuated mRNA expression of the H. pylori virulence genes cagE and cagF in a dose-dependent manner and inhibited translocation and phosphorylation of CagA in gastric epithelial cells. H. pylori strains isolated from dietary curcumin-treated mice showed attenuated ability to induce cSrc phosphorylation and the mRNA expression of the gene encoding for IL-8, suggesting long-lasting effects of curcumin on the virulence of H. pylori. Our work provides mechanistic evidence that encourages testing of curcumin as a dietary approach to inhibit the virulence of CagA.

Expression and distribution of EPHA4 and Ephrin A3 in Aohan fine-wool sheep skin

The objective of this study was to identify the expression and distribution of EPHA4 and Ephrin A3 genes in the development and morphogenesis of hair follicles in fine-wool sheep. The results could lay a theoretical basis for understanding the molecular mechanism that regulates hair follicle development. The skin of Aohan fine-wool sheep at different developmental stages (embryonic day 90, E90d, and 120, E120d, and postnatal day 1, B1d, and 30, B30d) were selected. Real-time quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry were used to study the levels of mRNA and proteins, respectively. The RT-qPCR results showed that the mRNA expression level of EPHA4 at B1d was significantly lower than at E120d (p<0.01). The expression of Ephrin A3 at E120d was significantly higher than that at E90d and B1d (p<0.01). Immunohistochemical detection results showed that the level and localisation of EPHA4 and Ephrin A3 proteins had spatial and temporal specificity. EPHA4 expression in dermal papilla cells might be important for inducing Aohan fine-hair follicle regeneration and for controlling the properties of the hair. Ephrin A3 might play an important role in the redifferentiation of secondary hair follicles and might also be involved in the inhibition of apoptosis-related gene expression in hair follicles. The Ephrin A3 signalling pathway might accelerate the growth of fine-hair follicles and increase the density of hair follicles.

Hippocampus kuda protein hydrolysate improves male reproductive dysfunction in diabetic rats

The global prevalence of diabetes mellitus is rapidly increasing. This disease is associated with many complications including male reproductive dysfunctions and infertility. Seahorse ( Hippocampus kuda) is a marine teleost fish well known for its beneficial effects on the reproductive system in traditional Chinese medicine books. Recently, several studies have been shown that the enzymatic hydrolysate of seahorse has multiple pharmacological activities. This study aimed to investigate the seahorse peptide hydrolysate (SH) ameliorative effects on the diabetic-induced male reproductive dysfunction in rat models. The in vivo studies were carried out with three different doses of SH (4, 8, and 20 mg/kg) and the diabetes condition was induced by administrating with streptozotocin (35 mg/kg) and fed a 40% high-fat diet. Seahorse hydrolysate (20 mg/kg) inhibited lipid peroxidation, increased antioxidant enzyme activity, and restored seminiferous tubules morphology in testis. Moreover, it improved reproductive dysfunction by increasing the level of testosterone, follicle-stimulating hormone, luteinizing hormone, sperm count, and motility. According to these results, we suggested that SH exhibited amelioration effects on the reproductive dysfunction.

The protective effect of Rubus fruticosus L. on blood composition in cyclophosphamide treated male rats

Background

Some chemotherapy drugs such cyclophosphamide (CP) has destructive effects on hematopoietic cells in the bone marrow tissue. Due to antioxidant and anti-inflammatory features, medicinal herbs have protective effects on the bone marrow tissue. The aim of this experimental study is to examine the protective effects of Rubus fruticosus L. extract (RF) on blood parameters in male rats treated with CP.

Methods

In this experimental study, 35 male Wistar rats (220–250 g) were randomly divided into 5 groups (n = 7): Control (0.5 mL normal saline), CP (15 mg/kg), positive control (RF per se 200 mg/kg), treatment 1 (CP 15 mg/kg + RF 100 mg/kg), and treatment 2 (CP 15 mg/kg + RF 200 mg/kg). All drugs and extracts were given intraperitoneally for 15 consecutive days. At the end of the intervention, all animals were euthanized and their blood samples were collected by cardiac puncture in anti-coagulant tubes for blood parameters evaluation.

Results

The data analysis showed that CP has decreased significantly in RBC, WBC, Platelets number, hemoglobin and hematocrit in rats (p < 0.05). RF could protect hematopoiesis in CP-induced rats (p < 0.05).

Conclusion

The use of RF can protect the blood hematopoietic tissue in bone marrow and prevent CP toxic effects.

Stop the rot. Enzyme inactivation at brain harvest prevents artifacts: A guide for preservation of the in vivo concentrations of brain constituents

Post-mortem metabolism is widely recognized to cause rapid and prolonged changes in the concentrations of multiple classes of compounds in brain, that is, they are labile. Post-mortem changes from levels in living brain include components of pathways of metabolism of glucose and energy compounds, amino acids, lipids, signaling molecules, neuropeptides, phosphoproteins, and proteins. Methods that stop enzyme activity at brain harvest were developed almost 50 years ago and have been extensively used in studies of brain functions and diseases. Unfortunately, these methods are not commonly used to harvest brain tissue for mass spectrometry-based metabolomic studies or for imaging mass spectrometry studies (IMS, also called mass spectrometry imaging, MSI, or matrix-assisted laser desorption/ionization-MSI, MALDI-MSI). Instead these studies commonly kill animals, decapitate, dissect out brain and regions of interest if needed, then 'snap' freeze the tissue to stop enzymatic activity after harvest, with post-mortem intervals typically ranging from ~0.5 to 3 min. To increase awareness of the importance of stopping metabolism at harvest and preventing the unnecessary complications of not doing so, this commentary provides examples of labile metabolites and the magnitudes of their post-mortem changes in concentrations during brain harvest. Brain harvest methods that stop metabolism at harvest eliminate post-mortem enzymatic activities and can improve characterization of normal and diseased brain. In addition, metabolomic studies would be improved by reporting absolute units of concentration along with normalized peak areas or fold changes. Then reported values can be evaluated and compared with the extensive neurochemical literature to help prevent reporting of artifactual data.

Influence of Isoflurane Exposure for 15 Consecutive Days on Ovarian Function in Adult Female Mice

Female infertility after occupational exposure to inhaled anesthetic agents has attracted critical attention, but systematic studies focusing on the impact of inhaled anesthetics on the female reproductive system have not been well-established. We used a murine model to study the effect of isoflurane exposure on infertility in female adult mice and investigated the potential underlying mechanism. One hundred adult female C57 mice were randomly allocated into 5 groups exposed in air containing 0, 2500, 5000, 10 000 or 20 000 ppm isoflurane for 15 consecutive days. Estrous cycle length was measured based on vaginal smear examination, ovarian histopathologic enumeration of follicles, and serum estradiol (E₂), anti-Mullerian hormone (AMH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) levels to assess the effect of isoflurane on ovarian reserve. Compared to the control group, significant prolongation of the estrous cycle of the adult female mice was observed in the 20 000 ppm isoflurane exposure group. Serum AMH was significantly decreased, and FSH and LH levels profoundly increased in the 5000, 10 000, and 20 000 ppm isoflurane exposure groups compared to the control group. The histopathologic examination revealed a reduced number of developing follicles and an increased number of atretic follicles after isoflurane exposure, but the difference was not statistically significant. Thus, exposure to a higher concentration of isoflurane might have an adverse effect on ovarian reserve in sexually-mature female mice.

Chronic Oxytocin treatment has long lasting therapeutic potential in a rat model of neonatal hypercapnic-hypoxia injury, through enhanced GABAergic signaling and by reducing hippocampal gliosis with its anti-inflammatory feature

Previous studies have shown that, oxytocin has anticonvulsant and neuroprotective effects. One of the most important complications of Hypercapnic-hypoxia is drug resistance epilepsy. Effects of chronic intraperitoneal oxytocin treatment on gliosis, neuroinflammation and seizure activity was investigated in a model in which rats were exposed to hypoxia on postnatal day 1 and later challenged to the seizure-inducing pentylenetetrazol Forty pups were included in the study on their first day of birth. 16 pups were exposed to 100% CO₂ for 5 minutes and other 16 pups for 10 minutes. The remaining 8 pups comprised the control group. Groups were classified according to oxytocin administration within the first 4 weeks. Pentylenetetrazol was administered 6 months after the oxytocin treatment. The Racine's Convulsion Scale and onset times of first myoclonic jerk (FMJ) were evaluated. To determine the mechanisms by which oxytocin exerted its effects on hypercapnic-anoxia exposed rats, we performed CA1 total neuron count & CA1 GFAP immunostaining, and measured brain levels of TNF-α and GAD-67. The Racine scale and TNF-α values were significantly lower in both groups that received oxytocin, while time-to-FMJ and GAD-67 level were significantly higher. The histopathological evaluations showed that oxytocin had significant ameliorative effects (especially regarding gliosis) on the hippocampus of hypoxic rats. Regarding the results of present study, it can be speculated that after acute hypercapnic-anoxia exposure, chronic Oxytocin treatment has long lasting therapeutic potential on rats, possibly by reducing the gliosis with its anti-inflammatory feature and by activating the GABA pathway.

Cardiovascular and Metabolic Responses to Carbon Dioxide Euthanasia in Conscious and Anesthetized Rats

Euthanasia is a necessary component in research and must be conducted humanely. Currently, regulated CO₂ exposure in conscious rats is acceptable, but data are divided on whether CO₂ alone is more distressing than anesthesia prior to CO₂. To evaluate distress in rats, we compared physiologic responses to CO₂ euthanasia with and without isoflurane preanesthesia. Male Sprague-Dawley rats were implanted with telemetry devices to measure mean arterial pressure (MAP), heart rate (HR), and blood glucose. Animals recovered for 2 wk and were then exposed to either 5% isoflurane (n = 6) or 100% CO₂ (n = 7; calculated 30% chamber volume/min displacement) in their home cages to induce loss of consciousness. Euthanasia was then completed with CO₂ in both groups. MAP and HR increased when the gas delivery lids were placed on the home cages of both groups. Both MAP and HR gradually decreased with isoflurane exposure. MAP increased and HR decreased with CO₂ exposure. Glucose levels remained stable throughout the procedure, except for a small drop in conscious animals initially exposed to 100% CO₂. These data suggest that both gases affect the measured parameters in a similar manner, and that environmental factors, such as gas delivery lid placement, also change these measurements.

The effects of thylakoid-rich spinach extract and aqueous extract of caraway (Carum carvi L.) in letrozole-induced polycystic ovarian syndrome rats

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common endocrine disorder. The aim of the present study was to evaluate the effects of the oral administration of thylakoid-rich spinach extract and the caraway aqueous extract in letrozole-induced polycystic ovary syndrome rats.

METHODS

Sixty female Sprague-Dawley rats were randomly divided into five groups of 12 animals each. Letrozole (1 mg/kg) was administered orally for a period of 28 days to induce PCOS. Sham and PCOS control rats received 1 mL/day of distilled water, and the three groups of PCOS rats were given 150 mg/kg of metformin, 3 g/kg of caraway, and thylakoid at a dose of 6 mg chlorophyll/gr food intake/day by oral gavage for 8 weeks. Finally, blood samples were collected and the right ovary of rats was removed, weighed, and fixed in 4% buffered formalin to determine the biochemical and stereological parameters.

RESULTS

Compared to the PCOS control group, consuming metformin, thylakoid, and caraway extracts significantly improved the fasting blood sugar (FBS), tumor necrosis factor-alpha (TNF-α), malondialdehyde (MDA), luteinizing hormone (LH), insulin resistance, and body weight, increased the volume of the corpus luteum, and reduced the number of atretic follicles after 8 weeks (푃< 0.05). Although caraway treatment caused a significant increase in the HDL-C (High-density lipoprotein cholesterol) level (P < 0.001), no significant change was observed in terms of HDL-C in the thylakoid and metformin groups compared to the PCOS control group.

CONCLUSION

Our data showed that the consumption of thylakoid and caraway extracts for 8 weeks may have beneficial effects on the biochemical and stereological factors in PCOS-induced rats.

Humane Euthanasia of Guinea Pigs (Cavia porcellus) with a Penetrating Spring-Loaded Captive Bolt

Simple Summary

Various euthanasia methods are currently employed for guinea pigs at their experimental or humane endpoint; however, many have significant limitations or negative animal welfare implications. Captive bolt euthanasia has been used in the guinea pig meat industry but has not been explored in a research setting. This work aimed to investigate the use of a penetrating spring-loaded captive bolt gun as a refinement to guinea pig euthanasia in research. The study found that when compared to blunt force trauma, the captive bolt procedure performed well against all parameters of humane slaughter of production animals and appears to be a feasible refinement for animal welfare.

Abstract

Guinea pigs (Cavia porcellus) have been used in research since the 19th century to collect data due to their physiological similarities to humans. Today, animals perform a vital role in experiments and concerns for laboratory animal welfare are enshrined in the 3R framework of reduction, refinement and replacement. This case study explores a refinement in humane euthanasia of guinea pigs via the use of an irreversible penetrating spring-loaded captive bolt (CB). Penetrating spring-loaded CB stunning for euthanasia (CBE) was performed on 12 guinea pigs with the parameters for humane slaughter of production animals in order to assess the suitability of this method of euthanasia in contrast to blunt force trauma (BFT). All 12 of the guinea pigs were rendered immediately unconscious with excellent experimental tissue quality collection, high repeatability of results and operator (n = 8) preference over BFT. Overall, CBE in guinea pigs appears to be a feasible refinement for animal welfare, human preference and improved tissue quality for experimental collection in settings where uncontaminated tissues are required.

Welfare Impact of Carbon Dioxide Euthanasia on Laboratory Mice and Rats: A Systematic Review

Background: There has been increased concern about the suitability of CO2 as a method for euthanasia of laboratory mice and rats, including the potential discomfort, pain or distress that animals may experience prior to loss of consciousness; time to loss of consciousness; best methods for use of CO2; and the availability of better alternatives. These discussions have been useful in providing new information, but have resulted in significant confusion regarding the acceptability of CO2 for rodent euthanasia. In some cases, researchers and veterinarians have become uncertain as to which techniques to recommend or use for euthanasia of laboratory mice and rats. Methods: The International Association of Colleges of Laboratory Animal Medicine (IACLAM) convened a taskforce to examine the evidence for adverse welfare indicators in laboratory rats and mice undergoing CO2 euthanasia using a SYRCLE-registered systematic review protocol. Of 3,772 papers identified through a database search (PubMed, Web of Science, CAB Direct, Agricola, and grey literature) from 1900 to 2017, 37 studies were identified for detailed review (some including more than one species or age group), including 15 in adult mice, 21 in adult rats, and 5 in neonates of both species. Experiments or reports were excluded if they only assessed parameters other than those directly affecting animal welfare during CO2 induction and/or euthanasia. Results: Study design and outcome measures were highly variable and there was an unclear to high risk of bias in many of the published studies. Changes in the outcome measures evaluated were inconsistent or poorly differentiated. It is likely that repeated exposures to carbon dioxide inhalation are aversive to adult rats and mice, based on avoidance behavior studies; however, this effect is largely indistinguishable from aversion induced by repeated exposures to other inhalant anesthetic gasses. Conclusion: There is insufficient evidence to permit an unbiased assessment of the effect of CO2 inhalation during euthanasia on welfare indicators in laboratory mice and rats. Additional well-designed, unbiased, and adequately powered studies are needed to accurately assess the welfare of laboratory mice and rats undergoing euthanasia via CO2 gas.

Review of Intraperitoneal Injection of Sodium Pentobarbital as a Method of Euthanasia in Laboratory Rodents

Euthanasia is one of the most commonly performed procedures in biomedical research, involving tens of millions of animals in North America and Europe every year. The use of sodium pentobarbital, injected intraperitoneally, for killing rodents is described as an acceptable technique by the AVMA and CCAC euthanasia guidelines. This drug and route are recommended over inhalant anesthetics, carbon dioxide, and physical methods for ethical and aesthetic reasons as well as efficiency. However, a growing body of evidence challenges the efficacy and utility of intraperitoneal pentobarbital. This methodology has been described as inconsistent and may induce pain and stress. With these considerations in mind, a review of the literature is needed to assess the evidence surrounding this killing method, the associated welfare implications, and potential for refinement.

Review of Rodent Euthanasia Methods

The optimal choice of euthanasia method for laboratory rodents depends on a number of factors, including the scientific goals of the study, the need to minimize animal pain and/or distress, applicable guidelines and laws, the training and proficiency of personnel, and the safety and emotional needs of the personnel performing the euthanasia. This manuscript aims to provide guidance to researchers so they may select the method of euthanasia that results in minimal experimental confounds, such as the creation of artifact and alteration of tissues and analytes. Specific situations addressed include euthanasia of large numbers of rodents and euthanasia of neonates. Recent literature supports the notion of significant strain-dependent differences in response to euthanasia methods such as CO₂ inhalation. To assist researchers in selecting a strain-appropriate method of euthanasia, the authors present a summary of methodologies for assessing the effectiveness of euthanasia techniques, including elements and parameters for a scoring rubric to assess them.

A new method for quantitative detection of Lactobacillus casei based on casx gene and its application

Background

The traditional method of bacterial identification based on 16S rRNA is a widely used and very effective detection method, but this method still has some deficiencies, especially in the identification of closely related strains. A high homology with little differences is mostly observed in the 16S sequence of closely related bacteria, which results in difficulty to distinguish them by 16S rRNA-based detection method. In order to develop a rapid and accurate method of bacterial identification, we studied the possibility of identifying bacteria with other characteristic fragments without the use of 16S rRNA as detection targets.

Results

We analyzed the potential of using cas (CRISPR-associated proteins) gene as a target for bacteria detection. We found that certain fragment located in the casx gene was species-specific and could be used as a specific target gene. Based on these fragments, we established a TaqMan MGB Real-time PCR method for detecting bacteria. We found that the method used in this study had the advantages of high sensitivity and good specificity.

Conclusions

The casx gene-based method of bacterial identification could be used as a supplement to the conventional 16 s rRNA-based detection method. This method has an advantage over the 16 s rRNA-based detection method in distinguishing the genetic relationship between closely-related bacteria, such as subgroup bacteria, and can be used as a supplement to the 16 s rRNA-based detection method.

Amelioration of antioxidant potential, toxicity, and antihyperglycemic activity of Hippophae salicifolia D. Don leaf extracts in alloxan-induced diabetic rats

Efficacy of several plant extracts in the clinical research for modulating oxidative stress correlated with diabetes mellitus (DM) is well documented. In the present study, we investigated the in vitro antioxidant activity, toxicity, and anti-diabetic activity of methanolic extract of Hippophae salicifolia leaves in normal and alloxan-induced diabetic wistar rats. H. salicifolia leaves were found to be rich in antioxidants. The acute toxicity test of methanolic extract of H. salicifolia leaves revealed that the median lethal dose (LD50) was found to be 3.92 g/kg body weight in mice. Administration of H. salicifolia leaves at 200 mg/kg and 400 mg/kg in alloxan-induced diabetic rats illustrated significant reduction (22% and 39%, respectively) in fasting blood glucose compared to diabetic control. Both the doses were found to be effective when compared to diabetic rats. The Hippophae-treated diabetic rats showed significant increase in the endogenous antioxidant enzymes, superoxide dismutase (50% and 74%, respectively), glutathione peroxidase (57% and 41%, respectively) and decrease in malondialdehyde (33% and 15%, respectively) levels. These results suggested that the methanolic leaf extract of H. salicifolia enhanced the antioxidant defence against reactive oxygen species produced under hyperglycaemic conditions.

Alternatives to Carbon Dioxide-Taking Responsibility for Humanely Ending the Life of Animals

Simple Summary

Carbon dioxide has long been considered one of the better methods for euthanizing laboratory rodents because it allows termination of several animals at one time, does not require handling of the animal, is easy to use, is inexpensive, and is environmentally friendly. Research, though, has shown that this gas is aversive to rodents and that it may be inhumane to expose them to this gas while they are conscious. Therefore, the Swiss Federal Food Safety and Veterinary Office has set out to find a suitable replacement and organized a meeting that included representatives and experts of the different stakeholders involved in this process in order to find a solution. The conclusion of this meeting was that a replacement is required, and the next step would be to draft a research strategy to find a suitable replacement.

Abstract

Carbon dioxide (CO₂) is commonly used to kill rodents. However, a large body of research has now established that CO₂ is aversive to them. A multidisciplinary symposium organized by the Swiss Federal Food Safety and Veterinary Office discussed the drawbacks and alternatives to CO₂ in euthanasia protocols for laboratory animals. Dialogue was facilitated by brainstorming sessions in small groups and a “World Café”. A conclusion from this process was that alternatives to CO₂ were urgently required, including a program of research and extension to meet the needs for humane killing of these animals. The next step will involve gathering a group of international experts to formulate, draft, and publish a research strategy on alternatives to CO₂.

Laxative effects of triple fermented barley extracts (FBe) on loperamide (LP)-induced constipation in rats

BACKGROUND

Constipation, a common health problem, causes discomfort and affects the quality of life. This study intended to evaluate the potential laxative effect of triple fermented barley (Hordeum vulgare L.) extract (FBe), produced by saccharification, Saccharomyces cerevisiae, and Weissella cibaria, on loperamide (LP)-induced constipation in Sprague-Dawley (SD) rats, a well-established animal model of spastic constipation.

METHODS

Spastic constipation was induced via oral treatment with LP (3 mg/kg) for 6 days 1 h before the administration of each test compound. Similarly, FBe (100, 200 and 300 mg/kg) was orally administered to rats once a day for 6 days. The changes in number, weight, and water content of fecal, motility ratio, colonic mucosa histology, and fecal mucous contents were recorded. The laxative properties of FBe were compared with those of a cathartic stimulant, sodium picosulfate. A total of 48 (8 rats in 6 groups) healthy male rats were selected and following 10 days of acclimatization. Fecal pellets were collected one day before administration of the first dose and starting from immediately after the fourth administration for a duration of 24 h. Charcoal transfer was conducted after the sixth and final administration of the test compounds.

RESULTS

In the present study, oral administration of 100-300 mg/kg of FBe exhibited promising laxative properties including intestinal charcoal transit ratio, thicknesses and mucous producing goblet cells of colonic mucosa with decreases of fecal pellet numbers and mean diameters remained in the lumen of colon, mediated by increases in gastrointestinal motility.

CONCLUSION

Therefore, FBe might act as a promising laxative agent and functional food ingredient to cure spastic constipation, with less toxicity observed at a dose of 100 mg/kg.

Euthanasia via CO2 inhalation causes premature cortical granule exocytosis in mouse oocytes and influences in vitro fertilization and embryo development

Generation of high quality mouse metaphase II oocytes is an integral part for efficient in vitro fertilization (IVF), and subsequent embryo production for reproductive studies and genome banking. The main objectives of this study were to investigate the impact of various euthanasia methods on IVF, embryo development, and subcellular structures of MII mouse oocytes. Following superovulation regimen, female mice were euthanized by high flow CO₂ (H CO₂ ), low flow CO₂ (L CO₂ ), or cervical dislocation (CD). The MII oocytes obtained from these mice were evaluated for subcellular integrity by assessing their cortical granules and F-actin. Furthermore, fertilization and subsequent embryonic development competence up to blastocyst stage were also evaluated in vitro. The oocytes collected from females euthanized by CD resulted in significantly higher two-cell development rates (p = 0.028) and subsequently lead to in higher embryo development rates (p = 0.027) compared with oocytes from females euthanized by L CO₂ . The cortical granule integrity analysis revealed significantly higher rate of premature cortical granules exocytosis (PCGE) for L CO₂ group compared with CD and H CO₂ groups (p < 0.001). These data collectively suggest that CO₂ associated PCGE during euthanasia procedure is the main cause of decreased IVF rates and CD is the optimal euthanasia method for the purpose of obtaining good quality MII oocytes for mouse IVF and other reproductive studies.

Euthanasia- and Lavage-mediated Effects on Bronchoalveolar Measures of Lung Injury and Inflammation

Accurate and reproducible assessments of experimental lung injury and inflammation are critical for basic and translational research. In particular, investigators use various methods for BAL and euthanasia; however, the impact of these methods on assessments of injury and inflammation is unknown. To define potential effects, we compared methods of lavage and euthanasia in uninjured mice and after a mild lung injury model (ozone). C57BL/6J male mice (8-10 weeks old) underwent BAL after euthanasia with ketamine/xylazine, carbon dioxide (CO₂), or isoflurane. BAL methods included 800 μl of isotonic solution instilled and withdrawn three times, and one or three passive fills and drainage to 20 cm H₂O. Parallel experiments were performed 24 hours after 3 hours of ozone (O₃) exposure at 2 ppm. BAL total cell counts/differentials and total protein/albumin were determined. Lung histology was evaluated for lung inflammation or injury. BAL cells were cultured and stimulated with PBS, PMA, or LPS for 4 hours and supernatants were evaluated for cytokine content. In uninjured mice, we observed differences due to the lavage and euthanasia methods used. The lavage method increased total cells and total protein/albumin in uninjured and O₃-exposed mice, with the 800-μl instillation having the highest values. Isoflurane increased total BAL cells, whereas CO₂ euthanasia increased the total protein/albumin levels in uninjured mice. These effects limited our ability to detect differences in BAL injury measures after O₃ exposure. In conclusion, the method used for lavage and euthanasia affects measures of lung inflammation/injury and should be considered a variable in model assessments.

Comparison of pentobarbital-phenytoin alone vs propofol prior to pentobarbital-phenytoin for euthanasia in 436 client-owned dogs

OBJECTIVE

To report the incidence of adverse events during euthanasia of client-owned dogs administered either intravenous pentobarbital/phenytoin (PP) or PP after propofol delivery.

DESIGN/SETTING

Prospective, observational, multi-site study.

ANIMALS

Four hundred thirty-six dogs undergoing client-elected euthanasia over a 1-year period.

INTERVENTIONS

Interventions included placement of an IV catheter and delivery of euthanasia agents (PP for the PP group, propofol followed by PP for the propofol group). Seven pre-determined adverse events were recorded: agonal breaths, urination, defecation, vocalization, muscle activity, dysphoria, and catheter complications. Euthanasia scores for each patient were defined as the sum of all adverse events (0-7) the patient exhibited.

MEASUREMENTS AND MAIN RESULTS

Two hundred thirty-six dogs were in the PP group and 200 dogs were in the propofol group. No significant differences were detected in the dose of PP administered (166.9 ± 105.6 mg/kg for PP group, 182.6 ± 109.8 mg/kg for propofol group). Propofol dogs received 4.5 ± 2.9 mg/kg propofol. The incidence of ≥ 1 adverse event was 35.2% in the PP group and 26.5% in the propofol group (P = 0.052). Mean euthanasia scores (0.47 PP group, 0.32 propofol group) were not significantly different (P = 0.08). Propofol significantly reduced the incidence of muscle activity (6% vs. 14%, odds ratio 0.39; P = 0.0079).

CONCLUSIONS

There was no difference in the likelihood of the studied adverse events during client-elected euthanasia in dogs when propofol was used prior to PP. There was a significant reduction in perimortem muscle activity if propofol was given prior to PP.

Nitrogen gas produces less behavioural and neurophysiological excitation than carbon dioxide in mice undergoing euthanasia

Carbon dioxide (CO₂) is one of the most commonly used gas euthanasia agents in mice, despite reports of aversion and nociception. Inert gases such as nitrogen (N₂) may be a viable alternative to carbon dioxide. Here we compared behavioural and electrophysiological reactions to CO₂ or N₂ at either slow fill or rapid fill in C57Bl/6 mice undergoing gas euthanasia. We found that mice euthanised with CO₂ increased locomotor activity compared to baseline, whereas mice exposed to N₂ decreased locomotion. Furthermore, mice exposed to CO₂ showed significantly more vertical jumps and freezing episodes than mice exposed to N₂. We further found that CO₂ exposure resulted in increased theta:delta of the EEG, a measure of excitation, whereas the N₂ decreased theta:delta. Differences in responses were not oxygen-concentration dependent. Taken together, these results demonstrate that CO₂ increases both behavioural and electrophysiological excitation as well as producing a fear response, whereas N₂ reduces behavioural activity and central neurological depression and may be less aversive although still produces a fear response. Further studies are required to evaluate N₂ as a suitable euthanasia agent for mice.

[Central monoaminergic systems sensitivity to acute hypoxia with hypercapnia changes after the maintenance under the long-term social isolation]

The experiments were performed in male albino outbred mice kept in a group and under the conditions of long-term social isolation. The changes in the monoaminergic systems of the left and right hemispheres of the brain after acute hypoxia with hypercapnia have been studied. The levels of dopamine (DA), serotonin (5-HT) and their metabolites - dioxyphenylacetic (DOPAC), homovanillic (HVA), and 5-hydroxyindoleacetic (5-HIAA) acids - were determined by HPLC in the cerebral cortex, hippocampus and striatum of the right and left sides of the brain. In the control mice kept both in the group and under the conditions of social isolation, a higher content of DA in the cortex of the left hemisphere has been found. In the other brain structures the monoamine content was symmetric. In the cerebral cortex of the mice in the group, acute hypoxia with hypercapnia led to a right-sided increase in the DA and 5HT levels. At the same time, the DOPAC content decreased in the left cortex. In mice in the group, under the hypoxia with hypercapnia conditions, the DA level in the left hippocampus increased. In the striatum, the content of monoamines and their metabolites did not change significantly. In animals kept for a long time under the conditions of social isolation, hypoxia with hypercapnia no statistically significant changes in the monoamines and their metabolites levels were found. It has been concluded that the preliminary maintenance under the conditions of prolonged social isolation changes the reaction of central monoaminergic systems to acute hypoxia with hypercapnia.

Laboratory Guidelines for Animal Care

Animal research is a controversial subject because of the ethical and moral implications of using unwilling research subjects in potentially painful or distressful procedures usually ending in euthanasia. As such, it must be conducted in a compassionate and responsible manner geared toward maximizing the animals' quality of life prior to and during experimentation. Because of its contentious nature, the conduct of animal research is highly regulated at the federal, state, city, and institutional levels. It is essential that researchers acquire a thorough knowledge of the procedures to be conducted as well as a working knowledge of the regulations. This will maximize humane care of research animals and prevent potentially negative or detrimental interactions with groups opposed to using animals in biomedical research. Perhaps the best way to attain these goals is to avoid inadvertent instances of noncompliance with their research protocol or applicable regulations. Regulatory noncompliance can also have serious negative consequences on investigators' research careers ranging from temporary suspension of their protocols to loss of funding and revocation of principal investigator status and associated privileges. To minimize such adverse outcomes, it is advised that researchers build positive and collaborative relationships with key institutional players such as the veterinary staff, the Institutional Animal Care and Use Committee (IACUC), and top administrators. Guidance is provided regarding the appropriate handling of regulatory noncompliance.

Wellbeing of Alcohol-preferring Rats Euthanized with Carbon Dioxide at Very Low and Low Volume Displacement Rates

The 2013 AVMA Guidelines on Euthanasia recommend the use of very-low or low flow rates of 100% carbon dioxide to euthanize small rodents. Although inhalation of high concentrations of carbon dioxide are generally recognized as painful in humans, whether the use of these low-flow methods of euthanasia increase potential distress for rats is unclear. This study compared physiologic and behavioral markers of animal wellbeing for rats euthanized by using 10% volume displacement per minute (VD/min), 30% VD/min, and 70% VD/min of 100% carbon dioxide. Rats were recorded during euthanasia for subsequent behavioral scoring, and blood samples were taken after euthanasia for assessment of blood glucose and serum corticosterone levels. In this study, rats euthanized with 10% or 30% VD/min of 100% carbon dioxide demonstrated increases in various behaviors, such as rearing and standing, concurrent with increases in serum corticosterone. Rats euthanized with 70% VD/min of 100% carbon dioxide did not exhibit these changes. The results suggest that a euthanasia method of 70% VD/min of 100% carbon dioxide may minimize potential pain and distress and thus be more humane for rats, as compared with very-low- and low-flow methods of carbon dioxide euthanasia.

Does the Stress of Laboratory Life and Experimentation on Animals Adversely Affect Research Data? A Critical Review

Recurrent acute and/or chronic stress can affect all vertebrate species, and can have serious consequences. It is increasingly and widely appreciated that laboratory animals experience significant and repeated stress, which is unavoidable and is caused by many aspects of laboratory life, such as captivity, transport, noise, handling, restraint and other procedures, as well as the experimental procedures applied to them. Such stress is difficult to mitigate, and lack of significant desensitisation/habituation can result in considerable psychological and physiological welfare problems, which are mediated by the activation of various neuroendocrine networks that have numerous and pervasive effects. Psychological damage can be reflected in stereotypical behaviours, including repetitive pacing and circling, and even self-harm. Physical consequences include adverse effects on immune function, inflammatory responses, metabolism, and disease susceptibility and progression. Further, some of these effects are epigenetic, and are therefore potentially transgenerational: the biology of animals whose parents/grandparents were wild-caught and/or have experienced chronic stress in laboratories could be altered, as compared to free-living individuals. It is argued that these effects must have consequences for the reliability of experimental data and their extrapolation to humans, and this may not be recognised sufficiently among those who use animals in experiments.

Euthanasia of laboratory mice: Are isoflurane and sevoflurane real alternatives to carbon dioxide?

In the European Union (EU) millions of laboratory mice are used and killed for experimental and other scientific purposes each year. Although controversially discussed, the use of carbon dioxide (CO₂) is still permitted for killing rodents according to the Directive 2010/63/EU. Within the scope of refinement, our aim was to investigate if isoflurane and sevoflurane are an appropriate alternative killing method to CO₂ in mice. Different concentrations of CO₂ (filling rates of 20%, 60%, 100%; CO₂ 20, 60, 100), isoflurane (Iso 2%, 5%) and sevoflurane (Sevo 4.8%, 8%) were compared in two mouse strains (NMRI, C57Bl/6J) using a broad spectrum of behavioral parameters, including the approach-avoidance test, and analyzing blood for stress parameters (glucose, adrenaline, noradrenaline). We focused in our study on the period from the beginning of the gas inlet to loss of consciousness, as during this period animals are able to perceive pain and distress. Our results show that only higher concentrations of CO₂ (CO₂ 60, 100) and isoflurane (5%) induced surgical tolerance within 300 s in both strains, with CO₂ 100 being the fastest acting inhalant anesthetic. The potency of halogenated ethers depended on the mouse strain, with C57Bl/6J being more susceptible than NMRI mice. Behavioral analysis revealed no specific signs of distress, e. g. stress-induced grooming, and pain, i. e. audible vocalizations, for all inhalant gases. However, adrenaline and noradrenaline plasma concentrations were increased, especially in NMRI mice exposed to CO₂ in high concentrations, whereas we did not observe such increase in animals exposed to isoflurane or sevoflurane. Escape latencies in the approach-avoidance test using C57Bl/6J mice did not differ between the three inhalant gases, however, some animals became recumbent during isoflurane and sevoflurane but not during CO₂ exposure. The rise in catecholamine concentrations suggests that CO₂ exposure might be linked to a higher stress response compared to isoflurane and sevoflurane exposure, although we did not observe a behavioral correlate for that. Follow-up studies investigating other fast-acting stress hormones and central anxiety circuits are needed to confirm our findings.

Epileptiform activity during inert gas euthanasia of mice

Carbon dioxide (CO₂) is one of the most commonly used euthanasia agents for mice, yet it is highly aversive and nociceptive. Inert gases are a possible alternative, however there are qualitative reports of seizures resulting from exposure. Here we evaluate epileptiform activity caused by inert gases (N₂, He, Ar and Xe) and CO₂ in mice chronically instrumented for EEG/EMG undergoing single-gas euthanasia. We found that N₂, He and Ar caused epileptiform activity in all animals, CO₂ in half of animals and no epileptiform activity produced by Xe. Atmospheric O₂ concentrations at epileptiform activity onset were significantly higher for CO₂ than for all other gases and occurred soon after loss of motion, whereas N₂ and Ar epileptiform activity occurred at cessation of neocortical activity. Helium caused the longest epileptiform activity and these commenced significantly before isoelectric EEG. We did not detect any epileptiform activity during active behaviour. Taken together, these results demonstrate that whilst epileptiform activity from inert gases and particularly Ar and N₂ are more prevalent than for CO₂, their occurrence at the onset of an isoelectric EEG is unlikely to impact on the welfare of the animal. Epileptiform activity from these gases should not preclude them from further investigation as euthanasia agents. The genesis of epileptiform activity from CO₂ is unlikely to result from hypoxia as with the inert gases. Helium caused epileptiform activity before cessation of neocortical activity and for a longer duration and is therefore less suitable as an alternative to CO₂.

Depopulation of Caged Layer Hens with a Compressed Air Foam System

During the 2014-2015 US highly pathogenic avian influenza (HPAI) outbreak, 50.4 million commercial layers and turkeys were affected, resulting in economic losses of $3.3 billion. Rapid depopulation of infected poultry is vital to contain and eradicate reportable diseases like HPAI. The hypothesis of the experiment was that a compressed air foam (CAF) system may be used as an alternative to carbon dioxide (CO₂) inhalation for depopulating caged layer hens. The objective of this study was to evaluate corticosterone (CORT) and time to cessation of movement (COM) of hens subjected to CAF, CO₂ inhalation, and negative control (NEG) treatments. In Experiment 1, two independent trials were conducted using young and spent hens. Experiment 1 consisted of five treatments: NEG, CO₂ added to a chamber, a CO₂ pre-charged chamber, CAF in cages, and CAF in a chamber. In Experiment 2, only spent hens were randomly assigned to three treatments: CAF in cages, CO₂ added to a chamber, and aspirated foam. Serum CORT levels of young hens were not significantly different among the CAF in cages, CAF in a chamber, NEG control, and CO₂ inhalation treatments. However, spent hens subjected to the CAF in a chamber had significantly higher CORT levels than birds in the rest of the treatments. Times to COM of spent hens subjected to CAF in cages and aspirated foam were significantly greater than of birds exposed to the CO₂ in a chamber treatment. These data suggest that applying CAF in cages is a viable alternative for layer hen depopulation during a reportable disease outbreak.

Relevance of deprivation studies in understanding rapid eye movement sleep

Rapid eye movement sleep (REMS) is a unique phenomenon essential for maintaining normal physiological processes and is expressed at least in species higher in the evolution. The basic scaffold of the neuronal network responsible for REMS regulation is present in the brainstem, which may be directly or indirectly influenced by most other physiological processes. It is regulated by the neurons in the brainstem. Various manipulations including chemical, elec-trophysiological, lesion, stimulation, behavioral, ontogenic and deprivation studies have been designed to understand REMS genesis, maintenance, physiology and functional significance. Although each of these methods has its significance and limitations, deprivation studies have contributed significantly to the overall understanding of REMS. In this review, we discuss the advantages and limitations of various methods used for REMS deprivation (REMSD) to understand neural regulation and physiological significance of REMS. Among the deprivation strategies, the flowerpot method is by far the method of choice because it is simple and convenient, exploits physiological parameter (muscle atonia) for REMSD and allows conducting adequate controls to overcome experimental limitations as well as to rule out nonspecific effects. Notwithstanding, a major criticism that the flowerpot method faces is that of perceived stress experienced by the experimental animals. Nevertheless, we conclude that like most methods, particularly for in vivo behavioral studies, in spite of a few limitations, given the advantages described above, the flowerpot method is the best method of choice for REMSD studies.

The effect of light level, CO2 flow rate, and anesthesia on the stress response of mice during CO2 euthanasia

Euthanasia protocols are designed to mitigate the stress experienced by animals, and an environment that induces minimal stress helps achieve that goal. A protocol that is efficient and practical in a typical animal research facility is also important. Light intensity, isoflurane, and CO2 flow rate were studied for their impact on the stress response of mice during CO2 euthanasia. Behavior was observed and scored during euthanasia and serum corticosterone was measured immediately after death. Unsurprisingly, animals euthanized with a high-flow rate of CO2 became unconscious in the least amount of time, while animals euthanized with a low-flow rate required the most time to reach unconsciousness. There was a significant increase in anxious behaviors in animals in the isoflurane group (F1,12 = 6.67, P = 0.024), the high-flow rate CO2 group (F1,12 = 10.24, P = 0.007), and bright chamber group (F1,12 = 7.27, P = 0.019). Serum corticosterone was highest in the isoflurane group (124.72 ± 83.98 ng/ml), however there was no significant difference in corticosterone levels observed for the other study variables of light and flow-rate. A darkened chamber and low CO2 flow rates help to decrease stress experienced during CO2 euthanasia, while the use of isoflurane was observed to increase the stress response during euthanasia.