The Influence of Feed and Drinking Water on Terrestrial Animal Research and Study Replicability

Dry Heat Sterilization of a Pelleted, Natural Ingredient Rodent Diet

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.

The Elephant in the Room: Recognition and Documentation of Personnel Practices That Confound Reproducibility

The ability to apply findings from animal studies efficiently and effectively is predicated on an understanding of biology and pathobiology, how that biology relates to the human systems being modeled, and how the studies are conducted and reported. This overview discusses various factors in research within the animal environment (referred to as extrinsic factors) that the NIH now expects to be documented to foster replicability in science and expand interpretations of study outcomes. Specifically, an important extrinsic factor in research with animals is that of individual personnel who perform handling practices, participate in research interactions, and share an overall presence in the housing facility with animals, all of which can confound reproducibility efforts in biomedical science. An improved understanding of the influences and behaviors of animal research personnel on animal responses is critical with regard to research results and the interpretation of data collected from animal models of biomedical disease.

Differential Roles of Diet on Development and Spinal Cord Regeneration in Larval Zebrafish

The zebrafish is a powerful model organism for studying development and regeneration. However, there is a lack of a standardized reference diet for developmental and regeneration experiments. Most studies evaluate the rate of growth, survival, and fecundity. In this study, we compare three diets and their effects on growth and regeneration after a spinal cord injury (SCI). Fish were fed daily for 1 week with daily measurements of overall length and width of spinal injury. Fish fed a live rotifer diet grew 32%, whereas a commercially available diet only led to a 4% increase in body length. Similarly, differences in rate of regeneration were observed with over 80% of rotifer-fed larvae forming a glial bridge after injury compared to <10% of zebrafish fed with the commercial diet. Our data highlight the need for establishing a standardized diet for regeneration studies to improve research reproducibility.

Advocating for Generalizability: Accepting Inherent Variability in Translation of Animal Research Outcomes

Advancing scientific discovery requires investigators to embrace research practices that increase transparency and disclosure about materials, methods, and outcomes. Several research advocacy and funding organizations have produced guidelines and recommended practices to enhance reproducibility through detailed and rigorous research approaches; however, confusion around vocabulary terms and a lack of adoption of suggested practices have stymied successful implementation. Although reproducibility of research findings cannot be guaranteed due to extensive inherent variables in attempts at experimental repetition, the scientific community can advocate for generalizability in the application of data outcomes to ensure a broad and effective impact on the comparison of animals to translation within human research. This report reviews suggestions, based upon work with National Institutes of Health advisory groups, for improving rigor and transparency in animal research through aspects of experimental design, statistical assessment, and reporting factors to advocate for generalizability in the application of comparative outcomes between animals and humans.

Safety evaluation of 5-hydroxytryptophan and S-(2-aminoethyl)isothiouronium bromide hydrobromide on rodent lungs

OBJECTIVES

During the past few decades, various compounds have been researched for their potential as radioprotectants, and many of them were found to be safe and effective in several preclinical models. However, many of these compounds were found to have serious adverse effects when evaluated in clinical settings, thereby making them unsuitable for human applications. 5-hydroxytryptophan (5-HTP) and S-(2-aminoethyl) isothiouronium bromide hydrobromide (AET) act in a synergistic fashion to promote radioprotection. The present study primarily emphasizes the safety of fixed dose of 5-HTP + AET in the lungs of C57BL/6 mice, a well-known model used in drug safety studies.

MATERIALS AND METHODS

Post-administration of the combination of HTP+AET at specific time points, blood and bronchoalveolar lavage fluid (BALF) were collected for the analysis of inflammatory and oxidative stress markers of the lungs. Thereafter, the mice were sacrificed and the lungs were dissected out, weighed, and fixed in formalin for histopathological studies.

RESULTS

The inflammatory biomarkers: tumor necrosis factor-alpha and interleukin-10 and oxidative stress biomarkers: 8-isoprostane and 8-hydroxy-2'-deoxyguanosine were found to have normal levels in blood and BALF in both control and treatment groups, which was further supported by normal histological findings. In addition, other endpoints such as food and water intake were found to be within normal limits.

CONCLUSION

The present safety study reflects that the combination has no adverse effects on the lungs of the experimental mouse. Further, evaluation in higher mammals including nonhuman primates is essential prior to validation of the safety of the combination in humans.

Quality of hematology and clinical chemistry results in laboratory and zoo nonhuman primates: Effects of the preanalytical phase. A review

Most errors in clinical pathology originate in the preanalytical phase, which includes all steps from the preparation of animals and equipment to the collection of the specimen and its management until analyzed. Blood is the most common specimen collected in nonhuman primates. Other specimens collected include urine, saliva, feces, and hair. The primary concern is the variability of blood hematology and biochemistry results due to sampling conditions with the effects of capture, restraint, and/or anesthesia. Housing and diet have fewer effects, with the exception of food restriction to reduce obesity. There has been less investigation regarding the impact of sampling conditions of nonblood specimens.

Impact of two different rodent diets on maternal ethanol consumption, serum ethanol concentration and pregnancy outcome measures

Recent studies report varying levels of ethanol consumption by rodents maintained on different commercially available laboratory diets. As varied ethanol consumption by dams may impact offspring outcome measures in prenatal ethanol exposure paradigms, we compared ethanol consumption by rats maintained on the Envigo 2920 diet, used in our vivarium, with an isocalorically equivalent PicoLab 5L0D diet used in some alcohol consumption studies. Compared to 5L0D diet, female rats maintained on 2920 diet consumed 14% less ethanol during daily 4-h drinking sessions prior to pregnancy and 28% less ethanol during gestation. Rat dams consuming 5L0D diet gained significantly less weight during pregnancy. However, their pup birth weights were significantly higher. A subsequent study revealed that hourly ethanol consumption was not different between diets during the first 2 h, but was significantly lower on 2920 diet at the end of the third and fourth hours. The mean serum ethanol concentration in 5L0D dams after the first 2 h of drinking was 46 mg/dL compared to 25 mg/dL in 2920 dams. Further, ethanol consumption at the 2-h blood sampling time point was more variable in 2920 dams compared to 5L0D dams. An in vitro analysis mixing each powdered diet with 5% ethanol in acidified saline revealed that a 2920 diet suspension adsorbed more aqueous medium than the 5L0D diet suspension. The total ethanol remaining in aqueous supernatant of 5L0D mixtures was nearly twice the amount of ethanol in supernatants of the 2920 mixtures. These results suggest that the 2920 diet expands to a greater extent in aqueous medium than the 5L0D diet. We speculate that increasing adsorption of water and ethanol by the 2920 diet may reduce or delay the amount of ethanol absorbed and may decrease serum ethanol concentration to a greater extent than would be predicted from the amount of ethanol consumed.

The role of IL-31 and IL-34 in the diagnosis and treatment of chronic periodontitis

This study was devoted to demonstrating the role of IL-31 and IL-34 in the diagnosis and treatment of chronic periodontitis (CP). From the results, we found that the IL-31 and IL-34 levels were significantly increased in GCF and serum of CP patients compared with healthy controls or obese patients. Meanwhile, the area under the curve results further verified the diagnostic potential of IL-31 and IL-34 in terms of discriminating CP from obese patients at the GCF and serum levels. Finally, after 1 year of continuous treatment, we found that IL-31 and IL-34 levels were decreased in CP, suggesting their potential as biomarkers in CP treatment response. Monitoring GCF and serum levels of IL-31 and IL-34 contributed to CP detection and treatment response.

High-Coverage Metabolome Analysis Reveals Significant Diet Effects of Autoclaved and Irradiated Feed on Mouse Fecal and Urine Metabolomics

SCOPE

Using metabolomics to study the relations of nutrition and health requires stringent control of the experimental conditions used in an animal model. This work investigates the diet effects of autoclaved and irradiated feed on mouse urine and fecal metabolomics.

METHODS AND RESULTS

C57BL/6 mice are fed normal-irradiation sterilized diet (n = 9), autoclave sterilized diet (n = 9), and high-irradiation sterilized diet (n = 9) for 4 weeks. Differential chemical isotope labeling liquid chromatography mass spectrometry is used to quantify the metabolome variations of urine and feces collected at five time points. Significant differences are observed in urine or fecal metabolomes of mice fed autoclaved diet versus mice fed high-irradiation diet or fed normal-irradiation diet, while the differences are small between the mice fed normal-irradiation and high-irradiation diet. Correlation studies of metabolite changes of diet- and aging-related biomarkers indicate a large overlap of significantly affected metabolites by the two factors.

CONCLUSIONS

Diet can be a confounding factor that needs to be carefully considered when a metabolomics study is designed and metabolomic results of a mouse model of nutritional or other biological study are interpreted. Using the same sterilized diet for a given metabolomics project is essential to control the diet effect.

The Impact of Social and Behavioral Factors on Reproducibility in Terrestrial Vertebrate Models

The use of animal models remains critical in preclinical and translational research. The reliability of the animal models and aspects of their validity is likely key to effective translation of findings to medicine. However, despite considerable uniformity in animal models brought about by control of genetics, there remain a number of social as well as innate and acquired behavioral characteristics of laboratory animals that may impact on research outcomes. These include the effects of strain and genetics, age and development, sex, personality and affective states, and social factors largely brought about by housing and husbandry. In addition, aspects of the testing environment may also influence research findings. A number of considerations resulting from the animals' innate and acquired behavioral characteristics as well as their social structures are described. Suggestions for minimizing the impact of these factors on research are provided.

Improving Replicability, Reproducibility, And Reliability In Preclinical Research: A Shared Responsibility

Reproducible and reliable scientific investigation depends on the identification and consideration of various intrinsic and extrinsic factors that may affect the model system used. The impact of these factors must be managed during all phases of a study: planning, execution, and reporting. The value of in vivo (animal) research has come under increasing scrutiny over the past decade because of multiple reports documenting poor translatability to human studies. These failures have been attributed to various causes, including poor study design and execution as well as deficiencies in reporting. It is important to recognize that achieving reproducible and reliable preclinical research results is a joint responsibility that requires a partnership between the investigative team and the animal care and use program staff. The myriad of intrinsic factors, such as species, strain/substrain, age, sex, physiologic and health status, and extrinsic factors, including temperature, humidity, lighting, housing system, and diet, need to be recognized and managed during study planning and execution, as they can influence animal physiology and biological response. Of equal importance is the need to document and report these details. The ARRIVE and PREPARE guidelines were developed by concerned scientists, veterinarians, statisticians, journal editors, and funding agencies to assist investigative teams and scientific journals manage and report on intrinsic and extrinsic factors to improve reproducibility and reliability. This issue of the ILAR Journal will focus on the various extrinsic factors that have been recognized to confound animal research.