Male Laboratory Mice Research Articles

Effects of Red Meat Consumption on Histology of Coronary Arteries in Adult Albino Mice

Objective: To determine the effects of the red meat (Buffalo) on coronary arteries of adult albino male Mice. Study Design: Experimental study. Settings: Anatomy Department of Liaquat University of Medical and Health Sciences, Jamshoro in collaboration with animal house of Sindh Agriculture University Tando Jam. Duration: 6 months from January 2017 to July 2017. Methodology: Total 45 adult Albino male mice (laboratory male mice) of average 180–220 grams bodyweight was selected. Animals were housed (about 4-6 per cage) in a temperature-controlled room (22± 2°C) and at a humidity of 55%±5%, with a 12-hr light/dark cycle. Animals were divided into three groups as: group A (control), group B white meat (poultry) and group C (red meat). At the end of the experiment animals were sacrificed and hearts were taken from every animal as soon as possible and specimens were assessed for histopathology. Results: Mean cholesterol level was significantly higher among red meat consuming group as compared to control group (P- 0.001). Mean body weight was markedly higher among red meat consuming group in contrast to control group; p-values were quite significant. Total 6.66% mice suffered in red meat consuming group and out of them 3.34% died. Conclusion: It was concluded that red meat consumption is associated to a higher risk of cholesterol elevation and mortality, without any histological alteration.

Toxicological characteristics of the preparation FORTICEPTTM Hoof Oinment

Antibiotic resistance of the main infectious disease pathogens is one of the biggest problems of present time, which causes the need for searching for new antimicrobial medicinal substances and developing effective medicinal agents. One of the innovative medicinal preparations with the antimicrobial action, which is recommended for application for animals with hoof diseases, is ForticeptTM Hoof Oinment. Integration in the practice new medicinal preparations needs their strict toxicological control, which involves the exploring of acute and chronic toxicity and remote effects of possible side effect. The purpose of work was the determination of the acute toxicity parameters of the ForticeptTM Hoof Oinmentduring the oral administration to white laboratory mice and evaluation of the skin resorptive action of the preparation after it was administrated on rats’ skin. For determination of the acute toxicity there were used male laboratory mice with the average weight of the body 20 g – two groups with 10 animals in each. For the first group (the control one) with the help of the probe there was injected the distilled water (0.1 ml) into stomach. For the second group there was injected ForticeptTM Hoof Oinment (0.1 g), where the dose of the preparation is equal 500 mg/kg. For evaluation of the skin resorptive action of the preparation there were used 6 white rats with the average weight of the body 175 g. On the pre-prepared patch of skin there was administrated the preparation in the number that is equal 2857 mg/kg of body weight. For control there was leaved a free from preparation patch of bare skin. Exposition lasted for 4 hours. The indicators were explored in dynamics after 6, 24, 48 hours from the exposition started. After the research results there was established that ForticeptTM Hoof Oinment doesn’t cause death after its intragastric administration to the white laboratory mice in the number that is equal 5000 mg/kg of the body weight, that’s why depending on the degree of toxicity it belongs to the V toxicity class (Practically nontoxic). After one-time application of the preparation to the white rats in the number which is equal 2857 mg/kg of the body weight there wasn’t observes no death or pronounced changes in the behavior reactions, motor activity, state of the nervous system, amount of the consumed food and water. Therefore ForticeptTM Hoof Oinmentaccording to the results of the determination of the acute toxicity after its administration on the skin to the white rats depending on the degree of toxicity it belongs to the V toxicity class (Practically nontoxic). ForticeptTM Hoof Oinment doesn’t detect skin resorptive action, that points on the absence of toxic effects of the preparation due to its application on the skin.

Herbicide Paraquat provokes the stress responses of HPA axis of laboratory mouse, Mus musculus

Paraquat (PQ) is a herbicide and well characterized pneumotoxicant which is also known to induce neurodegeneration in organisms. Aim of this study was to investigate the effect of PQ on hypothalamic – pituitary – adrenal (HPA) axis. PQ was administered i.p.10 mg/kg body weight once a week for 5 weeks in laboratory male mice. Results indicate that SOD activity decreased while catalase activity and nitrate-nitrite level increased significantly in the hypothalamus of PQ treated mice. The expression of both AVP and CRH mRNA in the hypothalamus as well as ir-AVP and ir-CRH increased in the PVN of PQ treated mice compared to control. Immunoreactivity of nNOS and Hsp70 including NF-κB mRNA expression increased in the PVN of PQ treated mice. As expected, serum corticosterone level was also elevated significantly in the herbicide PQ treated mice. From these findings it is concluded that paraquat treatment is capable of activating the HPA axis via upregulating transcription and translation of the hypothalamic neuropeptides AVP and CRH as well as serum corticosterone level. Increase in both oxidative and nitrosative stress in PQ treated mice might be the driver which also contributed to the activation of HPA axis. It seems that stress induced reactive species (ROS, RNS) might be also responsible for the induced expression of NF-κB mRNA and Hsp70 protein which are considered as the reliable markers of certain types of stressors including PQ toxicity.

Exposure assessment of laboratory workers to hazardous waste from mice treated with tamoxifen and bromodeoxyuridine

Animal research frequently involves the use of hazardous chemicals such as carcinogens, reproductive toxins or other highly toxic substances. Animal facility workers and researchers may be exposed to these chemicals when treating animals, or handling cages or bedding of animals excreting these chemicals or their toxic intermediates. Handling of hazardous chemicals in animal facilities follows the chemical hygiene plan conventionalized for research laboratories but not animal facilities. Exposure to these chemicals in animal excretions (urine and feces) has not been fully evaluated. The goal of this case study was to understand how much and for how long hazardous select chemicals are excreted by male and female laboratory mice. We examined the metabolic fate of two hazardous chemicals commonly used in animal research: tamoxifen and bromodeoxyuridine (BrdU). In this study, excretion rates of tamoxifen and its two bioactive metabolites (hydroxytamoxifen and endoxifen) showed a dose-sex interaction; but, excreted concentrations reached very low to undetectable levels by 72 hour post treatment no matter the dose or sex of the animal. BrdU excretion rates showed little to no sex difference, and excreted concentrations reached low levels by 48 hour post treatment in both males and females. The outcomes of this study can be used by health & safety experts to develop evidence-based policies for risk management of handling cages and bedding of animals treated with tamoxifen and BrdU.

Breaking up is hard to do: Does splitting cages of mice reduce aggression?

Injurious aggression in group housed male laboratory mice is a common welfare issue that can also negatively affect study outcomes. Often, one mouse in the cage appears unwounded, and the current standard practice is to remove this presumed aggressor. This procedure is not based on empirical evidence and may impede welfare by singly housing animals. We experimentally tested the hypothesis that the apparently uninjured mouse is indeed the aggressor, and that aggression is reduced in his absence. We separated cages of four or five male mice, reported for fight wounds to our university’s veterinary service, into cages of two or three mice containing either only wounded mice (“wounded” treatment) or both wounded and unwounded mice (“mixed” treatment). We recorded aggressive behavior for 30 min immediately pre- and post-separation, and scored wound severity at separation and over two weeks after. We predicted that if unwounded mice are aggressors: mice in the wounded treatment would show less escalated aggression (involving biting) than mice in the mixed treatment, and would be wounded less and/or heal faster during the two weeks following separation. Wound scores decreased significantly after separation in both treatments (wounded: p < 0.0001; mixed: p = 0.011), but mice in the wounded treatment healed faster than those in the mixed treatment (p = 0.006). There was no significant effect of treatment on duration of escalated aggression in the 30 min following separation (p = 0.240), nor did treatment predict which cages would be re-separated due to continued aggression (p = 0.104). Our results support the hypothesis that the unwounded mouse is the aggressor, as mice in cages with an unwounded mouse healed more slowly than those without. Both types of groups healed significantly over time, suggesting that separation into groups of two or three is a possible management alternative to social isolation of the presumed aggressor. By identifying spontaneous cases of severe aggression in an existing colony, we obtained a heterogeneous and representative sample of clinical cases, bolstering the generalizability of our conclusions.

Effects of non-purified and semi-purified commercial diets on behaviors, plasma corticosterone levels, and cecum microbiome in C57BL/6J mice

Diverse commercially available feeds are used in animal studies according to the purpose of the studies. We sought to understand the relationship between feed ingredients and their effects on animal physiology and behaviors. Here, we investigated how male laboratory mice (C57BL/6J (“B6”) mice) were affected by chronic feeding with two commercially available diets, a non-purified diet (MF) and a semi-purified diet (AIN-93G). In B6 mice, both diets similarly induced spontaneous activities in the home cage and the open field box, anxiety in the elevated plus maze test, and depressive-like behaviors in tail-suspension and forced-swimming tests, and with both diets, similar data were obtained on calorie intake, water intake, body weight gain, and plasma corticosterone levels. By contrast, liver weight was significantly higher in MF-fed B6 mice than in AIN-93G-fed B6 mice. Furthermore, the cecum microbiome was drastically affected by the diets, and, specifically, Allobaculum was the major genus (43.4%) in the cecum microbiota of AIN-93G-fed mice but its abundance was reduced (to 3.8%) in the case of MF-fed mice. Future studies should address whether the differences in diet purity and cecum microbiota influence brain functions and behaviors in B6 mice.

Partial cage division significantly reduces aggressive behavior in male laboratory mice.

Aggression in mice often results in injury leading to unplanned euthanasia or the initiation of protocols to isolate animals, thereby increasing research costs and straining resources. Here, we tested if adding a partial cage divider into existing mouse cages affected aggressive-like behavior in group-housed male mice (18 mice; 3 per cage). Mice were randomly assigned to one of two groups upon arrival to the vivarium: (1) standard cage; (2) cage with a partial cage divider. Behavioral observation over 12 hours were conducted at day one, two, and seven after receipt at the facility in order to assess aggression during the course of establishing dominance hierarchies. Observers blinded to study design and hypothesis scored each video for the number and type of aggressive behaviors, which were summed for each hour and analyzed. Results indicated a statistically significant decrease in aggressive behaviors of mice in cages with dividers compared to mice in standard cages. We conclude that cage dividers, which resemble burrows and provide access to common food/water, may promote rigorous research by reducing the number of animals used in a study and refining housing, thus, improving animal welfare.

To Group or Not to Group? Good Practice for Housing Male Laboratory Mice.

Simple SummaryWild mice live in territories inhabited by one adult male, several females, and their offspring. This cannot be replicated in the laboratory, so male mice are usually housed in single-sex groups or individually. However, there can be serious animal welfare problems associated with both these approaches, such as lack of social contact when housed individually or aggression between males when kept in groups. Group housing is widely recommended to give male laboratory mice the opportunity to behave as ‘social animals’, but social stress can be detrimental to the welfare of these animals, even without injurious fighting. All of this can also affect the quality of the science, giving rise to ethical concerns. This review discusses whether it is in the best welfare interests of male mice to be housed in groups, or alone. We conclude that it is not possible to give general recommendations for good practice for housing male laboratory mice, as responses to single- and group-housing can be highly context-dependent. The welfare implications of housing protocols should be researched and considered in each case. It is widely recommended to group-house male laboratory mice because they are ‘social animals’, but male mice do not naturally share territories and aggression can be a serious welfare problem. Even without aggression, not all animals within a group will be in a state of positive welfare. Rather, many male mice may be negatively affected by the stress of repeated social defeat and subordination, raising concerns about welfare and also research validity. However, individual housing may not be an appropriate solution, given the welfare implications associated with no social contact. An essential question is whether it is in the best welfare interests of male mice to be group- or singly housed. This review explores the likely impacts—positive and negative—of both housing conditions, presents results of a survey of current practice and awareness of mouse behavior, and includes recommendations for good practice and future research. We conclude that whether group- or single-housing is better (or less worse) in any situation is highly context-dependent according to several factors including strain, age, social position, life experiences, and housing and husbandry protocols. It is important to recognise this and evaluate what is preferable from animal welfare and ethical perspectives in each case.

Central ghrelin receptor stimulation modulates sex motivation in male rats in a site dependent manner

Ghrelin, a hormone produced primarily by the stomach, has been associated with motivational processes that include reward-seeking behaviors. In male laboratory mice, elevation of ghrelin levels enhances some aspects of sexual motivation and behavior, whereas in other experiments with male mice, rats, and other species, ghrelin treatment or food deprivation decreases sexual motivation and/or behavior. The present tested the hypothesis that stimulation of ghrelin receptors in different brain regions have opposite effects on male sexual motivation and behavior. To do this we examined appetitive and consummatory sex behaviors of male rats with a truncated ghrelin receptor (FHH-GHSRm1/Mcwi), and that of their WT (FHH) littermates. We also examined the effects of ghrelin or the ghrelin antagonist D-Lys-GHRP6 delivered into the VTA or the MPOA on appetitive and consummatory sex behaviors in male Long Evans rats. Results demonstrate that rats with a truncated ghrelin receptor, or rats that are food deprived, show deficits in anticipatory sex. Furthermore, although ghrelin does not further stimulate sex anticipation in rats when infused into the VTA, intra-VTA infusions of D-Lys-GHRP6 into the VTA further decreases in sex anticipation in food deprived rats. In contrast, ghrelin delivery into the mPOA decreased sex anticipation compared to saline or D-Lys-GHRP6 infused rats. Overall, these data suggest that ghrelin receptor signalling is important for full expression of appetitive sex behaviors. Within the VTA, ghrelin may act to enhance sex motivation, while acting on the mPOA to decrease sex motivation and promote foraging.

Specialist-generalist model of body temperature regulation can be applied at the intraspecific level.

According to theoretical predictions, endothermic homeotherms can be classified as either thermal specialists or thermal generalists. In high cost environments, thermal specialists are supposed to be more prone to using facultative heterothermy than generalists. We tested this hypothesis at the intraspecific level using male laboratory mice (C57BL/cmdb) fasted under different thermal conditions (20 and 10°C) and for different time periods (12-48 h). We predicted that variability of body temperature (Tb) and time spent with Tb below normothermy would increase with the increase of environmental demands (duration of fasting and cold). To verify the above prediction, we measured Tb and energy expenditure of fasted mice. We did not record torpor bouts but we found that variations in Tb and time spent in hypothermia increased with environmental demands. In response to fasting, mice also decreased their energy expenditure. Moreover, animals that showed more precise thermoregulation when fed had more variable Tb when fasted. We postulate that the prediction of the thermoregulatory generalist-specialist trade-off can be applied at the intraspecific level, offering a valid tool for identifying mechanistic explanations of the differences in animal responses to variations in energy supply.

Dynamic changes in social dominance and mPOA GnRH expression in male mice following social opportunity

Social competence - the ability of animals to dynamically adjust their social behavior dependent on the current social context – is fundamental to the successful establishment and maintenance of social relationships in group-living species. The social opportunity paradigm, where animals rapidly ascend a social hierarchy following the removal of more dominant individuals, is a well-established approach for studying the neural and neuroendocrine mechanisms underlying socially competent behavior. In the current study, we demonstrate that this paradigm can be successfully adapted for studying socially competent behavior in laboratory mice. Replicating our previous reports, we show that male laboratory mice housed in a semi-natural environment form stable linear social hierarchies. Novel to the current study, we find that subdominant male mice immediately respond to the removal of the alpha male from a hierarchy by initiating a dramatic increase in aggressive behavior towards more subordinate individuals. Consequently, subdominants assume the role of the alpha male. Analysis of brain gene expression in individuals 1h following social ascent indicates elevated gonadotropin-releasing hormone (GnRH) mRNA levels in the medial preoptic area (mPOA) of the hypothalamus compared to individuals that do not experience a social opportunity. Moreover, hormonal analyses indicate that subdominant individuals have increased circulating plasma testosterone levels compared to subordinate individuals. Our findings demonstrate that male mice are able to dynamically and rapidly adjust both behavior and neuroendocrine function in response to changes in social context. Further, we establish the social opportunity paradigm as an ethologically relevant approach for studying social competence and behavioral plasticity in mammals.

Spermatogenesis parameters and testosterone production at puberty as predictors of testicular functional activity in mice (Mus musculus)

The aim of this study was to investigate fertility-associated parameters of spermatogenesis and androgenic status in male laboratory mice at puberty and to assess their prognostic significance in the realization of the definitive testicular function. In three inbred murine strains, BALB/cLac, CBA/Lac and PT, the serum testosterone level, its testicular concentration, epididymal sperm count (sperm reserve) and portion of sperm with abnormal head morphology were evaluated on days 45 (puberty) and 90 (adulthood) of postnatal development. CBA/Lac males were characterized by a lower epididymal sperm count vs. other strains at both ages indicative of poorer spermatogenesis. At the same time, CBA/Lac males had a lower portion of sperm with abnormal head morphology, and this could be considered as a compensatory reaction aimed at improving sperm fertility. Distinct inter-strain differences in the portion of sperm with morphologically abnormal heads were established at both ages, while the inter-strain ratio remained invariable (BALB/cLac > PT > CBA/Lac). Thus, the level of abnormal spermatogenesis in the pubertal period may have a predictive significance for the definitive testicular activity in adult mice. No inter-strain and age-dependent changes were found in serum and testicular testosterone levels except for the PT strain, in which both testosterone levels rose from puberty to adulthood, suggesting a shift of the pubertal testosterone peak towards later times. Our data show that in male laboratory mice the genetic peculiarities of the testicular function manifest themselves during puberty and persist until adulthood.

Expression of stress hormones AVP and CRH in the hypothalamus of Mus musculus following water and food deprivation

Neurohypophyseal hormone, arginine vasopressin (AVP), in addition to acting as antidiuretic hormone is also considered to be stress hormone like hypothalamic corticotropin-releasing hormone (CRH). Present study was designed to investigate the relative response of these stress hormones during water and food deprivation. In this study, male laboratory mice of Swiss strain were divided in 5 groups, control – provided water and food ad libitum, two experimental groups water deprived for 2 and 4days respectively (WD2 and WD4) and another two groups food deprived for 2 and 4days respectively (FD2 and FD4). Results indicate an increased expression of AVP mRNA as well as peptide in the hypothalamus of WD2 mice and the expression was further upregulated after 4days of water deprivation but the expression of CRH remained unchanged compare to their respective controls. On the other hand no change was observed in the expression of hypothalamic AVP mRNA while AVP peptide increased significantly in FD2 and FD4 mice compare to control. Further, the expression of CRH mRNA although increased in hypothalamus of both FD2 and FD4 mice, the immunofluorescent staining shows decreased expression of CRH in PVN of food deprived mice. Based on these findings it is concluded that since during osmotic stress only AVP expression is upregulated but during metabolic stress i.e. food deprivation transcription and translation of both the stress hormones are differentially regulated. Further, it is suggested that role of AVP and CRH may be stress specific.

A study of histopathological effects and functional tests in liver and kidney of laboratory male mice treated with ammonium chloride

A study of histopathological effects and functional tests in liver and kidney of laboratory male mice treated with ammonium chloride

Distinct preoptic-BST nuclei dissociate paternal and infanticidal behavior in mice.

Paternal behavior is not innate but arises through social experience. After mating and becoming fathers, male mice change their behavior toward pups from infanticide to paternal care. However, the precise brain areas and circuit mechanisms connecting these social behaviors are largely unknown. Here we demonstrated that the c-Fos expression pattern in the four nuclei of the preoptic-bed nuclei of stria terminalis (BST) region could robustly discriminate five kinds of previous social behavior of male mice (parenting, infanticide, mating, inter-male aggression, solitary control). Specifically, neuronal activation in the central part of the medial preoptic area (cMPOA) and rhomboid nucleus of the BST (BSTrh) retroactively detected paternal and infanticidal motivation with more than 95% accuracy. Moreover, cMPOA lesions switched behavior in fathers from paternal to infanticidal, while BSTrh lesions inhibited infanticide in virgin males. The projections from cMPOA to BSTrh were largely GABAergic. Optogenetic or pharmacogenetic activation of cMPOA attenuated infanticide in virgin males. Taken together, this study identifies the preoptic-BST nuclei underlying social motivations in male mice and reveals unexpected complexity in the circuit connecting these nuclei.

Assessment of reproductive toxicity of multiwalled carbon nanotubes and their putative effects on population ecology of mouselike rodents

An assessment of the reproductive toxicity of multiwalled carbon nanotubes (MWCNTs) for male laboratory mice according to a set of morphophysiological, biochemical, and histological criteria is reported. Oral administration of MWCNTs at doses of 0.3, 3, and 30 mg/kg evoked a dose-dependent decrease in the level of free testosterone in blood plasma, as well as a 15–40% decrease in male fertilization capacity. Mathematical modeling allowed for the assumption that a decrease in the parameter named above can induce changes in the population dynamics of mouselike rodents, namely, a reduction in the peak numbers of animals and an increase of the oscillation period by ∼30%. The results can be used for developing environmental standards of MWCNT intake by mammals, as well for the development of new products for controlling rodent populations.

The lonely mouse - single housing affects serotonergic signaling integrity measured by 8-OH-DPAT-induced hypothermia in male mice.

Male BALB/c mice single-housed for a period of three weeks were found to respond with a more marked hypothermia to a challenge with a selective serotonergic agonist (8-OH-DPAT) than their group-housed counterparts. This effect of single housing was verified by screening a genetically heterogeneous population of male mice on a C57BL/6 background from a breeding colony. Enhanced activity of the implicated receptor (5-HT1A) leading to an amplified hypothermic effect is strongly associated with depressive states. We therefore suggest that the 8-OH-DPAT challenge can be used to demonstrate a negative emotional state brought on by e.g. long-term single housing in male laboratory mice. The study emphasizes the importance of social housing, and demonstrates that male mice deprived of social contact respond with altered serotonergic signaling activity. Male mice not only choose social contact when given the option, as has previously been shown, but will also, when it is deprived, be negatively affected by its absence. We propose that the 8-OH-DPAT challenge constitutes a simple, but powerful, tool capable of manifesting the effect of social deprivation in laboratory mice. It potentially allows not only for an unbiased, biochemical evaluation of psychological stressors, but may also allow for determining whether the effect of these can be counteracted.

Test of immunocompetence handicap hypothesis in mice (Mus musculus) infected with Trichinella spiralis

The immunocompetence handicap hypothesis (ICHH) proposes that testosterone enhances the expression of sexual traits but suppresses immune function. However, studies to test the hypothesis have shown mixed results. Alternatively, sexual traits, immune function, and parasite susceptibility may be mediated by the stress hormone corticosterone. Here, we report an experimental test of the ICHH that included the manipulation of both testosterone and parasites in male laboratory mice (Mus musculus L., 1758). We conducted a factorial experiment, injecting each individual mouse with testosterone or not and infecting them with the nematode parasite Trichinella spiralis (Owen, 1835) or not. As predicted, testosterone enhanced the scent attractiveness of male mice, whereas parasite infection reduced it, but only in male mice not injected with testosterone. However, we found no evidence that corticosterone is involved in mediating the effects of testosterone. These results confirm that maintaining high testosterone levels entails the cost of increased parasite abundance. This study provides direct evidence supporting the ICHH.

Toxic Effects of Miller on Chromosomes and Sperms of Albino Males Mice

The genotoxicity of Miller (glyphosate) herbicide was evaluated in males albino mice Mus muscles BALB/c strain. The tested parameters were chromosomal aberrations and sperm abnormalities to evaluate a possible damage effects on genetic material and sperms. The herbicide was administered orally to adult male laboratory mice in 4 different doses (0, 250, 500, and 750 mg/kg of body weight). The mice were killed at two periods: after 3 and 6 weeks. The results of chromosome aberration assay revealed that all the tested doses and periods induced structural chromosomal aberrations (CAs) such as centromeric gaps, chromatid gaps, delations, dicentric chromosomes and ring chromosomes. The results of sperm abnormality assay revealed that miller has the ability to induce sperm abnormalities in all doses used comparing to untreated mice, which represented by hookless sperm, swollen head sperm, amorphous head sperm, sperm without head, defective hook sperm, banana head sperm, double head sperm, sperm without tail, double tail sperm, bent midpiece defect and coiled tails.

Social domination and reproductive success in male laboratory mice (Mus musculus)

The goal of the present study was to evaluate effect of social status and genotype on success of reproduction of male laboratory mice with use of ethological model of social hierarchy of "minimal socium". The model represents the paired maintenance of two male mice of different genotype (PT and CBA/Lac). The mice lived for 30 days in one experimental cage males, two females of the DD/He strain were supplemented. Regardless of genotype, the dominants became fathers more often than the subordinants and got more progeny. It was established that in subordinates there did not occur the complete suppression of fertility. This is suggested to allow them to realize the genetical contribution to the next generation and to remain in the gene pool of population.