Experimental Animals最新文献

Depression affects females more than males, with responses to antidepressants also exhibiting a distinct difference between sexes. Stress models in rodents have predominantly been developed for males, and their application in females remains challenging. This study investigated how post stress sensory contact with male mice affects the behavioral outcomes of female C57BL/6JJcl (B6) mice subjected to vicarious social defeat stress (VDS). We compared three types of VDS paradigms in female mice: the conventional paradigm and two adapted protocols that eliminated sensory contact with male ICR mice during the post-stress period under either single-housed (SH) or pair-housed (PH) conditions. In the conventional paradigm, female B6 mice did not exhibit a significant increase in social avoidance. In contrast, in the adapted paradigm, social avoidance behavior was observed in the PH group, indicating that post stress sensory contact with male ICR affects the stress susceptibility of female VDS model. Furthermore, the estrous cycle stage did not affect social avoidance behavior in each group. Next, we compared two different housing conditions to examine the appropriate method for eliminating sensory contact in female VDS model. SH mice showed reduced feed intake, increased water consumption, and attenuated body weight gain, regardless of VDS exposure. These findings suggest that post-stress sensory contact with a male mouse may influence social behavior in female mice exposed to VDS. The present study highlights the potential impacts of these experimental variables when interpreting behavioral outcomes in female VDS models.

Mammalian hibernation is an adaptive strategy for surviving harsh cold seasons and food scarcity by suppressing the metabolic rate and thermogenesis. The Syrian hamster (Mesocricetus auratus) (hereafter termed as hamsters), a small mammalian hibernator, hibernates upon exposure to winter-like, short-photoperiod and cold (SP-Cold) conditions throughout a year in a laboratory, and therefore is a useful animal model obtained from a commercial breeder to study mechanisms of hibernation. However, the rates of hibernation occurrence often vary among experiments and facilities, the reason for which is largely unclear. Here we examined the effects of diet given to hamsters during post-weaning stages on hibernation occurrence. Hamsters fed either a high-nutrient (H) diet suitable for reproduction or a standard (STD) diet during the post-weaning period (from 3 or 4 weeks of age to sexual maturation) were exposed to winter-like conditions, and the occurrence of hibernation was assessed. Females showed a higher hibernation induction rate (over 80%) regardless of the post-weaning diet type than males. Approximately half (52%) of the males fed the STD diet from 3 weeks hibernated, whereas males fed the STD diet from 4 weeks or the H diet showed markedly lower hibernation induction rates (≤33%). These results suggest that female Syrian hamsters are more prone to hibernation than males and that the hibernation induction rate in male hamsters is influenced by diet during a critical developmental window between 3 and 4 weeks of age.

Insulin resistance (IR) and hepatic steatosis are key pathological features of type 2 diabetes mellitus (T2DM). Fraxin, a natural flavonoid with potential metabolic regulatory properties, has been proposed to modulate metabolic disorders. This study aimed to investigate whether fraxin protects against IR and steatosis via Sirt1/AMPK/mTOR-mediated autophagy activation. A T2DM rat model was established using high-fat diet (HFD) feeding combined with streptozotocin (STZ) injection. Rats were treated with fraxin (25 or 50 mg/kg) for 4 weeks, followed by assessment of fasting blood glucose (FBG), insulin (FINS), HOMA-IR index, serum lipid profiles and liver function. Histopathological examination (H&E and Oil Red O staining) evaluated hepatic steatosis. BRL 3A cells exposed to palmitic acid (PA) were treated with fraxin (40 or 80 μM), and glucose uptake, lipid accumulation, and protein expression (IRS-1 phosphorylation, GLUT-2 translocation, autophagy markers and Sirt1/AMPK/mTOR pathway components) were analyzed. The specific autophagy inhibitor chloroquine (CQ) was used to verify whether the regulatory effects of fraxin were dependent on autophagy activation. Fraxin significantly reduced FBG, FINS, HOMA-IR, and dyslipidemia in diabetic rats. In PA-treated BRL 3A cells, fraxin enhanced glucose uptake, reduced lipid droplets, and restored IRS-1 phosphorylation and GLUT-2 membrane localization. Mechanistically, fraxin activated autophagy and modulated the Sirt1/AMPK/mTOR pathway, which were abolished by the Sirt1 inhibitor EX527. In conclusion, fraxin alleviates IR and hepatic steatosis in HFD/STZ-induced diabetic rats by activating autophagy through Sirt1/AMPK/mTOR pathway, suggesting its potential as a therapeutic agent for diabetes-associated metabolic disorders.

The Lepus yarkandensis (L. yarkandensis) is an endemic species inhabiting the arid ecosystem of the Tarim Basin, characterized by extreme dryness and scarce water resources. In contrast, Oryctolagus cuniculus (O. cuniculus) is adapted to temperate environments rich in water. Over the course of long-term evolution, the L. yarkandensis has likely developed unique physiological and histological adaptations to cope with the survival challenges posed by such arid conditions. This study aims to investigate the differences between the L. yarkandensis and O. cuniculus in terms of hematological and biochemical blood parameters, renal histology, water-salt regulation capacity, and the expression of glomerular filtration barrier proteins, in order to investigate the adaptive strategies of the L. yarkandensis to drought environments. The results showed that the L. yarkandensis exhibited higher red blood cell counts, hematocrit levels, urine osmolality, and total urinary protein levels compared to O. cuniculus, while the urine pH was lower. Histological analysis revealed increased collagen content in the outer medulla and more complex tubular structures in the kidneys of the L. yarkandensis. Molecular analysis further demonstrated upregulated expression of glomerular filtration barrier proteins nephrin, podocin, and CD2AP, alongside downregulated expression of laminin and WT1. In summary, these findings provide insights into the potential physiological and molecular adaptations of L. yarkandensis, laying the groundwork for future research into the evolution of desert fauna.

Noda epileptic rat (NER) is a mutant model for epilepsy that exhibits spontaneous generalized tonic-clonic seizure. Epileptogenesis of NER remains to be elucidated; but it is detected an insertion of an endogenous retrovirus sequence in intron 2 of the PHD finger protein 24 (Phf24) gene. PHF24 is widely expressed in the soma of neurons and neuropil in the wild-type rat brain and spinal cord but significantly less expressed in NER. In addition, the characteristic PHF24 expressions were noted in the soma of specific populations of the inhibitory interneurons. Here, we first examined the morphology of the neurons and synapses in the brain of NER to evaluate the epileptogenesis of NER. In NER, the total number of neurons was decreased, but the inhibitory neurons were increased. Inhibitory synapses increased while excitatory synapses tended to decrease in NER. Secondary, we examined Phf24-null rat without symptom of seizures in the same manner and evaluate a contribution of PHF24 to the epileptogeneis of NER. Interestingly, the opposite trend was observed in Phf24-null rats, with a decrease in the inhibitory neurons and synapses, an increase trend in the excitatory synapses. PHF24 is considered to play an important role in maintaining of the inhibitory neurons in the rat brain. We conclude that the reduction of PHF24 might lead to impaired inhibitory signals and increase susceptibility to epilepsy in NER. The histopathological changes of NER in the present study may represent a secondary change to repeated seizures.

Repeated surgical oocyte collection in mice enables the harvest of multiple cohorts of eggs from a single female, thereby reducing the need for animal use. Traditionally, oocyte collection for the mouse requires euthanasia, and only two sequential collections have been reported. The most efficient superovulation protocol involves the use of inhibin antiserum; however, repeated administration may pose a risk of anaphylactic reactions. In this study, we used severely immunodeficient NOG mice to evaluate the feasibility of performing three serial oocyte collections with inhibin antiserum treatments. We found that three consecutive cycles of antiserum administration followed by surgical retrieval cycles were achieved without mortality. Although the number of mice from which oocytes could be collected decreased over successive cycles, oocyte retrieval remained feasible. The application of the anti-adhesion film improved the number of mice from which oocytes could be recovered. Furthermore, embryos derived from the third retrieval developed to term after transfer. However, compared with the control group, we were unable to achieve a proportional increase in the number of retrieved oocytes corresponding to the number of collection cycles. Further improvements to this repeated collection method may include increasing the number of consecutive retrievals, optimizing the protocol to enhance both the oocytes yield and the fertilization rates. Such advances could increase oocyte yield per female, enable the mass production of embryos from fewer animals.

Sex differences have been observed in the onset of type 2 diabetes, with men being more likely to develop the disease than women. There is a clear sex difference in the development of diabetes in obese type 2 diabetes model ZFDM rats, with all males developing diabetes, but none of the females. In the present study, we examined the effects of sex hormones on the development of diabetes and gene expression in the pancreatic islets of ZFDM rats. All experiments were performed using 6-week-old ZFDM rats homozygous for the leptin receptor mutation (fatty, fa). Orchiectomy did not affect the development of diabetes but slightly suppressed non-fasting blood glucose levels in male ZFDM rats. Except for one diabetic rat, ovariectomy did not affect non-fasting blood glucose levels but impaired glucose tolerance in female ZFDM rats, which was accompanied by accelerated islet fibrosis and pancreatic β-cell loss. Administration of the female hormone (17β-estradiol, E2) did suppress the development of diabetes in male ZFDM rats. Pair feeding matched with the E2-administered group also suppressed the development of diabetes in male ZFDM rats. Direct E2 treatment of the pancreatic islets of diabetic male ZFDM rats changed the expression of genes related to type 2 diabetes and insulin secretion closer to those of obese non-diabetic male ZF rats. These results suggest that female hormones have the suppressive effects on the development of diabetes, whereas male hormones, if any, have the opposite effects in ZFDM rats.

The major histocompatibility complex (MHC) plays a critical role in individual immune responses and susceptibility to various conditions, including autoimmune diseases and drug reactions. In dogs, the canine MHC (dog leukocyte antigen, DLA) polymorphism is key to understanding immune mechanisms, but technical challenges have impeded its comprehensive genetic analysis. This study addressed these issues by using a novel DLA genotyping method combining long-range PCR and PacBio single-molecule real-time sequencing to analyze the full-length DLA class I and II gene sequences in 83 beagle dogs from two different strains (TOYO and Marshall), which are commonly used as laboratory animals. As a result of genotyping using the full-length sequences, 9, 5, 2, 6, and 8 extended alleles were newly discovered for the DLA class I genes in DLA-88, DLA-12, DLA-88L, DLA-64, and DLA-79, respectively. For the DLA class II genes, 11, 18, 12, and 8 extended alleles were newly discovered in DLA-DRA, DLA-DRB1, DLA-DQA1, and DLA-DQB1, respectively. There were 25 haplotypes consisting of extended alleles, in contrast to only 10 haplotypes classified using only peptide binding site sequences. Furthermore, comparisons between the strains revealed differences in haplotype frequencies and genetic differentiation. The full-length analysis also provided preliminary insights into regulatory elements, such as promoter and CpG island polymorphisms in DLA-DQB1. The results of this research have important implications for the understanding of the relationship between DLA polymorphism at full length and individual immune responses in dogs.

The Cre-loxP system has been widely used in neuroscience for spatial and temporal control of gene expression. Although it is considered a powerful genetic tool, increasing evidence suggests that the Cre recombinase itself, without targeting loxP sites, may affect brain function and behavior. In this study, we assessed behavioral phenotypes in several Cre-driver rat lines, each expressing Cre under a different promoter (CAG, Pvalb, TH, Drd2, Tac1, or Thy1) to determine whether Cre expression influences behavioral outcomes. Behavioral testing included open field (for locomotor activity), hot plate (for nociceptive responses), prepulse inhibition (for sensorimotor gating), and contextual and cued fear conditioning (for associative learning). The Drd2-Cre rats exhibited significantly increased locomotor activity and movement speed compared to wild-type controls, suggesting heightened baseline activity. The CAG-Cre rats spent more time in the center area of the open field and showed reduced freezing during fear conditioning, suggesting changes in emotional regulation or learning. In contrast, no significant differences in the nociceptive responses or prepulse inhibition were observed in any of the Cre-driver lines. Following behavioral testing, we conducted structural MRI scans and found no obvious abnormalities in brain morphology across any of the Cre-driver lines, suggesting that the observed behavioral changes may reflect subtle neural alterations. These results suggested that Cre expression can produce promoter-dependent behavioral alterations, particularly in emotion or cognition. Therefore, behavioral validation of Cre-driver lines is recommended in neural circuit studies.

Uncovering protein interaction networks in vivo is essential for understanding physiological and pathological processes. Here, we report the generation of a novel knock-in mouse model expressing miniTurbo, a highly active biotin ligase, fused to the endogenous Usp46 gene. This model enables proximity-dependent biotin labeling (BioID) of USP46-associated proteins in the brain. In adult mice, biotinylation was induced by feeding a 0.1% biotin diet. We further evaluated whether the combination of miniTurbo and dietary biotin supplementation is effective for BioID in the developing brain. Biotinylation was successfully induced in embryonic and neonatal brains via maternal biotin intake, demonstrating the transfer of biotin to the offspring through the placenta during pregnancy and through milk during lactation. This strategy enables proximity labeling under physiological conditions without invasive procedures, such as repetitive subcutaneous injections, during developmental stages. Using mass spectrometry, we identified USP46-proximal proteins, including known cofactors WDR48 and WDR20, in the adult brain. Gene Ontology analysis revealed enrichment in postsynaptic pathways, consistent with known localization of USP46. Among the identified proteins, PLPP3, a phospholipid phosphatase, was significantly downregulated in the hippocampus of Usp46-knockout mice. These findings establish the USP46-miniTurbo knock-in mouse as a powerful tool for in vivo interactome analysis and provide new insights into the molecular functions of USP46 in the brain.