Effects of non-nutritive sweeteners on growth and intestinal health by regulating hypothalamic RNA profile and ileum microbiota in guinea pigs

BACKGROUND

Non-nutritive sweeteners (NNS) are commonly used in sweetened foods and beverages; however their role in metabolic regulation is still not clear. In this experiment, we used guinea pigs as an animal model to study the effect of NNS on body growth and intestinal health by modifying gut microbiota and hypothalamus-related proteins.

RESULTS

For a 28-day feeding experiment a total of 40 guinea pigs were randomly divided into four groups, one control (CN) group and three treatments, in which three NNS were added to the diet: rebaudioside A (RA, 330 mg kg-1), sodium saccharin (SS, 800 mg kg-1), and sucralose (TGS, 167 mg kg-1), respectively. The TGS group exhibited significantly reduced food consumption in comparison with the CN group (P < 0.05) whereas the RA group showed increased food consumption in comparison with the CN group (P < 0.05). Notably, Taste receptor type 1 subunit 2 (T1R2) expression in the hypothalamus was significantly higher in the RA group than in the CN group (P < 0.05). The mRNA expressions of appetite-stimulated genes arouti-related neuropeptide (AGRP), neuropeptide Y (NPY), and thyroid stimulating hormone (TSHB) were significantly higher than those in the CN group (P < 0.05) but mRNA expressions of appetite-suppressed genes tryptophan hydroxylase 2(THP2) were significantly lower in the TGS group (P < 0.05). Furthermore, NNS in the guinea pig diets (RA, SS, TGS) significantly increased the relative abundance of Muribaculaceae but decreased the relative abundance of Clostridia_vadin BB60 in comparison with the CN group (P < 0.05). We also found that dietary supplementation with RA also significantly altered the relative abundance of Lactobacillus.

CONCLUSION

Our finding confirmed that dietary supplementation with RA and TGS affected body growth and intestinal health by modulating hypothalamic RNA profiles and ileum microbiota, suggesting that NNS should be included in guinea-pig feeding. © 2024 Society of Chemical Industry.

Ongoing effects of preterm birth on the dopaminergic and noradrenergic pathways in the frontal cortex and hippocampus of guinea pigs

Children born preterm have an increased likelihood of developing neurobehavioral disorders such as attention-deficit hyperactivity disorder (ADHD) and anxiety. These disorders have a sex bias, with males having a higher incidence of ADHD, whereas anxiety disorder tends to be more prevalent in females. Both disorders are underpinned by imbalances to key neurotransmitter systems, with dopamine and noradrenaline in particular having major roles in attention regulation and stress modulation. Preterm birth disturbances to neurodevelopment may affect this neurotransmission in a sexually dimorphic manner. Time-mated guinea pig dams were allocated to deliver by preterm induction of labor (gestational age 62 [GA62]) or spontaneously at term (GA69). The resultant offspring were randomized to endpoints as neonates (24 h after term-equivalence age) or juveniles (corrected postnatal day 40, childhood equivalence). Relative mRNA expressions of key dopamine and noradrenaline pathway genes were examined in the frontal cortex and hippocampus and quantified with real-time PCR. Myelin basic protein and neuronal nuclei immunostaining were performed to characterize the impact of preterm birth. Within the frontal cortex, there were persisting reductions in the expression of dopaminergic pathway components that occurred in preterm males only. Conversely, preterm-born females had increased expression of key noradrenergic receptors and a reduction of the noradrenergic transporter within the hippocampus. This study demonstrated that preterm birth results in major changes in dopaminergic and noradrenergic receptor, transporter, and synthesis enzyme gene expression in a sex- and region-based manner that may contribute to the sex differences in susceptibility to neurobehavioral disorders. These findings highlight the need for the development of sex-based treatments for improving these conditions.

Egg Yolk-Supplemented Tris-Citric Acid Extender Improves the Prefreezing and Post-Thaw Sperm Quality Indices of Guinea Pig (Cavia porcellus) Epididymal Spermatozoa

This study aimed to assess the suitability of egg yolk (EY) supplementation to a tris-citric acid-based extender on cryosurvival of guinea pig (Cavia porcellus) epididymal spermatozoa. Two synthetic-based extenders, tris-citric acid-glucose plus 20% EY (TCG-EY) and tris-citric acid-fructose (TCF) both with 5% glycerol, were compared. Thirty-two epididymides were recovered from 16 adult guinea pig males by gonadectomy, and then the sperm samples were retrieved by retrograde flushing using TCG-EY and TCF extenders for left or right epididymis, respectively. TCG-EY and TCF sperm samples were frozen in static liquid nitrogen vapors through a two-step cooling procedure. Before freezing, the percentage of progressive sperm motility and sperm with intact plasma and acrosome membranes from TCG-EY sperm samples were higher (p < 0.05) than those diluted with TCF. Post-thaw sperm kinematic variables and membrane integrity were drastically reduced (p < 0.001) compared with prefreezing samples, regardless of extender type. The post-thaw plasmatic and acrosome membrane integrity from TCG-EY sperm samples was higher (p < 0.05) than those from TCF samples. Except for the length, the morphometric head dimensions of sperm diluted with TCG-EY or TCF did not vary (p > 0.05) after the freezing-thawing process compared with the prefreezing samples. In conclusion, despite greater cell cryoinjury with both extenders, the EY supplementation exerted greater cell membrane protection before and after the freezing-thawing process. This research shows an in-depth analysis of guinea pig sperm cryopreservation; however, more studies are recommended.

Aging and brain free cholesterol concentration on amyloid-β peptide accumulation in guinea pigs

Alzheimer's disease is a complex multifactorial neurodegenerative disorder wherein age is a major risk factor. The appropriateness of the Hartley guinea pig (GP), which displays high sequence homologies of its amyloid-β (Aβ40 and Aβ42) peptides, Mdr1 and APP (amyloid precursor protein) and similarity in lipid handling to humans, was appraised among 9-40 weeks old guinea pigs. Protein expression levels of P-gp (Abcb1) and Cyp46a1 (24(S)-hydroxylase) for Aβ40, and Aβ42 efflux and cholesterol metabolism, respectively, were decreased with age, whereas those for Lrp1 (low-density lipoprotein receptor related protein 1), Rage (receptor for advanced glycation endproducts) for Aβ efflux and influx, respectively, and Abca1 (the ATP binding cassette subfamily A member 1) for cholesterol efflux, were unchanged among the ages examined. There was a strong, negative correlation of the brain Aβ peptide concentrations and Abca1 protein expression levels with free cholesterol. The correlation of Aβ peptide concentrations with Cyp46a1 was, however, not significant, and concentrations of the 24(S)-hydroxycholesterol metabolite revealed a decreasing trend from 20 weeks old toward 40 weeks old guinea pigs. The composite data suggest a role for free cholesterol on brain Aβ accumulation. The decreases in P-gp and Lrp1 protein levels should further exacerbate the accumulation of Aβ peptides in guinea pig brain.

Complete genome sequence of Parabacteroides distasonis strain GP102, isolated from the cecum of a morbid pregnant laboratory guinea pig (Cavia porcellus)

Parabacteroides distasonis is an anaerobic bacterium with ambivalent health effects. P. distasonis strain GP102 was isolated from the cecum content of a morbid pregnant laboratory guinea pig (Cavia porcellus). The genome consists of one circular 5.39-Mbp chromosome with a G + C content of 44.79%.

Digital measuring the ocular morphological parameters of guinea pig eye in vivo with Python

AIM

To quantitatively measure ocular morphological parameters of guinea pig with Python technology.

METHODS

Thirty-six eyeballs of eighteen 3-week-old guinea pigs were measured with keratometer and photographed to obtain the horizontal, coronal, and sagittal planes respectively. The corresponding photo pixels-actual length ratio was acquired by a proportional scale. The edge coordinates were identified artificially by ginput function. Circle and conic curve fitting were applied to fit the contour of the eyeball in the sagittal, coronal and horizontal view. The curvature, curvature radius, eccentricity, tilt angle, corneal diameter, and binocular separation angle were calculated according to the geometric principles. Next, the eyeballs were removed, canny edge detection was applied to identify the contour of eyeball in vitro. The results were compared between in vivo and in vitro.

RESULTS

Regarding the corneal curvature and curvature radius on the horizontal and sagittal planes, no significant differences were observed among results in vivo, in vitro, and the keratometer. The horizontal and vertical binocular separation angles were 130.6°±6.39° and 129.8°±9.58° respectively. For the corneal curvature radius and eccentricity in vivo, significant differences were observed between horizontal and vertical planes.

CONCLUSION

The Graphical interface window of Python makes up the deficiency of edge detection, which requires too much definition in Matlab. There are significant differences between guinea pig and human beings, such as exotropic eye position, oblique oval eyeball, and obvious discrepancy of binoculus. This study helps evaluate objectively the ocular morphological parameters of small experimental animals in emmetropization research.

Maternal Vitamin C Intake during Pregnancy Influences Long-Term Offspring Growth with Timing- and Sex-Specific Effects in Guinea Pigs

Our previous work in guinea pigs revealed that low vitamin C intake during preconception and pregnancy adversely affects fertility, pregnancy outcomes, and foetal and neonatal growth in a sex-dependent manner. To investigate the long-term impact on offspring, we monitored their growth from birth to adolescence (four months), recorded organ weights at childhood equivalence (28 days) and adolescence, and assessed physiological parameters like oral glucose tolerance and basal cortisol concentrations. We also investigated the effects of the timing of maternal vitamin C restriction (early vs. late gestation) on pregnancy outcomes and the health consequences for offspring. Dunkin Hartley guinea pigs were fed an optimal (900 mg/kg feed) or low (100 mg/kg feed) vitamin C diet ad libitum during preconception. Pregnant dams were then randomised into four feeding regimens: consistently optimal, consistently low, low during early pregnancy, or low during late pregnancy. We found that low maternal vitamin C intake during early pregnancy accelerated foetal and neonatal growth in female offspring and altered glucose homeostasis in the offspring of both sexes at an age equivalent to early childhood. Conversely, low maternal vitamin C intake during late pregnancy resulted in foetal growth restriction and reduced weight gain in male offspring throughout their lifespan. We conclude that altered vitamin C during development has long-lasting, sex-specific consequences for offspring and that the timing of vitamin C depletion is also critical, with low levels during early development being associated with the development of a metabolic syndrome-related phenotype, while later deprivation appears to be linked to a growth-faltering phenotype.

Development of LIBRA-seq for the guinea pig model system as a tool for the evaluation of antibody responses to multivalent HIV-1 vaccines

Consistent elicitation of serum antibody responses that neutralize diverse clades of HIV-1 remains a primary goal of HIV-1 vaccine research. Prior work has defined key features of soluble HIV-1 Envelope (Env) immunogen cocktails that influence the neutralization breadth and potency of multivalent vaccine-elicited antibody responses including the number of Env strains in the regimen. We designed immunization groups that consisted of different numbers of SOSIP Env strains to be used in a cocktail immunization strategy: the smallest cocktail (group 2) consisted of a set of two Env strains, which were a subset of the three Env strains that made up group 3, which, in turn, were a subset of the six Env strains that made up group 4. Serum neutralizing titers were modestly broader in guinea pigs that were immunized with a cocktail of three Envs compared to cocktails of two and six, suggesting that multivalent Env immunization could provide a benefit but may be detrimental when the cocktail size is too large. We then adapted the LIBRA-seq platform for antibody discovery to be compatible with guinea pigs, and isolated several tier 2 neutralizing monoclonal antibodies. Three antibodies isolated from two separate guinea pigs were similar in their gene usage and CDR3s, establishing evidence for a guinea pig public clonotype elicited through vaccination. Taken together, this work investigated multivalent HIV-1 Env immunization strategies and provides a novel methodology for screening guinea pig B cell receptor antigen specificity at a high-throughput level using LIBRA-seq.IMPORTANCEMultivalent vaccination with soluble Env immunogens is at the forefront of HIV-1 vaccination strategies but little is known about the influence of the number of Env strains included in vaccine cocktails. Our results suggest that adding more strains is sometimes beneficial but may be detrimental when the number of strains is too high. In addition, we adapted the LIBRA-seq platform to be compatible with guinea pig samples and isolated several tier 2 neutralizing monoclonal antibodies, some of which share V and J gene usage and >70% CDR3 identity, thus establishing the existence of public clonotypes in guinea pigs elicited through vaccination.

Dual isolation of primary neurons and oligodendrocytes from guinea pig frontal cortex

Primary cell culture is a technique that is widely used in neuroscience research to investigate mechanisms that underlie pathologies at a cellular level. Typically, mouse or rat tissue is used for this process; however, altricial rodent species have markedly different neurodevelopmental trajectories comparatively to humans. The use of guinea pig brain tissue presents a novel aspect to this routinely used cell culture method whilst also allowing for dual isolation of two major cell types from a physiologically relevant animal model for studying perinatal neurodevelopment. Primary neuronal and oligodendrocyte cell cultures were derived from fetal guinea pig's frontal cortex brain tissue collected at a gestational age of 62 days (GA62), which is a key time in the neuronal and oligodendrocyte development. The major advantage of this protocol is the ability to acquire both neuronal and oligodendrocyte cellular cultures from the frontal cortex of one fetal brain. Briefly, neuronal cells were grown in 12-well plates initially in a 24-h serum-rich medium to enhance neuronal survival before switching to a serum-free media formulation. Oligodendrocytes were first grown in cell culture flasks using a serum-rich medium that enabled the growth of oligodendrocyte progenitor cells (OPCs) on an astrocyte bed. Following confluency, the shake method of differential adhesion and separation was utilized via horizontally shaking the OPCs off the astrocyte bed overnight. Therefore, OPCs were plated in 12-well plates and were initially expanded in media supplemented with growth hormones, before switching to maturation media to progress the lineage to a mature phenotype. Reverse transcription-polymerase chain reaction (RT-PCR) was performed on both cell culture types to analyze key population markers, and the results were further validated using immunocytochemistry. Primary neurons displayed the mRNA expression of multiple neuronal markers, including those specific to GABAergic populations. These cells also positively stained for microtubule-associated protein 2 (MAP2; a dendritic marker specific to neurons) and NeuN (a marker of neuronal cell bodies). Primary oligodendrocytes expressed all investigated markers of the oligodendrocyte lineage, with a majority of the cells displaying an immature oligodendrocyte phenotype. This finding was further confirmed with positive oligodendrocyte transcription factor (OLIG2) staining, which serves as a marker for the overall oligodendrocyte population. This study demonstrates a novel method for isolating both neurons and oligodendrocytes from the guinea pig brain tissue. These isolated cells display key markers and gene expression that will allow for functional experiments to occur and may be particularly useful in studying neurodevelopmental conditions with perinatal origins.

Flavones isolated from Pseudognaphalium liebmannii with tracheal smooth muscle relaxant properties

The inflorescences of Pseudognaphalium liebmannii are used as folk medicine to treat various respiratory diseases. In this work, we report the isolation of seven known flavones: 5-hydroxy-3,7-dimethoxyflavone 1, 5,8-dihydroxy-3,7-dimethoxyflavone 2, 5,7-dihydroxy-3,8-dimethoxyflavone 3 (gnaphaliin A), 3,5-dihydroxy-7,8-dimethoxyflavone 4 (gnaphaliin B), 3,5-dihydroxy-6,7,8-trimethoxyflavone 5, 3,5,7-trimethoxyflavone 6 and 3-O-methylquercetin 7. All these flavones except 1 and 6 showed a relaxant effect on guinea pig tracheal preparation with EC50 between 69.91 ± 15.32 and 118.72 ± 7.06 µM. Aminophylline (EC50 = 122.03 ± 7.05 µM) was used as a relaxant reference drug. The active flavones shifted the concentration-response curves of forskolin and nitroprusside leftward, and significantly reduced the EC50 values of these drugs. Furthermore, these flavones dose-dependently inhibited phosphodiesterase (PDE) in an in vitro assay. This reveals that the inflorescences of P. liebmannii contain several flavones with relaxant effect on airway smooth muscle and with PDEs inhibition that contribute to supporting the anti-asthmatic traditional use.

Investigation of a maxillary nerve block technique in guinea pigs (Cavia porcellus): A cadaveric study comparing two injectate volumes

OBJECTIVE

To investigate and describe an extraoral approach to perform a maxillary nerve block in guinea pigs.

STUDY DESIGN

Prospective, randomized, blinded, descriptive, cadaveric study.

ANIMALS

A total of 14 adult guinea pig cadavers.

METHODS

Two cadavers were used for anatomic dissection and determination of maxillary nerve block approach. A maxillary nerve block via infraorbital approach was then performed in 12 cadavers. A low volume (0.1 mL) or high volume (0.2 mL) of diluted methylene blue injectate was randomly assigned to the right or left side, with the other volume used for the contralateral side. The maxillary nerve was dissected after each injection by an investigator blinded to injectate volume. The region of dye distribution was identified, and the degree of staining assigned an accuracy score (0-2). Nerve coverage was considered adequate if ≥6 mm of circumferential staining was present.

RESULTS

Accuracy evaluation indicated successful dye deposition in 10/12 [2 (0-2), median (range)] injections in the low volume group and 8/12 [2 (1-2)] injections in the high volume group. The majority (79.2%) of injections resulted in adequate nerve staining. There were no statistically significant differences between injectate volumes for accuracy (p = 0.64) or adequacy (p > 0.99) of staining.

CONCLUSIONS

The infraorbital approach is a simple and practical method for maxillary nerve blockade in guinea pigs. An injectate volume of 0.1 mL results in adequate maxillary nerve coverage; however, additional studies are needed to assess the efficacy in clinical use.

Unilateral segmental uterine horn hypoplasia with fallopian tube aplasia in a guinea pig (Caviaporcellus)

A 2-year-3-month-old female guinea pig (Cavia porcellus) was referred for lethargy, weight gain and severe abdominal pain. Ultrasound examination revealed thickening and enlargement of the left uterine horn and an unremarkable right uterine horn. The animal died during ovariohysterectomy due to respiratory and cardiac arrest. Necropsy revealed unilateral segmental uterine horn hypoplasia and aplasia of the fallopian tube of the corresponding side. This is the first report of a congenital uterine malformation in the guinea pig and we describe the clinical and pathological presentation of segmental uterine horn hypoplasia and fallopian tube aplasia. Congenital uterine malformations are rare in guinea pigs but should be considered as differential diagnoses for the more common acquired uteropathies.

Thymus atlanticus (Ball) Roussine Aqueous Extract Exerts Lipid-lowering and Anti-atherosclerotic Effects in Hyperlipidemic Guinea Pigs

BACKGROUND

Thymus atlanticus (Ball) Roussine (T. atlanticus) is traditionally used in the Moroccan high Atlas Mountains to treat several disorders, including cardiovascular disease. In the present study, the lipid-lowering and anti-atherosclerotic activities of the traditionally used aqueous extract of T. atlanticus were evaluated on guinea pigs subjected to chronic hyperlipidemia.

METHODS

Animals were given a diet containing 2% cholesterol and 20% lard for 12 weeks. Moreover, thyme extract was given daily at 400 mg/kg. At the end of the experiment, lipid levels and paraoxonase arylesterase activity were measured, and aorta histology was studied.

RESULTS

Our findings revealed that there was an important elevation of blood lipids in the HFD group along with a significant decrease in paraoxonase arylesterase activity (-40.06%). Moreover, the consumption of fat altered the histology of aorta by thickening the intima media and forming atherosclerotic lesions and foam cells in these tissues. However, the administration of thyme extract attenuated HFD-caused alterations by decreasing blood lipids, elevating paraoxonase activity (+24.04%), and limiting the progression of atherosclerotic lesions.

CONCLUSION

We conclude that the supplementation with the aqueous extract of T. atlanticus could potentially protect against hyperlipidemia and consequently, the development of atherosclerosis.

Sex differences in plasma metabolites in a guinea pig model of allergic asthma

Sex seems to be a contributing factor in the pathogenesis of bronchial asthma. This study aimed to find sex-related differences in metabolome measured by hydrogen-1 nuclear magnetic resonance ((1)H NMR) spectroscopy in healthy and ovalbumin (OVA)-sensitized guinea pigs. Adult male and female animals were divided into controls and OVA-sensitized groups. OVA-sensitization was performed by OVA systemic and inhalational administration within 14 days; on day 15, animals were killed by anesthetic overdose followed by exsanguination. Blood was taken and differential white blood cell count was measured. Left lung was saline-lavaged and differential cell count in the bronchoalveolar lavage fluid (BALF) was measured. After blood centrifugation, plasma was processed for (1)H NMR analysis. Metabolomic data was evaluated by principal component analysis (PCA). Eosinophil counts elevated in the BALF confirming eosinophil-mediated inflammation in OVA-sensitized animals of both sexes. Sex differences for lactate, glucose, and citrate were found in controls, where these parameters were lower in males than in females. In OVA-sensitized males higher glucose and lower pyruvate were found compared to controls. OVA-sensitized females showed lower lactate, glucose, alanine, 3-hydroxy-butyrate, creatine, pyruvate, and succinate concentrations compared to controls. In OVA-sensitized animals, lactate concentration was lower in males. Data from females (healthy and OVA-sensitized) were generally more heterogeneous. Significant sex differences in plasma concentrations of metabolites were found in both healthy and OVA-sensitized animals suggesting that sex may influence the metabolism and may thereby contribute to different clinical picture of asthma in males and females.

Characterization of spatial lipidomic signatures in tick-bitten guinea pig skin as a model for host-vector-pathogen interaction profiling

IMPORTANCE

Here, we demonstrate the adaptability of spatial "omics" methods to identify interphylum processes regulated at the vector-host interface of ticks during a mammalian blood meal. This approach enables a better understanding of complex bipartite or tripartite molecular interactions between hosts, arthropod vectors and transmitted pathogens, and contributes toward the development of spatially aware therapeutic target discovery and description.

Computed Tomographic Findings Secondary to Dental Pathologies: Comparison between Rabbits and Guinea Pigs

(1) Background: dental pathologies are the most frequent reason for requesting a CT scan of the head in rabbits and guinea pigs. The study aimed to review head CT exams of both species to identify and characterize lesions secondary to dental disease. (2) Methods: head CT studies of 48 rabbits and 52 guinea pigs with dental pathologies were reviewed. (3) Results: dental abnormalities of mandibular teeth were the most represented, both in rabbits (81.2%) and guinea pigs (98%). The aggressive bone lesion associated with teeth was the more frequently observed bone lesion in rabbits' mandible and maxilla; in guinea pigs, the more frequent bone lesions were bulging around the roots of the teeth with focal lysis in the maxilla, and without focal lysis in the mandible. In the maxilla, the increased attenuation of nasal cavities (rhinitis) was the most frequently observed abnormality both in rabbits (60%) and guinea pigs (83.3%); the exophthalmos was more represented in rabbits (53.3%). In the mandible, the cavernous space-occupying lesion was more represented both in rabbits (92.3%) and guinea pigs (73.3%). (4) Conclusions: lesions secondary to dental pathologies were often observed both in rabbits and guinea pigs; CT examination has proven to be valuable in detecting secondary alterations in both species.

Ryanodine receptor 2 inhibition reduces dispersion of cardiac repolarization, improves contractile function, and prevents sudden arrhythmic death in failing hearts

Sudden cardiac death (SCD) from ventricular tachycardia/fibrillation (VT/VF) is a leading cause of death, but current therapies are limited. Despite extensive research on drugs targeting sarcolemmal ion channels, none have proven sufficiently effective for preventing SCD. Sarcoplasmic ryanodine receptor 2 (RyR2) Ca2+ release channels, the downstream effectors of sarcolemmal ion channels, are underexplored in this context. Recent evidence implicates reactive oxygen species (ROS)-mediated oxidation and hyperactivity of RyR2s in the pathophysiology of SCD. We tested the hypothesis that RyR2 inhibition of failing arrhythmogenic hearts reduces sarcoplasmic Ca2+ leak and repolarization lability, mitigates VT/VF/SCD and improves contractile function. We used a guinea pig model that replicates key clinical aspects of human nonischemic HF, such as a prolonged QT interval, a high prevalence of spontaneous arrhythmic SCD, and profound Ca2+ leak via a hyperactive RyR2. HF animals were randomized to receive dantrolene (DS) or placebo in early or chronic HF. We assessed the incidence of VT/VF and SCD (primary outcome), ECG heart rate and QT variability, echocardiographic left ventricular (LV) structure and function, immunohistochemical LV fibrosis, and sarcoplasmic RyR2 oxidation. DS treatment prevented VT/VF and SCD by decreasing dispersion of repolarization and ventricular arrhythmias. Compared to placebo, DS lowered resting heart rate, preserved chronotropic competency during transient β-adrenergic challenge, and improved heart rate variability and cardiac function. Inhibition of RyR2 hyperactivity with dantrolene mitigates the vicious cycle of sarcoplasmic Ca2+ leak-induced increases in diastolic Ca2+ and ROS-mediated RyR2 oxidation, thereby reducing repolarization lability and protecting against VT/VF/SCD. Moreover, the consequent increase in sarcoplasmic Ca2+ load improves contractile function. These potentially life-saving effects of RyR2 inhibition warrant further investigation, such as clinical studies of repurposing dantrolene as a potential new therapy for heart failure and/or SCD.

Validation of computed tomography as a diagnostic tool in guinea pigs with non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) and subsequent steatohepatitis (NASH) is the most common cause of liver disease and liver transplantation in humans. Affecting millions of patients worldwide, diagnosis relies on a biopsy, not without risk to the patient, and emphasises the need for improved diagnostic measures to determine and monitor disease progression. Despite intensive research, approved pharmacological treatment modalities are few, underlining that animal models with increased translational validity are important to advance preclinical drug development. This study validates the applicability of computed tomography (CT) as a non-invasive diagnostic tool for the assessment of liver steatosis in a guinea pig model of NAFLD/NASH. Guinea pigs with induced NAFLD or NASH were compared to healthy controls at two separate time points: week 16, serving as baseline measure, and week 25 to monitor disease progression over time. The animals were subsequently euthanised, and samples were collected to confirm disease stage. The data showed a strong negative correlation between liver triglycerides and Hounsfield unit (HU) values (R2 = 0.8157; p < 0.0001). A significant difference in histopathological scoring and HU values between grade 0 and more advanced stages of steatosis was recorded (p < 0.001), although the degree of liver fibrosis could not be accurately evaluated by differences in HU. In conclusion, the present study validates CT scanning for the determination of hepatic steatosis in guinea pigs, and it strongly supports the technique as a relevant non-invasive diagnostic tool in this species.

Use of a propofol infusion for anaesthetic maintenance in Guinea pigs (Cavia porcellus): a retrospective case series

OBJECTIVE

To retrospectively evaluate the feasibility of a propofol infusion for anaesthetic maintenance in guinea pigs.

STUDY DESIGN

Retrospective case series.

ANIMALS

Client-owned guinea pigs undergoing general anaesthesia.

METHODS

Anaesthetic records of guinea pigs anaesthetized between March 2015 and March 2018 were reviewed. Animals administered a propofol infusion for > 20 minutes were identified and evaluated. Procedure performed, pre-anaesthetic medication, preoperative and intraoperative respiratory rate (fR) and heart rates (HRs), total amount of propofol administered, total anaesthesia and recovery times were extracted from the records and analysed using descriptive statistics and Pearson correlation tests. Data are reported as mean (range).

RESULTS

Records of 14 animals meeting the criteria were identified. Following drug combinations were administered for premedication: butorphanol 0.43 (0.3-0.5) mg kg-1, medetomidine 0.1 (0.05-0.2) mg kg-1 and midazolam 1 (0.5-2) mg kg-1 (n = 3); methadone 0.33 (0.25-0.5) mg kg-1, medetomidine 0.07 (0.01-0.1) mg kg-1 and midazolam 0.66 (0.5-1) mg kg-1 (n = 3); butorphanol 0.5 mg kg-1, medetomidine 0.05 mg kg-1 and ketamine 5 mg kg-1 (n = 2); buprenorphine 0.01 mg kg-1, medetomidine 0.07 (0.04-1) mg kg-1 and ketamine 4 (3-5) mg kg-1 (n = 3); butorphanol 0.5 mg kg-1, alfaxalone 1 mg kg-1 and midazolam 0.5 mg kg-1 (n = 1); and methadone 0.38 (0.25-0.5) mg kg-1, medetomidine 0.08 (0.06-1) mg kg-1 with midazolam 0.75 (0.5-1) mg kg-1 (n = 2). Preoperative and intraoperative HRs were 240 (160-300) and 170 (140-200) beats minute-1, respectively. Preoperative and intraoperative fR were 63 (50-86) and 37 (18-80) breaths minute-1, respectively. The propofol infusion rate was 0.45 (0.17-0.80) mg kg-1 minute-1. Total anaesthesia and recovery times were 60 (25-145) and 17 (8-60) minutes, respectively. A slight correlation was found between total propofol dose infused and recovery time (r = 0.58).

CONCLUSION AND CLINICAL RELEVANCE

Propofol infusions may be a useful alternative to inhalant anaesthetics.

A comparison of commercially available feeds for rabbits, guinea pigs, chinchillas and degus with evidence of their diet and feeding behaviour in natural habitats

INTRODUCTION

A large variety of pet feeds is commercially available for pet herbivores; these feeds may differ in nutrient composition from the natural diet, and may trigger different feeding behaviours than observed in natural habitats. Here, we surveyed literature on the natural diet and activity budget of rabbits (Oryctolagus cuniculus), guinea pigs (Cavia porcellus), chinchilla (Chinchilla lanigera) and degus (Octodon degus), as well as 260 compound feeds commercially available for these species between 1982 and 2020. The species are classified as herbivores, with available data on natural diets suggesting a crude fibre (CF) level of approximately 250 g/kg dry matter (DM), natural feeding activity at a magnitude of 4-7 h per day, with distinctively shorter feeding when fed on compound pet feeds. Only for a minority of feeds did the first 5 listed ingredients not include a starchy ingredient, or only ingredients not considered suitable for human consumption. The percentage of feeds whose CF level was less than 150 g/kg DM was 22 % for production rabbits, 18 % for pet rabbits, 26 % for guinea pigs, 18 % for chinchillas and 14 % for degus; in other words, a majority of currently marketed products have CF levels in accord with published recommendations, even if that means a discrepancy to natural diets. Screening the producers' feeding instructions suggests they should generally not be followed uncritically. No temporal trends in the CF levels of these diets was evident. There is no consensus whether only products resembling natural diet items should be included in pet feeds, or whether vegetable byproducts not edible by humans should also be included. The observed practice of pet feed composition largely did not follow either concept, questioning the general rationale of pet feed composition. Whole forage like hay is recommended as the main diet component for these species, and 76 % of pet feed products noted that hay should be fed in the feeding instructions.

Spontaneously Myopic Guinea Pig: Model of Early Pathologic Myopia

Purpose

To evaluate whether pigmented guinea pigs with spontaneous myopia present characteristic changes of pathologic myopia.

Methods

The fundus images of guinea pigs (3 weeks old) were graded according to fundus tessellation (FT) degree. Biometric parameters, including refraction, vitreous chamber depth (VCD), and axial length (AL), were measured at ages 21 and 43 days. Some of these animals were divided into three groups: hyperopic without FT (H w/o FT), myopic without FT (M w/o FT), and myopic with FT (M w/ FT). The horizontal and vertical radii of curvature of posterior sclera (RP-H and RP-V, respectively) and the radii of curvature and arc lengths of superior sclera (RS and LS, respectively), inferior sclera (RI and LI, respectively), nasal sclera (RN and LN, respectively), and temporal sclera (RT and LT) were evaluated by Fuji.

Results

The fundi were graded as type A or type B (both without FT), type C (mild FT), or type D (severe FT). The prevalence of FT was correlated with myopic refraction, longer VCD, and longer AL. Eyes of M w/FT animals had shorter RP-H and RP-V, longer RS and RT, and longer LS and LT than eyes of H w/o FT or M w/o FT animals. Refractions shifted toward hyperopia in eyes lacking FT, but not in eyes having FT. The changes in VCD were consistent with the changes in refraction. This relatively myopic shift in refraction and shortening of VCD were found only in myopic eyes with FT, but not in myopic eyes without FT.

Conclusions

Spontaneously myopic guinea pig eyes have a high prevalence of FT. Myopic eyes with FT presented characteristic signs of pathologic myopia.

The Co-Expression Pattern of Calcium-Binding Proteins with γ-Aminobutyric Acid and Glutamate Transporters in the Amygdala of the Guinea Pig: Evidence for Glutamatergic Subpopulations

The amygdala has large populations of neurons utilizing specific calcium-binding proteins such as parvalbumin (PV), calbindin (CB), or calretinin (CR). They are considered specialized subsets of γ-aminobutyric acid (GABA) interneurons; however, many of these cells are devoid of GABA or glutamate decarboxylase. The neurotransmitters used by GABA-immunonegative cells are still unknown, but it is suggested that a part may use glutamate. Thus, this study investigates in the amygdala of the guinea pig relationships between PV, CB, or CR-containing cells and GABA transporter (VGAT) or glutamate transporter type 2 (VGLUT2), markers of GABAergic and glutamatergic neurons, respectively. The results show that although most neurons using PV, CB, and CR co-expressed VGAT, each of these populations also had a fraction of VGLUT2 co-expressing cells. For almost all neurons using PV (~90%) co-expressed VGAT, while ~1.5% of them had VGLUT2. The proportion of neurons using CB and VGAT was smaller than that for PV (~80%), while the percentage of cells with VGLUT2 was larger (~4.5%). Finally, only half of the neurons using CR (~53%) co-expressed VGAT, while ~3.5% of them had VGLUT2. In conclusion, the populations of neurons co-expressing PV, CB, and CR are in the amygdala, primarily GABAergic. However, at least a fraction of neurons in each of them co-express VGLUT2, suggesting that these cells may use glutamate. Moreover, the number of PV-, CB-, and CR-containing neurons that may use glutamate is probably larger as they can utilize VGLUT1 or VGLUT3, which are also present in the amygdala.

Use of chin sling for conservative treatment of mandibular fracture in a guinea pig (Cavia porcellus)

OBJECTIVE

To describe a treatment for a mandibular fracture in a guinea pig (Cavia porcellus).

ANIMAL

A 6-month-old sexually intact male guinea pig referred for a 24-hour history of hyporexia.

CLINICAL PRESENTATION, PROGRESSION, AND PROCEDURES

Physical examination showed lateral displacement of the incisors and inflammation and crepitation during mandible lateralization. Imaging tests revealed a minimally displaced complete oblique fracture of the left mandible with fracture of the left mandibular first premolar tooth and incisor tooth.

TREATMENT AND OUTCOME

Conservative treatment was established by placing a chin sling (CS) to immobilize the jaw and a nasogastric tube for nutritional support. Imaging tests repeated 3 weeks later showed initial callus formation, and the conservative treatment was discontinued. Follow-up examinations showed appetite and progressive weight gain. Five months later, the clinical crown of the left mandibular incisor was absent and a resorptive lesion on the left mandibular first premolar tooth was detected. Complete ossification of the fracture without premolar and moler teeth elongation was observed on control imaging tests. Ten months after initial examination, the patient was reportedly healthy with no signs of pain or dental disease.

CLINICAL RELEVANCE

Jaw fracture treatments in guinea pigs are poorly described in the literature. Surgical treatment can be challenging in this species due to its skull and dental anatomy. Although CS was originally employed to increase the congruency of premolar and molar teeth after coronal reduction, this device yielded satisfactory results as a noninvasive, inexpensive treatment of a mandibular fracture in this guinea pig. Alopecia on the back of the head was the only undesired adverse effect associated with the CS.

Boosting of vaginal HSV-2-specific B and T cell responses by intravaginal therapeutic immunization results in diminished recurrent HSV-2 disease

Boosting herpes simplex virus (HSV)-specific immunity in the genital tissues of HSV-positive individuals to increase control of HSV-2 recurrent disease and virus shedding is an important goal of therapeutic immunization and would impact HSV-2 transmission. Experimental therapeutic HSV-2 vaccines delivered by a parenteral route have resulted in decreased recurrent disease in experimental animals. We used a guinea pig model of HSV-2 infection to test if HSV-specific antibody and cell-mediated responses in the vaginal mucosa would be more effectively increased by intravaginal (Ivag) therapeutic immunization compared to parenteral immunization. Therapeutic immunization with HSV glycoproteins and CpG adjuvant increased glycoprotein-specific IgG titers in vaginal secretions and serum to comparable levels in Ivag- and intramuscular (IM)-immunized animals. However, the mean numbers of HSV glycoprotein-specific antibody secreting cells (ASCs) and IFN-γ SCs were greater in Ivag-immunized animals demonstrating superior boosting of immunity in the vaginal mucosa compared to parenteral immunization. Therapeutic Ivag immunization also resulted in a significant decrease in the cumulative mean lesion days compared to IM immunization. There was no difference in the incidence or magnitude of HSV-2 shedding in either therapeutic immunization group compared to control-treated animals. Collectively, these data demonstrated that Ivag therapeutic immunization was superior compared to parenteral immunization to boost HSV-2 antigen-specific ASC and IFN-γ SC responses in the vagina and control recurrent HSV-2 disease. These results suggest that novel antigen delivery methods providing controlled release of optimized antigen/adjuvant combinations in the vaginal mucosa would be an effective approach for therapeutic HSV vaccines. IMPORTANCE HSV-2 replicates in skin cells before it infects sensory nerve cells where it establishes a lifelong but mostly silent infection. HSV-2 occasionally reactivates, producing new virus which is released back at the skin surface and may be transmitted to new individuals. Some HSV-specific immune cells reside at the skin site of the HSV-2 infection that can quickly activate and clear new virus. Immunizing people already infected with HSV-2 to boost their skin-resident immune cells and rapidly control the new HSV-2 infection is logical, but we do not know the best way to administer the vaccine to achieve this goal. In this study, a therapeutic vaccine given intravaginally resulted in significantly better protection against HSV-2 disease than immunization with the same vaccine by a conventional route. Immunization by the intravaginal route resulted in greater stimulation of vaginal-resident, virus-specific cells that produced antibody and produced immune molecules to rapidly clear virus.

Characterisation and development of histopathological lesions in a guinea pig model of Mycobacterium tuberculosis infection

Tuberculosis (TB) remains a very significant infectious disease worldwide. New vaccines and therapies are needed, even more crucially with the increase of multi-drug resistant Mycobacterium tuberculosis strains. Preclinical animal models are very valuable for the development of these new disease control strategies. Guinea pigs are one of the best models of TB, sharing many features with the pathology observed in human TB. Here we describe the development of TB lesions in a guinea pig model of infection. We characterise the granulomatous lesions in four developmental stages (I-IV), using histopathological analysis and immunohistochemical (IHC) techniques to study macrophages, T cells, B cells and granulocytes. The granulomas in the guinea pigs start as aggregations of macrophages and few heterophils, evolving to larger lesions showing central caseous necrosis with mineralisation and abundant acid-fast bacilli, surrounded by a rim of macrophages and lymphocytes in the outer layers of the granuloma. Multinucleated giant cells are very rare and fibrotic capsules are not formed in this animal model.

Effects of Low Vitamin C Intake on Fertility Parameters and Pregnancy Outcomes in Guinea Pigs

Identifying how specific nutrients can impact fertility, pregnancy, and neonatal outcomes will yield important insights into the biological mechanisms linking diet and reproductive health. Our study investigates how dietary vitamin C intake affects various fertility parameters and pregnancy and neonatal outcomes in the guinea pig, a natural model of vitamin C dependency. Dunkin Hartley guinea pigs were fed an optimal (900 mg/kg feed) or low (100 mg/kg feed) vitamin C diet ad libitum for at least three weeks prior to mating and throughout pregnancy. We found that animals receiving the low vitamin C diet had an increased number of unsuccessful matings, a higher incidence of foetal reabsorption, and, among pregnancies resulting in delivery at term, produced fewer offspring. Neonates from mothers on the low vitamin C diet had significantly decreased plasma vitamin C concentrations at birth and exhibited mild growth impairments in a sex-dependent manner. We conclude that a diet low of vitamin C induces a state of subfertility, reduces overall fecundity, and adversely impacts both pregnancy outcomes and growth in the offspring. Our study provides an essential foundation for future investigations to determine whether these findings translate to humans. If so, they could have important clinical implications for assisted reproductive technologies and nutritional recommendations for couples trying to conceive, pregnant women, and breastfeeding mothers.

Healing Effect of a Nano-Functionalized Medical-Grade Honey for the Treatment of Infected Wounds

Based on the qualities of Ulmo honey (Eucryphia cordifolia), a medical-grade honey (Ulmoplus®) has been developed. Relevant to this, the use of copper represents an emerging therapy for the treatment of wounds. Therefore, the aim of this study was to see how this medical-grade honey with copper nanoparticles (CuNPs) helped to heal infected or non-infected wounds. Twenty-four guinea pigs (Cavia porcellus) were divided into four groups for phase 1 (without and with infection, U + F1 and U + F2), and two groups for phase 2 (selected formulation, without and with infection, U + F2NI and U + F2I). Bacteriological and histopathological studies, collagen fibers content evaluation, and stereological analysis were performed. The selected formulation displayed the same antibacterial potency as Ulmoplus®, indicating that this medical-grade honey by itself can be used as an antibacterial agent. However, the evaluation of collagen content demonstrated a significant increase in fibroblast and type III collagen fibers for infected and uninfected groups, which correlated with the histopathological study. Therefore, it is correct to affirm that adding CuNPs to Ulmoplus® improved the maturation of collagen fibers. Finally, polymorphonuclear cells presented similar values between experimental groups, which would indicate that the formulation under study was able to regulate the inflammatory process despite their infectious condition.

Incidental Findings in Computed Tomography Examination of the Head in Rabbits and Guinea Pigs

(1) Background: Rabbits and guinea pigs are popular pet animals and often undergo computed tomography (CT) examination for assessment of pathologies of the head. The goal of the study was to review CT examinations of the heads of rabbits and guinea pigs to identify and classify incidental findings. (2) Methods: 60 CT studies of the heads of rabbits and 65 of guinea pigs presented at 2 Institutions were reviewed and the indications for the study recorded. (3) Results: The presence of CT findings not directly related to the reason for the CT examination was present in 40/60 (66.7%) studies of rabbits and in 42/65 (64.4%) studies of guinea pigs. Most commonly, the incidental findings involved the ears, in 24/60 studies in rabbits and in 29/65 studies in guinea pigs. Incidental findings involved the nasal cavities, respectively, in 9 and 7 rabbits and guinea pigs. Soft tissue mineralization was present in 11 rabbits and 17 guinea pigs. (4) Conclusions: Based on the present study, incidental findings detected on CT studies are often present in rabbits and guinea pigs. Veterinarians should be aware of the possible clinical impact of these findings.

Multivalent vaccines demonstrate immunogenicity and protect against Coxiella burnetii aerosol challenge

Vaccines are among the most cost-effective public health measures for controlling infectious diseases. Coxiella burnetii is the etiological agent of Q fever, a disease with a wide clinical spectrum that ranges from mild symptoms, such as fever and fatigue, to more severe disease, such as pneumonia and endocarditis. The formalin-inactivated whole-cell vaccine Q-VAX® contains hundreds of antigens and confers lifelong protection in humans, but prior sensitization from infection or vaccination can result in deleterious reactogenic responses to vaccination. Consequently, there is great interest in developing non-reactogenic alternatives based on adjuvanted recombinant proteins. In this study, we aimed to develop a multivalent vaccine that conferred protection with reduced reactogenicity. We hypothesized that a multivalent vaccine consisting of multiple antigens would be more immunogenic and protective than a monovalent vaccine owing to the large number of potential protective antigens in the C. burnetii proteome. To address this, we identified immunogenic T and B cell antigens, and selected proteins were purified to evaluate with a combination adjuvant (IVAX-1), with or without C. burnetii lipopolysaccharide (LPS) in immunogenicity studies in vivo in mice and in a Hartley guinea pig intratracheal aerosol challenge model using C. burnetii strain NMI RSA 493. The data showed that multivalent vaccines are more immunogenic than monovalent vaccines and more closely emulate the protection achieved by Q-VAX. Although six antigens were the most immunogenic, we also discovered that multiplexing beyond four antigens introduces detectable reactogenicity, indicating that there is an upper limit to the number of antigens that can be safely included in a multivalent Q-fever vaccine. C. burnetii LPS also demonstrates efficacy as a vaccine antigen in conferring protection in an otherwise monovalent vaccine formulation, suggesting that its addition in multivalent vaccines, as demonstrated by a quadrivalent formulation, would improve protective responses.

Review of Rat (Rattus norvegicus), Mouse (Mus musculus), Guinea pig (Cavia porcellus), and Rabbit (Oryctolagus cuniculus) Indicators for Welfare Assessment

The monitoring and assessment of animals is important for their health and welfare. The appropriate selection of multiple, validated, and feasible welfare assessment indicators is required to effectively identify compromises or improvements to animal welfare. Animal welfare indicators can be animal or resource based. Indicators can be collated to form assessment tools (e.g., grimace scales) or animal welfare assessment models (e.g., 5 Domains) and frameworks (e.g., 5 Freedoms). The literature contains a wide variety of indicators, with both types needed for effective animal welfare assessment; however, there is yet to be an ideal constellation of indicators for animal-based welfare assessment in small mammals such as guinea pigs (Cavia Porcellus), mice (Mus musculus), rabbits (Oryctolagus cuniculus), and rats (Rattus norvegicus). A systematic review of grey and peer-reviewed literature was performed to determine the types of animal-based welfare indicators available to identify and assess animal health and welfare in these small mammals maintained across a wide variety of conditions. The available indicators were categorised and scored against a selection of criteria, including potential ease of use and costs. This review and analysis aim to provide the basis for further research into animal welfare indicators for these species. Future applications of this work may include improvements to animal welfare assessments or schemes, guiding better management, and implementing future strategies to enable better animal welfare.

Prevalence of Encephalitozoon cuniculi Infection in Guinea Pigs (Cavia porcellus) in Poland with Different Clinical Disorders-A Pilot Study

Encephalitozoonosis is a disease caused by E. cuniculi. It is diagnosed primarily in rabbits but is less frequently so in other animal species. E. cuniculi is classified among Microsporidia-fungi frequently found in the environment, that are resistant to numerous external factors. Apart from rabbits, rodents form the next group of animals most exposed to infection with these pathogens. The objective of the study was to analyze the prevalence of E. cuniculi infection in guinea pigs with different clinical disorders. The study included 67 animals with E. cuniculi infection confirmed via real-time PCR. The infected animals most frequently exhibited nervous and urinary system symptoms, as well as issues with vision organs, while several animals were also recorded as having problems with the respiratory system and thyroid gland dysfunction. The study shows that encephalitozoonosis constitutes a significant problem in rodents kept as domestic animals, which in turn may be a source of infection for humans.

An analysis of the cecum microbiome of three breeds of the guinea pig: Andina, Inti, and Peru

This study investigated the effect of host genetics on the structure and composition of the cecum microbiota of three breeds of guinea pigs: Andina, Inti, and Peru. Fifteen guinea pigs were distributed into three groups according to their breed: Andina (5), Inti (5), and Peru (5). We discovered that four main phyla were shared between the three breeds: Bacteroidota, Firmicutes, Spirochaetota, and Synergistota. Although there were no significant differences in the alpha and beta diversity analysis, we found that the Linear discriminant analysis effect size and the heat tree analysis showed significant differences between the abundance of several taxa present in the cecum microbiome of the three breeds. These results suggest that host genetics could be a factor in the structure and composition of the guinea pig cecum microbiome. In addition, we found unique genera for each breed that have fermentation capacity and, therefore can be analyzed in further studies to determine if there is a functional relationship between them and the breed and its industrial profile.

Lumpy, bumpy guinea pigs: a retrospective study of 619 biopsy samples of externally palpable masses submitted from pet guinea pigs for histopathology

Biopsy data on externally palpable masses in pet guinea pigs were retrieved from the archives of a large commercial pathology laboratory between November 2013 and July 2021. Of the 619 samples submitted from 493 animals, 54 (8.7%) had arisen from the mammary glands and 15 (2.4%) from the thyroid glands, with the remaining 550 (88.9%) involving the skin and subcutis, muscle (n = 1), salivary glands (n = 4), lips (n = 2), ears (n = 4) and peripheral lymph nodes (n = 23). Most of the samples were neoplastic, with 99 masses classified as epithelial in origin, 347 as mesenchymal, 23 as round cell, five as melanocytic and eight as unclassified malignant neoplasms. Lipomas were the most common neoplasm diagnosed, accounting for 286 of all samples submitted.

Atropine-eluting silicone contact lenses for myopia control

Myopia, also known as nearsightedness, is one of the prime reasons for vision impairment worldwide. Atropine in topical ophthalmic solutions (e.g., 0.01% atropine sulfate eye drops) is the primary medical treatment for controlling myopia, especially for pseudomyopia or true myopia in rapid progress. However, aqueous atropine solution is unstable and easily breaks down to tropic acid, which will result in vision blur. Drug-eluting contact lenses (CLs) have been explored as a potentially superior alternative to effectively control the drug release and improve the drug efficacy. In this work, an atropine-eluting contact lens was developed by encapsulating an atropine implant in a silicon-based contact lens, towards functioning in vision correction and controlling myopia. The safety and effectiveness of this atropine-eluting contact lens were verified with rabbit and guinea pig models. The results showed that the lenses reduced the side effects like mydriasis and no other adverse events were observed in rabbit eyes. More importantly, atropine-loaded lenses could effectively delay the progress of form-deprivation myopia with guinea pig eyes as the model. Thus, we concluded that atropine-eluting CLs prepared by implantation technology may be an option for the treatment of myopia.

Pharmacokinetics and Efficacy of the Benzothiazinone BTZ-043 against Tuberculous Mycobacteria inside Granulomas in the Guinea Pig Model

Tuberculosis (TB), caused by Mycobacterium tuberculosis, is the world's leading cause of mortality from a single bacterial pathogen. With increasing frequency, emergence of drug-resistant mycobacteria leads to failures of standard TB treatment regimens. Therefore, new anti-TB drugs are urgently required. BTZ-043 belongs to a novel class of nitrobenzothiazinones, which inhibit mycobacterial cell wall formation by covalent binding of an essential cysteine in the catalytic pocket of decaprenylphosphoryl-β-d-ribose oxidase (DprE1). Thus, the compound blocks the formation of decaprenylphosphoryl-β-d-arabinose, a precursor for the synthesis of arabinans. An excellent in vitro efficacy against M. tuberculosis has been demonstrated. Guinea pigs are an important small-animal model to study anti-TB drugs, as they are naturally susceptible to M. tuberculosis and develop human-like granulomas after infection. In the current study, dose-finding experiments were conducted to establish the appropriate oral dose of BTZ-043 for the guinea pig. Subsequently, it could be shown that the active compound was present at high concentrations in Mycobacterium bovis BCG-induced granulomas. To evaluate its therapeutic effect, guinea pigs were subcutaneously infected with virulent M. tuberculosis and treated with BTZ-043 for 4 weeks. BTZ-043-treated guinea pigs had reduced and less necrotic granulomas than vehicle-treated controls. In comparison to the vehicle controls a highly significant reduction of the bacterial burden was observed after BTZ-043 treatment at the site of infection and in the draining lymph node and spleen. Together, these findings indicate that BTZ-043 holds great promise as a new antimycobacterial drug.

Assessing Kidney Injury Induced by Mercuric Chloride in Guinea Pigs with In Vivo and In Vitro Experiments

Acute kidney injury, which is associated with high levels of morbidity and mortality, affects a significant number of individuals, and can be triggered by multiple factors, such as medications, exposure to toxic chemicals or other substances, disease, and trauma. Because the kidney is a critical organ, understanding and identifying early cellular or gene-level changes can provide a foundation for designing medical interventions. In our earlier work, we identified gene modules anchored to histopathology phenotypes associated with toxicant-induced liver and kidney injuries. Here, using in vivo and in vitro experiments, we assessed and validated these kidney injury-associated modules by analyzing gene expression data from the kidneys of male Hartley guinea pigs exposed to mercuric chloride. Using plasma creatinine levels and cell-viability assays as measures of the extent of renal dysfunction under in vivo and in vitro conditions, we performed an initial range-finding study to identify the appropriate doses and exposure times associated with mild and severe kidney injuries. We then monitored changes in kidney gene expression at the selected doses and time points post-toxicant exposure to characterize the mechanisms of kidney injury. Our injury module-based analysis revealed a dose-dependent activation of several phenotypic cellular processes associated with dilatation, necrosis, and fibrogenesis that were common across the experimental platforms and indicative of processes that initiate kidney damage. Furthermore, a comparison of activated injury modules between guinea pigs and rats indicated a strong correlation between the modules, highlighting their potential for cross-species translational studies.

Evaluation of the Interactions between Mumps Virus and Guinea Pig

Mumps is a highly contagious viral disease that can be prevented by vaccination. In the last decade, we have encountered repeated outbreaks of mumps in highly vaccinated populations, which call into question the effectiveness of available vaccines. Animal models are crucial for understanding virus-host interactions, and viruses such as mumps virus (MuV), whose only natural host is the human, pose a particular challenge. In our study, we examined the interaction between MuV and the guinea pig. Our results present the first evidence that guinea pigs of the Hartley strain can be infected in vivo after intranasal and intratesticular inoculation. We observed a significant viral replication in infected tissues up to 5 days following infection and induction of cellular and humoral immune responses as well as histopathological changes in infected lungs and testicles, without clinical signs of disease. Transmission of the infection through direct contact between animals was not possible. Our results demonstrate that guinea pigs and guinea pig primary cell cultures represent a promising model for immunological and pathogenetic studies of the complex MuV infection. IMPORTANCE Understanding of mumps virus (MuV) pathogenesis and the immune responses against MuV infection is limited. One of the reasons is the lack of relevant animal models. This study explores the interaction between MuV and the guinea pig. We demonstrated that all tested guinea pig tissue homogenates and primary cell cultures are highly susceptible to MuV infection and that α2,3-sialylated glycans (MuV cellular receptors) are being abundantly expressed at their surface. The virus remains in the guinea pig lungs and trachea for up to 4 days following intranasal infection. Although asymptomatic, MuV infection strongly activates both humoral and cellular immune response in infected animals and provides protection against virus challenge. Infection of the lungs and testicles after intranasal and intratesticular inoculation, respectively, is also supported by histopathological changes in these organs. Our findings give perspective for application of guinea pigs in research on MuV pathogenesis, antiviral response, and vaccine development and testing.

CT anatomy of the lungs, bronchi and trachea in the Mature Guinea pig (cavia porcellus)

BACKGROUND

Since there is no complete study of topographic features of thorax structures in guinea pigs, this study strives to define the exact topographic features of thorax structures.

OBJECTIVES

The aim of this study is to provide comprehensive topographic information about the location of the trachea, bronchi, lungs and heart inside the thoracic cavity in guinea pig, as well as to study the features of these structures, their proximity to other organs and comparative anatomical studies with CT scan images in living samples.

METHODS

Ten adult male and healthy guinea pigs were selected. CT scan transverse images were taken. The morphometric parameters of the lungs, bronchi, trachea, heart, thoracic cavity and abdominal cavity were measured.

RESULTS

In these studies, the position of organs such as the trachea, lungs and heart were monitored, and specified descriptions of CT scan images and anatomical observations were obtained. We realised that the heart in this animal was not inclined to the left, and due to the equal size of the lungs, the heart was almost on the midline. According to the measurements, 20.05% of the ventral cavity volume was thoracic cavity and 79.95% was abdominal cavity.

CONCLUSIONS

According to studies on guinea pigs, the right and left have the volume, and the heart is located between them on the midline without a tendency to the left. It seems that one of the reasons for the reluctance of the heart to the left and its placement on the midline in the guinea pig is that the volume of the two lungs is equal. In the case of guinea pigs, both numerical parameters are smaller than rabbits', but close to it. One of the most important factors in this study is that none of the animals were euthanised, and all of samples were alive after our study.

Effect of Parental Age, Parity, and Pairing Approach on Reproduction in Strain 13/N Guinea Pigs (Cavia porcellus)

Guinea pigs are important animal models for human disease, and both outbred and inbred lines are utilized in biomedical research. The optimal maintenance of guinea pig colonies, commercially and in research settings, relies on robust informed breeding programs, however, breeding data on specialized inbred strains are limited. Here, we investigated the effects of parental age, parity, and pairing approaches on mean total fetus count, percentage of female pups in the litter, and pup survival rate after 10 days in strain 13/N guinea pigs. Our analysis of colony breeding data indicates that the average litter size is 3.3 pups, with a 25.2% stillbirth rate, a failure-to-thrive outcome in 5.1% of pups, and a 10 day survival rate of 69.7%. The only variable to significantly affect the reproductive outcomes examined was parental age (p < 0.05). In comparison to adults, both juvenile and geriatric sows had lower total fetus counts; juvenile boars had a higher percentage of females in litters, and geriatric boars had a lower 10 day survival rate of pups. These studies provide valuable information regarding the reproductive characteristics of strain 13/N guinea pigs, and support a variety of breeding approaches without significant effects on breeding success.

The evaluation of the effect of tafluprost on the intraocular pressure of healthy male guinea pigs under different light-and-darkness regimes

BACKGROUND

Ocular hypertension is one of the most underdiagnosed ocular abnormalities among guinea pigs around the world.

OBJECTIVES

The current study investigates the effect of 0.0015% preservative-free tafluprost ophthalmic solution (Zioptan) on the intraocular pressure of 16 healthy male guinea pigs (Cavia porcellus) under different light/darkness regimes.

METHODS

All guinea pigs received a single drop of tafluprost at 5:30 in the right eye, whereas the contralateral eyes served as control to receive a placebo. Then, the animals were randomly divided into two groups; group A was exposed to light, whereas group B was placed in darkness from 5:30 to 18:00. Rebound tonometry (TonoVet) was instrumented to measure IOP values at 5:30 (baseline), 6:00, 7:00, 8:00, 9:00 and then every 3 h until 18:00.

RESULTS

The maximum IOP reduction associated with tafluprost was observed at 6:00 by -1.4 ± 1.1 mmHg (p-value = 0.026) and -2.5 ± 1.2 mmHg (p-value = 0.011) in group A and B, respectively (repeated measure ANOVA test). There was a significant difference between the mean right and left eye IOP values in both groups at 5:30, 6:00, 7:00 and 8:00 (p-value <0.05), which was greater in amount in group B compared to group A due to the effect of darkness on IOP reduction.

CONCLUSIONS

It is suggested that the variations of IOP in different light/dark conditions be taken into consideration when applying ocular hypotensive agents on guinea pigs' eyes.

What Is the Benefit of Ramped Pulse Shapes for Activating Auditory Cortex Neurons? An Electrophysiological Study in an Animal Model of Cochlear Implant

In all commercial cochlear implant (CI) devices, the activation of auditory nerve fibers is performed with rectangular pulses that have two phases of opposite polarity. Recently, several papers proposed that ramped pulse shapes could be an alternative shape for efficiently activating auditory nerve fibers. Here, we investigate whether ramped pulse shapes can activate auditory cortex (ACx) neurons in a more efficient way than the classical rectangular pulses. Guinea pigs were implanted with CI devices and responses of ACx neurons were tested with rectangular pulses and with four ramped pulse shapes, with a first-phase being either cathodic or anodic. The thresholds, i.e., the charge level necessary for obtaining significant cortical responses, were almost systematically lower with ramped pulses than with rectangular pulses. The maximal firing rate (FR) elicited by the ramped pulses was higher than with rectangular pulses. As the maximal FR occurred with lower charge levels, the dynamic range (between threshold and the maximal FR) was not modified. These effects were obtained with cathodic and anodic ramped pulses. By reducing the charge levels required to activate ACx neurons, the ramped pulse shapes should reduce charge consumption and should contribute to more battery-efficient CI devices in the future.

Evaluation of aglepristone and oxytocin on induction of parturition in guinea pig

BACKGROUND

Induction of parturition in guinea pigs appears to be essential because these animals have a higher rate of reproductive problems than rabbits and small rodents.

OBJECTIVES

Since aglepristone (AGL) is a competitive progesterone antagonist acting through binding to progesterone receptors while oxytocin (OT) is a powerful constituent of uterine smooth muscle, the aim of this study was to evaluate the clinical and ultrasonographic impacts of AGL and OT on guinea pig parturition induction.

METHODS

In this study, guinea pigs were allocated into five groups; each included five animals on the 61st day of pregnancy. In the aglepristone group (Agle), AGL was administrated subcutaneously (SC) once daily on 2 consecutive days (Days 61 and 62 post mating). Oxytocin (OT) was administered subcutaneously once and twice at 4-h intervals on Day 62 post mating in oxytocin 1 (Oxy1) and oxytocin 2 (Oxy2) groups, respectively. The animals in the aglepristone-oxytocin group (Agle-Oxy) received AGL subcutaneously once daily on 2 consecutive days (Days 61 and 62 post mating) and OT on Day 62 post mating. The remaining sows received saline solution (0.9% NaCl) in the control group.

RESULTS

According to the results, fetal heart rate, temperature, neonatal and maternal survival rates were not significantly different between the treatment and control groups (p > 0.05). Biparietal diameter of head and body weight of neonates in the Agle, Oxy2 and Agle-Oxy groups showed a significant decline, compared to the control group (p < 0.05). The time interval between injection and delivery and the duration of pregnancy was significantly reduced in Agle, Oxy2, Agl-Oxy groups, compared to the control and Oxy1 groups.

CONCLUSIONS

In conclusion, it seems that treatment Oxy2 can induce parturition in guinea pigs without side effects and lower pain during induction of parturition.

Microstructural changes of cartilage and subchondral bone in a guinea pig model of early- and middle-stage patellofemoral arthritis

OBJECTIVE

Patellofemoral arthritis is a common type of knee osteoarthritis and a prime cause of anterior knee pain and disability. Most of the existing research on knee osteoarthritis focuses on tibial-femoral arthritis, while studies on patellofemoral arthritis are relatively rare. This study aims to observe changes in osteochondral and subchondral bone structure over time in the patella and femoral trochlea in an animal model of spontaneous patellofemoral arthritis.

METHODS

A total of 24 1-, 3- or 5-month-old healthy female Hartley guinea pigs were used for experiments. No intervention was applied, and the mechanical pain threshold was assessed prior to euthanasia. Bilateral knee joints were collected in the animals at the different ages, and the patellofemoral joints were taken to evaluate the bone microstructure of patellofemoral articular cartilage and subchondral bone by macroscopy, histopathology and micro-computed tomography (micro-CT).

RESULTS

There was a significant difference in the severity of femoral trochlea injury assessed by the Macro score between 5- and 1-month-old groups (P<0.01), as well as in patellar cartilage damage (P<0.05). The mechanical pain threshold of lower extremities in each group was statistically different between different age groups (P<0.05). The OARSI articular cartilage histopathological scores, including patella and femoral trochlea, were significantly different among 1-, 3- and 5-month-old groups. The 5-month-old group exhibited statistically lower values of bone volume/trabecular volume, trabecular number and trabecular thickness in the femoral subchondral bone and evidently higher structure model index than the 1-month-old group.

CONCLUSIONS

This study demonstrated that 3- to 5-month-old female Hartley guinea pigs can develop early-to-mid-stage spontaneous patellofemoral arthritis that causes significant cartilage degeneration and loss of subchondral bone. In addition, the bone microarchitecture of the femur is more severely degraded.

Physical and chemical characterization of the femur during and after the body development period in male and female guinea pigs

In this study, it was aimed to reveal the physical and chemical characterization of the bone structures during body development periods (prepubertal period, period between adolescence and adulthood) and after (young adult period and old adult period) in male and female guinea pigs. In this study, 40 guinea pigs (20 male, 20 female) were used. Morphometric measurements, X-ray fluorescence (XRF) analysis for mineral levels, Brunauer-Emmett-Teller (BET) analysis for surface area, and porosity analysis were applied to the bones. The male guinea pigs had greater values than females in the other three categories, with the exception of the second group, when the females have higher values in morphometric measurements. Ca levels rose up to the third group, as did P levels in the males, peaking in the third group and declining in the fourth. As with phosphorus, there was a progressive rise in females from the first to the fourth group. Fe, Zn, and Sr elements had the greatest values in both genders in the first group. In all four groups, the females had greater Zn levels than males. The highest Ca/P ratio was found in the third male group and the fourth female group. This study revealed that adolescence, adulthood, and gender are effective in the physical and chemical characterization of bone structure in guinea pigs.

Characteristics of histamine H4 receptor agonist-induced allergic conjunctivitis model in Guinea pigs

Histamine is strongly associated with the onset of allergic conjunctivitis. The most recent cloned histamine H₄ receptor antagonist is highly expected as a new therapeutic drug candidate. As a model for a therapeutic drug targeting the histamine H₄ receptor, a mouse model in which conjunctivitis symptoms are induced by instilling 4-methylhistamine, a histamine H₄ receptor agonist, has been reported. However, the affinity of the H₄ receptor for histamine varies in species, and it is known that the histamine binding affinity for the guinea pig H₄ receptor is closer to that for human receptor than mice receptor. In this paper, we investigated a possibility that a guinea pig model would become a drug efficacy evaluation model with higher evaluation accuracy than the mouse model. As a result, hyperemia was observed in the conjunctivae and iris of guinea pigs after instillation of 4-methylhistamine and specifically suppressed by the histamine H₄ receptor antagonist. Unlikely to the previously reported mouse model, however, none of edema, increased vascular permeability or scratching behavior was observed, suggesting that there may be differences between mice and guinea pigs not only in the binding affinity of histamine to the H₄ receptor but also in the biological reaction to 4-methylhistamine. Although the symptoms of allergic conjunctivitis do not appear comprehensively in the guinea pig model, results of this study indicated a possibility that this model can be used as a simple screening model in the early stages of drug development.

Characterization of the Second Apoptosis Inhibitor Encoded by Guinea Pig Cytomegalovirus

Despite the usefulness of guinea pig cytomegalovirus (GPCMV) for studies on congenital CMV infection, its viral mechanisms for the evasion of host defense strategies have not been fully elucidated. We reported previously that GPCMV gp38.1 functions as a viral mitochondria-localized inhibitor of apoptosis-like function, and its weak activity suggested the presence of an additional inhibitory molecule(s). Here, we identified gp38.3-2, a 42-amino-acid (aa) reading frame embedded within the gp38.3 gene that encodes a positional homolog of murine CMV (MCMV) m41. Characterization of gp38.3-2 resulted in the following findings: (i) the aa sequence of gp38.3-2 shows some similarity to that of MCMV m41.1, a viral inhibitor of oligomerization of a member of Bcl-2 family protein BAK, but there is no correspondence in their predicted secondary structures; (ii) gp38.3-2, but not gp38.3, showed inhibitory activities against staurosporine-induced apoptosis; (iii) three-dimensional protein complex prediction suggests that the N-terminal α-helix of gp38.3-2 interacts with residues in the BH3 and BH1 motifs of BAK, and analysis of gp38.3-2 and BAK mutants supported this model; (iv) guinea pig fibroblast cells infected with gp38.3-2-deficient GPCMV strain Δ38.3-2 died earlier than cells infected with rescued strain r38.3-2, resulting in lower yields of Δ38.3-2; (v) Δ38.3-2 exhibited a partial but significant decrease in monocyte and macrophage infection in comparison with r38.3-2; and, however, (vi) little difference in the viral infection of guinea pigs was observed between these two strains. Therefore, we hypothesize that gp38.3-2 contributes little to the evasion of host defense mechanisms under the experimental conditions used. IMPORTANCE Although GPCMV provides a useful animal model for studies on the pathogenesis of congenital CMV infection and the development of CMV vaccine strategies, our understanding of the viral mechanisms by which it evades apoptosis of infected cells has been limited in comparison with those of murine and human CMVs. Here, we report a second GPCMV apoptosis inhibitor (42 amino acids in length) that interacts with BAK, a Bcl-2 family proapoptotic protein. Three-dimensional structural prediction indicated a unique BAK recognition by gp38.3-2 via the BH3 and BH1 motif sequences. Our findings suggest the potential development of BH3 mimetics that can regulate inhibition or induction of apoptosis based on short ~40-amino-acid peptide molecules as with GPCMV.

Role of Guinea Pigs (Cavia porcellus) Raised as Livestock in Ecuadorian Andes as Reservoirs of Zoonotic Yeasts

Guinea pigs (Cavia porcellus) have been reared for centuries in the Andean region for ceremonial purposes or as the main ingredient of traditional foods. The animals are kept in close proximity of households and interact closely with humans; this also occurs in western countries, where guinea pigs are considered pets. Even though it is acknowledged that domestic animals carry pathogenic yeasts in their tissues and organs that can cause human diseases, almost nothing is known in the case of guinea pigs. In this work we used traditional microbiological approaches and molecular biology techniques to isolate, identify, and characterize potentially zoonotic yeasts colonizing the nasal duct of guinea pigs raised as livestock in Southern Ecuador (Cañar Province). Our results show that 44% of the 100 animals studied were colonized in their nasal mucosa by at least eleven yeast species, belonging to eight genera: Wickerhamomyces, Diutina, Meyerozyma, Candida, Pichia, Rhodotorula, Galactomyces, and Cryptococcus. Noticeably, several isolates were insensitive toward several antifungal drugs of therapeutic use, including fluconazole, voriconazole, itraconazole, and caspofungin. Together, our results emphasize the threat posed by these potentially zoonotic yeasts to the farmers, their families, the final consumers, and, in general, to public and animal health.

Human Adipose- and Amnion-Derived Mesenchymal Stromal Cells Similarly Mitigate Osteoarthritis Progression in the Dunkin Hartley Guinea Pig

BACKGROUND

Clinical trials are currently underway to investigate the efficacy of intra-articular administration of mesenchymal stromal cells (MSCs) to mitigate osteoarthritis (OA) progression in the knee. Although multiple MSC sources exist, studies have yet to determine whether differences in therapeutic efficacy exist between them.

PURPOSE

To compare the ability of intra-articularly injected adipose-derived MSCs (AD-MSCs) and amnion-derived MSCs (AM-MSCs) to mitigate the progression of knee OA in a small animal model of spontaneous OA, as well as to compare the therapeutic potential of MSCs in hyaluronic acid (HA) and in HA only with saline (OA) controls.

STUDY DESIGN

Controlled laboratory study.

METHODS

Injections of AD-MSCs or AM-MSCs suspended in HA or HA only were performed in the rear stifle joints of 3-month-old Dunkin Hartley guinea pigs (DHGPs). Repeat injections occurred at 2 and 4 months after the initial injection in each animal. Contralateral limbs received saline injections and served as untreated controls. Subsequently, joints were analyzed for osteoarthritic changes of the cartilage and subchondral bone via histologic and biochemical analyses. To evaluate MSC retention time in the joint space, DHGPs received a single intra-articular injection of fluorescently labeled AD-MSCs or AM-MSCs, and the fluorescence intensity was longitudinally tracked via an in vivo imaging system.

RESULTS

No statistically significant differences in outcomes were found when comparing the ability of AD-MSCs and AM-MSCs to mitigate OA. However, the injection of AD-MSCs, AM-MSCs, and HA-only treatments more effectively mitigated cartilage damage compared with that of saline controls by demonstrating higher amounts of cartilage glycosaminoglycan content and improved histological proteoglycan scoring while reducing the percentage of osteophytes present.

CONCLUSION

Intra-articular injection of AD-MSCs, AM-MSCs, or HA only was able to similarly mitigate the progression of cartilage damage and reduce the percentage of osteophytes compared with that of saline controls in the DHGP. However, this study was unable to establish the superiority of AD-MSCs versus AM-MSCs as a treatment to mitigate spontaneous OA.

CLINICAL RELEVANCE

MSCs demonstrate the ability to mitigate the progression of knee OA and thus may be used in a prophylactic approach to delay the need for end-stage treatment strategies.

Anesthetized guinea pig as a model for drug testing

Based on the World Health Organization statistics, cardiovascular diseases represent the major cause of death worldwide. Although a wide range of treatment approaches and pharmaceuticals is available, the therapy is often not effective enough and therefore health risks for the patient persist. Thus, it is still essential to test new drug candidates for the treatment of various pathophysiological conditions related to cardiovascular system. In vivo models represent indispensable part of preclinical testing of such substances. Anesthetized guinea pig as a whole-body model allows to evaluate complex reactions of cardiovascular system to tested substance. Moreover, action potential of guinea pig cardiomyocyte is quite comparable to that of human. Hence, the results from this model are then quite well translatable to clinical medicine. Aim of this paper was to summarize the methodology of this model, including its advantages and/or limitations and risks, based on the effects of two substances with adrenergic activity on the ECG parameters. The model of anesthetized guinea pig proved to be valuable and suitable for testing of drugs with cardiovascular effects.

Characterization of Coxiella burnetii Dugway Strain Host-Pathogen Interactions In Vivo

Coxiella burnetii is a Gram-negative, intracellular bacterium that causes the zoonosis Q fever. Among the many natural isolates of C. burnetii recovered from various sources, the Dugway group exhibits unique genetic characteristics, including the largest C. burnetii genomes. These strains were isolated during 1954-1958 from wild rodents from the Utah, USA desert. Despite retaining phase I lipopolysaccharide and the type 4B secretion system, two critical virulence factors, avirulence has been reported in a guinea pig infection model. Using guinea pig models, we evaluated the virulence, whole-cell vaccine (WCV) efficacy, and post-vaccination hypersensitivity (PVH) potential of a representative Dugway strain. Consistent with prior reports, Dugway appeared to be highly attenuated compared to a virulent strain. Indeed, Dugway-infected animals showed similarly low levels of fever, body weight loss, and splenomegaly like Nine Mile II-infected animals. When compared to a human Q fever vaccine, QVax®, Dugway WCV exhibited analogous protection against a heterologous Nine Mile I challenge. PVH was investigated in a skin-testing model which revealed significantly decreased maximum erythema in Dugway Δdot/icm WCV-skin-tested animals compared to that of QVax®. These data provide insight into this unique bacterial strain and implicate its potential use as a mutated WCV candidate.