Juvenile Guinea Pigs Research Articles

A Guinea Pig Model of Pediatric Metabolic Dysfunction-Associated Steatohepatitis: Poor Vitamin C Status May Advance Disease.

Background/Objectives: Children and teenagers display a distinct metabolic dysfunction-associated steatohepatitis (MASH) phenotype, yet studies of childhood MASH are scarce and validated animal models lacking, limiting the development of treatments. Poor vitamin C (VitC) status may affect MASH progression and often co-occurs with high-fat diets and related metabolic imbalances. As a regulator of DNA methylation, poor VitC status may further contribute to MASH by regulating gene expression This study investigated guinea pigs-a species that, like humans, depends on vitC in the diet-as a model of pediatric MASH, examining the effects of poor VitC status on MASH hallmarks and global DNA methylation levels. Methods: Sixty-two juvenile guinea pigs were exposed to a high-fat diet for 16 weeks. Results: Juvenile guinea pigs exhibited hepatic histopathology representative of pediatric MASH, confirmed by portal inflammation and fibrosis. Consistent with pediatric MASH, juvenile guinea pigs displayed increased lobular and portal inflammation (p < 0.05 and p < 0.0001, respectively) but less steatosis (p < 0.001) compared to adults. Compared to the controls, the guinea pigs deprived in VitC showed lower body weight (p < 0.01), higher expression of hepatic inflammatory genes (p < 0.05), and a lower global hydroxymethylcytosine to methylcytosine ratio in the high-fat groups (p < 0.05). Conclusions: Our study validates guinea pigs as a model of pediatric MASH and suggests that VitC contributes to an altered gene expression signature through the regulation of DNA hydroxymethylation. We postulate that nutritional co-deficiencies in MASH, such as low VitC, may accelerate disease progression and deserve further attention.

Effects of Different Light Environments with Varying Spectral Composition on the Axial Lengths and Scleral Specificity Protein 1 and Collagen Type I Expression in Juvenile Guinea Pigs.

The study aimed to investigate changes in the eye axial length in juvenile guinea pigs and the expression of scleral specificity protein 1 (Sp1) and collagen type I (Col-I) under different light environments with varying spectral composition. The animals were randomly divided into five groups: natural light (N), LED light with a low colour temperature (L), E light (E), Fulia light (F), and Gulia light (G). Axial lengths were measured every two weeks, and the expression of Sp1 and Col-I in the sclera was assessed by immunohistochemistry, Western blot and RT-qPCR. After 4, 6, 8, 10, and 12 weeks of light exposure, the L and G groups showed considerably longer axial lengths than the N group, with the L group exhibiting significantly longer axial lengths compared with the E and F groups. The protein and mRNA expression levels of Sp1 and Col-I, ranked from highest to lowest, were as follows: N, E, F, G, and L. The expression of Sp1 and Col-I was positively correlated, but both were negatively correlated with the length of the eye axis. The E group demonstrated higher Sp1 and Col-I expression than the other artificial light groups. Artificial light with a continuous, full spectrum lacking peaks and valleys can inhibit the elongation of the eye axis in juvenile guinea pigs and has a protective effect against myopia. There may be a certain relationship between Sp1 and Col-I, and the transforming growth factor-β1-Sp1-Col-I signalling pathway may play a crucial role in myopic scleral extracellular matrix remodelling.

Efficacy and Safety Evaluation of Scleral Cross-Linking Using Genipin in the Treatment of Juvenile Guinea Pigs with High Myopia.

Purpose: To investigate the efficacy and safety of scleral cross-linking (CXL) using Genipin in the treatment of juvenile guinea pigs with high myopia. Methods: Twenty-four 4-week-old tricolor guinea pigs with high myopia of diopter ≤ -6.0 DS in the right eye were randomly divided into two groups: Genipin CXL group and control group (n = 12 for each group). They received separately form-deprivation (FD) combined with sub-tenon injection, and the former was 0.5% Genipin solution, while the latter was 0.9% saline solution. Refractive error, axial length (AL), intraocular pressure (IOP), and structural and vasculature optic disc changes in optical coherence tomography (OCT) and OCT angiography (OCTA) were analyzed at baseline and at 3 weeks after injection. Results: Baseline parameters were similar between the two groups (P > 0.05). After 3 weeks of the intervention, the difference of AL between the two groups was statistically significant (t = -11.28, P < 0.001). Besides, IOP increased in both groups, and the changes of IOP between the two groups were statistically significant (t = 2.80, P = 0.01). The average cup-disc ratio (C/D) (t = 3.11, P = 0.006) and the vertical C/D (t = 2.96, P = 0.009) of OCT-related optic disc parameters in the Genipin CXL group increased, and the differences were statistically significant compared with the control group. Conclusion: The CXL method of sub-tenon injection of Genipin solution could effectively inhibit the progression of myopia in juvenile guinea pigs with highly myopic eyes combined with FD. The slightly elevated IOP and increased C/D of some fundus optic discs should be further assessed.

Effects of artificial light with different spectral composition on eye axial growth in juvenile guinea pigs.

The purpose of the study was to investigate the effect of artificial light with different spectral composition and distribution on axial growth in guinea pigs. Three-week-old guinea pigs were randomly assigned to groupsexposed to natural light, low color temperature light-emitting diode (LED) light, two full spectrum artificial lights (E light and Julia light) and blue light filtered light with the same intensity. Axial lengths of guinea pigs'eyes were measured by A-scan ultrasonography prior to the experiment and every 2 weeks during the experiment. After light exposure for 12 weeks, retinal dopamine (DA), dihydroxy-phenylacetic acid (DOPAC) levelsand DOPAC/DA ratio were analyzed by high-pressure liquid chromatography electrochemical detection and retinal histological structure was observed. Retinal melanopsin expression was detected using Western blot andimmunohistochemistry. After exposed to different kinds of light with different spectrum for 4 weeks, the axial lengths of guinea pigs' eyes in LED group and Julia light group were significantly longer than those of naturallight group. After 6 weeks, the axial lengths in LED light group were significantly longer than those of E light group and blue light filtered group. The difference between axial lengths in E light group and Julia light groupshowed statistical significance after 8 weeks (p<0.05). After 12 weeks of light exposure, the comparison of retinal DOPAC/DA ratio and melanopsin expression in each group was consistent with that of axial length. Inguinea pigs, continuous full spectrum artificial light with no peak or valley can inhibit axial elongation via retinal dopaminergic and melanopsin system.

Examining Neurosteroid-Analogue Therapy in the Preterm Neonate For Promoting Hippocampal Neurodevelopment.

Background: Preterm birth can lead to brain injury and currently there are no targeted therapies to promote postnatal brain development and protect these vulnerable neonates. We have previously shown that the neurosteroid-analogue ganaxolone promotes white matter development and improves behavioural outcomes in male juvenile guinea pigs born preterm. Adverse side effects in this previous study necessitated this current follow-up dosing study, where a focus was placed upon physical wellbeing during the treatment administration and markers of neurodevelopment at the completion of the treatment period. Methods: Time-mated guinea pigs delivered preterm (d62) by induction of labour or spontaneously at term (d69). Preterm pups were randomized to receive no treatment (Prem-CON) or ganaxolone at one of three doses [0.5 mg/kg ganaxolone (low dose; LOW-GNX), 1.0 mg/kg ganaxolone (mid dose; MID-GNX), or 2.5 mg/kg ganaxolone (high dose; HIGH-GNX) in vehicle (45% β-cyclodextrin)] daily until term equivalence age. Physical parameters including weight gain, ponderal index, supplemental feeding, and wellbeing (a score based on respiration, activity, and posture) were recorded throughout the preterm period. At term equivalence, brain tissue was collected, and analysis of hippocampal neurodevelopment was undertaken by immunohistochemistry and RT-PCR. Results: Low and mid dose ganaxolone had some impacts on early weight gain, supplemental feeding, and wellbeing, whereas high dose ganaxolone significantly affected all physical parameters for multiple days during the postnatal period when compared to the preterm control neonates. Deficits in the preterm hippocampus were identified using neurodevelopmental markers including mRNA expression of oligodendrocyte lineage cells (CSPG4, MBP), neuronal growth (INA, VEGFA), and the GABAergic/glutamatergic system (SLC32A1, SLC1A2, GRIN1, GRIN2C, DLG4). These deficits were not affected by ganaxolone at the doses used at the equivalent of normal term. Conclusion: This is the first study to investigate the effects of a range of doses of ganaxolone to improve preterm brain development. We found that of the three doses, only the highest dose of ganaxolone (2.5 mg/kg) impaired key indicators of physical health and wellbeing over extended periods of time. Whilst it may be too early to see improvements in markers of neurodevelopment, further long-term study utilising the lower doses are warranted to assess functional outcomes at ages when preterm birth associated behavioural disorders are observed.

Fetal glucocorticoid exposure leads to sex‐specific changes in drug‐transporter function at the blood‐brain barrier in juvenile guinea pigs

Antenatal synthetic glucocorticoids (sGCs) are a life‐saving treatment in managing pre‐term birth. However, off‐target effects of sGCs can impact blood‐brain barrier (BBB) drug transporters essential for fetal brain protection, including P‐glycoprotein (P‐gp/Abcb1) and breast cancer resistance protein (BCRP/Abcg2). We hypothesized that maternal antenatal sGC treatment modifies BBB function in juvenile offspring in a sex‐dependent manner. Thus, the objective of this study was to determine the long‐term impact of a single or multiple courses of betamethasone on P‐gp/Abcb1 and BCRP/Abcg2 expression and function at the BBB. Pregnant guinea pigs (N = 42) received 3 courses (gestation days (GDs) 40, 50, and 60) or a single course (GD50) of betamethasone (1 mg/kg) or vehicle (saline). Cerebral microvessels and brain endothelial cells (BEC) were collected from the post‐natal day (PND) 14 offspring to measure protein, gene expression, and function of the drug transporters P‐gp/Abcb1 and BCRP/Abcg2. P‐gp protein expression was decreased (p < .05) in microvessels from male offspring that had been exposed to multiple courses and a single course of sGC, in utero. Multiple courses of sGC resulted in a significant decrease in P‐gp function in BECs from males (p < .05), but not females. There was a very strong trend for increased P‐gp function in males compared to females (p = .055). Reduced P‐gp expression and function at the BBB of young male offspring following multiple prenatal sGC exposures, is clinically relevant as many drugs administered postnatally are P‐gp substrates. These novel sex differences in drug transporter function may underlie potential sexual dimorphism in drug sensitivity and toxicity in the newborn and juvenile brain.

Differential effects of four intramuscular sedatives on cardiorespiratory stability in juvenile guinea pigs (Cavia porcellus).

BackgroundNon-invasive physiological monitoring can induce stress in laboratory animals. Sedation reduces the level of restraint required, thereby improving the validity of physiological signals measured. However, sedatives may alter physiological equilibrium introducing unintended bias and/or, masking the experimental outcomes of interest. We aimed to investigate the cardiorespiratory effects of four short-acting sedatives in juvenile guinea pigs.Method12 healthy, 38 (26–46) day-old Dunkin Hartley guinea pigs were included in this blinded, randomised, crossover design study. Animals were sedated by intramuscular injection using pre-established minimum effective doses of either alfaxalone (5 mg/kg), diazepam (5 mg/kg), ketamine (30 mg/kg), or midazolam (2 mg/kg) administered in random order with a minimum washout period of 48 hours between agents. Sedative depth, a composite score comprised of five assessment criteria, was observed every 5-min from dosing until arousal. Physiological monitoring of cardiorespiratory status included measures of heart rate, blood pressure, respiratory rate, and peripheral microvascular perfusion.ResultsKetamine and alfaxalone were most effective in inducing stable sedation suitable for physiological monitoring, and diazepam less-so. Midazolam was unsuitable due to excessive hypersensitivity. All sedatives significantly increased heart rate above non-sedated control rates (P<0.0001), without altering blood pressure or microvascular perfusion. Alfaxalone and ketamine reduced respiratory rate relative to their control condition (P<0.0001, P = 0.05, respectively), but within normative ranges.ConclusionKetamine and alfaxalone are the most effective sedatives for inducing short duration, stable sedation with minimal cardiorespiratory depression in guinea pigs, while diazepam is less-so. However, alfaxalone is the most appropriate sedative for longitudinal studies requiring multiple physiological timepoints.

Nitrous oxide improves cardiovascular, respiratory, and thermal stability during prolonged isoflurane anesthesia in juvenile guinea pigs.

Anesthesia is frequently used to facilitate physiological monitoring during interventional animal studies. However, its use may induce cardiovascular (central and peripheral), respiratory, and thermoregulatory depression, confounding results in anesthetized animals. Despite the wide utility of guinea pigs as a translational platform, anesthetic protocols remain unstandardized for extended physiological studies in this species. Therefore, optimizing an anesthetic protocol that balances stable anesthesia with intact cardiorespiratory and metabolic function is crucial. To achieve this, 12 age and sex‐matched juvenile Dunkin Hartley guinea pigs underwent extended anesthesia (≤150 min) with either (a) isoflurane (ISO: 1.5%), or (b) isoflurane + N2O (ISO+ N2O: 0.8% +70%), in this randomized cross‐over designed study. Cardiovascular (HR, SBP, peripheral microvascular blood flow), respiratory (respiratory rate, SpO2), and thermal (Tre and Tsk) measures were recorded continuously throughout anesthesia. Blood gas measures pre‐ and post‐ anesthesia were performed. Incorporation of 70% N2O allowed for significant reductions in isoflurane (to 0.8%) while maintaining an effective anesthetic depth for prolonged noninvasive physiological examination in guinea pigs. ISO+N2O maintained heart rate, peripheral blood flow, respiratory rate, and thermoregulatory function at levels closest to those of conscious animals, especially in females; however, it did not fully rescue anesthesia‐induced hypotension. These results suggest that for studies requiring prolonged physiological examination (≤150 min) in guinea pigs, 0.8% isoflurane with a 70% N2O adjuvant provides adequate anesthesia, while minimizing associated cardiorespiratory depression. The preservation of cardiorespiratory status is most marked throughout the first hour of anesthesia.

Prenatal Glucocorticoid Exposure Results in Changes in Gene Transcription and DNA Methylation in the Female Juvenile Guinea Pig Hippocampus Across Three Generations

Synthetic glucocorticoids (sGC) are administered to women at risk for pre-term delivery, to mature the fetal lung and decrease neonatal morbidity. sGC also profoundly affect the fetal brain. The hippocampus expresses high levels of glucocorticoid (GR) and mineralocorticoid receptor (MR), and its development is affected by elevated fetal glucocorticoid levels. Antenatal sGC results in neuroendocrine and behavioral changes that persist in three generations of female guinea pig offspring of the paternal lineage. We hypothesized that antenatal sGC results in transgenerational changes in gene expression that correlate with changes in DNA methylation. We used RNASeq and capture probe bisulfite sequencing to investigate the transcriptomic and epigenomic effects of antenatal sGC exposure in the hippocampus of three generations of juvenile female offspring from the paternal lineage. Antenatal sGC exposure (F0 pregnancy) resulted in generation-specific changes in hippocampal gene transcription and DNA methylation. Significant changes in individual CpG methylation occurred in RNApol II binding regions of small non-coding RNA (snRNA) genes, which implicates alternative splicing as a mechanism involved in transgenerational transmission of the effects of antenatal sGC. This study provides novel perspectives on the mechanisms involved in transgenerational transmission and highlights the importance of human studies to determine the longer-term effects of antenatal sGC on hippocampal-related function.

Effects of the long wavelength-filtered continuous spectrum on natural refractive development in juvenile guinea pigs.

To investigate the effects of spectral composition and light intensity on natural refractive development in guinea pigs. A total of 124 pigmented guinea pigs (2-week-old) were randomly assigned to three groups at high (Hi; 4000 lx), medium (Me; 400 lx) and low (Lo; 50 lx) light intensities under a 12:12 light/dark cycle for 6wk. Each group was subdivided into subgroups with the following spectra: broad spectrum Solux halogen light (BS), 600 nm above-filtered continuous spectrum (600F), 530 nm above-filtered continuous spectrum (530F), and 480 nm above-filtered continuous spectrum (480F; HiBS: n=10, Hi600F: n=10, Hi530F: n=10, Hi480F: n=10, MeBS: n=10, Me600F: n=10, Me530F: n=10, Me480F: n=10, LoBS: n=11, Lo600F: n=12, Lo530F: n=10, Lo480F: n=11). Refractive error, corneal curvature radius, and axial dimensions were determined by cycloplegic retinoscopy, photokeratometry, and A-scan ultrasonography before and after 2, 4, and 6wk of treatment. Average changes from both eyes in the ocular parameters and refractive error were compared among different subgroups. After 6wk of exposure, high-intensity lighting enhanced hyperopic shift; medium- and low-intensity lighting enhanced myopic shift (P<0.05). Under the same spectrum, axial increase was larger in the low light intensity group than in the medium and high light intensity groups (HiBS: 0.65±0.02 mm, MeBS: 0.67±0.01 mm, LoBS: 0.82±0.02 mm; Hi600F: 0.64±0.02 mm, Me600F: 0.67±0.01 mm, Lo600F: 0.81±0.01 mm; Hi530F: 0.64±0.02 mm, Me530F: 0.67±0.01 mm, Lo530F: 0.73±0.02 mm; Hi480F: 0.64±0.01 mm, Me480F: 0.66±0.01 mm, Lo480F: 0.72±0.02 mm; P<0.05). Under 400 lx, there was a faster axial increase in the MeBS group than in the Me480F group (P<0.05). Under 50 lx, axial length changes were significantly larger in LoBS and Lo600F than in Lo530F and Lo480F (P<0.01). Under high-intensity lighting, high light intensity rather than spectrum distributions that inhibits axial increase. Under medium- and low-intensity lighting, filtering out the long wavelength inhibits axial growth in juvenile guinea pigs.

Disruptions to the cerebellar GABAergic system in juvenile guinea pigs following preterm birth

BackgroundChildren that are born preterm are at an increased risk of developing cognitive problems and behavioural disorders, such as attention deficit hyperactivity disorder (ADHD). There is increasing interest in the role of the cerebellum in these processes and the potential involvement of GABAergic pathways in neurodevelopmental disorders. We propose that preterm birth, and the associated loss of the trophic intrauterine environment, alters the development of the cerebellum, contributing to ongoing neurobehavioral disorders. MethodsGuinea pigs were delivered preterm (GA62) or spontaneously at term (GA69), and tissues collected at corrected postnatal day (PND) 28. Neurodevelopmental and GABAergic markers myelin basic protein (MBP), neuronal nuclei (NeuN), calbindin (Purkinje cells), and GAD67 (GABA synthesis enzyme) were analysed in cerebellar lobules IX and X by immunohistochemistry. Protein expression of GAD67 and GAT1 (GABA transporter enzyme) were quantified by western blot, whilst neurosteroid-sensitive GABAA receptor subunits were measured by RT-PCR. ResultsMBP immunostaining was increased in lobule IX of preterm males, and reduced in lobule X of preterm females when compared to their term counterparts. GAD67 staining was decreased in lobule IX and X of the preterm males, but only in lobule X of the preterm females compared to term cohorts for each sex. Internal granule cell layer width of lobule X was decreased in preterm cohorts of both sexes compared to terms. There were no differences between gestational age groups for NeuN staining, GAD67 and GAT1 protein expression as measured by western blotting, or GABAA receptor subunits as measured by RT-PCR between preterm and term for either sex. ConclusionsThe present findings suggest that components of the cerebellar GABAergic system of the ex-preterm cerebellum are disrupted. The higher expression of myelin in the preterm males may be due to a deficit in axonal pruning, whereas females have a deficit in myelination at 28 corrected days of age. Together these ongoing alterations may contribute to the neurodevelopmental and behavioural disorders observed in those born preterm.

Long-term effects of preterm birth on behavior and neurosteroid sensitivity in the guinea pig.

Ex-preterm children and adolescents are at risk of developing late-onset neurodevelopmental and behavioral disorders. The mechanisms by which this happens are poorly understood and relevant animal models are required. Ex-preterm (delivered at 62 d gestation) and term (spontaneously delivered) juvenile guinea pigs underwent behavioral testing at 25 d corrected postnatal age, with tissues collected at 28 d. Neurodevelopmental markers (myelin basic protein (MBP) and glial fibrillary acidic protein (GFAP)) were analyzed in the hippocampus and subcortical white matter by immunohistochemistry. Gamma-aminobutyric acid A (GABAA) receptor subunit mRNA levels were quantified by reverse transcription polymerase chain reaction (RT-PCR), and salivary cortisol measured by enzyme-linked immunosorbent assay. Preterm males travelled greater distances, were mobile for longer, spent more time investigating objects, and approached or interacted with familiar animals more than controls. Myelination and reactive astrocyte coverage was lower in the hippocampus and the subcortical white matter in preterm males. Hippocampal levels of the α5 subunit were also lower in the preterm male brain. Baseline salivary cortisol was higher for preterm males compared to controls. We conclude that juvenile ex-preterm male guinea pigs exhibit a hyperactive phenotype and feature impaired neurodevelopment, making this a suitable model for future therapeutic studies.

Effects of Artificial Ultraviolet Radiation on Serum 25-Hydroxyvitamin D3 Concentrations in Captive Guinea Pigs (Cavia Porcellus)

Under natural conditions, guinea pigs (Cavia porcellus) are exposed to ultraviolet B (UVB) radiation. Although the role of UVB radiation in the photobiochemical synthesis of vitamin D is well documented in humans and other vertebrates, to date it has not been evaluated in guinea pigs. The purpose of this study was to determine whether artificial UVB radiation has an effect on serum 25-hydroxyvitamin D3 levels in guinea pigs. A total of 12 juvenile guinea pigs were randomly assigned to 1 of 2 treatment groups: Group A was exposed to 12 hours of artificial UVB radiation (290 to 315nm) daily and Group B received ambient fluorescent light with no UVB supplementation for 12 hours/day. Blood samples were collected under anesthesia on days 0 and 18 to measure serum 25-hydroxyvitamin D3 levels. Animals in both groups were offered the same diet. There was a significant difference in 25-hydroxyvitamin D3 concentrations over time (F = 399.3, P = 0.0001) and by group (F = 63.6, P = 0.0001), with an average increase between sampling periods of 56.5nmol/L in Group A (UVB) and 2.33nmol/L in Group B (no UVB). This study represents the first attempt to measure the effect of UVB radiation on 25-hydroxyvitamin D3 levels in guinea pigs. In vertebrates, vitamin D is an essential hormone that regulates many physiologic functions within the body. These preliminary findings confirm that guinea pigs can obtain vitamin D via photobiochemical synthesis, but additional work is needed to determine the physiologic importance of this finding and potential risks associated with UVB exposure in these rodents.

Diagnostic Challenge

Under natural conditions, guinea pigs (Cavia porcellus) are exposed to ultraviolet B (UVB) radiation. Although the role of UVB radiation in the photobiochemical synthesis of vitamin D is well documented in humans and other vertebrates, to date it has not been evaluated in guinea pigs. The purpose of this study was to determine whether artificial UVB radiation has an effect on serum 25-hydroxyvitamin D3 levels in guinea pigs. A total of 12 juvenile guinea pigs were randomly assigned to 1 of 2 treatment groups: Group A was exposed to 12 hours of artificial UVB radiation (290 to 315 nm) daily and Group B received ambient fluorescent light with no UVB supplementation for 12 hours/day. Blood samples were collected under anesthesia on days 0 and 18 to measure serum 25-hydroxyvitamin D3 levels. Animals in both groups were offered the same diet. There was a significant difference in 25-hydroxyvitamin D3 concentrations over time (F = 399.3, P = 0.0001) and by group (F = 63.6, P = 0.0001), with an average increase between sampling periods of 56.5 nmol/L in Group A (UVB) and 2.33 nmol/L in Group B (no UVB). This study represents the first attempt to measure the effect of UVB radiation on 25-hydroxyvitamin D3 levels in guinea pigs. In vertebrates, vitamin D is an essential hormone that regulates many physiologic functions within the body. These preliminary findings confirm that guinea pigs can obtain vitamin D via photobiochemical synthesis, but additional work is needed to determine the physiologic importance of this finding and potential risks associated with UVB exposure in these rodents.

Quiescent neuronal progenitors are activated in the juvenile guinea pig lateral striatum and give rise to transient neurons.

In the adult brain, active stem cells are a subset of astrocytes residing in the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampus. Whether quiescent neuronal progenitors occur in other brain regions is unclear. Here, we describe a novel neurogenic system in the external capsule and lateral striatum (EC-LS) of the juvenile guinea pig that is quiescent at birth but becomes active around weaning. Activation of neurogenesis in this region was accompanied by the emergence of a neurogenic-like niche in the ventral EC characterized by chains of neuroblasts, intermediate-like progenitors and glial cells expressing markers of immature astrocytes. Like neurogenic astrocytes of the SVZ and DG, these latter cells showed a slow rate of proliferation and retained BrdU labeling for up to 65 days, suggesting that they are the primary progenitors of the EC-LS neurogenic system. Injections of GFP-tagged lentiviral vectors into the SVZ and the EC-LS of newborn animals confirmed that new LS neuroblasts originate from the activation of local progenitors and further supported their astroglial nature. Newborn EC-LS neurons existed transiently and did not contribute to neuronal addition or replacement. Nevertheless, they expressed Sp8 and showed strong tropism for white matter tracts, wherein they acquired complex morphologies. For these reasons, we propose that EC-LS neuroblasts represent a novel striatal cell type, possibly related to those populations of transient interneurons that regulate the development of fiber tracts during embryonic life.

Effects of the Cycloplegic, Cyclopentolate, on Measurements of Refraction in Eyes of a Strain of Wild-Type Juvenile Guinea Pig (Cavia porcellus): A Comparative Study

Objective: To investigate the effect(s) of the cycloplegic, cyclopentolate, on measurements of refraction in eyes of a strain of wild-type guinea pig.Methods: Both eyes of 13 wild-type juvenile guinea pigs (n = 26 eyes) were examined both pre- and post-mydriasis, using streak retinoscopy (SR) and eccentric infrared photoretinoscopy (EIP). On the day of measurement, three SR measurements were taken for each eye at 0900, 1000, 1100, 1400, 1500 and 1600, and three EIP measurements for each eye at 0930, 1030, 1130, 1430, 1530 and 1630. Cyclopentolate hydrochloride (1%) was topically administered three times to each eye at 5-min intervals: 1300, 1305 and 1310.Results: Repeated measurements made by either method revealed that mydriasis did not significantly affect refractive stability (repeated measures, p > 0.05). Depending on the stage of mydriasis, however, there were significant differences in measured refractive changes both SR and EIP (0.27 ± 0.65 D, tSR = −2.095, PSR = 0.04 and 0.73 ± 1.06 D, tEIP = −3.494, PEIP = 0.002, respectively) measurements.Conclusions: Cyclopentolate had only limited effects on measurements of refraction, indicating that direct SR or EIP measurements of refraction in this wild-type strain of juvenile guinea pig, without the use of a cycloplegic, yield reliable and stable results.

Significant shift in median guinea pig infectious dose shown by an outbreak-associated Listeria monocytogenes epidemic clone strain and a strain carrying a premature stop codon mutation in inlA.

Listeria monocytogenes contains (i) epidemic clone (EC) strains, which have been linked to the majority of listeriosis outbreaks worldwide and are overrepresented among sporadic cases in the United States, and (ii) strains commonly isolated from ready-to-eat foods that carry a mutation leading to a premature stop codon (PMSC) in inlA, which encodes the key virulence factor internalin A (InlA). Internalin A binds certain isoforms of the cellular receptor E-cadherin to facilitate crossing the intestinal barrier during the initial stages of an L. monocytogenes infection. Juvenile guinea pigs, which express the human isoform of E-cadherin that binds InlA, were intragastrically challenged with a range of doses of (i) an EC strain associated with a listeriosis outbreak or (ii) a strain carrying a PMSC mutation in inlA. Recovery of L. monocytogenes from tissues (i.e., liver, spleen, mesenteric lymph nodes, and ileum) was used to develop strain-specific dose-response curves on the basis of individual and combined organ data. Modeling of individual and combined organ data revealed an approximate 1.2 to 1.3 log(10) increase in the median infectious dose for the strain carrying a PMSC in inlA relative to that for the EC strain. Inclusion of the strain parameter significantly improved the goodness of fit for individual and combined organ models, indicating a significant shift in median infectious dose for guinea pigs challenged with an inlA PMSC strain compared to that for guinea pigs challenged with an EC strain. Results from this work provide evidence that the L. monocytogenes dose-response relationship is strain specific and will provide critical data for enhancement of current risk assessments and development of future risk assessments.

Controlled hyperkalemic reperfusion with magnesium rescues ischemic juvenile hearts by reducing calcium loading

Our objectives were (1) to determine whether elevated Mg(2+) in controlled hyperkalemic reperfusate without intervention during ischemia protects the juvenile heart against reperfusion injury; and (2) to identify the mechanism(s) underlying any protective effect of Mg(2+). Langendorff-perfused hearts from juvenile (11- to 14-day-old) guinea pigs were subjected to mild(30-minute) or severe (45-minute) normothermic global ischemia and 35-minute reperfusion. Hearts were subjected to controlled hyperkalemic reperfusion without or with various concentrations of Mg(2+) (5, 10, 16, 23 mM). The mechanisms underlying the effect of Mg(2+) on intracellular Ca(2+) ([Ca(2+)]i) were also studied in isolated cardiomyocytes exposed to metabolic inhibition followed by washout using hyperkalemic solutions (reperfusion). Sixteen mM Mg(2+) conferred maximal cardioprotection as assessed by improved functional recovery and reduced cardiac injury; this was associated with a significant recovery of cardiac energetics and metabolism following both mild and severe ischemia. The Mg(2+)-induced protection was additive to that of hyperkalemia following mild ischemia and conferred protection following severe ischemia when hyperkalemia alone had no significant effect. Elevated Mg(2+) in the hyperkalemic reperfusate of cardiomyocytes acutely prevented [Ca(2+)]i loading following mild metabolic inhibition and augmented the fall in [Ca(2+)]i following severe metabolic inhibition. This work demonstrates for the first time in juvenile hearts that elevated Mg(2+) during controlled hyperkalemic reperfusion rescues the heart following ischemia, and that this is likely to be facilitated by reducing [Ca(2+)]i which, in turn, would aid metabolic recovery.

Intranasal pretreatment with toll like receptor 9 ligand CpG oligodeoxynucleotides prevents the development of allergic rhinitis in juvenile guinea pigs

To evaluate the therapeutic effect of intranasal oligodeoxynucleotides with CpG motifs (CpG ODN) in prevention of allergic rhinitis in juvenile guinea pigs. Juvenile guinea pigs aged from 7 to 10 weeks were administrated with CpG ODN alone or combined with OVA at single dose concentration intranasally (on day 0, 5, 10, 15 in sequence) while control and blank group were administrated with saline. Both experimental and control animals were again sensitized by OVA (on day 18, 25), and 14 days after second sensitization animals were challenged by OVA intranasally (on days 39 and 46). Two hours after challenge, the animals were sacrificed. Then Hemotoxin and Eosin stain were carried out to analyze local eosinophilic reactions and nasal lesions. Local and systemic cytokines interleukin IL-5 and IFN-γ levels were examined by ELISA. Immunofluorescence was carried out with ICAM-1 antibody. Statistical analysis was performed using a SPSS 11.0 software. In CpG ODN-administration or CpG ODN with OVA-administration group allergic rhinitis symptoms were not as severe as model control group (P < 0.05). Compared with the model control group, CpG ODN-administration did not increase production of OVA-specific Th1 cytokine IFN-γ but decreased productions of ovalbumin-specific Th2 cytokines IL-5 both in serum and nasal specimen (q value were 3.890 and 4.019, P < 0.05). Moreover, nasal lesions with infiltration of mean (x ± s) eosinophils (20.0 ± 9.6) in CpG group animal were prominently reduced by the CpG ODN-treatment compared with the control animals (53.5 ± 19.8) and CpG+OVA group (9.5 ± 5.7) were lower than CpG-M+OVA group (49.2 ± 18.9), the differences were significant (q value were 3.785 and 4.576, P < 0.05). Immunofluorescence results showed lower ICAM-1 expression in nasal specimen of CpG group compared with model group and CpG plus OVA group animal to CpG mimics plus OVA group (Z value were 3.697 and 3.765, P < 0.05). Intranasal administration of CpG oligodeoxynucleotides with or without allergen may be an effective way to prevent the development of allergic rhinitis.

The effects of allergens and tobacco smoke on the laryngeal mucosa of guinea pigs

The purpose of this study was to investigate the effects of environmental tobacco smoke (ETS) and house dust mite allergen (HDMA) on the laryngeal mucosa of guinea pigs. Prospective, controlled animal study. Sixteen juvenile guinea pigs were randomly assigned to one of four treatment groups: (1) filtered air, (2) HDMA, (3) ETS, and (4) ETS and HDMA. The mucosal response of retrieved larynges was measured by eosinophil grade and stored mucin index. HDMA exposure increased eosinophil grade in the supraglottis. The mean eosinophil grade in the supraglottis was 1.25 (+/-1.26) in the filtered air group. The grade increased to 3.60 (+/-0.89) in the HDMA group (P = 0.021) and 3.00 (+/-1.16) in the ETS/HDMA group (P = 0.078). HDMA and ETS exposure was associated with increased mucin index in the subglottis. The grade increased from 1.50 (+/-1.73) in the control group to 3.25 (+/-0.50) in the ETS, 2.80 (+/-1.64) in the HDMA, and 3.25 (+/-0.50) in the ETS/HDMA group (P < 0.05). Exposure to HDMA was associated with eosinophilia in the supraglottis. Exposure to HDMA and ETS was associated with elevated mucin in the subglottis. These results provide further evidence that ETS and inhaled allergens may play a role in the development of chronic laryngitis.