Control Sprague-Dawley Rats Research Articles

Targeting endothelial KCa channels in vivo restores arterial and endothelial function in type 2 diabetic rats

ObjectiveThis study tested the hypothesis that administration of the KCa channel activator SKA-31 restores endothelium-dependent vasodilation in vivo in Type 2 Diabetic (T2D) rats. BackgroundAcute treatment of isolated resistance arteries from T2D rats and humans with SKA-31 significantly improved endothelium-dependent vasodilation. However, it is unknown whether these in situ actions translate to intact vascular beds in vivo. MethodsMale Sprague Dawley (SD) and T2D Goto-Kakizaki (GK) rats (26–32 weeks of age) were injected intraperitoneally with either drug vehicle or 10 mg/kg SKA-31. Doppler ultrasound imaging was used to record reactive hyperemia/flow-mediated dilation (FMD) in the femoral artery following release of an occlusion cuff on the distal hind limb, along with diameter changes in the left main coronary artery in response to inhaled isoflurane (2 % → 5 %). ResultsVehicle treated SD rats exhibited a robust and reversible FMD response, the magnitude and time course of which did not differ in SD rats treated with SKA-31. In contrast, only a weak FMD response was observed in vehicle-treated T2D GK rats, whereas prior SKA-31 administration restored FMD to the level observed in control SD rats. Exposure of SD rats to 5 % isoflurane caused robust coronary artery dilation, which was not altered by prior treatment with SKA-31. In T2D GK rats, 5 % isoflurane inhalation alone did not increase coronary artery diameter, however, a strong vasodilatory response was observed following SKA-31 treatment. SKA-31 administration did not modify intrinsic heart rate responses in either protocol. ConclusionsEnhancement of KCa channel activity in vivo restores endothelium-dependent vasodilation in T2D rats that exhibit peripheral endothelial dysfunction.

Relationship Between Oxidative Stress in the Rotator Cuff and Transcutaneous Advanced Glycation End-Products Measurement in Diabetic Rats.

Diabetes mellitus increases oxidative stress due to hyperglycemia, resulting in the degeneration of rotator cuff tissue. Currently, there is no established method to non-invasively assess the extent of this oxidative stress. To address this, we aimed to investigate the relationship between the accumulation of advanced glycation end-products (AGEs), a marker of oxidative stress, and transcutaneous autofluorescence intensity in rotator cuff tissue harvested from diabetic rats. Ten control Sprague-Dawley (SD) rats and streptozotocin-induced diabetic rats (n = 10 per group) were used. The rats were euthanized eight and 16 weeks after the induction of diabetes, and rotator cuff attachment sites were collected and histologically analyzed. Prior to euthanasia, autofluorescence intensity was measured transcutaneously in the rotator cuff area. The expressions of AGEs and type I collagen were evaluated immunohistochemically with specific antibodies and the stained areas were quantified. All data were statistically analyzed using the Mann-Whitney U test. Correlation analysis was performed for skin autofluorescence intensity and the percentage of AGEs staining area using Spearman's rank correlation coefficient. The immunohistochemical expression of AGEs at the rotator cuff attachment sites and transcutaneous AGEs measurements were significantly higher in diabetic rats than in the control group at 16 weeks. There was no significant difference in the level of type 1 collagen between the two groups. This study reveals that the accumulation of AGEs in rotator cuff tissue increases due to prolonged hyperglycemia in diabetes. In addition, transcutaneous skin fluorescence intensity may be related to histological oxidative stress at the rotator cuff.

Behaviorally Inhibited Individuals Learn to Avoid Transdermal Stimulation More Quickly, and this Learning Is Accelerated Throughout the Study

Information on how behavioral inhibition (BI) affects the amount of time it takes an individual to avoid a stressful situation could answer many questions about anxiety disorders and whether BI influences avoidance behavior. BI is a temperament characteristic associated with increased vulnerability to stress compared to their non-behaviorally inhibited (NBI) counterparts. Our previous study demonstrated that BI individuals have lower heart rate variability (HRV) than NBI individuals. This suggests that BI individuals have significantly less parasympathetic nervous system (PNS) output at rest; however, it is unknown how BI affects avoidance acquisition using a mildly stressful stimulus. Previous studies have shown differences in the behavior found in Wistar-Kyoto rats, which exhibit BI behavior, compared to Sprague-Dawley control rats. Our current study will test the hypothesis that BI individuals learn to make escape and avoidance responses using subdermal ulnar nerve transdermal electrical stimulation (TES) more rapidly than NBI individuals and also experience a more significant increase in heart rate (HR) and blood pressure (BP). BI individuals were identified through a series of self-reported questionnaires. Three levels (30 mV, 50 mV, and 70 mV) of subdermal ulnar nerve TES were delivered to participants while receiving warning signals that predicted the delivery of the TES. Participants had access to a button that, when pressed during the light, prevented the delivery of the TES. This was scored as an avoidance response. If the button was pressed during the TES, it terminated the stimulation and was scored as an escape. HR and BP were also measured using a BIOPAC data acquisition system during TES. Our preliminary results indicate that BI individuals show a decrease in latency in the amount of time it took them to make an avoidance as the study progressed, while NBI individuals show a slight increase in latency, highlighting the idea that BI individuals are more curious to press the button or they are more likely to want to avoid the TES quicker. We would like to thank the Carthage College Research, Scholarship, and Creativity Committee as well as the Carthage College Neurophysiology Laboratory professors for their continued support throughout the study. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Taurine influences the phagocytic function of retinal pigment epithelium cells in healthy and dystrophic animals

Aims/Purpose: To investigate the influence of taurine on the phagocytic function of the retinal pigment epithelium (RPE) in normal and dystrophic rats.Methods: Normal albino Sprague–Dawley (SD) and pigmented dystrophic Royal College of Surgeons (RCS‐p+) rats that suffer an inherited photoreceptor degeneration due to RPE phagocytosis impairment were used for the study. Taurine depletion was induced in SD rats (n = 8) by providing β‐alanine in drinking water (3%) from postnatal day 21 (P21). Taurine supplementation was administered to RCS‐p+ rats (n = 8) in drinking water (0.2 M) from P21. Untreated RCSp+ (n = 8) and SD (n = 8) rats served as control groups. Rats were processed at P81 (SD) and at P45 (RCS) and received an intravitreal injection (IV) of. 1.5 μL of Fluorogold (FG, 3%) diluted in saline 24 h before processing. The RPE was dissected, flat‐mounted and immunodetected with anti‐S opsin antibodies to label the RPE phagosomes which were quantified using ImageJ and size criteria.Results: The mean numbers (± SD) of phagosomes per RPE whole mount was 414 ± 118 in control SD rats, 1034 ± 528 in taurine‐depleted SD rats 88 ± 12 in untreated RCS and 119 ± 9 in taurine‐treated RCS rats. The numbers of phagosomes were significantly higher in SD rats than in RCS‐p+ rats (t‐test, p < 0.0001) documenting the impaired phagocytic function of RCS‐p+ rats. In SD rats, the number of phagosomes were significantly higher in taurine‐depleted rats evidencing that taurine depletion decreases the RPE phagocytic capacity (t‐test, p < 0.0059). Finally, in RCSp+ rats, the numbers of phagosomes were significantly higher in taurine‐treated than in non‐treated RCS rats (t‐test, p < 0.0001) indicating that taurine supplementation ameliorates the phagocytic capacity of the RPE cells in RCS‐p+ rats.Conclusions: Taurine influences the phagocytic capacity of the RPE cells in normal rats and in dystrophic RCS‐p+ rats.

Late Pregnant Dahl Salt-Sensitive Rats from Charles River Laboratories Do Not Exhibit Superimposed Preeclampsia.

Healthy pregnancy is characterized by a reduction in total peripheral vascular resistance which produces a decrease in maternal blood pressure. Failure of this normal maternal adaptation to pregnancy results in hypertensive disorders of pregnancy, which are dangerous for both the mother and fetus. Recently, it has been proposed that Dahl salt-sensitive (SS) rats are a model of spontaneous superimposed preeclampsia when maintained on a normal salt diet. Since these reports are from animals that are derived from sources that are not commercially available, the purpose of this study was to evaluate the blood pressure and pregnancy outcomes of SS rats from a commercial vendor. Mean arterial blood pressure was measured by indwelling femoral catheter in anesthetized SS virgin and SS day 21 late pregnant rats from Charles River Laboratories (CRL). Fetal outcomes from SS rats and control Sprague-Dawley (SD) rats were also measured. All rats were euthanized by exsanguination under anesthesia and tissues weighed. Virgin SS rats were found to have normal mean arterial blood pressure (102 ± 2mmHg), and late pregnant SS rats had the normal decrease in maternal blood pressure. SS rats were also found to have normal pregnancy outcomes. These results suggest that SS rats from CRL are not a model of superimposed preeclampsia. Further studies will be aimed at determining the differences between the blood pressure phenotype and pregnancy outcomes of existing colonies of SS rats in order to elucidate the mechanisms permitting the development of preeclampsia in certain colonies of this strain.

Pseudotargeted metabolomics analysis of pine pollen intervention in the liver of premature ovarian failure rats

Premature ovarian failure (POF) is a prevalent gynecological disease. In traditional Chinese medicine, it is believed that POF is directly related to abnormal function of the liver and kidneys. As such, regulation of the liver metabolism through the use of medicinal and edible substances is important for the treatment of POF. Pine pollen, a traditional Chinese medicinal and edible pollen variety, contains various active substances, such as sex hormones and phytohormones, which have been used to inhibit inflammation, regulate the immune system, and protect reproductive tissues. Using ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC-MS/MS), this study examined the influence of pine pollen on the liver metabolome of cyclophosphamide-induced POF model Sprague Dawley (SD) rats. The variations in the metabolites present in the liver tissue of control SD rats, model SD rats, and SD rats treated with various doses of pine pollen or estrogen were analyzed using principal component analysis (PCA) in combination with orthogonal partial least squares discriminant analysis (OPLS-DA) and other multivariate statistical methods to reveal the mechanism of pine pollen intervention in the livers of POF SD rats. An animal model experiment was conducted using six groups of ten-week-old rats. Cyclophosphamide was administered intraperitoneally to the model group and four intervention groups at a dosage of 60 mg/kg for 1 d followed by a dosage of 10 mg/kg for 14 d. Within the following four weeks, each of the four intervention groups received the intragastric administration of 0.1, 0.5, or 1.5 g/kg bodyweight (BW) of pine pollen, or 0.075 g/kg BW of conjugated estrogens (positive control). Equal quantities of normal saline were administered to the control and cyclophosphamide-treated model groups. Subsequently, the rat livers were subject to pseudotargeted metabolomics, and a total of 687 liver metabolites were discovered using both positive and negative ions. The metabolites differing in content were screened using the t-test (p<0.05) and the fold change (FC>2 or <0.5) in univariate analysis, and the variable importance in projection (VIP>1) in multivariate analysis. It was found that in comparison with the control group, the contents of 32 metabolites significantly increased, while those of 28 metabolites significantly decreased in the model group. The majority of these metabolites were involved α-linolenic acid metabolism, vitamin B6 metabolism, and purine metabolism, along with the lysine degradation and glycolysis/gluconeogenesis metabolic pathways. Compared with the cyclophosphamide-induced model group, the estrogen group exhibited increased levels of 47 metabolites and decreased levels of 29 metabolites, wherein 34 metabolites were restored to the levels found in the control group. These metabolites mainly involved the vitamin B6, lysine, glycolysis/gluconeogenesis, arginine and proline, and cysteine and methionine metabolic pathways. In the low/medium/high-dose pine pollen groups, the contents of 34/32/34 metabolites increased, the contents of 30/37/24 metabolites decreased, and the contents of 47/38/34 metabolites were restored to the levels found in the control group, respectively. These metabolites were mainly involved in vitamin B6 metabolism, purine metabolism, and the glycolysis/gluconeogenesis metabolic pathway. These results therefore indicate that the restoring effect of pine pollen is equivalent or superior to that of conjugated estrogen. Additionally, based on the known metabolic pathways, it appears that when estrogen interferes with the liver metabolism, the key metabolic pathways that become affected are the arginine and proline metabolism and cysteine and methionine metabolism pathways. In contrast, pine pollen intervention affected existing metabolic pathways that were known to be disordered by cyclophosphamide. The use of pine pollen may therefore restore the levels of many metabolites. It should be noted that 23 overlaps exist between the estrogen-restored metabolites and the pine pollen-restored metabolites, including a variety of acylcarnitines, such as ACar 10∶0. As a result, pine pollen extract may be able to normalize the liver metabolic abnormalities induced by POF. This study therefore establishes a theoretical reference for the development of functional applications for pine pollen and for the treatment of POF.

Paneth Cell Hyperplasia and Metaplasia in Hirschsprung-associated Enterocolitis in An Aganglionosis Rat Model

BACKGROUND: Many hypotheses regarding the pathophysiology of enterocolitis in aganglionic megacolon or Hirschsprung disease (HSCR) has been proposed. Paneth cells are columnar intestinal epithelial cells that have an important role in maintaining of intestinal homeostasis as a bactericide. Since enterocolitis in HSCR may have association with Paneth cells metaplasia and hyperplasia, current study investigated Paneth cells metaplasia and hyperplasia in the sigmoid colon of HSCR rat model and its products, namely a-defensins and IL-1b, in the sigmoid colon tissues.METHODS: Aganglionosis-induced and control Sprague-Dawley rats were euthanized on Day (D)-7, -14, -17, -19, -21, -23, -25, and -28. Sigmoid colon tissue was isolated at each time point, and degree of enterocolitis as well as Paneth cells metaplasia and hyperplasia were analyzed by Hematoxylin-eosin staining, then protein levels of a-defensins and interleukin (IL)-1b were determined by enzyme-linked immunosorbent assay (ELISA).RESULTS: Enterocolitis scores increased with time. The Paneth cells metaplasia and hyperplasia were observed on D14 until D28 (p&lt;0.01 vs. control group) followed by an increased in the levels of IL-1b. The levels of a-defensins protein expression were initially increased (D7-D14; p&lt;0.01 vs. control group) but then undergo reciprocal changes on D19 until D28 (p&lt;0.01 vs. D7 and D14). Positive correlations between the degree of enterocolitis and Paneth cells number were detected in the sigmoid colon (r=0.42).CONCLUSION: Paneth cells underwent metaplasia and hyperplasia in the sigmoid colon of HSCR rats corresponding to an increase in the degree of enterocolitis, but not followed by an increase in the level of a-defensins as well as IL-1b, suggesting that there is an involvement of Paneth cells in the pathophysiology of enterocolitis due to HSCR.KEYWORDS: Hirschsprung, enterocolitis, defensins; metaplasia, Paneth cell, animal model

Monitoring Progression of Diabetic Nephropathy Using T1- and T2-Weighted Imaging: An Animal Study

PurposeCurrently, diabetes and the consequent DN are considered a major public health issue. However, the mechanism of DN and its treatment require further clarification. This study proposed noninvasive T1-weighted (T1W) and T2-weighted (T2W) MRI protocols for the longitudinal assessment of kidney disease progression after DN induction in Sprague Dawley (SD) rats.MethodsThe changes in MRI image indices over time between control and DN SD rats were investigated. The volumes of the bilateral kidneys and the signals intensities (SIs) of the bilateral kidneys, renal pelvis, renal cortex, and renal medulla on turbo spin echo T1W and T2W images were obtained to observe DN progression in the rat kidneys.ResultsThe results indicated that the edges of kidneys were clearer and sharper in the DN rats than in the control rats. The time-varying SIs of the bilateral whole kidneys, renal cortex, renal pelvis, and renal medulla on T1W and T2W images were significantly larger in the DN rats than in the control rats. Moreover, the volumes of both the left and right kidneys were significantly larger in the DN rats than in the control rats.ConclusionHigh-quality T1W and T2W images can be used to assess DN progression in SD rats’ kidney. Our results might be applicable to clinical routine diagnostic examinations that may improve diagnostic accuracy. Further development of the MRI technology for early DN detection and treatment is warranted.

Abstract P059: Carotid Artery Stiffness Is Elevated In Young Hypertensive Rats Relative To Age-matched Normotensive Rats

Hypertension has a bidirectional relationship with arterial stiffening, a hallmark feature that reduces vascular compliance, resulting in increased blood velocity, disruptions to laminar flow, and target organ injury. Our prior studies in transgenic hypertensive (mRen2)27 rats document age-related sex differences in cardiac dysfunction associated with cerebrovascular changes that develop earlier in males than females. Both sexes develop cardiac dysfunction and cerebrovascular damage by 1 year of age. The current objective was to determine systolic blood pressure (SBP) and arterial stiffness (AS) in both the carotid artery and aortic arch in young adult male and female (mRen2)27 versus normotensive Sprague Dawley (SD) rats. SBP was measured at 20 weeks of age via tail-cuff, to which rats were acclimated prior to measurements. AS data was obtained from transthoracic echocardiograms using the Vevo 2100 LAZR ultrasound. Data are presented as mean ± SEM; t- tests were conducted using GraphPad Prism 8 (p&lt;0.05 considered significant). SBP was higher in both male (182 ± 3 mm Hg) and female (184 ± 7 mm Hg) (mRen2)27 rats compared with male (136 ± 5 mm Hg) and female (121 ± 5 mm Hg) SD rats. AS was significantly higher in the aortic arch of female (mRen2)27 rats: 5.9 ± 0.6 mm/ms compared with 2.8 ± 0.6 mm/ms for SD female rats. In male (mRen2)27 rats, aortic arch stiffness was 5.1 ± 0.5 compared with 3.5 ± 0.1 for SD male rats. The carotid artery was significantly stiffer in both male and female (mRen2)27 rats versus the SD control rats: female (mRen2)27, 6.9 ± 0.6 mm/ms, versus female SD, 2.6 ± 0.5 mm/ms; male (mRen2)27, 4.1 ± 0.2 mm/ms, versus male SD rats, 3.0 ± 0.2 mm/ms. Our findings suggest that young adult hypertensive rats, regardless of sex, exhibit greater AS relative to normotensive rats. While the increased carotid stiffness could contribute to cerebrovascular damage, further studies at different time points in both sexes are necessary to understand the mechanisms involved in the development of AS and the relationship, if any, to the sex differences in progression of cerebrovascular disease.

Immune disorders and sex differences in spontaneously diabetic Torii rats, type 2 diabetic model.

Type 2 diabetes (T2D) is believed to be a non-autoimmune metabolic disorder. However, there are increasing reports that some T2D patients have immune abnormalities. In addition, it is known that there are sex differences in the onset of diabetes and immune responses in humans. Spontaneously Diabetic Torii (SDT) rats, a non-obese T2D model, also have sex differences in the onset of diabetes, but the involvement of immune abnormalities in diabetes is unknown. In this study, we investigated immune abnormalities in SDT rats. Immune cell subset analysis was performed in male and female SDT rats and control Sprague-Dawley (SD) rats at 5, 11, and 17 weeks of age. Male and female SDT rats had swelling of the spleen and lymph nodes and a higher number of T cells and B cells in the blood, spleen, and lymph nodes than SD rats. Only male SDT rats developed diabetes at 17 weeks of age, and the number of classical and non-classical monocytes in the blood and spleen of male SDT rats was higher than that in male SD rats and female SDT rats that did not develop diabetes. Most of these findings were observed before the onset of diabetes (~11 weeks of age), suggesting that classical and non-classical monocytes may contribute to the development of diabetes in male SDT rats. In conclusion, SDT rats may be a useful T2D model involved in immune abnormalities, and further research will help elucidate the pathophysiology of T2D with immune abnormalities and develop new therapeutic agents.

Autism-Like Behavior in the Offspring of CYP11A1-Overexpressing Pregnant Rats.

Autism spectrum disorders (ASD) represent a complex group of neurodevelopmental disorders that are characterized by impaired social behavior and communication as well as repetitive behavior and restricted interests. Prenatal exposure to high levels of testosterone and preeclampsia are thought to be risk factors of ASD. We had previously reported that overexpression of the mitochondrial cholesterol side-chain cleavage enzyme (CYP11A1) could lead to both preeclampsia-like symptoms and increased testosterone levels in pregnant rats. In this study, we investigated the association between high CYP11A1 levels in pregnant rats and autism-like behavior in their offspring. Timed-pregnant Sprague-Dawley (SD) rats were injected with CYP11A1 gene-carrying adenoviruses on gestational day 8.5, and their offspring were then compared with those from timed-pregnant control SD rats. Compared with their control counterparts, the offspring of the CYP11A1-ovexpressing dams displayed more symptoms of anxiety and spent less time in social interactions and more time in self-grooming and rearing, all indicators of autism-like behavior. Sequencing of the transcriptome in primary microglia from the offspring of CYP11A1-overexpressing dams revealed that immune pathways were highly activated, and the gamma-aminobutyric acid type A (GABAA) receptor genes were among the top differentially expressed genes. Using primary microglia cultures generated from neonatal rats, tumor necrosis factor-alpha expression was found to be elevated in the cells transfected with CYP11A1-carrying adenoviruses. Additionally, the offspring of CYP11A1-overexpressing dams displayed dysregulated GABAA receptor expression. Taken together, these results suggest that abnormal CYP11A1 gene expression in pregnant rats could lead to microglial immune activation and dysregulated GABAA receptor expression in their offspring and thereby anxiety and autism-related behavior. Our study suggests that the pathways regulated by CYP11A1 could be promising preventative and therapeutic targets for ASD.

Evaluation of the impact of transgenic maize BT799 on growth, development and reproductive function of Sprague-Dawley rats in three generations

BT799 was Bacillus thuringiensis-genetic modified (GM) maize, and Sprague-Dawley (SD) rats were treated with different diet formulations containing BT799 maize grain (33% and 66%) or its non-transgenic Zhengdan 958 (ZD958, 33% and 66%). The feeding lasted for 10 (P)/14 (F1 and F2) weeks. The reproductive capacity and pathological responses were detected in each generation of rats fed with BT799 and ZD958. During the growth and development of parental rats, each group showed the same trend in body weight gain and food intake, with a few fluctuations at individual time points. No statistically significant difference was observed in reproductive data (copulation index, fertility index, and live birth rate) of rats fed with transgenic maize compared with non-transgenic maize. We observed some apparent changes in reproductive data (sperm numbers and motility) and pathological responses (organ relative weights, hematological parameters, serum chemistry parameters, and sex hormone levels) among rats fed with BT799 maize grain. However, these differences were within the laboratory's historical normal range of control SD rats and not maize grain dose-dependent. These changes were not considered to be adverse or toxic. No significant difference in macroscopic or histological adverse effects was observed between rats consuming transgenic BT799 diet and non-transgenic diet. In conclusion, the long-term intake of BT799 maize was as safe as the corresponding non-transgenic maize for three-generation SD rats.

Diabetes diminishes a typical metabolite of litchi pericarp oligomeric procyanidins (LPOPC) in urine mediated by imbalanced gut microbiota.

Animal studies and clinical trials have shown that dietary polyphenols and polyphenol-rich foods can reduce the risk of type 2 diabetes (T2D) and its complications, but how diabetes regulates the metabolism of polyphenol has not been fully elucidated. This study investigated the effects of diabetes on litchi pericarp oligomeric procyanidin (LPOPC) dynamic metabolism and its major static metabolites in urine. First, a high-fat and streptozotocin (STZ)-induced diabetic Sprague Dawley (SD) rat model was established. In the diabetic rat model, elevated fasting blood glucose, severely impaired glucose tolerance test, and increased reactive oxygen species (ROS) levels in serum and the liver were observed. Subsequently, 200 mg per kg body weight of LPOPC was administrated to control and diabetic SD rats, and the gastrointestinal tract was collected at 0.5 h, 1 h, 3 h, and 6 h. The results showed that the retention time of LPOPC was not changed in our diabetic rat model. However, the gut microbiota were significantly altered, with elevated Proteobacteria and Verrucomicrobia abundance in diabetic rats and decreased short chain fatty acid (SCFA)-producing bacteria. Interestingly, after one dose of 300 mg per kg body weight LPOPC, the total antioxidant capacity of urine in diabetic rats significantly decreased. We then tested the static metabolites of LPOPC, demonstrating that epicatechin had not changed in urine in diabetic rats, but that shikimic acid was significantly reduced in urine in diabetic rats. The changes in shikimic acid may be due to the alteration of gut microbiota and elevated ROS levels in serum.

Abstract 13140: Right Ventricular Remodeling and Changes in Tissue Biomechanics in Healthy Aging

Introduction: Normal aging in healthy adults has been associated with pulmonary vasculature remodeling and alterations in right ventricular (RV) systolic and diastolic function, which may lead to increased RV afterload and pulmonary hypertension (PH). Previous studies have found a close link between RV biomechanics and function. While current findings suggest a connection between aging and survival rates of PH patients, limited data exist on age-associated differences in the biomechanical properties of RV myocardium. Hypothesis: Aging results in increased RV afterload, hypertrophy, and myocardial stiffening. Methods: Two groups of control (11 weeks) and aging (80 weeks) Sprague-Dawley rats were studied via terminal invasive hemodynamic measurements (n=5/group), quantitative transmural histological analysis (n=3/group; Masson’s trichrome), biaxial mechanical testing (n=6/group) and constitutive modeling (n=6/group) for a comprehensive multi-scale study on the effects of aging on RV biomechanics. Results: Aging increased RV peak pressures by 15% (26.79±0.87 vs. 23.28±0.83 mmHg for aging vs. control; p=0.020). Increased RV wall thickness (0.89±0.06 vs. 0.66±0.04 mm for aging vs. control; p=0.010) and cardiomyocyte width (25.42±0.34 vs. 14.94±0.64 μm for aging vs. control; p&lt;0.001) were observed in the aging group, while not showing any effects on the Fulton index. Histological analyses showed transmural realignment of RV collagen and myofibers towards the apex-to-base direction by 14.6° (p=0.017). This was accompanied by transmural loss of cardiomyocytes (cardiomyocyte area fraction: 88.4%±0.4% vs. 95.3%±0.7% for aging vs. control; p&lt;0.001) and increased myofiber stiffness (169.9±20.6 vs. 65.8±4.7 kPa for aging vs. control; p&lt;0.001). While aging resulted in RV fibrosis (collagen area fraction: 5.1%±0.5% vs. 3.8%±0.1% for aging vs. control; p=0.049), collagen fibers in the aging myocardium showed decreased effective intrinsic stiffness compared to young controls (23.9±3.8 vs. 73.1±15.4 MPa for aging vs. control; p=0.031). Conclusions: Healthy aging has the potential to modulate RV dysfunction via increased myofiber stiffness, fiber reorientation, loss of ventricular cardiomyocytes, RV hypertrophy and fibrosis.

Incidences and Range of Spontaneous Microscopic Lesions in the Eye of Sprague-Dawley Rats and Han Wistar Rats Used in Toxicity Studies

The incidence and range of spontaneous microscopic lesions were determined in the eyes of male and female control Sprague-Dawley and Han Wistar rats. Data were collected retrospectively from 1411, 817, 970, 658, and 3999 rats from control groups of 4-, 13-, 26-, 52-, and 104-week studies, respectively, carried out between 1997 and 2019. Microscopic lesions of the eye were rare in 4- and 13-week studies, uncommon in 26- and 52-week studies, and were of relatively higher incidence in 104-week studies. Neoplastic lesions were sporadic and were only observed in 104-week studies. In Sprague-Dawley rats, the most common lesions (>1% in 104-week studies) were retinal degeneration, retinal rosettes/folds, and lenticular degeneration. The Han Wistar rats presented a range of ocular lesions similar to the Sprague-Dawley rats. However, retinal degeneration occurred with an earlier onset and at higher incidences, ranging from >5% in 26-week studies up to 45.72% in 104-week studies. In both strains, females exhibited higher incidences and severities of retinal degeneration. It is hoped that reference to the incidences reported here will facilitate the differentiation of spontaneous lesions from test article-induced lesions in toxicology studies in these strains of rat.

The deficiency of myelin in the mutant taiep rat induces a differential immune response related to protection from the human parasite Trichinella spiralis.

Taiep rat is a myelin mutant with a progressive motor syndrome characterized by tremor, ataxia, immobility episodes, epilepsy and paralysis of the hindlimbs. Taiep had an initial hypomyelination followed by a progressive demyelination associated with an increased expression of some interleukins and their receptors. The pathology correlated with an increase in nitric oxide activity and lipoperoxidation. In base of the above evidences taiep rat is an appropriate model to study neuroimmune interactions. The aim of this study was to analyze the immune responses in male taiep rats after acute infection with Trichinella spiralis. Our results show that there is an important decrease in the number of intestinal larvae in the taiep rat with respect to Sprague-Dawley control rats. We also found differences in the percentage of innate and adaptive immune cell profile in the mesenteric lymphatic nodes and the spleen that correlated with the demyelination process that took place on taiep subjects. Finally, a clear pro-inflammatory cytokine pattern was seen on infected taiep rats, that could be responsible of the decrement in the number of larvae number. These results sustain the theory that neuroimmune interaction is a fundamental process capable of modulating the immune response, particularly against the parasite Trichinella spiralis in an animal model of progressive demyelination due to tubulinopathy, that could be an important mechanism for the clinical course of autoimmune diseases associated with parasite infection.

Effects of type 1 diabetes on reflexive cardiovascular responses to intermittent muscle contraction.

Studies have shown that early-stage type 1 diabetes mellitus (T1DM) leads to an exaggerated reflex pressor response to both static muscle contraction and tendon stretch. However, whether similar responses are present during dynamic exercise (i.e., intermittent contraction) is not known. Therefore, the purpose of this study was to determine whether T1DM leads to an exaggerated reflex pressor response to intermittent muscle contraction. We measured the exercise pressor reflex in unanesthetized, decerebrated T1DM (50 mg/kg streptozotocin; STZ) and healthy control (CTL) Sprague-Dawley rats by intermittently contracting the hindlimb muscles for 30 s while measuring mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA), and heart rate (HR). Intermittently contracting the hindlimb muscles evoked exaggerated mean RSNA (STZ: Δ109 ± 21%, n = 4 rats; CTL: Δ61 ± 8%, n = 5 rats, P < 0.05), peak MAP (STZ: Δ32 ± 2 mmHg, n = 9 rats; CTL: Δ12 ± 2 mmHg, n = 6 rats, P < 0.05), blood pressure index (STZ: Δ625 ± 60 mmHg/s, n = 9 rats; CTL: Δ241 ± 46 mmHg/s, n = 6 rats, P < 0.05), and HR (STZ: Δ24 ± 3 beats/min, n = 9 rats; CTL: Δ9 ± 3 beats/min, n = 6 rats, P < 0.05) responses to similar developed tensions (P > 0.05) in T1DM compared with CTL rats. T1DM rats also exhibited exaggerated early-onset sympathetic (onset: 1 s) and pressor (onset: 5 s) responses. These data show that early-stage T1DM leads to an exaggerated pressor reflex evoked by intermittent muscle contraction. The early onset and greater blood pressure index suggest that cardiovascular strain during dynamic exercise may be significantly higher in individuals with T1DM.NEW & NOTEWORTHY This is the first study to provide evidence that early-stage type 1 diabetes mellitus (T1DM) leads to an exaggerated exercise pressor reflex evoked by intermittent muscle contraction, resulting in substantially higher cardiovascular strain. These findings are significant as they indicate that interventions targeting the exercise pressor reflex may work to alleviate the increased cardiovascular strain and overall burden during exercise in T1DM.

Oxidative Stress and Mitochondrial Abnormalities Contribute to Decreased Endothelial Nitric Oxide Synthase Expression and Renal Disease Progression in Early Experimental Polycystic Kidney Disease.

Vascular abnormalities are the most important non-cystic complications in Polycystic Kidney Disease (PKD) and contribute to renal disease progression. Endothelial dysfunction and oxidative stress are evident in patients with ADPKD, preserved renal function, and controlled hypertension. The underlying biological mechanisms remain unknown. We hypothesized that in early ADPKD, the reactive oxygen species (ROS)-producing nicotinamide adenine dinucleotide phosphate hydrogen (NAD(P)H)-oxidase complex-4 (NOX4), a major source of ROS in renal tubular epithelial cells (TECs) and endothelial cells (ECs), induces EC mitochondrial abnormalities, contributing to endothelial dysfunction, vascular abnormalities, and renal disease progression. Renal oxidative stress, mitochondrial morphology (electron microscopy), and NOX4 expression were assessed in 4- and 12-week-old PCK and Sprague-Dawley (wild-type, WT) control rats (n = 8 males and 8 females each). Endothelial function was assessed by renal expression of endothelial nitric oxide synthase (eNOS). Peritubular capillaries were counted in hematoxylin–eosin (H&E)-stained slides and correlated with the cystic index. The enlarged cystic kidneys of PCK rats exhibited significant accumulation of 8-hydroxyguanosine (8-OHdG) as early as 4 weeks of age, which became more pronounced at 12 weeks. Mitochondria of TECs lining cysts and ECs exhibited loss of cristae but remained preserved in non-cystic TECs. Renal expression of NOX4 was upregulated in TECs and ECs of PCK rats at 4 weeks of age and further increased at 12 weeks. Contrarily, eNOS immunoreactivity was lower in PCK vs. WT rats at 4 weeks and further decreased at 12 weeks. The peritubular capillary index was lower in PCK vs. WT rats at 12 weeks and correlated inversely with the cystic index. Early PKD is associated with NOX4-induced oxidative stress and mitochondrial abnormalities predominantly in ECs and TECs lining cysts. Endothelial dysfunction precedes capillary loss, and the latter correlates with worsening of renal disease. These observations position NOX4 and EC mitochondria as potential therapeutic targets in PKD.

Effects of Long-Term Exercise on Liver Cyst in Polycystic Liver Disease Model Rats.

Polycystic liver disease (PLD) is a hereditary liver disease with progressive enlargement of fluid-filled liver cysts, which causes abdominal discomfort and worsens quality of life. Long-term exercise has beneficial effects in various organs, but the effects of long-term exercise on PLD are unclear. Therefore, the aim of this study was to investigate whether long-term exercise inhibits liver cyst formation and fibrosis. Polycystic kidney (PCK) rats, a model of PLD, were randomly divided into a sedentary group and a long-term exercise group, which underwent treadmill running for 12 wk (28 m·min, 60 min·d, 5 d·wk). Sprague-Dawley (SD) rats were set as a control group. After 12 wk, exercise capacity, histology, and signaling cascades of PLD were examined. Compared with control SD rats, PCK rats showed a low exercise capacity before exercise protocol. After 12 wk, the exercise improved the exercise capacity and ameliorated liver cyst formation and fibrosis. The exercise significantly decreased the number of Ki-67-positive cells; the expression of cystic fibrosis transmembrane conductance regulator, aquaporin 1, transforming growth factor β, and type 1 collagen; and the phosphorylation of extracellular signal-regulated kinase, mammalian target of rapamycin and S6. It also increased the phosphorylation of AMP-activated protein kinase in the liver of PCK rats. The present results indicated that long-term moderate-intensity exercise ameliorates liver cyst formation and fibrosis with the inhibition of signaling cascades responsible for cellular proliferation and fibrosis in PCK rats.

Study of the functional integrity of the retinal pigment epithelium with a new technique in two models of inherited retinal degeneration

AbstractIntroductionRetinal pigment epithelium (RPE) is a cell layer located between the neurosensory retina and the choroid. RPE has many functions that are essential for photoreceptor nutrition and renewal, among others. To understand the pathogenesis of retinal degenerations, it is crucial to study the integrity, morphology and functionality of this layer.Material and methodsDystrophic young and old adult female albino P23H‐1 (rhodopsin mutation) and Royal College of Surgeon, (RCS, RPE mutation that impairs phagocytosis), rats were used in this experiment. Control strains were Sprague‐Dawley (SD) and Pievald Virol Glaxo (PVG). To label the RPE, 1.5 µl of 3% Fluorogold (FG) diluted in saline was administered intravitreally under general anaesthesia. RPE in‐vivo analysis were performed with SD‐OCT and by eye fundus observation; for ex‐vivo analysis flat mounted RPE and cryostat cross‐sections were used.ResultsIn‐vivo analysis of the dystrophic strains showed an overexpression of lipofuscin in the RPE and a reduction of the retinal thickness, both pathological conditions increased with time. Ex‐vivo analysis in cross sections revealed that in control SD and PVG rats, RPE was labelled with FG showing its typical cubic morphology. The retinal structure and RPE morphology however, was altered in the dystrophic strains. In flat mounts we observed that FG accumulates inside the somas of RPE cells in SD, PVG and young P23H‐1 rats, indicating that the RPE has a correct function. However, in old P23H‐1 rats, FG was found inside and outside the RPE somas, which in addition were bigger and unstructured. When analysing RCS rats, we observed that FG accumulated outside the RPE somas, indicative of the phagocytosis malfunction that characterises this strain.ConclusionsIntraocular injection of FG is a reliable technique to label functional RPE. In both models of inhered retinal degeneration RPE functional integrity was affected by the evolution of degeneration.