Middle-aged Wistar Rats Research Articles

Prolonged Copper Supplementation Modified Minerals in the Kidney, Liver and Blood, and Potentiated Oxidative Stress and Vasodilation of Isolated Aortic Rings in Young Wistar Rats.

Previous studies have highlighted that copper supplementation at 200% of the recommended daily dietary allowance modified vascular contraction and relaxation through increased reactive oxygen species (ROS) and prostaglandin formation, which modified the antioxidant status of middle-aged Wistar rats. In this study, young (1 month old) male Wistar rats (n/group = 10) received a diet supplemented with 6.45 mg copper/kg (100% of daily recommendation-Group A) for 8 weeks. The experimental group received 12.9 mg copper/kg of diet (200% of the daily recommendation-Group B). Experimental supplementation with 200% copper modified the copper concentration in the blood (1.21-fold, p = 0.04), liver (1.15-fold, p = 0.032), and kidneys (1.23-fold, p = 0.045), potentiated the ROS formation in the aortic rings, and enhanced the sensitivity of the aortic rings to the vasodilator acetylcholine. We observed an increased participation of nitric oxide (NO) derived from inducible NO synthase (iNOS) in vascular contraction and a decreased net effect of vasodilator prostanoids derived from cyclooxygenase-2 in vascular relaxation. In rat kidneys, the concentrations of potassium (1.08-fold, p = 0.001) and iron (1.13-fold, p = 0.046) were higher, while, calcium (0.88-fold, p = 0.001) and chromium (0.77-fold, p = 0.005) concentrations were lower. In the rat liver, magnesium (1.06-fold, p = 0.012) was higher. No differences were observed in the concentrations of sodium, zinc, manganese, selenium, cobalt, molybdenum, and vanadium. The antioxidant activity of water- and lipid-soluble compounds; total antioxidant status in the blood; and superoxide dismutase, catalase, and malondialdehyde levels in the heart did not change. In young rats, prolonged supplementation with 200% copper had a lesser effect than anticipated on oxidative stress and vascular reactivity. Detailed data on the status of trace elements and their interactions in patients of different age groups are strongly required for effective nutritional and therapeutic intervention.

Decreased vascular contraction and changes in oxidative state in middle–aged Wistar rats after exposure to increased levels of dietary zinc

Both copper and zinc are known to be important for maintaining health, but most research has focused on deficiencies of these elements. Recent studies have shown that high levels of Cu can be toxic, especially to the cardiovascular (CV) system. However, little research has been done on the effects of higher levels of Zn on the CV system. In this study, male Wistar rats aged 12 months were given a diet with twice the recommended daily allowance of zinc (31.8 mg/kg of diet) and compared to a control group (15.9 mg/kg of diet) after 8 weeks. Blood plasma and internal organs of both groups were examined for levels of copper, zinc, selenium and iron, as well as several key enzymes. Aortic rings from both groups were also examined to determine vascular functioning. There were very few changes in the vascular system functioning after chronic exposure to zinc, and only one enzyme, heme oxygenase–1 (HO–1) was elevated, whereas vascular contraction to noradrenaline decreased with no changes in vasodilation to acetylcholine. Of the micronutrients, zinc and selenium were elevated in the blood plasma, while copper decreased. Meanwhile, the total antioxidant status increased. These were not observed in the liver. Therefore, it is proposed that there is a mechanism in place within the vascular system to protect against the overproduction of heme, caused by chronic zinc exposure.

Antagonists of somatostatin and NK1 receptors synergistically induce catalepsy in middle-aged Wistar rats

Objectives: A decrease in levels of somatostatin (SST) and substance P (SP) is observed in the parkinsonian brain. Previously, brain SST deficit in rats simulated by i.c.v. injections of SST receptor antagonist, cyclosomatostatin (cSST), was found to promote the development of catalepsy. The role of SP, a natural ligand of neurokinin-1 (NK1) receptors, in the development of catalepsy is currently unclear. Here, we evaluated whether simultaneous blockade of central somatostatin and NK1 receptors is able to initiate catalepsy and affect dopamine turnover in the nigrostriatal area of the brain.\nMaterials and methods: The experiments were carried out on middle-aged Wistar rats. The blockade of somatostatin and NK1 receptors was simulated by intracerebroventricular injections of cSST and substance L-733,060, respectively. Catalepsy was evaluated by the bar test. The levels of dopamine and its metabolites in the dorsal striatum and substantia nigra were measured by using HPLC.\nResults: No catalepsy was induced by cSST at 1.0 µg and L-733,060 at 10.0 ng injected separately. However, co-administration of these agents initiated catalepsy and influenced dopamine metabolism in the nigrostriatal area. Cataleptogenic action of the combination was reversed by SP. \nConclusion: The present findings testify that there is some sort of synergy between cSST and L-733,060 in initiation of catalepsy. In the light of these data, PD-related simultaneous brain deficit in SST and SP might be relevant for pathogenesis of extrapyramidal dysfunctions. Given the presented results, the processes mediated by central SST and NK1 receptors may be potential therapeutic targets for parkinsonism.

Early therapeutic effects of an Angiopoietin-1 mimetic peptide in middle-aged rats with vascular dementia.

Vascular Dementia (VaD) refers to dementia caused by cerebrovascular disease and/or reduced blood flow to the brain and is the second most common form of dementia after Alzheimer's disease. We previously found that in middle-aged rats subjected to a multiple microinfarction (MMI) model of VaD, treatment with AV-001, a Tie2 receptor agonist, significantly improves short-term memory, long-term memory, as well as improves preference for social novelty compared to control MMI rats. In this study, we tested the early therapeutic effects of AV-001 on inflammation and glymphatic function in rats subjected to VaD. Male, middle-aged Wistar rats (10-12 m), subjected to MMI, were randomly assigned to MMI and MMI + AV-001 treatment groups. A sham group was included as reference group. MMI was induced by injecting 800 ± 200, 70-100 μm sized, cholesterol crystals into the internal carotid artery. Animals were treated with AV-001 (1 μg/Kg, i.p.) once daily starting at 24 h after MMI. At 14 days after MMI, inflammatory factor expression was evaluated in cerebrospinal fluid (CSF) and brain. Immunostaining was used to evaluate white matter integrity, perivascular space (PVS) and perivascular Aquaporin-4 (AQP4) expression in the brain. An additional set of rats were prepared to test glymphatic function. At 14 days after MMI, 50 μL of 1% Tetramethylrhodamine (3 kD) and FITC conjugated dextran (500 kD) at 1:1 ratio were injected into the CSF. Rats (4-6/group/time point) were sacrificed at 30 min, 3 h, and 6 h from the start of tracer infusion, and brain coronal sections were imaged using a Laser scanning confocal microscope to evaluate tracer intensities in the brain. Treatment of MMI with AV-001 significantly improves white matter integrity in the corpus callosum at 14 days after MMI. MMI induces significant dilation of the PVS, reduces AQP4 expression and impairs glymphatic function compared to Sham rats. AV-001 treatment significantly reduces PVS, increases perivascular AQP4 expression and improves glymphatic function compared to MMI rats. MMI significantly increases, while AV-001 significantly decreases the expression of inflammatory factors (tumor necrosis factor-α (TNF-α), chemokine ligand 9) and anti-angiogenic factors (endostatin, plasminogen activator inhibitor-1, P-selectin) in CSF. MMI significantly increases, while AV-001 significantly reduces brain tissue expression of endostatin, thrombin, TNF-α, PAI-1, CXCL9, and interleukin-6 (IL-6). AV-001 treatment of MMI significantly reduces PVS dilation and increases perivascular AQP4 expression which may contribute to improved glymphatic function compared to MMI rats. AV-001 treatment significantly reduces inflammatory factor expression in the CSF and brain which may contribute to AV-001 treatment induced improvement in white matter integrity and cognitive function.

SIRT1 Signaling Is Involved in the Vascular Improvement Induced by Moringa Oleifera Seeds during Aging.

Vascular aging is linked to reduce NO bioavailability, endothelial dysfunction, oxidative stress, and inflammation. We previously showed that a 4-week treatment of middle-aged Wistar rats (MAWRs, 46 weeks old) with Moringa oleifera seed powder (MOI, 750 mg/kg/day) improved vascular function. Here, we investigated the involvement of SIRT1 in MOI-induced vascular improvement. MAWRs were treated with a standard or MOI-containing diet. Young rats (YWR, 16 weeks old) were the controls and received a standard diet. The hearts and aortas were harvested to evaluate SIRT1 and FOXO1 expression via Western blot and/or immunostaining, SIRT1 activity via a fluorometric assay, and oxidative stress using the DHE fluorescent probe. In the hearts and aortas, SIRT1 expression, reduced in MAWRs compared to YWRs, was enhanced in MOI MAWRs. In the hearts, SIRT1 activity did not differ between YWRs and MAWRs, whereas it was increased in MOI MAWRs compared with them. In the aortas, SIRT1 activity decreased in MAWRs, and it was similar in the MOI MAWRs and YWRs. FOXO1 expression increased in the nuclei of MAWR aortas compared to YWR and was reversed in MOI MAWRs. Interestingly, MOI treatment normalized oxidative stress enhanced in MAWRs, in both the heart and aorta. These results demonstrate the protective role of MOI against cardiovascular dysfunction due to aging via enhanced SIRT1 function and subsequently reduced oxidative stress.

Vitamin D3 Treatment Alters Thyroid Functional Morphology in Orchidectomized Rat Model of Osteoporosis.

Vitamin D plays an essential role in prevention and treatment of osteoporosis. Thyroid hormones, in addition to vitamin D, significantly contribute to regulation of bone remodeling cycle and health. There is currently no data about a possible connection between vitamin D treatment and the thyroid in the context of osteoporosis. Middle-aged Wistar rats were divided into: sham operated (SO), orchidectomized (Orx), and cholecalciferol-treated orchidectomized (Orx + Vit. D3; 5 µg/kg b.m./day during three weeks) groups (n = 6/group). Concentration of 25(OH)D in serum of the Orx + Vit. D3 group increased 4 and 3.2 times (p < 0.0001) respectively, compared to Orx and SO group. T4, TSH, and calcitonin in serum remained unaltered. Vit. D3 treatment induced changes in thyroid functional morphology that indicate increased utilization of stored colloid and release of thyroid hormones in comparison with hormone synthesis, to maintain hormonal balance. Increased expression of nuclear VDR (p < 0.05) points to direct, TSH independent action of Vit. D on thyrocytes. Strong CYP24A1 immunostaining in C cells suggests its prominent expression in response to Vit. D in this cell subpopulation in orchidectomized rat model of osteoporosis. The indirect effect of Vit. D on bone, through fine regulation of thyroid function, is small.

Moderate Aerobic Training Inhibits Middle-Aged Induced Cardiac Calcineurin-NFAT Signaling by Improving TGF-ß, NPR-A, SERCA2, and TRPC6 in Wistar Rats.

ObjectiveThe purpose of this study was to investigate the effect of moderate-intensity training on the calcineurin/ nuclear factor of activated t-cells (NFAT) pathway and factors affecting it in the middle-age Wistar rats.Materials and MethodsIn this experimental study, 40 young (n=10, 4-month-old) and middle-aged (n=30, 13-15 months old) Wistar rats were included in this experimental study. All young and 10 middle-aged rats did not training and served as a control comparision; while the remaining 20 middle-aged rats were trained at moderate intensity for 4-weeks (n=10) or 8-weeks (n=10) on a treadmill (speed: 16 m/minutes, slope: 0%, distance: 830 m, duration: 54 minutes). Results Calcineurin tissue expression was increased in the middle-aged control rats compared to the young control rats (P=0.001). Expression of sarco/endoplasmic reticulum Ca2+ -ATPase (SERC2A), natriuretic peptide receptor-A (NPR-A), phospholamban (PLB), plasma membrane Ca2+ ATPase (PMCA4b), and p-AKT was significantly decreased in the heart tissue of middle-aged control compared to the young control rats (P=0.001). Furthermore, transforming growth factor beta (TGF-β), including transient receptor potential canonical 6 (TRPC6), were up-regulated in the heart tissue of middle-aged control compared to the young control rats (P=0.001). However, aerobic training inhibited this pathway and reversed all changes in the trained middle-aged rats. ConclusionAerobic training effectively inhibited the calcineurin/NFATc pathway and modulated intracellular Ca2+ levels at least partially by restoring NPR-A, SERCA2, p-PLB, and p-AKT, and decreasing TRPC6 and TGF-β levels.

Effects of chronic dietary nitrate supplementation on longevity, vascular function and cancer incidence in rats

RationaleDietary nitrate and nitrite have a notoriously bad reputation because of their proposed association with disease, in particular cancer. However, more recent lines of research have challenged this dogma suggesting that intake of these anions also possess beneficial effects after in vivo conversion to the vital signaling molecule nitric oxide. Such effects include improvement in cardiovascular, renal and metabolic function, which is partly mediated via reduction of oxidative stress. A recent study even indicates that low dose of dietary nitrite extends life span in fruit flies. MethodsIn this study, 200 middle-aged Wistar rats of both sexes were supplemented with nitrate or placebo in the drinking water throughout their remaining life and we studied longevity, biochemical markers of disease, vascular reactivity along with careful determination of the cause of death. ResultsDietary nitrate did not affect life span or the age-dependent changes in markers of oxidative stress, kidney and liver function, or lipid profile. Ex vivo examination of vascular function, however, showed improvements in endothelial function in rats treated with nitrate. Neoplasms were not more common in the nitrate group. ConclusionWe conclude that chronic treatment with dietary nitrate does not affect life span in rats nor does it increase the incidence of cancer. In contrast, vascular function was improved by nitrate, possibly suggesting an increase in health span.

Effects of low-to-moderate ethanol consumption on colonic growth and gene expression in young adult and middle-aged male rats.

Excessive alcohol consumption is a risk factor associated with colorectal cancer; however, some epidemiological studies have reported that moderate alcohol consumption may not contribute additional risk or may provide a protective effect reducing colorectal cancer risk. Prior research highlights the importance of proliferation, differentiation, and apoptosis as parameters to consider when evaluating colonic cell growth and tumorigenesis. The present study investigated whether chronic low-to-moderate ethanol consumption altered these parameters of colonic cell growth and expression of related genes. Twenty-four nondeprived young adult (109 days old) and 24 nondeprived middle-aged (420 days old) Wistar rats were randomly assigned to an ethanol-exposed or a water control group (n = 12/group). The ethanol group was provided voluntary access to a 20% v/v ethanol solution on alternate days for 13 weeks. Colon tissues were collected for quantitative immunohistochemical analyses of cell proliferation, differentiation and apoptosis using Ki-67, goblet cell and TUNEL, respectively. Gene expression of cyclin D1 (Ccnd1), Cdk2, Cdk4, p21waf1/cip1 (Cdkn1a), E-cadherin (Cdh1) and p53 were determined by quantitative real-time polymerase chain reaction in colonic scraped mucosa. Ethanol treatment resulted in a lower cell proliferation index and proliferative zone, and lower Cdk2 expression in both age groups, as well as trends toward lower Ccnd1 and higher Cdkn1a expression. Cell differentiation was modestly but significantly reduced by ethanol treatment only in older animals. Overall, older rats showed decreases in apoptosis and gene expression of Cdk4, Cdh1, and p53 compared to younger rats, but there was no observed effect of ethanol exposure on these measures. These findings suggest that low-to-moderate ethanol consumption improves at least one notable parameter in colonic tumorigenesis (cell proliferation) and associated gene expression regardless of age, however, selectively decreased cell differentiation among older subjects.

Dietary supplementation of Hemidesmus indicus and swimming exercise attenuates oxidative stress in the rat brain

Background: In the current investigation, we explored the impact of swimming training and dietary fortification of Hemidesmus indicus (HI) extract on markers of oxidative stress (OS) and antioxidant capacity in the middle-aged Wistar rats. Materials and Methods: Male rats received oral supplementation of HI at a dosage of 50 and 100 mg/kg B.W and swim trained for 30 min/day with 3% intensity, 6 days/week for a duration of 84 days. Results: Training and dietary intake of 100 mg/Kg B.W HI extract enhanced antioxidant enzyme activities in the discrete regions of the brain. The OS indicators were attenuated in response to single or combined interventions. The levels of thiols were significantly upregulated in SW-T (+HI2) group. Conclusion: Our findings suggest that both interventions improve antioxidant status, by attenuating the OS markers, which can be used as a therapeutic strategy in preventing age-associated neurological disorders.

Effect of L-Methionine Feeding on Serum Homocysteine and Glutathione Levels in Male and Female Wistar Rats

Homocysteine (Hcy) is a critical indicator of cardiovascular disease. High levels of Hcy have now been recognised as a risk factor for the development of a wide range of diseases. Hyperhomocysteinemia (Hhcy) can be induced by methionine or Hcy supplementation. On the other hand, Glutathione (GSH) is a major antioxidant in the body and also an important compound for oxidative defence. It is composed of 3 amino acids: cysteine, glutamate, and glycine. Interestingly, methionine is also a crucial compound in GSH synthesis. This study aims to assess the impact of 1% L-methionine feeding (10 or 30 weeks) on the body weight and serum Hcy and GSH levels of young adult (16 weeks) and middle-aged (36 weeks) Wistar rats of both sexes. Serum was analysed for Hcy and reduced GSH levels by liquid chromatography mass spectrometry (LCMS) in response to 1% L-methionine feeding. One percent L-methionine feeding decreased body weight in all conditions investigated, although this only reached significance in males after 10 weeks supplementation and females after 30 weeks supplementation. It also induced a significant increase in the serum Hcy levels of male Wistar rats, whilst having no significant effect on Hcy serum levels in female rats. Finally, we also observed a small increase in serum GSH levels in female Wistar rats but no change in serum GSH levels in the males. These results suggest that methionine feeding affects body weight homeostasis and alters by products of methionine catabolism.

Moringa oleifera Seeds Improve Aging-Related Endothelial Dysfunction in Wistar Rats

Vascular aging is characterized by functional and structural changes of the vessel wall, including endothelial dysfunction, with decreased endothelial NO· bioavailability and elevated vasoconstrictor and inflammatory mediator production, vascular rigidity, and tone impairment. Moringa oleifera (MOI) is a little tree, and different parts of which are used in traditional medicine in tropical Africa, America, and Asia for therapeutic applications in several disorders including cardiovascular disease. The present study is aimed at assessing the effect of MOI on aging-associated alteration of the endothelial function in Wistar rats. Middle-aged Wistar rats (46-week-old males) have been fed with food containing or not 750 mg/kg/day of MOI seed powder for 4 weeks. A group of young Wistar rats (16-week-old) was used as control. Measurement of isometric contraction, western blot analysis, and immunostaining has then been performed in the aortas and mesenteric arteries to assess the endothelium function. MOI treatment improved carbachol-induced relaxation in both aortas and mesenteric arteries of middle-aged rats. In the aortas, this was associated with an increased Akt signalling and endothelial NO synthase activation and a downregulation of arginase-1. In the mesenteric arteries, the improvement of the endothelial-dependent relaxation was related to an EDHF-dependent mechanism. These results suggest a vascular protective effect of MOI seeds against the vascular dysfunction that develops during aging through different mechanisms in conductance and resistance arteries.

Immunohistomorphometric Changes of The Pituitary Gonadotropic Cells After Testosterone Application in a Rat Model of the Andropause

Abstract Andropause, the culminating phase of male ageing, is characterized by deregulation of the hypothalamic-pituitarygonadal axis and low circulating free testosterone. The aim of this study was to investigate the immunohistomorphometric characteristics of the pituitary gonadotropic i.e. follicle-stimulating hormone (FSH) and the luteinizing hormone (LH) producing cells after testosterone application in a rat model of the andropause. Middle-aged Wistar rats were divided into orchidectomized (ORX; n=8) and testosterone treated orchidectomized (ORX+T; n=8) groups. Testosterone propionate (5 mg/kg b.m./day) was administered for three weeks, while the ORX group received the vehicle alone. Immunohistochemically stained FSH and LH cells underwent morphometric and optical density-related analysis, while circulating concentrations of the sex steroids were measured by immunoassays. Serum concentrations of testosterone and estradiol were significantly (p&lt;0.05) increased by 24 and 2.7 fold respectively, compared to the ORX group. The volume of FSH and LH cells was significantly (p&lt;0.05) decreased by 51.3% and 56.6% respectively, in comparison with ORX rats. Relative volume density of FSH and LH cells was also significantly (p&lt;0.05) decreased by 54.0% and 72.8% respectively, compared to the ORX group. Results related to the optical density of gonadotropic cells (reflecting their hormonal content) were in line with the morphometric findings i.e. this parameter of FSH and LH cells was significantly (p&lt;0.05) decreased by 25.7% and 16.2% respectively, in comparison with ORX rats. Conclusion: In conclusion, applied testosterone increased the serum concentrations of sex steroids, as well as it decreased morphometric parameters and optical density of gonadotropic cells in ORX rats.

The Effects of Aging on Rho-Kinase and Insulin Signaling in Skeletal Muscle and White Adipose Tissue of Rats.

The insulin receptor substrate 1 regulates insulin-mediated glucose uptake and is a target of Rho-kinase (Rock); however, the relationship between age-related insulin resistance and Rock signaling specifically in skeletal muscle and adipose tissue is unknown. We evaluated the content and activity of Rock in C2C12 myotubes, and in skeletal muscle and white adipose tissue (WAT) from two rodent models that differ in their patterns of body fat accumulation during aging (Wistar and Fischer 344 rats). Body fat gain in the Wistar rats was greater than in Fischer rats and only Wistar rats had impairment of whole-body insulin sensitivity. Rock activity and insulin signaling were impaired in skeletal muscle in both rat models, but only middle-aged Wistar rats had higher Rock activity in WAT. These data are consistent with a positive role of Rock in regulating insulin signaling in both skeletal muscle and its negative role in the adipose tissue, suggesting that Rock activity in adipose tissue is important in age-related insulin resistance.

Chronic cachaça consumption affects the structure of tibial bone by decreasing bone density and density of mature collagen fibers in middle-aged Wistar rats

Several studies have demonstrated that alcohol consumption can decrease bone density and alter its structure. However, most of the studies did not investigate the effects of specific alcoholic beverages. This study determined the effects of chronic consumption of cachaça (a Brazilian beverage containing alcohol) on body weight (BW), tibia bone density and on the tibia collagen density in middle-aged Wistar rats. Rats with 9 months old were submitted for 100 days, to a liquid diet of cachaça diluted in water with a progressive and controlled concentration (10°GL, 15°GL, 20°GL, 25°GL, and 30°GL). Chronic cachaça intake produced a significant decrease in BW and altered bone remodeling, decreasing trabecular bone density. In chronic cachaça-treated group (CT), the production of collagen fibers in bone tissue has predominantly green birefringence. It appears that they are immature fibers that do not exist in the control group, in which there are standard predominantly yellowish mature fibers. In conclusion, chronic cachaça consumption affects the structure of the tibial bone of middle-aged rats by decreasing the bone density and reducing the density of mature collagen fibers.

Impaired insulin signaling and spatial learning in middle-aged rats: The role of PTP1B

The insulin and Brain-Derived Neurotrophic Factor (BDNF) signaling in the hippocampus promotes synaptic plasticity and memory formation. On the other hand, aging is related to the cognitive decline and is the main risk factor for Alzheimer's Disease (AD). The Protein-Tyrosine Phosphatase 1B (PTP1B) is related to several deleterious processes in neurons and emerges as a promising target for new therapies. In this context, our study aims to investigate the age-related changes in PTP1B content, insulin signaling, β-amyloid content, and Tau phosphorylation in the hippocampus of middle-aged rats. Young (3 months) and middle-aged (17 months) Wistar rats were submitted to Morris-water maze (MWM) test, insulin tolerance test, and molecular analysis in the hippocampus. Aging resulted in increased body weight, and insulin resistance and decreases learning process in MWM. Interestingly, the middle-aged rats have higher levels of PTP-1B, lower phosphorylation of IRS-1, Akt, GSK3β, mTOR, and TrkB. Also, the aging process increased Tau phosphorylation and β-amyloid content in the hippocampus region. In summary, this study provides new evidence that aging-related PTP1B increasing, contributing to insulin resistance and the onset of the AD.

Behavioral and Neurochemical Consequences of Pentylenetetrazol-Induced Kindling in Young and Middle-Aged Rats.

(1) Objectives: Epilepsy disorder is likely to increase with aging, leading to an increased incidence of comorbidities and mortality. In spite of that, there is a lack of information regarding this issue and little knowledge of cognitive and emotional responses in aging subjects following epileptogenesis. We investigated whether and how aging distress epilepsy-related behavioral and biochemical outcomes are associated with cognition and emotion. (2) Methods: Young and middle-aged Wistar rats (3 or 12 months old) were treated with pentylenetetrazol (PTZ, 35 mg/kg) and injected on alternated days for 20 (young rats) and 32 days (middle-aged rats). Kindling was reached after two consecutive stages 4 plus one stage 5 or 6 in Racine scale. Control and kindled rats were evaluated in the elevated plus-maze (EPM) and object-recognition tests and their hippocampus was collected 24 h later for mitogen-activated protein kinases (MAPK) dosage. (3) Results: Middle-aged rats presented a higher resistance to develop kindling, with a decrease in the seizure severity index observed following the 4th and 9th PTZ injections. Middle-aged rats displayed an increased duration of the first myoclonic seizure and an increased latency to the first generalized seizure when compared to younger rats. The induction of kindling did not impair the animals’ performance (regardless of age) in the object-recognition task and the EPM test as well as it did not alter the hippocampal levels of MAPKs. (4) Significance: Our findings reveal that, despite age-related differences during epileptogenesis, middle-aged rats evaluated after kindling performed similarly during discriminative learning and emotional tasks in comparison to young animals, with no alteration of hippocampal MAPKs. Additional investigation must be carried out to explore the electrophysiological mechanisms underlying these responses, as well as the long-term effects displayed after kindling.

Melatonin: Antioxidant and modulatory properties in age-related changes during Trypanosoma cruzi infection.

The purpose of this study was to investigate the effects of melatonin on selected biomarkers of innate and humoral immune response as well as the antioxidant/oxidant status (superoxide dismutase-SOD and reduced glutathione levels (GSH) to understand whether age-related changes would influence the development of acute Trypanosoma cruzi (T.cruzi) infection. Young- (5weeks) and middle-aged (18months) Wistar rats were orally treated with melatonin (gavage) (05mg/kg/day), 9days after infection. A significant increase in both SOD activity and GSH levels was found in plasma from all middle-aged melatonin-treated animals. Melatonin triggered enhanced expression of major histocompatibility class II (MHC-II) antigens on antigen-presenting cell (APC) and peritoneal macrophages in all treated animals. High levels of CD4+ CD28-negative T cells (*P<.05) were detected in middle-aged control animals. Melatonin induced a significant reduction (***P<.001) in CD28-negative in CD4+ and CD8+ T cells in middle-aged control animals. Contrarily, the same group displayed upregulated CD4+ CD28+ T and CD8+ CD28+ T cells. Melatonin also triggered an upregulation of CD80 and CD86 expression in all young-treated groups. Significant percentages of B and spleen dendritic cells in middle-aged infected and treated animals were observed. Our data reveal new features of melatonin action in inhibiting membrane lipid peroxidation, through the reduction in 8-isoprostane, upregulating the antioxidant defenses and triggering an effective balance in the antioxidant/oxidant status during acute infection. The ability of melatonin to counteract the immune alterations induced by aging added further support to its use as a potential therapeutic target not only for T.cruzi infection but also for other immunocompromised states.

β-Cell dedifferentiation, reduced duct cell plasticity, and impaired β-cell mass regeneration in middle-aged rats.

Limitations in β-cell regeneration potential in middle-aged animals could contribute to the increased risk to develop diabetes associated with aging. We investigated β-cell regeneration of middle-aged Wistar rats in response to two different regenerative stimuli: partial pancreatectomy (Px + V) and gastrin administration (Px + G). Pancreatic remnants were analyzed 3 and 14 days after surgery. β-Cell mass increased in young animals after Px and was further increased after gastrin treatment. In contrast, β-cell mass did not change after Px or after gastrin treatment in middle-aged rats. β-Cell replication and individual β-cell size were similarly increased after Px in young and middle-aged animals, and β-cell apoptosis was not modified. Nuclear immunolocalization of neurog3 or nkx6.1 in regenerative duct cells, markers of duct cell plasticity, was increased in young but not in middle-aged Px rats. The pancreatic progenitor-associated transcription factors neurog3 and sox9 were upregulated in islet β-cells of middle-aged rats and further increased after Px. The percentage of chromogranin A+/hormone islet cells was significantly increased in the pancreases of middle-aged Px rats. In summary, the potential for compensatory β-cell hyperplasia and hypertrophy was retained in middle-aged rats, but β-cell dedifferentiation and impaired duct cell plasticity limited β-cell regeneration.

Histological parameters of the adrenal cortex after testosterone application in a rat model of the andropause.

Histological analysis of the adrenal cortex, after testosterone application in a rat model of the andropause, was the main subject of the present study. Middle-aged Wistar rats were divided into sham-operated (SO; n=8), orchidectomized (Orx; n=8) and testosterone treated orchidectomized (Orx+T; n=8) groups. Testosterone propionate (5 mg/kg b.w. /day) was administered for three weeks, while SO and Orx groups received the vehicle alone. Histological objectives were achieved using stereology, histochemistry and steroid receptor immunostaining. The concentrations of testosterone, aldosterone, corticosterone and DHEA were determined by immunoassays. Expectedly, increased (p<0.05) serum concentration of testosterone was observed in Orx+T group. The volume of ZG cells and nuclei increased in Orx+T animals by 50% and 25% (p<0.05) respectively, but the serum concentrations of aldosterone decreased (p<0.05) by 60%, all compared to the same parameters in Orx group. The immunostaining for androgen receptors (ARs) suggested their cytoplasmic localization in ZG cells of Orx+T rats. Volume of the ZF cell nuclei in Orx+T group decreased (p<0.05) by 17%, which was followed by the significant (p<0.05) fall in corticosterone production and secretion, all in comparison with Orx animals. Also, nuclear immunolocalization of ARs of high optical density was observed through the ZF of Orx+T group. In Orx+T rats volume of ZR cells and nuclei, and circulating DHEA concentration increased (p<0.05) by 68%, 22% and about 6.6 times respectively, compared to Orx animals. Besides the extra-receptor actions in adrenal cortex, testosterone supposedly affects some steroidogenesis-related gene expression, as indicated by centripetal rise in the number of nuclear ARs.