Stress-reactive rats (high-avoidance female rats) have a shorter lifespan than stress-nonreactive rats (low-avoidance female rats)

The effects of long-term moderate exercise and Western-type diet on oxidative/nitrosative stress, serum lipids and cytokines in female Sprague Dawley rats

Purpose

Regular exercise reduces obesity and the risk of cardiovascular disease. However, health-promoting benefits of physical activity are commonly associated with increased inflammation and oxidative stress. Here, we tested whether constant moderate exercise is able to prevent or attenuate the oxidative/nitrosative stress, inflammation, and serum lipids in lean and obese rats.

Methods

Four-month-old female Sprague Dawley rats received standard or a high-fat diet. Animals were subjected to a physical activity protocol, consisting of 30 min forced treadmill exercise for 5 consecutive days per week during 10 months. Baseline and sedentary (non-exercised) rats were used as controls. Lipids, oxidized low-density lipoprotein cholesterol, nitric oxide metabolites, and pro- and anti-inflammatory markers were measured in blood collected upon euthanasia.

Results

At variance to young baseline control rats, 14-month-old animals fed normal diet had increased plasma lipid levels, including total cholesterol and triglycerides, which were further elevated in rats that consumed a high-fat diet. While treadmill exercise did not lower the amount of serum lipids in standard diet group, forced physical activity reduced non-high-density lipoprotein cholesterol in response to high-fat diet feeding. Exercised rats fed standard diet or high-fat diet had lower abundancy of nitric oxide metabolites, which coincided with increased levels of oxidized low-density lipoprotein cholesterol. Accordingly, the amount of nitric oxide metabolites correlated inversely with oxidized low-density lipoprotein cholesterol and homo-arginine. Exercise significantly reduced inflammatory cytokines in high-fat diet fed rats only.

Conclusion

Our study suggests that regular exercise alters the equilibrium between oxidative and anti-oxidative compounds and reduces pro-inflammatory cytokines.

Intrarenal Renin–Angiotensin System Involvement in the Pathogenesis of Chronic Progressive Nephropathy—Bridging the Informational Gap Between Disciplines

Chronic progressive nephropathy (CPN) is the most commonly encountered spontaneous background finding in laboratory rodents. Various theories on its pathogenesis have been proposed, but there is a paucity of data regarding specific mechanisms or physiologic pathways involved in early CPN development. The current CPN mechanism of action for tumorigenesis is largely based on its associated increase in tubular cell proliferation without regard to preceding subcellular degenerative changes. Combing through the published literature from multiple biology disciplines provided insight into the preceding cellular events. Mechanistic pathways involved in the progressive age-related decline in rodent kidney function and several key inflexion points have been identified. These critical pathway factors were then connected using data from renal models from multiple rodent strains, other species, and mechanistic work in humans to form a cohesive picture of pathways and protein interactions. Abundant data linked similar renal pathologies to local events involving hypoxia (hypoxia-inducible factor 1α), altered intrarenal renin–angiotensin system (RAS), oxidative stress (nitric oxide), and pro-inflammatory pathways (transforming growth factor β), with positive feedback loops and downstream effectors amplifying the injury and promoting scarring. Intrarenal RAS alterations seem to be central to all these events and may be critical to CPN development and progression.

Effects of pregnancy experience on ovarian senescence and longevity in Hatano rats bred for high- and low-avoidance learning

We investigated the effects of pregnancy experience on ovarian senescence and longevity using two inbred strains of Hatano rats. These strains have been selectively bred for high- and low-avoidance animals (HAA and LAA, respectively), but the HAA line has a slower onset of ovarian senescence and a shorter lifespan compared with the LAA line. The onset of abnormal estrous cycles and survival curves were compared between nulliparous and parous rats in each line. In the HAA line, pregnancy experience did not change the onset of ovarian senescence but increased longevity. This suggests that a pituitary tumor, which is a causal factor for accelerated mortality in this line, developed slowly in parous rats. In the LAA line, pregnancy experience delayed the onset of ovarian senescence and reduced the incidence of mammary tumors but did not increase longevity because of an increased frequency of constipation with megacolon. These data suggest that the effects of pregnancy experience on ovarian senescence and longevity depend on the reproductive characteristics of the rat strains.

Hatano rats selectively bred for high- and low-avoidance learning: an overview

This review compiles the results of a series of studies on Hatano high- and low-avoidance animals (HAA and LAA, respectively) established at the Hatano Research Institute, Food and Drug Safety Center, Japan. The HAA and LAA lines were selected and bred from Sprague Dawley rats for high and low avoidance learning, respectively, in a shuttlebox task since 1985. Although Hatano rats were selected only based on their behavioral traits in the active avoidance task, strain differences between the HAA and LAA lines were also observed in their stress responses and reproductive functions. However, the most noticeable finding of Hatano rats is a matched result in both active and passive avoidance tasks. The HAA and LAA lines are useful for next-generation toxicological studies, because the hereditary characters of behaviors or endocrine functions are well controlled.

An acellular bioresorbable ultra-purified alginate gel promotes intervertebral disc repair: A preclinical proof-of-concept study

Background

The current surgical procedure of choice for lumbar intervertebral disc (IVD) herniation is discectomy. However, defects within IVD produced upon discectomy may impair tissue healing and predispose patients to subsequent IVD degeneration. This study aimed to investigate whether the use of an acellular bioresorbable ultra-purified alginate (UPAL) gel implantation system is safe and effective as a reparative therapeutic strategy after lumbar discectomy.

Methods

Human IVD cells were cultured in a three-dimensional system in UPAL gel. In addition, lumbar spines of sheep were used for mechanical analysis. Finally, the gel was implanted into IVD after discectomy in rabbits and sheep in vivo.

Findings

The UPAL gel was biocompatible with human IVD cells and promoted extracellular matrix production after discectomy, demonstrating sufficient biomechanical characteristics without material protrusion.

Interpretation

The present results indicate the safety and efficacy of UPAL gels in a large animal model and suggest that these gels represent a novel therapeutic strategy after discectomy in cases of lumbar IVD herniation.

Fund

Grant-in-Aid for the Ministry of Education, Culture, Sports, Science, and Technology of Japan, Japan Agency for Medical Research and Development, and the Mochida Pharmaceutical Co., Ltd.

Genetic variation in low-dose effects of neonatal DES exposure in female rats

To confirm genetic variation in low-dose effects of diethylstilbestrol (DES), two inbred strains of rats, which have been selectively bred for high- and low-avoidance learning (HAA and LAA, respectively), were used in this study. LAA rats characteristically show later sexual maturation, earlier reproductive senescence, and lower body weight as compared to HAA rats. Female neonates of each strain were daily administered DES by oral gavage at doses of 0 (vehicle only), 0.05 and 0.5μg/kg for the first 5days after birth. As a result, early onset of abnormal estrous cycles was observed during the same period in HAA and LAA rats treated with 0.5μg/kg. However, accelerated puberty and excessive body weight gains were observed only in LAA rats treated with 0.05 and 0.5μg/kg. These results suggest that the effects of neonatal DES exposure vary with the genetic background of the female rats used.