The Effect of Age and Intrinsic Aerobic Exercise Capacity on the Expression of Inflammation and Remodeling Markers in Rat Achilles Tendons

Old age, adiposity, and metabolic disorders are known as risk factors for chronic tendinopathy, which is a common problem in both athletes and the general population. However, the importance of these influencing factors has not yet been well understood. This study investigated alterations in gene expression and histology of Achilles tendons of young (10 weeks) and old (100 weeks) rats bred for low (low capacity runners, LCR) and high (high capacity runners, HCR) intrinsic aerobic exercise capacity. In this rat model, LCR displayed a phenotype of reduced exercise capacity, higher body weight, and metabolic dysfunctions compared to HCR. We hypothesized that the risk factors for tendinopathy in old LCR could lead to more pronounced impairments in Achilles tendon tissue. In quantitative real-time PCR (qPCR), age-related downregulation of tenocyte markers e.g., tenomodulin, genes related to matrix modeling and remodeling (e.g., collagens, elastin, biglycan, fibronectin, tenascin C) as well as transforming growth factor beta 3 (Tgfb3) have been detected. Inflammation marker cyclooxygenase 2 (Cox2) was downregulated in old rats, while microsomal prostaglandin E synthase 2 (Ptges2) was upregulated in old HCR and old LCR. In all groups, interleukin 6 (Il6), interleukin 1 beta (Il1b), and tumor necrosis factor alpha (Tnfa) showed no significant alteration. In histological evaluation, tendons of old rats had fewer and more elongated tenocyte nuclei than young rats. Even though a higher content of glycosaminoglycans, a sign of degeneration, was found in old HCR and LCR, no further signs of tendinopathy were detectable in tendons of old rats by histological evaluation. Low intrinsic aerobic exercise capacity and the associated phenotype did not show significant effects on gene expression and tendon histology. These findings indicate that aging seems to play a prominent role in molecular and structural alterations of Achilles tendon tissue and suggests that other risk factors associated with intrinsic aerobic exercise capacity are less influential in this rat model.

Anticonvulsive Effects and Pharmacokinetic Profile of Cannabidiol (CBD) in the Pentylenetetrazol (PTZ) or N-Methyl-D-Aspartate (NMDA) Models of Seizures in Infantile Rats

In spite of use of cannabidiol (CBD), a non-psychoactive cannabinoid, in pediatric patients with epilepsy, preclinical studies on its effects in immature animals are very limited. In the present study we investigated anti-seizure activity of CBD (10 and 60 mg/kg administered intraperitoneally) in two models of chemically induced seizures in infantile (12-days old) rats. Seizures were induced either with pentylenetetrazol (PTZ) or N-methyl-D-aspartate (NMDA). In parallel, brain and plasma levels of CBD and possible motor adverse effects were assessed in the righting reflex and the bar holding tests. CBD was ineffective against NMDA-induced seizures, but in a dose 60 mg/kg abolished the tonic phase of PTZ-induced generalized seizures. Plasma and brain levels of CBD were determined up to 24 h after administration. Peak CBD levels in the brain (996 ± 128 and 5689 ± 150 ng/g after the 10- and 60-mg/kg doses, respectively) were reached 1–2 h after administration and were still detectable 24 h later (120 ± 12 and 904 ± 63 ng/g, respectively). None of the doses negatively affected motor performance within 1 hour after administration, but CBD in both doses blocked improvement in the bar holding test with repeated exposure to this task. Taken together, anti-seizure activity of CBD in infantile animals is dose and model dependent, and at therapeutic doses CBD does not cause motor impairment. The potential risk of CBD for motor learning seen in repeated motor tests has to be further examined.

Age-Dependent Changes in the Function of Mitochondrial Membrane Permeability Transition Pore in Rat Liver Mitochondria

Mitochondria play an important role in the cell aging process. Changes in calcium homeostasis and/or increased reactive oxygen species (ROS) production lead to the opening of mitochondrial permeability transition pore (MPTP), depolarization of the inner mitochondrial membrane, and decrease of ATP production. Our work aimed to monitor age-related changes in the Ca2+ ion effect on MPTP and the ability of isolated rat liver mitochondria to accumulate calcium. The mitochondrial calcium retention capacity (CRC) was found to be significantly affected by the age of rats. Measurement of CRC values of the rat liver mitochondria showed two periods when 3 to17-week old rats were tested. 3-week and 17-week old rats showed lower CRC values than 7-week old animals. Similar changes were observed while testing calcium-induced swelling of rat liver mitochondria. These findings indicate that the mitochondrial energy production system is more resistant to calcium-induced MPTP opening accompanied by the damaging effect of ROS in adult rats than in young and aged animals.

Corticosterone and Glucocorticoid Receptor in the Cortex of Rats during Aging—The Effects of Long-Term Food Restriction

Numerous beneficial effects of food restriction on aging and age-related pathologies are well documented. It is also well-established that both short- and long-term food restriction regimens induce elevated circulating levels of glucocorticoids, stress-induced hormones produced by adrenal glands that can also exert deleterious effects on the brain. In the present study, we examined the effect of long-term food restriction on the glucocorticoid hormone/glucocorticoid receptor (GR) system in the cortex during aging, in 18- and 24-month-old rats. Corticosterone level was increased in the cortex of aged ad libitum-fed rats. Food restriction induced its further increase, accompanied with an increase in the level of 11β-hydroxysteroid dehydrogenase type 1. However, alterations in the level of GR phosphorylated at Ser232 were not detected in animals on food restriction, in line with unaltered CDK5 level, the decrease of Hsp90, and an increase in a negative regulator of GR function, FKBP51. Moreover, our data revealed that reduced food intake prevented age-related increase in the levels of NFκB, gfap, and bax, confirming its anti-inflammatory and anti-apoptotic effects. Along with an increase in the levels of c-fos, our study provides additional evidences that food restriction affects cortical responsiveness to glucocorticoids during aging.

INFLUENCE OF DIFFERENT LIGHTING REGIMEN ON THE MORPHOMETRIC CHARACTERISTICS OF NEURONS IN THE PARAVENTRICULAR NUCLEI OF THE RAT HYPOTHALAMUS

Paraventricular nuclei (PVN) of the hypothalamus are the autonomic center forcoordination of functions and consists of a number of neuronal populations - sub-nuclei,which differ in structural and functional features and the nature of nerve connectionswith various parts of the nervous and neuroendocrine systems. When studying stressreactions and actions of the stress-limiting factors, it is important to study subpopulationsof PVN neurons of the hypothalamus, synthesizing stress-releasing hormones, whichinitiate stress reactions of the body. One of the main factors that show a pronouncedeffect in the regulation of ACTH secretion is corticotropin-releasing factor (CRF). TheCRF-immunoreactive tracer was found mainly in the medial small-cell subnucleus of theparaventricular nuclei of the rat hypothalamus. Despite deep and comprehensive studiesof the hypothalamus, until now there are no unifed ideas about its individual reactivityand the degree of involvement of these structures into the stress reaction caused by theprolonged change in the lighting regime.Purpose - to fnd out the effect of different illumination regimes on the morphometriccharacteristics of the medial small-cell subnuclei of the paraventricular nuclei of thehypothalamus of mature and old rats.Material and methods. The experiments were conducted on 72 nonlinear white malerats, divided into 6 series of studies, in each of which the biomaterial sampling wascarried out at 14.00 and 02.00 h using morphometric and statistical research methods.Results. Morphometric assessment of the medial small-cell sub-nuclei of theparaventricular nuclei (msPVN) of the hypothalamus of rats revealed the diurnaldynamics of indices. It has been established that in both old and mature rats, theiraverage volume (p <0.05) signifcantly decreases at 2.00 compared to 14.00 undernormal lighting. The nuclear-cytoplasmatic ratio at 02.00 increases in comparison with14.00 respectively.When the animals were kept under constant illumination, more pronounced changesin the structures under study were established. In particular, the volume of neurons inthe msPVN of the hypothalamus decreases both mature and old rats compared withrats under standard illumination and even more in comparison with rats under lightdeprivation. In accordance with this, the NCR also changes. The average number ofneurons on the standard plane of the histological section also decreases in comparisonwith other illumination regimes. It is also necessary to point out that under conditionsof light stimulation in mature rats in msPVN, the average volume of neurons (p <0.05)noticeably decreases at 02:00 in comparison with 14:00, when the volume of theirnuclei does not change on average during the indicated study periods. This is reflected,respectively, in the NCR change, which increases at 02.00 in comparison with 14.00.As to the old rats, the average neuron volume does not decrease at 2.00 in comparisonwith 14.00 in msPVN neurons at light stimulation, as well as the volume of their neucleichanges, on average, is barely noticeable ,and according to it, NCR at 02.00 remainsstable in comparison with 14.00, and the average quantity of neurocytes in msPVN doesnot change on a standard plane of the histological section during various periods ofthe twenty four hours. At the same time, with various modifcations of the light regime,cytometric parameters of neurons under study in old rats, on average, are signifcantlylower (p <0.001) than those in mature rats.Conclusions. 1. The duration of the photoperiod signifcantly affects the 24 hoursactivity of msPVN in the hypothalamus of mature and old rats. In particular, in bothinvestigated groups of rats, the average volume of neurons (p <0.05) reliably decreasesat 2.00 under normal illumination in comparison with 14.00, and, accordingly, the NCR at 02.00 increases compared to 14.00. All cytometric parameters of their neurons in oldrats are, on average, signifcantly lower (p <0.001) than in mature rats.2. Constant illumination causes more pronounced changes in the morphometricparameters of the msPVN of the hypothalamus than light deprivation. Thus, in maturerats in the msPVN, the average volume of neurons (p <0.05) decreases noticeably at02:00 in comparison with 14:00, which is reflected, respectively, in the change in NCR,which increases at 02:00 compared to 14:00. For old rats, under light stimulation, allthe studied cytometric parameters of their neurons, on average, are signifcantly lower(p <0.001) than those in mature rats.

ULTRASTRUCTURAL ORGANIZATION OF NEURONS OF THE LATERAL PREOPTIC NUCLEUS OF THE HYPOTHALAMUS OF OLD RATS UNDER VARIOUS LIGHT CONDITIONS

Purpose – to study the changes in the ultrastructure of neurons of the lateral preopticnucleus (LPON) of the hypothalamus of old rats under various light conditions.Material and methods. The experiments were carried out on 36 old white male rats.The material was fixed in a 2.5% solution of glutaraldehyde, prepared on the basisof phosphate buffer with a pH of 7.2–7.4. Then, postfixation was performed in a 1%solution of osmium tetraoxide and dehydrated in propylene oxide, after which it waspoured into a mixture of epoxy resins. Ultrathin sections made on an ultramicrotomeLKB-3 were contrasted with uranium acetate and lead citrate according to the Reynoldsmethod and studied under electron microscope TEM - 125 K.Results. Studies of LPON neurons under the standard light mode revealed nuclei withuneven contours. The nucleoli are quite large. The neuroplasm contains well-developedtubules of the rough endoplasmic reticulum (ER) and small cisternae of the Golgi complex(GC). Mitochondria are rounded, small, with moderately pronounced cristae. Underconditions of round-the-clock darkness, we have found that the cell nuclei are rounded,less often determined by the nucleoli. In the neuroplasm there are locally dilated tubulesof the ER and cisternae of the GC, mitochondria with enlightened matrix and fragmentedcristae. Under conditions of round-the-clock illumination, the nuclei of the rounded formwith uneven contours of a nuclear membrane forming deep intussusception are revealed.Nucleoli were rarely identified. In the hyaloplasm, locally dilated tubules of the ERare identified. Mitochondria are small in size with an enlightened matrix and reducedcristae.Conclusions. The obtained results of submicroscopic examination of LPON neuronsof the hypothalamus of old rats revealed their relatively increased functional activityin the dark period. Under conditions of round-the-clock lighting, more pronouncedhypertrophic and initial destructive changes of the nuclei and organelles of the neuronsof the LPON of the hypothalamic were revealed, compared with the animals that wereunder the conditions of round-the-clock darkness. This is confirmed by the change in theultrastructure of nerve cells at 2 am the appearance of "dark" cells.

Loss of ischemic tolerance with age: can we protect an old kidney

The most abundant and vulnerable cohort of patients with acute kidney injury (AKI) is represented by the older people. It is well-known, the kidney tissue undergoes some changes with age, both at the morphological and molecular level. Therefore, when treating AKI in older patients, it is necessary to take into account the morphofunctional features of aging kidney tissue and metabolic alterations. We have shown that the kidney of old rats does not perceive signals from the most well-known protective approaches such as ischemic preconditioning (IPC) and caloric restriction (CR). Although the old kidney did not develop more severe AKI after ischemia, we found no pronounced effect on attempts to increase its resistance by IPC and CR. Analysis of the mechanisms underlying this loss of tolerance has shown that the most affected pathways are the mechanism of mitochondrial quality control, the effectiveness of autophagy, and the proliferative potential of kidney cells. However, several protective pathways activated in the young kidney were also active in the old one in response to the CR. In particular, an increase in SIRT1 deacetylase, antiapoptotic Bcl-xL, and a decrease in oxidative stress were observed. Our results show that some defense systems demonstrating their effectiveness in young organisms lose their beneficial effect in old organisms, while others still can be activated by protective approaches. Thus, it is necessary to carefully analyze the possibilities of increasing ischemic tolerance for old organisms. This work was supported by the Russian science foundation (grant #21-75-30009).

Rats exhibit age-related mosaic loss of chromosome Y

Mosaic loss of the Y chromosome (LOY) is the most frequent chromosomal aberration in aging men and is strongly correlated with mortality and disease. To date, studies of LOY have only been performed in humans, and so it is unclear whether LOY is a natural consequence of our relatively long lifespan or due to exposure to human-specific external stressors. Here, we explored whether LOY could be detected in rats. We applied a locus-specific PCR and target sequencing approach that we used as a proxy to estimate LOY in 339 samples covering eleven tissues from young and old individuals. We detected LOY in four tissues of older rats. To confirm the results from the PCR screening, we re-sequenced 60 full genomes from old rats, which revealed that the Y chromosome is the sole chromosome with low copy numbers. Finally, our results suggest that LOY is associated with other structural aberrations on the Y chromosome and possibly linked to the mosaic loss of the X chromosome. This is the first report, to our knowledge, demonstrating that the patterns of LOY observed in aging men are also present in a rodent, and conclude that LOY may be a natural process in placental mammals.

Study of the skin-resorptive effect of a skin antiseptic based on polyvinylpyrollidone-iodineОценка эффективности профилактических дезинфекционных мероприятий на основе комплексного анализа микробиома мест содержания служебных собак

The skin-resorptive effect of a skin antiseptic based on polyvinylpyrollidone-iodine on immature rats of different ages was studied.The skin-resorptive effect of the drug in doses of 5.0 and 0.5 g/kg was revealed on 2–6 week-old rats. The animals showed changes in thyroxine and thyroid-stimulating hormone, as well as general toxic indicators. Absorption of the drug through the skin at a dose of 0.5 g/kg on 4–8 week old rat pups has not been established. The rationale for the use of a skin antiseptic for the hygienic treatment of hands containing PVP-iodine in the age group of children from 8 years old is given. Keywords: toxicity, skin-resorptive effect, immature white rats, skin antiseptic, iodine, thyroxine, thyroid-stimulating hormone.