Increasing environmental contamination with microplastics (MPs) raises significant concerns regarding their potential impact on reproductive health. This study evaluated the effects of prolonged oral exposure to fluorescent polystyrene microplastics (FPS-MPs) of different sizes on the male reproductive system in Wistar rats. Juvenile male rats at 21 days of age were exposed to FPS-MPs of 1 µm and 5 µm for 52 days, covering the period of sexual maturation and a complete spermatogenesis cycle. Body weight, reproductive organ indices, serum levels of testosterone (T), estradiol (E2), follicle-stimulating hormone (FSH), and luteinizing hormone (LH), as well as sperm motility and morphology, were assessed. Reproductive potential and accumulation of microplastics in reproductive tissues were also evaluated. No significant differences were observed in body weight or most reproductive organ indices, except for a slight reduction in the left epididymis index in the group exposed to 5 µm particles. FPS-MPs induced size-dependent changes in the hormonal profile, including decreases in T and E2 and compensatory increases in FSH and LH, as well as impairments in sperm quality, which were more pronounced in rats exposed to smaller particles. In conclusion, fertility potential remained preserved, while FPS-MPs accumulated in the testes and epididymides, demonstrating subclinical, size-dependent effects on the male reproductive system.

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system, characterized by inflammatory demyelination and neurodegeneration. Fampyridine (4-aminopyridine, 4-AP) is a drug used for MS treatment as it readily passes through the blood-brain barrier exhibiting anti-inflammatory effects. Its high toxicity, however, limits its wider application. To reduce 4-AP high toxicity, we have designed new peptides-containing 4-AP derivatives showing about 150 times lower toxicity than 4-AP. This work aims to investigate the cytotoxicity and in vivo anti-inflammatory effects of three newly synthesized peptide derivatives of 4-AP, defined as substances A, B, and C. In addition, their inhibitory potential against MMP-2 and -9 proteolytic activity was evaluated as well. To study the anti-inflammatory effect of the 4-AP-derivatives we used a rat model for immune complex-induced inflammation. In vitro cytotoxicity test was performed on WEHI-164 cells. Inhibition of matrix metalloproteinase (MMP-9 and -2) proteolytic activity was assessed by gelatinase zymography and densitometric analysis. Our results showed that treatment with the 4-AP derivatives kept cells viable and metabolically active showing no cytotoxicity. Substances A and C inhibited the proteolytic activity of both isoforms of MMP-2 and -9 even when applied in the lowest concentration, whereas substance B had no inhibitory effect on the MMP-9 activity and inhibited MMP-2 activity only applied at higher concentrations. Along with its inhibitory effect on the MMP-2 and -9 proteolytic activity, substance A demonstrated a clear anti-inflammatory effect either preventing or inhibiting the production of antibodies in the blood circulation of rats. Substance A might be very promising as a drug molecule.

The potential of the epiphyseal hormone melatonin to effect on seasonally breeding species has been extensively studied, but the data remain inconclusive. Levels of reproductive parameters modulation are important to monitoring, given the breed affiliation, as example analyzed breed, which has a pronounced seasonal type of reproduction. The objective of this study was to determine whether application of exogenous melatonin has an effect on ram fertility of the North-east Bulgarian fine-wool sheep breed, as estimated by the reproductive performances of ewes, in the non-breeding season. In addition, the study quantified the effects of exogenous melatonin on ejaculate volume and concentration of sperm in rams with melatonin implants (n = 5) and per os treated rams (n = 5). The application of exogenous melatonin improves the fertility of rams of the studied breed. As a result of the current study, in the 2nd experimental group there was a positive trend on ejaculate volume and concentration of sperm throughout the experiment compared to control group. Although rams exhibited an improvement in sperm parameters, a significantly increased birth rate was found in sheep mating with male receiving melatonin both through implants (P < 0.05) and per os (P < 0.05). It was found to increase the total percentage of birth lambs in 1st (28%) and 2nd (29%) experimental groups compared to control. The results are guiding for North-east Bulgarian fine-wool sheep farmers and breeders, in terms of opportunities to improve the breeding process and obtain more lambs.