Entrainment of the circadian clock within the rat suprachiasmatic nukleus during fetal and early postnatal development

All mammals exhibit daily rhythms which persist in non-periodic environment with a period close to 24h. These rhythms are entrained to the 24h day mostly by the light-dark cycle. These circadian rhythms are controlled by a clock (pacemaker) located in the suprachiasmatic nuclei (SCN) of the hypothalamus. In the rat, the circadian clock within the SCN develops gradually from prenatal to postnatal period and is supposed to be synchronized mainly by maternal signals. However, the rat SCN is sensitive to light immediately after birth. The aim of the present work was to investigate the mechanism of entrainment of the circadian clock within the rat SCN during fetal and early postnatal development. The specific questions were whether and when the immature fetal and neonatal molecular SCN clocks can be reset by maternal cues, and whether and when the external light-dark cycle (LD) can affect the developing circadian rhythms. The role of light-dark cycle in the development of the photoperiodic entrainment during early postnatal period was also examined. Experiment no. (1): Pregnant rats were maintained under a light - dark regime with 12 h of light and 12 h of darkness (LD12:12). At gestational day 20 (E20), the fetuses were sampled throughout the day under either LD12:12 or constant darkness (DD). The...All mammals exhibit daily rhythms which persist in non-periodic environment with a period close to 24h. These rhythms are entrained to the 24h day mostly by the light-dark cycle. These circadian rhythms are controlled by a clock (pacemaker) located in the suprachiasmatic nuclei (SCN) of the hypothalamus. In the rat, the circadian clock within the SCN develops gradually from prenatal to postnatal period and is supposed to be synchronized mainly by maternal signals. However, the rat SCN is sensitive to light immediately after birth. The aim of the present work was to investigate the mechanism of entrainment of the circadian clock within the rat SCN during fetal and early postnatal development. The specific questions were whether and when the immature fetal and neonatal molecular SCN clocks can be reset by maternal cues, and whether and when the external light-dark cycle (LD) can affect the developing circadian rhythms. The role of light-dark cycle in the development of the photoperiodic entrainment during early postnatal period was also examined. Experiment no. (1): Pregnant rats were maintained under a light - dark regime with 12 h of light and 12 h of darkness (LD12:12). At gestational day 20 (E20), the fetuses were sampled throughout the day under either LD12:12 or constant darkness (DD). The...Dep. of Physiology and Develop. Biology (obsolete)Katedra fyziol. živočichů a vývoj. biol. (zrušena)Faculty of SciencePřírodovědecká fakult

THE IMMUNOTHERAPEUTIC EFFECT OF IL-22 VERSUS PRAZIQUANTEL TREATMENT AGAINST S.MANSONI –INDUCED LIVER FIBROSIS IN MICE

Background/Aim:Praziquantel (PZQ), the primary medication for schistosomiasis treatment, exhibits a potential resistance by the parasite. Therefore, the development of a new effective treatment is obligated. Interleukin-22 (IL-22) has been reported to have a hepatoprotective effect. The current study aimed to compare the effectiveness of IL-22 treatment versus PZQ against S. mansoni - induced liver fibrosis in mice. Materials and Methods: Forty male albino mice were divided into control, infected, IL-22 (0.36 µg/kg),  and PZQ (a single dose of 600 mg/kg) groups. PZQ was administered alone or in combination with IL-22. Inflammatory indicators [tumor necrosis factor-α (TNF-α), interleukin-17 (IL-17), IL-22, and immunoglobulin E (IgE)], hepatic expressions of signal transducer and activator of transcription 3 (STAT3), β-catenin, and miR let-7a gene expressions, and liver granuloma index (GI) were estimated. Results:The present result revealed a significant (P <0.05) reduction in liver GI and the pro-inflammatory cytokine, TNF-α, after the treatment with IL-22. Moreover, the treatment enhanced significantly (P <0.05) let-7a miRNA and STAT3 gene expressions as well as downregulated (P <0.05) β-catenin mRNA, which in turn could reduce fibrosis resulting from S. mansoni infection. On the other hand, PZQ treatment alone or in combination with IL-22 reduced significantly (P <0.05) proinflammatory cytokines and IgE but failed to decrease GI or β-catenin gene expression, which might cause a negative impact on liver fibrosis.  Conclusion:IL-22 could be a potential immunotherapeutic agent for S.mansoni-induced liver fibrosis, compared to PZQ, through activating STAT3 and let-7a downstream signalling pathways and inhibiting β-catenin pathway

Setting the biological time in central and peripheral clocks during ontogenesis

AbstractIn mammals, the principal circadian clock within the suprachiasmatic nucleus (SCN) entrains the phase of clocks in numerous peripheral tissues and controls the rhythmicity in various body functions. During ontogenesis, the molecular mechanism responsible for generating circadian rhythmicity develops gradually from the prenatal to the postnatal period. In the beginning, the maternal signals set the phase of the newly developing fetal and early postnatal clocks, whereas the external light–dark cycle starts to entrain the clocks only later. This minireview discusses the complexity of signaling pathways from mothers and the outside world to the fetal and newborn animals’ circadian clocks

Reversed Light-Dark Cycle and Restricted Feeding Regime Affect the Circadian Rhythm of Insulin and Glucose in Male Rats

Circadian clock is entrained by external time cues and influences nearly all aspects of physiology

Entrainment of the circadian clock within the rat suprachiasmatic nukleus during fetal and early postnatal development

All mammals exhibit daily rhythms which persist in non-periodic environment with a period close to 24h. These rhythms are entrained to the 24h day mostly by the light-dark cycle. These circadian rhythms are controlled by a clock (pacemaker) located in the suprachiasmatic nuclei (SCN) of the hypothalamus. In the rat, the circadian clock within the SCN develops gradually from prenatal to postnatal period and is supposed to be synchronized mainly by maternal signals. However, the rat SCN is sensitive to light immediately after birth. The aim of the present work was to investigate the mechanism of entrainment of the circadian clock within the rat SCN during fetal and early postnatal development. The specific questions were whether and when the immature fetal and neonatal molecular SCN clocks can be reset by maternal cues, and whether and when the external light-dark cycle (LD) can affect the developing circadian rhythms. The role of light-dark cycle in the development of the photoperiodic entrainment during early postnatal period was also examined. Experiment no. (1): Pregnant rats were maintained under a light - dark regime with 12 h of light and 12 h of darkness (LD12:12). At gestational day 20 (E20), the fetuses were sampled throughout the day under either LD12:12 or constant darkness (DD). The..

Impact of Coenzyme Q10 Administration on Lead Acetate-Induced Testicular Damage in Rats

Exposure to lead (Pb) causes multiorgan dysfunction including reproductive impairments. Here, we examined the protective effects of coenzyme Q10 (CoQ10) administration on testicular injury induced by lead acetate (PbAc) exposure in rats. This study employed four experimental groups (n=7) that underwent seven days of treatment as follows: control group intraperitoneally (i.p.) treated with 0.1 ml of 0.9% NaCl containing 1% Tween 80 (v:v), CoQ10 group that was i.p. injected with 10 mg/kg CoQ10, PbAc group that was i.p. treated with PbAc (20 mg/kg), and PbAc+CoQ10 group that was i.p. injected with CoQ10 2 h after PbAc. PbAc injection resulted in increasing residual Pb levels in the testis and reducing testosterone, luteinizing hormone, and follicle-stimulating hormone levels. Additionally, PbAc exposure resulted in significant oxidative damage to the tissues on the testes. PbAc raised the levels of prooxidants (malondialdehyde and nitric oxide) and reduced the amount of endogenous antioxidative proteins (glutathione and its derivative enzymes, catalase, and superoxide dismutase) available in the cell. Moreover, PbAc induced the inflammatory response as evidenced by the upregulation of inflammatory mediators (tumor necrosis factor-alpha and interleukin-1 beta). Further, PbAc treatment induced apoptosis in the testicular cells, as indicated by an increase in Bax and caspase 3 expression, and reduced Bcl2 expression. CoQ10 supplementation improved testicular function by inhibiting Pb accumulation, oxidative stress, inflammation, cell death, and histopathological changes following PbAc exposure. Our findings suggest that CoQ10 can act as a natural therapeutic agent to protect against the reproductive impairments associated with PbAc exposure