The corpus luteum is a temporary reproductive endocrine structure established from a ruptured follicle wall after ovulation. In the ovarian cycle of ruminant species, the corpus luteum organ undergoes a repeated pattern of specific cellular proliferation, differentiation, and transformation. The corpus luteum encounters several physiological events, including growth, function, and regression throughout its life span. Also, the corpus luteum comprises granulosa and theca cells and endothelial cells, such as luteal steroidogenic cells and luteal endothelial cells. These cells play an important role in the physiology of the corpus luteum and the maintenance and degeneration of the corpus luteum. Furthermore, the role of reproductive hormones in the ovaries is important. Representative hormones include estrogen, progesterone, prostaglandin F2α, and oxytocin. Understanding their functions is important in studying the physiological phenomena and various mechanisms of the corpus luteum in the ovary. Therefore, the following review will discuss the role of reproductive hormones and luteal cell types in the microenvironment of the corpus luteum in the bovine ovary.

Ral-interacting protein 76 (RLIP76) is a potential factor with vascular endothelial growth factor (VEGF) in the corpus luteum and tumor angiogenesis. RLIP76, VEGF, and hypoxia-inducible factor-1 (HIF-1) are proteins that activate angiogenic functions in tumor and endothelial cells. RLIP76 is a main factor in tumor growth, and VEGF is a major endothelial cell protein for angiogenesis. Also, RLIP76 regulates a small GTPase (R-Ras, oncogene) in cell survival, spreading, and migration. HIF-1 is important in the corpus luteum, tumor angiogenesis, and tumor growth. VEGF and HIF-1 regulate the angiogenic function of RLIP76, and RLIP76 controls vascular growth in endothelial and tumor cells. RLIP76, R-Ras, VEGF, and HIF-1 may be useful in the research of corpus luteum and cancer therapy and the study of mechanisms of tumor angiogenesis. This review will help to elucidate the roles of RLIP76/R-Ras and VEGF via HIF-1 in corpus luteum and tumor angiogenesis, tumorigenesis, and the specific regulation of RLIP76 in luteal, tumor, and endothelial cells. Thus, we reviewed the angiogenesis of the corpus luteum and tumor in the ovarian and tumor microenvironment.

Sperm during the freezing and thawing process is damaged by oxidative stress. Thus, its antioxidant scavenger is essential for sperm survival and death in frozen-thawed semen. We used melatonin and silymarin in experiments. Our study aimed to identify the effect of melatonin and silymarin on the motility and viability of sperm, reactive oxygen species (ROS), and nitric oxide (NO) production in frozen-thawed boar semen. Melatonin and silymarin were treated alone and co-treated in the fresh boar semen. Boar semen was collected using the gloved-hand method from ten crossbred pigs, and the age of the experimental ten male pigs was 28.7 ± 3.2 months. We evaluated sperm viability using SYBR-14 and PI kit, and ROS and NO production were detected by DCF-DA and DAF-2, respectively. The sperm motility was not significantly different between non-treatment and treatment. ROS and NO production in frozen-thawed sperm were decreased by melatonin and silymarin (P < 0.05). Moreover, silymarin significantly reduced NO production more than melatonin (P < 0.05). Melatonin (46.37 ± 1.10) and silymarin (46.13 ± 0.80) enhanced the viability of sperm (P < 0.05). We suggest that melatonin and silymarin are essential antioxidants in semen cryopreservation for protecting sperm damage and maintaining sperm viability. Melatonin and silymarin may be useful antioxidants in freezing boar sperm.

The corpus luteum is a temporary endocrine gland formed in the ovary after ovulation, and it plays a critical role in reproductive processes. Tumors rely on the development of an adequate blood supply to ensure the delivery of nutrients and oxygen and the removal of waste products. While angiogenesis occurs in various physiological and pathological contexts, the corpus luteum and tumors share similarities in the signaling pathways that promote angiogenesis. In the corpus luteum and tumors, apoptosis plays a crucial role in controlling cell numbers and ensuring proper tissue development and function. Interestingly, there are similarities in the apoptotic-regulated signaling pathways involved in apoptosis between the corpus luteum and tumors. However, the regulation of apoptosis can differ due to their distinct physiological and pathological characteristics. Thus, we reviewed the biological events of the corpus luteum and tumors in similar microenvironments of angiogenesis and apoptosis for studying novel research methods.

Probiotics play an important role as immunostimulants in improving growth and health status in fish. However, little is known on the effects of probiotics when fish offered a low fish meal diet. This study evaluated the effects of three probiotic bacteria isolated from the fish intestine to replace antibiotics in a reduced fish meal diet fed to the juvenile olive flounder Paralichthys olivaceus. A basal diet without feed additives was used as a control (CON) and five other diets were formulated by supplementation with Bacillus subtilis WB60 (BSWB60) at 1×108 CFU/g, B. subtilis SJ10 (BSSJ10) at 1×108 CFU/g, Enterococcus faecium SH30 (EFSH30) at 1×107 CFU/g, amoxicillin (AMO) at 4 g/kg and oxytetracycline (OTC) at 4 g/kg of the basal diet. Triplicate groups of 25 fish averaging 12.1±0.09 g (mean±SD) were fed one of the six experimental diet groups for 8 weeks. Then, 45 fish from each group were intraperitoneally injected with the pathogenic bacteria, Edwardsiella tarda, and mortality was recorded for 14 days. At the end of the feeding trial, weight gain, specific growth rate and feed efficiency of fish fed the BSWB60 diet were significantly greater than those of fish fed the CON, OTC and AMO diets (P &lt; 0.05). Furthermore, feeding efficiency and protein efficiency ratio of fish fed the BSWB60 diet were significantly greater than those of fish fed the CON, OTC and AMO diets. However, there were no significant differences in survival, hepatosomatic indices, viscerosomatic indices and condition factors among the fish fed the experimental diets. The whole-body proximate composition of the fish was unaffected by the dietary treatments. The serum biochemistry parameters, such as aspartate aminotransferase levels were significantly greater in fish fed the BSSJ10 diet than in those fed the BSWB60 diet. However, serum alanine aminotransferase, glucose and total protein levels were not significantly affected by the experimental diets. The lysozyme activity of fish fed the BSSJ10, BSWB60 and EFSH30 diets was significantly greater than that of the CON, OTC and AMO diets. The myeloperoxidase activity of fish fed the BSWB60 diet was significantly greater than that of the fish fed the CON and AMO diets. The flounder growth hormone levels of fish fed the BSSJ10, BSWB60, EFSH30 and AMO diets were significantly greater than that of the fish fed the CON diet. The interleukin 1β (IL-1β) gene expression levels in fish fed the BSSJ10 and EFSH30 diets were significantly greater than those in fish fed the CON, OTC and AMO diets. The interleukin 10 (IL-10) gene expression levels in fish fed the BSSJ10, BSWB60, EFSH30 and OTC diets were significantly greater than those of fish fed the CON and AMO diets. Intestinal histology revealed that the average villus length of fish fed the BSSJ10, BSWB60, and EFSH30 diets was significantly greater than that of fish fed the CON, OTC and AMO diets. The cumulative survival rates of fish fed the EFSH30 and BSWB60 diets were significantly greater than those of fish fed the CON diet after the 15th day of the challenge test. Overall, the results of the present study demonstrated that the supplementation of autochthonous bacteria, B. subtilis (108 CFU/g diet) or E. faecium (107 CFU/g diet) in the diet could be ideal probiotics to replace antibiotics based on growth performance, the serum biochemical composition, immune responses and disease resistance in olive flounder fed a low fish meal diet..