Alterations in reproductive hormones during heat stress in dairy cattle

In dairy cows inseminated during the hot months of the year, there is a decrease in fertility. Different factors contribute to this situation; the most important are a consequence of increased temperature and humidity that result in a decreased expression of overt estrus and a reduction in appetite and dry matter intake. Heat stress reduces the degree of dominance of the selected follicle and this can be seen as reduced steroidogenic capacity of its theca and granulosa cells and a fall in blood estradiol concentrations. Plasma progesterone levels can be increased or decreased depending on whether the heat stress is acute or chronic, and on the metabolic state of the animal. These endocrine changes reduce follicular activity and alter the ovulatory mechanism, leading to a decrease in oocyte and embryo quality. The uterine environment is also modified, reducing the likelihood of embryo implantation. Systems activated by heat stress can influence reproduction at the hypothalamus, pituitary gland or gonads. However, the major impact is thought to be within the brain or at the pituitary gland. Measurement of plasma concentrations of the gonadotrophins provides a good indication of the effects at these higher levels, since the pulsatile secretion of luteinizing hormone (LH) is a reflection of the secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus. Both the secretion and actions of GnRH are influenced by the feedback actions of gonadal sex steroids and inhibin. Recent studies suggest that the use of gonadotropins to induce follicular development and ovulation can decrease the severity of seasonal postpartum infertility in dairy cows.Key words: Reproductive hormones, dairy cow and heat stress

Therapeutic melanoma inhibition by local micelle-mediated cyclic nucleotide repression

The acidic tumor microenvironment in melanoma drives immune evasion by up-regulating cyclic adenosine monophosphate (cAMP) in tumor-infiltrating monocytes. Here we show that the release of non-toxic concentrations of an adenylate cyclase (AC) inhibitor from poly(sarcosine)-block-poly(L-glutamic acid γ-benzyl ester) (polypept(o)id) copolymer micelles restores antitumor immunity. In combination with selective, non-therapeutic regulatory T cell depletion, AC inhibitor micelles achieve a complete remission of established B16-F10-OVA tumors. Single-cell sequencing of melanoma-infiltrating immune cells shows that AC inhibitor micelles reduce the number of anti-inflammatory myeloid cells and checkpoint receptor expression on T cells. AC inhibitor micelles thus represent an immunotherapeutic measure to counteract melanoma immune escape.Drug Delivery Technolog

In vitro maturation of sheep oocytes in different concentrations of mare serum

The aim of the study was to determine the optimum concentration of the mare serum (MS) for sheep in vitro oocyte maturation. Sheep ovaries were collected from a local abattoir and transported within 1 h tothe laboratory in a warm saline solution (30 – 35oC), supplemented with 100 IU penicillin G and 100 g streptomycin sulfate/ml. Cumulus-oocyte complexes (COC’s) were obtained by slicing of follicles, washed in TCM-199 modification with NaHCO3 and supplemented with 50 g/ml gentamycin, and 0.25 mM sodium pyruvate without any serum supplementation. The COC’s were randomly divided into four groups. Group 1 (n = 105) COC’s were fresh control and cultured in TCM-199 medium without serum supplementation. Group 2 (n = 108) COC’s were washed five times and cultured in TCM-199 medium supplemented with 10% MS. Group 3 (n = 112) COC’s were washed five times and cultured in TCM-199medium supplemented with 15% MS. Group 4 (n = 114) COC’s were washed five times and cultured in TCM-199 medium supplemented with 20% MS. After 38 - 42 h of IVM, oocytes were denuded with the aidof 0.1% hyaluronidase and passing them through a fine pipette, fixed for 24 – 48 h in a mixture of acetic acid and alcohol (1:3) at room temperature, stained for 10 min with 1% (w/v) orcein in 45% acetic acid and examined for the evidence of different stages of maturation. Significantly higher (p < 0.05) maturation rates of oocytes (69 – 72%) were observed in all concentrations of mare serum compared tothose without serum supplementation. However, no significant difference was observed between the 10, 15 and 20% serum supplemented group

Alterations in reproductive hormones during heatstress in dairy cattle

In dairy cows inseminated during the hot months of the year, there is a decrease in fertility. Different factors contribute to this situation; the most important are a consequence of increased temperature and humidity that result in a decreased expression of overt estrus and a reduction in appetite and dry matter intake. Heat stress reduces the degree of dominance of the selected follicle and this can be seen as reduced steroidogenic capacity of its theca and granulosa cells and a fall in blood estradiol concentrations. Plasma progesterone levels can be increased or decreased depending on whether the heat stress is acute or chronic, and on the metabolic state of the animal. These endocrine changes reduce follicular activity and alter the ovulatory mechanism, leading to a decrease in oocyte and embryo quality. The uterine environment is also modified, reducing the likelihood of embryo implantation. Systems activated by heat stress can influence reproduction at the hypothalamus, pituitary gland or gonads. However, the major impact is thought to be within the brain or at the pituitary gland. Measurement of plasma concentrations of the gonadotrophins provides a good indication of the effects at these higher levels, since the pulsatile secretion of luteinizing hormone (LH) is a reflection of the secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus. Both the secretion and actions of GnRH are influenced by the feedback actions of gonadal sex steroids and inhibin. Recent studies suggest that the use of gonadotropins to induce follicular development and ovulation can decrease the severity of seasonal postpartum infertility in dairy cows

Suppression of cAMP formation by inhibitor-loaded polypept(o) ide micelles inhibits melanoma growth by preserving an inflammatory myeloid cell phenotype

Drug Delivery Technolog