Inhibition of lipopolysaccharide-induced suppression of luteal function in isolated perfused bovine ovaries.

Recently, we observed that lipopolysaccharide (LPS) suppresses corpus luteum (CL) function in isolated perfused ovaries. It remained unclear if this suppression was due to increased luteal PGF2α secretion or LPS-induced apoptosis. Therefore, possible impacts of PGF2α and LPS were inhibited by a non-steroidal anti-inflammatory drug (flunixin) and an endotoxin-binding agent (polymyxin B), respectively. Bovine ovaries with a mid-cycle CL were collected immediately after slaughter and perfused for 240 min. After 50 min of equilibration, either flunixin or polymyxin B (5 µg/ml of each) were added to the perfusion medium of six ovaries, respectively. All ovaries (n = 12) were treated with E. coli LPS (0.5 µg/ml) 60 min after the onset of perfusion, and received 500 I.U. of hCG after 210 min of perfusion. Progesterone and PGF2α were measured in the effluent perfusate every 10 and 30 min, respectively. Biopsies of the CL were collected every 60 min to determine the mRNA expression of the cytokine TNFA and factors of apoptosis (CASP3, -8). Flunixin-treatment inhibited the increase of PGF2α after LPS-challenge that was observed in the polymyxin B-treated (PX-LPS) ovaries. After hCG-stimulation, progesterone secretion increased (P < 0.05) in group PX-LPS but not in the flunixin-treated (F-LPS) ovaries. Compared to initial values before LPS-challenge, luteal mRNA expression of TNFA and CASP3 was increased (P < 0.05) in group F-LPS at 120 and 180 min, respectively, and those of CASP8 was decreased (P < 0.05) in PX-LPS at 60 and 120 min after LPS-treatment. In conclusion, although flunixin managed to inhibit PGF2α, it did not suffice to successfully prevent LPS-induced apoptosis. However, endotoxin-binding polymyxin B resulted in luteal responsiveness to hCG after LPS-challenge.

Different chronological patterns of appearance of blood derived milk components during mastitis indicate different mechanisms of transfer from blood into milk.

This study aimed to describe chronological patterns of changes of various candidate blood components in milk during the acute phase of a mammary immune response in detail. Eight dairy cows were challenged with Escherichia coli lipopolysaccharide in one udder quarter. Milk from challenged and control quarters and blood samples were taken before, and 1 and 2 h after challenge and then every 15 min until 5 h after challenge. The SCC, serum albumin, immunoglobulin (Ig)G1, IgG2, lactate dehydrogenase (LDH), and L-lactate in milk and blood, and α-lactalbumin in blood were analysed. All selected parameters in milk increased in challenged quarters but did not increase in control quarters. Milk IgG1, IgG2, serum albumin, and LDH were already significantly increased at 2 h after challenge whereas a significant increase of SCC was detectable at 2.75 h and L-lactate was increased at 2.25 h after challenge. In blood L-lactate was increased at 3.75 h after challenge, however, other factors in blood did not change significantly within the 5 h of experiment. In conclusion, the increase of blood components in milk during inflammation follows two different patterns: There is a rapid increase for IgG1, IgG2, or LDH, before the increase of SCC, and their concentrations reach a plateau within 3 h. On the other hand, SCC and L-lactate show a slower but consistent increase not reaching a plateau within 5 h after LPS challenge. L-lactate increases to higher concentrations in milk than in blood. This clearly shows that the increase of blood components follows different patterns and is therefore a controlled and compound-specific process and not exclusively an unspecific type of leakage.

Bovine luteal blood flow: basic mechanism and clinical relevance.

The introduction of transrectal colour Doppler sonography (CDS) has allowed the evaluation of luteal blood flow (LBF) in cows. Because appropriate angiogenesis plays a decisive role in the functioning of the corpus luteum (CL), studies on LBF may provide valuable information about the physiology and pathophysiology of the CL. Studies on cyclic cows have shown that progesterone concentrations in blood plasma can be more reliably predicted by LBF than by luteal size (LS), especially during the regression phase of the CL. In contrast with non-pregnant cows, a significant increase in LBF is seen in pregnant cows during the third week after insemination. However, because there are high interindividual variations in LBF between animals, LBF is not useful for the early diagnosis of pregnancy. Determination of LBF is more sensitive than LS for detecting the effects of acute systemic inflammation and exogenous hormones on the CL. Cows with low progesterone levels have smaller CL during the mid-luteal phase, but LBF related to LS did not differ between cows with low and high progesterone levels. In conclusion, LBF determined by CDS provides additional information about luteal function compared with LS and plasma progesterone concentrations, but its role concerning fertility in the cow is yet to be clarified.

Ultrasonographic Doppler Use for Female Reproduction Management.

Transrectal color Doppler ultrasonography is a useful technique to get new information about physiologic and pathophysiologic alterations of the uterus and ovaries in female cattle. During all reproductive stages characteristic changes in uterine blood flow are observed. Cows with puerperal disturbances show delayed decrease in uterine blood flow in the first few weeks postparturition compared with healthy cows. Measurement of follicular blood flow is used to identify normally developing follicles and predict superovulatory response. Determination of luteal blood is more reliable than B-mode sonography to distinguish between functional and nonfunctional corpora lutea. Color Doppler ultrasonography is a promising tool to improve reproductive management in female cattle.