Investigations into the mechanisms controlling parturition in cattle

Abstract

A pronounced increase in fetal cortisol concentrations stimulating an increase in estrogen production at the expense of progesterone precursors in the placenta, luteolysis, and progesterone withdrawal is considered as a key event during the complex signal cascade leading to the initiation of parturition in cattle. However, there are many questions concerning the exact functional and/or temporal relationships between these individual processes which finally result in the expulsion of the calf and the timely release of the placenta. Thus, parturition was induced in 270-day pregnant cows using the progesterone receptor blocker aglepristone (group AG, nZ3), the prostaglandin F 2a analog cloprostenol (group PG, nZ4), and the glucocorticoid dexamethasone (group GC, nZ4) to characterize the effect on maternal steroid and prostaglandin levels and to identify immediate subsequent changes in placental morphology and gene expression as compared with untreated controls sampled on day 272 (group D272, nZ3) and cows during normal parturition (group NT, nZ4). All calves of the treatment groups were born on days 271-272, whereas gestational length in NT cows was 280.5G1.3 days. However, none of the treatments significantly induced the prepartal remodeling of placentomes characterized by a decline in trophoblast giant cells and reduction of the caruncular epithelium. Data on placental CYP17 and COX2 expression confirm that these key enzymes are upregulated by GC, whereas placental aromatase expression was not affected by any treatment. Maternal progesterone and prostaglandin profiles suggest differential effects of the treatments on luteal function and placental or uterine prostaglandin production. The results provide new information on the initiation of parturition in cattle but raise many new questions.

Giraffe birth locations in the South Luangwa National Park, Zambia: site fidelity or microhabitat selection?

“…Birth site location is probably not only dependent upon ecological factors, but reflects female physiological state. A common cascade of endocrine interactions tends to precede parturition, although the specific nuances differ across species (Kamel, ; Ousey & Fowden, ; Shenavai et al ., ). In general, the primary stimulus to birth derives from the foetus, not the mother.…”

Diagnostic Value of Cyclooxygenase-2 Serum Levels in Predicting Preterm Labor

“…Pro-inflammatory cytokines stimulate the production of matrix metalloproteinases (MMP) -2, -8, -9, COX-2, collagenases and prostaglandins which cause cervical softening and rupture of the membranes. TNF-α and IL-β increase contractility whereas COX-2, PGE-2, IL-6 regulates OT receptors in myometrial cells that play a role in myometrial contractility 5 .…”

An Insight into the Pathophysiology, Preventive and Treatment Strategies of Retained Fetal Membranes in Bovines A Review

“…With the drop in progesterone and rise in estrogen levels, prostaglandin synthase 2 (PTGS2) causes synthesis of endometrial PGF 2 α (Streyl et al, 2012). With PGF 2 α secretion halt on progesterone production gets released around the parturition time and thereby facilitating myometrial contractions (Shenavai et al, 2012). During advanced stages of pregnancy (nearing calving) the PTGS2 expression has been seen to get initiated from fetal side first, followed by dam side, thus supporting the notion that partrurition starts from the fetal side (Arosh et al, 2004).…”