Rheological and ultrastructural properties of bovine vaginal fluid obtained at oestrus

Abstract

The properties of cervical-vaginal fluid are under strict hormonal control: and in mammals in which semen is deposited in the anterior vagina, changes produced in these properties can result in a lower or higher resistance to sperm motion. The aim of this study was to determine whether the structural organization of bovine vaginal fluid is related to its rheological properties. Vaginal fluid samples were collected from 41 cows at oestrus: 20 at the middle of oestrus (between 8 and 12 h after starting) and 21 at the end of oestrus (between 18 and 22 h). Flow behaviour was determined using a viscosimeter, and the ultrastructural analysis was performed by scanning electron microscopy. Six samples showed newtonian behaviour: three collected at the middle and three collected at the end of oestrus. Newtonian samples had dense and compact matrices arranged as membranes with rough, irregular surfaces, and sparse, thin filaments (< 150 nm). Non-newtonian samples collected at the end of oestrus (n = 18) had a higher (P = 0.016) consistency index (K = 944 ± 229 mPa.s n ) than those collected at the middle of oestrus (n = 17; K = 237 ± 84 mPa.s n ). Thick filaments (> 700 nm) that were either randomly arranged with thinner filaments forming a mesh or heavily cross-linked by thin filaments (50-150 nm) were observed in all non-newtonian samples collected at the end of oestrus, while medium-diameter filaments (between 200 and 500 nm) forming loose networks were observed in non-newtonian samples collected at the middle of oestrus. These findings indicate a close relationship between the molecular organization of the structural elements of bovine vaginal fluid and its rheological behaviour. Vaginal fluid dramatically reduces its mechanical barrier effect during the course of oestrus but always appears to maintain its three-dimensional filamentous structure. The images of vaginal fluid showing newtonian behaviour would appear to support previous results, suggesting that this property may be related to bovine infertility.

Evidence of Fractality in a Pattern of Crystallization of Bovine Cervical Mucus Obtained at Oestrus

“…Regarding the latter, the development of a method to assess the features of BCM fractality (and its alterations) at the different stages of the cycle, mainly oestrus, would yield some indicators of the endocrine and reproductive status of the animal. This could be of relevance to clinical veterinary practice considering that it is known that BCM characteristics not only change according to the fluctuating levels of ovarian sex steroids during the cycle (Bone; Noonan et al), but also that the characteristics of mucus can change and present alterations due to fertility problems (Rutllant et al, 2002).…”

“…The aqueous phase contains 92-95 % of water and several dissolved low-molecular-mass compounds, e.g., ions and metabolites (Tsiligianni et al, 2001); and the gel phase is formed mainly by glycoproteins called mucins (Rutllant et al, 2005;Pluta et al, 2011). Biophysical and biochemical properties of BCM are controlled by changes in sex steroid levels during the oestrous cycle (Rutllant et al, 2002). BCM is secreted during the whole cycle, yet its volume increases at oestrus under oestrogenic influence, which also induces its crystallization in branched arborescent patterns resembling fern fronds or palm leaves (Bone, 1954;Abusineina, 1962;Noonan et al, 1975), among other geometric arrangements (Cortés, 2012).…”

The effect of pH and viscosity on bovine spermatozoa motility under controlled conditions

“…In the realm of vaginal environmental factors, Rutllant et al have reported the rheological characteristics of vaginal fluid in remarkable detail [22]. Interestingly, the study shows potential hormonal changes in bovine vaginal secretions as a mechanism that changes glycoprotein structure.…”

“…A. Rizvi (&) 4004 North St. Louis, Apt #1N, Chicago, IL 60618, USA e-mail: aar2031@columbia.edu the sperm. Of these factors, pH and viscosity are two factors that could have a major initial effect on sperm motility during the process of fertilization [22]. Furthermore, studies involving chemotactic agents for sperm have yielded results suggesting evidence of follicular fluid involvement after ovulation as a sperm attractant [6,15].…”

Effects of viscosity on sperm motility studied with optical tweezers

“…Factors in the vaginal canal, such as pH, antibody response, and the overall structural and functional capacity of the sperm, can affect sperm motility. 2 Particularly, the viscous environment encountered by the sperm can have a major impact on its motility and its subsequent ability to reach and fertilize the egg. The objective of this study is to address the relationship between viscosity and sperm motility using optical trapping.…”