The impact of pregnancy and childbirth in the urethra of female rats

Morphological changes in the porcine cervix: A comparison between nulliparous and multiparous sows with regard to post-cervical artificial insemination

In recent decades, new artificial insemination (AI) methods, such as post-cervical AI (PCAI), have been developed in pig. PCAI involves crossing the cervix to deposit the sperm in the uterine body. Although PCAI application in sows is frequent, its application in nulliparous (gilts) females it is still limited due to the difficulty of passing through the cranial part of the cervical lumen. We hypothesized that ageing and parity would modify the cervical canal, facilitating the introduction of AI devices through the cervix. The aim was to compare the morphology of the uterus at different levels between multiparous and nulliparous females. Morphological analysis of the uterus pointed to a longer cervix (25.9 ± 4.6 vs. 21.6 ± 3.3 cm, p < 0.001) and greater length of the part of the reproductive tract involved in PCAI (from rima vulvae to the last cervical cushion) (56.2 ± 6.0 vs. 50.3 ± 5.2 cm, p < 0.001) in multiparous sows compared with nulliparous animals. As regards the structure of the vaginal and uterine parts of the cervix (the part in contact with the vagina and uterine body, respectively), the cross-sectional area, perimeter and total thickness were greater in the uterine part of multiparous than of nulliparous animals (area: 4.07 ± 1.46 vs. 2.46 ± 0.56 cm², p < 0.01; perimeter: 8.50 ± 1.44 cm vs. 6.28 ± 0.92 cm, p < 0.001; thickness: 10.79 ± 0.96 vs. 8.35 ± 0.62 mm, p < 0.05), but not in the vaginal part. The tissue content analysed in histological cross-sections also showed differences between female groups, a greater content of connective tissue (58.86 ± 10.78 vs. 67.60 ± 13.38%, p < 0.001) and a lower amount of muscle fibres (39.79 ± 10.24 vs. 30.66 ± 13.69%, p < 0.001) being observed in multiparous sows. Finally, silicone casts of the cervical lumen revealed differences between the two groups in the size and shape of the ridges in the lumen trajectory. Parity, which is also influenced by ageing, determines important changes in the size, structure and tissue content of the cervix wall, as well as in the morphology of the cervical canal, which may be responsible for the different levels of performance of PCAI in the female populations. Therefore, the future design of AI strategies and catheters should take into consideration the morphological variations of the cervix lumen, which will depend on age and parity of the females.

Neuroanatomic and behavioral correlates of urinary dysfunction induced by vaginal distension in rats

The aim of the present study was to use a model of simulated human childbirth in rats to determine the damage to genitourinary structures and behavioral signs of urinary dysfunction induced by vaginal distension (VD) in female rats. In experiment 1, the length of the genitourinary tract and the nerves associated with it were measured immediately after simulated human delivery induced by VD or sham (SH) procedures. Electroneurograms of the dorsal nerve of the clitoris (DNC) were also recorded. In experiment 2, histological characteristics of the bladder and major pelvic ganglion of VD and SH rats were evaluated. In experiment 3, urinary parameters were determined in conscious animals during 6 h of dark and 6 h of light before and 3 days after VD or SH procedures. VD significantly increased distal vagina width (P < 0.001) and the length of the motor branch of the sacral plexus (P < 0.05), DNC (P < 0.05), and vesical nerves (P < 0.01) and decreased DNC frequency and amplitude of firing. VD occluded the pelvic urethra, inducing urinary retention, hematomas in the bladder, and thinness of the epithelial (P < 0.05) and detrusor (P < 0.01) layers of the bladder. Major pelvic ganglion parameters were not modified after VD. Rats dripped urine in unusual places to void, without the stereotyped behavior of micturition after VD. The neuroanatomic injuries after VD occur alongside behavioral signs of urinary incontinence as determined by a new behavioral tool for assessing micturition in conscious animals.

Bony pelvis dimensions in women with and without stress urinary incontinence

AIMS

To test the null hypothesis that bony pelvis dimensions are similar in women with and without stress urinary incontinence (SUI), both in the postpartum and midlife periods.

METHODS

Secondary analyses were performed of two case-control studies comparing women with SUI to asymptomatic controls. One study examined primiparas in the first 9-12 months postpartum; the other study involved middle-aged women. SUI was confirmed by full-bladder stress test. All subjects underwent pelvic magnetic resonance imaging. The interspinous and intertuberous diameters, subpubic angle, and sacrococcygeal joint-to-the inferior pubic point distance were measured from the images independently by two authors.

RESULTS

In the young cohorts, we compared primiparas with de novo postpartum SUI to both continent primiparas and nulliparas. Postpartum SUI is associated with a wider subpubic angle. There is also a trend towards wider interspinous and intertuberous diameters in the stress-incontinent primiparas as compared to the continent cohorts, although this did not reach statistical significance with our sample sizes. By contrast, no significant differences in bony pelvis dimensions were identified when comparing middle-aged women with SUI and their continent controls.

CONCLUSIONS

Bony pelvis dimensions are different in women with SUI than in matched continent controls. However, these differences are only identified in young primiparas in the postpartum period, not in middle-aged women.

Impact of birth in the presence and absence of simulated birth injury on vaginal glycosaminoglycan content

INTRODUCTION AND HYPOTHESIS

This study aims to evaluate the effects of simulated birth trauma and vaginal and Cesarean delivery on glycosaminoglycans (GAGs) in the vagina of female rats.

METHODS

One hundred ten rats were divided into six groups: A (control), B (vaginal trauma), C (Cesarean delivery), D (Cesarean delivery followed by vaginal trauma), E (vaginal delivery), and F (20th day of gestation). In each group, half of the animals were killed 4 days after the procedure (time 1) and 12 weeks later (time 2). GAGs were extracted, isolated, and identified by using agarose gel electrophoresis and quantified by densitometry. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney tests.

RESULTS

We observed a significant decrease in total GAGs and dermatan sulfate (DS) at time 1. Evaluation at time 2 showed a significant increase in total GAGs, DS, and heparan sulfate.

CONCLUSIONS

Levels of sulfated GAGs in the rat vagina are affected by delivery and simulated birth trauma.

Vaginal delivery and pelvic floor dysfunction: current evidence and implications for future research

Vaginal delivery is the major risk factor for the development of pelvic organ prolapse and urinary and fecal incontinence, resulting from damage to the pelvic floor muscles, nerves and connective tissue. This article reviews the perineal trauma mechanism during vaginal delivery and discusses implications of current and future research projects.

Ex vivo biomechanical, functional, and immunohistochemical alterations of adrenergic responses in the female urethra in a rat model of birth trauma

Birth trauma and pelvic injury have been implicated in the etiology of stress urinary incontinence (SUI). This study aimed to assess changes in the biomechanical properties and adrenergic-evoked contractile responses of the rat urethra after simulated birth trauma induced by vaginal distension (VD). Urethras were isolated 4 days after VD and evaluated in our established ex vivo urethral testing system that utilized a laser micrometer to measure the urethral outer diameter at proximal, middle, and distal positions. Segments were precontracted with phenylephrine (PE) and then exposed to intralumenal static pressures ranging from 0 to 20 mmHg to measure urethral compliance. After active assessment, the urethra was rendered passive with EDTA and assessed. Pressure and diameter measurements were recorded via computer. Urethral thickness was measured histologically to calculate circumferential stress-strain response and functional contraction ratio (FCR), a measure of smooth muscle activity. VD proximal urethras exhibited a significantly increased response to PE compared with that in controls. Conversely, proximal VD urethras had significantly decreased circumferential stress and FCR values in the presence of PE, suggesting that VD reduced the ability of the proximal segment to maintain smooth muscle tone at higher pressures and strains. Circumferential stress values for VD middle urethral segments were significantly higher than control values. Histological analyses using antibodies against general (protein gene product 9.5) and sympathetic (tyrosine hydroxylase) nerve markers showed a significant reduction in nerve density in VD proximal and middle urethral segments. These results strongly suggest that VD damages adrenergic nerves and alters adrenergic responses of proximal and middle urethral smooth muscle. Defects in urethral storage mechanisms, involving changes in adrenergic regulation, may contribute to stress urinary incontinence induced by simulated birth trauma.

General tissue characteristics of the lower urethral and vaginal walls in the domestic rabbit

In European rabbits, the distal urethra (DU) opens into the anterior pelvic vagina forming a single canal by which females copulate, give birth, and urinate. We investigated whether the histological characteristics of the DU and the pelvic and perineal vagina are different. The DU and vagina of rabbits (Oryctolagus cuniculus) were cut and stained with hematoxylin-eosin and Masson's trichrome (n = 3). Data were compared by using Friedman's ANOVA for repeated measures. The walls of the DU and vagina are composed of mucosa, submucosa, smooth muscle, and an external layer. Differences in tissue characteristics of the mucosa, orientation of the smooth muscle fibers, components of the external layer (connective tissue, blood vessels, and striated musculature), and thickness of the tissue layers were found among regions. The lack of histological homogeneity along the urethra and vagina possibly reflects differences in the functions of each segment.