Shift from Pro- to Anti-Inflammatory Phase in Pelvic Floor Muscles at Postpartum Matches Histological Signs of Regeneration in Multiparous Rabbits.

Background and Objectives: Pelvic floor muscles (PFM) play a core role in defecation and micturition. Weakening of PFM underlies urogynecological disorders such as pelvic organ prolapse and stress urinary incontinence. Vaginal delivery damages PFM. Muscle trauma implies an inflammatory response mediated by myeloid cells, essential for subsequent recovery. Molecular signaling characterizing the pro-inflammatory phase shifts M1 macrophages to M2 macrophages, which modulate muscle repair. The present study aimed to evaluate histological characteristics and the presence of M1 and M2 macrophages in bulbospongiosus (Bsm) and pubococcygeus muscles (Pcm). Materials and Methods: Muscles from young nulliparous (N) and multiparous rabbits on postpartum days three (M3) and twenty (M20) were excised and histologically processed to measure the myofiber cross-sectional area (CSA) and count the centralized myonuclei in hematoxylin-eosinstained sections. Using immunohistochemistry, M1 and M2 macrophages were estimated in muscle sections. Kruskal-Wallis or one-way ANOVA testing, followed by post hoc tests, were conducted to identify significant differences (p < 0.05). Results: The myofiber CSA of both the Bsm and Pcm of the M3 group were more extensive than those of the N and M20 groups. Centralized myonuclei estimated in sections from both muscles of M20 rabbits were higher than those of N rabbits. Such histological outcomes matched significant increases in HLA-DR immunostaining in M3 rabbits with the CD206 immunostaining in muscle sections from M20 rabbits. Conclusions: A shift from the pro- to anti-inflammatory phase in the bulbospongiosus and pubococcygeus muscles of multiparous rabbits matches with centralized myonuclei, suggesting the ongoing regeneration of muscles.

Preventive Effect of Molecular Iodine in Pancreatic Disorders from Hypothyroid Rabbits.

Pancreatic alterations such as inflammation and insulin resistance accompany hypothyroidism. Molecular iodine (I2) exerts antioxidant and differentiation actions in several tissues, and the pancreas is an iodine-uptake tissue. We analyzed the effect of two oral I2 doses on pancreatic disorders in a model of hypothyroidism for 30 days. Adult female rabbits were divided into the following groups: control, moderate oral dose of I2 (0.2 mg/kg, M-I2), high oral dose of I2 (2.0 mg/kg, H-I2), oral dose of methimazole (MMI; 10 mg/kg), MMI + M-I2,, and MMI + H-I2. Moderate or high I2 supplementation did not modify circulating metabolites or pancreatic morphology. The MMI group showed reductions of circulating thyroxine (T4) and triiodothyronine (T3), moderate glucose increments, and significant increases in cholesterol and low-density lipoproteins. Acinar fibrosis, high insulin content, lipoperoxidation, and overexpression of GLUT4 were observed in the pancreas of this group. M-I2 supplementation normalized the T4 and cholesterol, but T3 remained low. Pancreatic alterations were prevented, and nuclear factor erythroid-2-related factor-2 (Nrf2), antioxidant enzymes, and peroxisome proliferator-activated receptor gamma (PPARG) maintained their basal values. In MMI + H-I2, hypothyroidism was avoided, but pancreatic alterations and low PPARG expression remained. In conclusion, M-I2 supplementation reestablishes thyronine synthesis and diminishes pancreatic alterations, possibly related to Nrf2 and PPARG activation.

G protein-coupled estrogen receptor (GPER/GPR30) levels in pelvic floor muscles and its association with estrogen status in female rabbits.

Objective: To assess the relative expression of the G-protein coupled estrogen receptor (GPER) in the bulbospongiosus (Bsm) and pubococcygeus (Pcm) muscles in control, ovariectomized (OVX), and OVX with estradiol benzoate supplementation (OVX + EB) rabbits.Methods: We used tissues from C, 1-month OVX, and OVX plus 15-day EB implanted (OVX + EB) groups. The GPER expression was evaluated by Western blot and immunohistochemistry for both Bsm and Pcm. Results: Both muscles showed a GPER immunoreactivity in blood vessels, inside myofibers next to myonuclei, and in polymorphonuclear cells. Four-week ovariectomy did not modify the GPER expression in the Bsm and Pcm, but two-week estradiol benzoate increased it in the latter muscle alone.Conclusions: We demonstrated that the Bsm and Pcm of female rabbits express GPER. High serum estradiol levels elevate GPER relative expression in the Pcm alone. The present study supports the remarkable estrogen sensitivity of the Pcm.

Differential estrogen-related responses in myofiber cross-sectional area of pelvic floor muscles in female rats.

OBJECTIVE: To determine the role of estrogens in myofiber cross-sectional area (CSA) of the pubococcyegeus (Pcm) and iliococcygeus muscles (Icm). METHODS: In Experiment 1, we excised the Pcm and Icm during the metestrus and proestrus stages of the estrous cycle to measure the myofiber CSA. In Experiment 2, we allocated other rats into the following groups: sham (Sh), ovariectomized (OVX), OVX plus 1,4,6-androstatriene-3,17-dione (ATD; OVX + ATD), an aromatase inhibitor, and OVX plus estradiol benzoate (OVX + EB). We carried out appropriate statistical tests to determine significant differences (p ≤ 0.05) in variables measured for both Experiments. RESULTS: The Pcm myofiber CSA at proestrus was higher than at metestrus, while the Icm myofiber CSA did not change. Ovariectomy increased the Pcm myofiber CSA, which was exacerbated with the ATD administration. The EB supplementation successfully reversed the ovariectomy-induced enlargement of the CSA. No significant changes were detected for the Icm myofiber CSA. CONCLUSIONS: Fluctuating ovarian steroid levels at the estrus cycle significantly influence the CSA myofiber of the Pcm but not that of the Icm. Estrogen actions, having a gonadal or extragonadal origin, influence importantly the CSA of the Pcm.

Lumbosacral ventral root avulsion alters reflex activation of bladder, urethra, and perineal muscles during micturition in female rabbits.

AIM: To determine the effect of the lumbosacral ventral root avulsion (VRA) on the reflex activation of bladder, urethra, and activation of perineal muscles during micturition in female rabbits. METHODS: We allocated 14 virgin female rabbits to evaluate, first, the gross anatomy of lumbosacral spinal cord root (n = 5) and, second, to determine the effect of VRA on perineal muscles during micturition (n = 9). We recorded cystometrograms, urethral pressure, and electromyograms of the bulbospongiosus (Bsm) and ischiocavernosus (Ism) muscles before and after the L6-S2 VRA. Standard variables were measured from each recording and analyzed to identify significant differences (P < .05). RESULTS: We found that the L6-S2 VRA affected directly the bladder and urethral function and reduced the duration and the frequency of the bursting of Ism and Bsm muscles during voiding. The Ism and Bsm showed a phasic activation, of different frequencies, during the voiding phase and the L6-S2 VRA inhibited the co-contraction of the Ism and Bsm-bladder-urethra. CONCLUSIONS: The Ism and Bsm are activated at different frequencies to trigger the voiding phase. The L6-S2 VRA affected the activity pattern of both perineal muscles. These modifications affected the bladder and urethra function. It is possible that the restoration of the activation frequency of perineal muscles contributed for an efficient bladder contraction.

Bladder and urethral dysfunction in multiparous and mature rabbits correlates with abnormal activity of pubococcygeus and bulbospongiosus muscles.

AIMS: To evaluate the combined effect of age and multiparity on the micturition reflex, including pelvic floor muscle activation. METHODS: Young and mature nulliparous rabbits were compared to young and mature multiparas (n = 6 per group). Cystometrograms and urethral pressure (UP) were performed while simultaneously recording the electromyogram (EMG) activity of the pubococcygeus and bulbospongiosus muscles to establish their functional correlation to urological function. RESULTS: Multiparity and age significantly influence the bladder and UP affecting the voiding efficiency and intercontraction interval. Such interaction also reduced the UP threshold, timing, and duration. Other bladder and urethral variables were predominantly affected only by age. Urodynamic alterations correlated with abnormal patterns or absent EMG activity of the pubococcygeus and bulbospongiosus muscles. CONCLUSIONS: The present findings strongly suggest that multiparity and age affects specific pelvic floor muscle reflex activation during micturition, and may contribute to alterations in bladder and urethral function. This data broadens our understanding of the critical role of the appropriate activity of the individual pelvic floor muscles in micturition.

Signs of damage in pelvic floor muscles at the end of pregnancy in rabbits.

INTRODUCTION AND HYPOTHESIS: Temporary effects to pelvic floor muscles are linked to impairments in micturition, particularly stress urinary incontinence (SUI), during pregnancy. We hypothesize that bulbospongiosus (Bsm) and pubococcygeus (Pcm) are differently damaged in primigravid and primiparous rabbits. METHODS: Twenty-four rabbits allocated evenly (n = 6) into nulliparous, pregnant, and primiparous groups on postpartum days 3 (P3) and 20 (P20) were used to evaluate the myofiber cross-sectional area (CSA), ß-glucuronidase activity, and anti-3-nitrotyrosine (anti-3-NTyr) immunoreactivity in Bsm and Pcm muscles. Appropriate statistical tests were done to determine significant differences among groups (P ≤ 0.05). RESULTS: The average CSA of Bsm was not significantly different, albeit a high percentage of myofibers was enlarged in late-pregnant and primiparous rabbits on P3; ß-glucuronidase activity and indirect parameter of muscle damage was also higher. These variables did not change in the Pcm muscle during the different reproductive stages. In contrast, the 3-NTyr immunoreactivity, an indicator of oxidative damage, was increased on P3 for Pcm myofibers and P20 for myofibers of both muscles. CONCLUSIONS: Our findings demonstrate reliable signs of damage to Bsm and Pcm muscles in young female rabbits passing different reproductive stages. Damage to the Bsm muscles as detected at the end of pregnancy persisted after delivery. This was not the case for Pcm muscles, in which damage seems to appear after delivery.

Multiparity modifies contractile properties of pelvic muscles affecting the genesis of vaginal pressure in rabbits.

AIMS: To characterize the contractile properties of the bulbospongiosus (Bsm), isquiocavernosus (Ism), and pubococcygeus muscles (Pcm), and their involvement in the genesis of vaginal pressure in nulliparous and multiparous rabbits. METHODS: Age-matched nulliparous and multiparous rabbits were used to record the isometric contractile responses of each muscle as well as the intravaginal pressure evoked by single square electrical pulses and stimulation trains of ascending frequency. To establish significant differences between groups, two-tail unpaired Student t tests were carried out. The linear correlation between intravaginal pressure and muscle contractile force was analyzed with Pearson correlation tests. For all cases, a P ≤ 0.05 was set as statistically significant. RESULTS: Multiparity decreased the contractile force of Bsm and Ism generated by high-frequency stimulation trains. The normalized force of the Pcm increased when evoked at 1, 4, and 10 Hz while this decreased at higher frequencies (20, 50, and 100 Hz). The contraction of both Bsm and Ism raised particularly the pressure on the perineal vagina while that of the Pcm increased the pressure in the pelvic vagina. Such a functional segregation is still present in multiparous rabbits albeit it was modified. CONCLUSIONS: Multiparity induces changes in the contractile responses of Bsm, Ism, and Pcm, which alterates the vaginal pressure.

Hypothyroidism impairs somatovisceral reflexes involved in micturition of female rabbits.

AIMS: To determine the impact of hypothyroidism on the bladder and urethral functions as well as in the activation of the pubococcygeous (Pcm) and bulbospongiosus (Bsm) during micturition. METHODS: Age-matched control and methimazole-induced hypothyroid female rabbits were used to simultaneously record cystometrograms, urethral pressure, and the reflex activation of Pcm and Bsm during the induced micturition. Urodynamic and urethral variables were measured. Activation or no activation of the Pcm and Bsm during the storage and voiding phases of micturition were categorized as 1 or 0. Significant differences (P ≤ 0.05) between control and hypothyroid groups were determined with unpaired Student-t or Mann-Whitney tests. RESULTS: One-month induced hypothyroidism increased the residual volume and threshold pressure while the opposite was true for the voided volume, maximal pressure, and voiding efficiency. Urethral pressure was also affected as supported by a notorious augmentation of the urethral resistance, among other changes in the rest of measured variables. Hypothyroidism also affected the reflex activation of the Pcm in the voiding phase of micturition. CONCLUSIONS: Our findings demonstrate hypothyroidism impairs the bladder and, urethral functions, and reflex activation of Pcm and Bsm affecting the micturition in female rabbits.

Hypothyroidism affects lipid and glycogen content and peroxisome proliferator-activated receptor δ expression in the ovary of the rabbit.

Dyslipidaemia and hyperglycaemia are associated with ovarian failure and both have been related to hypothyroidism. Hypothyroidism promotes anovulation and ovarian cysts in women and reduces the size of follicles and the expression of aromatase in the ovary of rabbits. Considering that ovarian steroidogenesis and ovulation depend on lipid metabolism and signalling, the aim of the present study was to analyse the effect of hypothyroidism on the lipid content and expression of peroxisome proliferator-activated receptor (PPAR) δ in the ovary. Ovaries from female rabbits belonging to the control (n=7) and hypothyroid (n=7) groups were processed to measure total cholesterol (TC), triacylglycerol (TAG) and glycogen content, as well as to determine the presence of granules containing oxidized lipids (oxysterols and lipofuscin) and the relative expression of perilipin A (PLIN-A) and PPARδ. Hypothyroidism increased TC and glycogen content, but reduced TAG content in the ovary. This was accompanied by a reduction in the expression of PLIN-A in total and cytosolic extracts, changes in the presence of granules containing oxidative lipids and low PPARδ expression. The results of the present study suggest that hypothyroidism modifies the content and signalling of lipids in the ovary, possibly affecting follicle maturation. These results could improve our understanding of the association between hypothyroidism and infertility in females.

Fiber type composition of pubococcygeus and bulbospongiosus striated muscles is modified by multiparity in the rabbit.

AIMS: We analyzed the effect of multiparity on the fiber type composition of two skeletal muscles involved in the maintenance of the micturition process, the pelvic pubococcygeus (Pc) and perineal bulbospongiosus (Bs) muscles in nulliparous and multiparous rabbits (Oryctolagus cuniculus). METHODS: We used the basic ATPase and NADH-TR techniques to identify and characterize slow, intermediate, and fast fiber types and glycolitic and oxidative fibers in muscles, respectively. RESULTS: Pc muscles of multiparous rabbits present relatively high percentages of slow and intermediate fibers but a low percentage of fast fibers (P < 0.05) as compared to Pc muscles from nulliparous rabbits, while percentages of glycolytic and oxidative fibers were similar (P > 0.05). Bs muscles of multiparous rabbits had a higher proportion of intermediate and glycolytic fibers (P < 0.05) than muscles of nulliparous. Both, Pc and Bs muscles of nulliparous and multiparous rabbits contain slow fibers with similar large cross sectional area, but fast fibers in multiparous muscles showed small cross sectional area than in nulliparous. CONCLUSIONS: Multiparity modified the fiber type composition of Pc and Bs muscles in female rabbits. We propose that the contractile force and the physiological role of both muscles during micturition are affected because of the observed changes in the relative composition of muscle fiber types.

The role of the pubococcygeus muscle in the urethrogenital reflex of male rats.

AIM: To determine the response of the pubococcygeus muscle (Pcm) during the urethrogenital reflex (UGR). METHODS: Urethane-anesthetized male rats (n = 20) were used to describe the gross anatomy of the Pcm (n = 3), the effect of the electrical stimulation of the Pcm on the urethral pressure (n = 3), and the reflex activity of the Pcm due to the mechanical stimulation of the urethra (n = 3) and during penile and urethrogenital reflexes (n = 11). The urethral pressure (UP) was recorded as a response to penile stimulation (brushing, extension, and occlusion) and during the UGR; the electromyographic activity of the Pcm was simultaneously evaluated. The role of the Pcm was assessed by measuring urethral pressure variables before and after denervation of this muscle. RESULTS: The Pcm is innervated by the caudal branch of the somatomotor branch of the pelvic nerve. The electrically induced contraction of the Pcm increased the UP. The mechanical stimulation of the urethra during the induced micturition caused the reflex activity of the Pcm. The different penile stimuli caused bursts of activity of the Pcm. During the UGR, the Pcm exhibited a tonic activity. The transection of the caudal branch of the Smb reduced the maximal UP during the penile stimulation. The same was true regarding the duration of the UGR, the pressure that triggers the UGR, and the highest pressure observed during the UGR. CONCLUSION: Our results suggest that the activation of the Pcm is relevant for the UGR in male rats. Neurourol. Urodynam. 36:80-85, 2017. © 2015 Wiley Periodicals, Inc.

Anatomical organization and somatic axonal components of the lumbosacral nerves in female rabbits.

AIM: To determine the anatomical organization and somatic axonal components of the lumbosacral nerves in female rabbits. METHODS: Chinchilla adult anesthetized female rabbits were used. Anatomical, electrophysiological, and histological studies were performed. RESULTS: L7, S1, and some fibers from S2 and S3 form the lumbosacral trunk, which gives origin to the sciatic nerve and innervation to the gluteal region. From S2 to S3 originates the pudendal nerve, whose branches innervates the striated anal and urethra sphincters, as well as the bulbospongiosus, ischiocavernosus, and constrictor vulvae muscles. The sensory field of the pudendal nerve is ∼1800 mm2 and is localized in the clitoral sheath and perineal and perigenital skin. The organization of the pudendal nerve varies between individuals, three patterns were identified, and one of them was present in 50% of the animals. From S3 emerge the pelvic nerve, which anastomoses to form a plexus localized between the vagina and the rectum. The innervation of the pelvic floor originates from S3 to S4 fibers. CONCLUSIONS: Most of the sacral spinal nerves of rabbit are mixed, carrying sensory, and motor information. Sacral nerves innervate the hind limbs, pelvic viscera, clitoris, perineal muscles, inguinal and anal glands and perineal, perigenital, and rump skin. The detailed description of the sacral nerves organization, topography, and axonal components further the knowledge of the innervation in pelvic and perinal structures of the female rabbit. This information will be useful in future studies about the physiology and physiopathology of urinary, fecal, reproductive, and sexual functions.

Moderate-to-high normal levels of thyrotropin is a risk factor for urinary incontinence and an unsuitable quality of life in women over 65 years.

The present study aimed to investigate the relationship between normal serum concentrations of thyrotropin (TSH) and urinary incontinence (IU), urinary infections, and quality of life in old women. Euthyroid post-menopausal women without sarcopenia, estrogen replacement, emotional illness, and/or cancer were enrolled as participants. Anthropometric indicators, serum glucose and estradiol, and thyroid profile were measured. Sociodemographic, clinical, physical activity, and quality of life (SF-36) surveys were applied. One-hour pad test and International Consultation on Incontinence Questionnaire Short Form (ICIQ-SF) were used to determine UI. Urinalysis was also done. In agreement with results from the pad test (cut-off point ≥1.4 g), the ICIQ-SF reveled approximately 50% of incontinent women. A high percentage of women had moderate-high bacteriuria and urinary infections. Logistic regression analysis showed that age is a risk factor for both UI and urinary infection. Diabetes, number of pregnancies or childbirths, urinary infections, and bacteriuria did not influence the presence of UI. To allocate women into four groups according to their age (<65 or ≥65 years old) and TSH concentrations (0.3-1.9 or 2-10 µUI/mL), we found that moderate-to-high normal levels of TSH is a risk factor for UI and a worse quality of life in the oldest women. Our results highlight the profit of measuring TSH concentrations in post-menopausal women.

Distribution of thyroid hormone and thyrotropin receptors in reproductive tissues of adult female rabbits.

PURPOSE: Thyroid dysfunctions are related to anovulation, miscarriages, and infertility in women and laboratory animals. Mechanisms associated with these effects are unknown, although indirect or direct actions of thyroid hormones and thyrotropin could be assumed. The present study aimed to identify the distribution of thyroid hormones (TRs) and thyrotropin (TSHR) receptors in reproductive organs of female rabbits. MATERIAL AND METHODS: Ovary of virgin and pregnant rabbits, as well as the oviduct, uterus, and vagina of virgin rabbits were excised, histologically processed, and cut. Slices from these organs were used for immunohistochemical studies for TRα1-2, TRß1, and TSHR. RESULTS: The presence of TRs and TSHR was found in the primordial, primary, secondary, tertiary, and Graafian follicles of virgin rabbits, as well as in the corpora lutea, corpora albicans, and wall of hemorrhagic cysts of pregnant rabbits. Oviductal regions (fimbria-infundibulum, ampulla, isthmus, and utero-tubal junction), uterus (endometrium and myometrium), and vagina (abdominal, pelvic, and perineal portions) of virgin rabbits showed anti-TRs and anti-TSHR immunoreactivity. Additionally, the distal urethra, paravaginal ganglia, levator ani and iliococcygeus muscles, dorsal nerve and body of the clitoris, perigenital skin, and prostate had TRs and TSHR. CONCLUSIONS: The wide presence of TRs and TSHR in female reproductive organs suggests varied effects of thyroid hormones and thyrotropin in reproduction.

Hypothyroidism modifies morphometry and thyroid-hormone receptor expression in periurethral muscles of female rabbits.

AIM: To evaluate the morphometry and thyroid-hormone receptor (TR) expression in pelvic (pubococcygeus, Pcm) and perineal (bulbospongiosus, Bsm) muscles of control and hypothyroid female rabbits. METHODS: Hypothyroidism was induced administering 0.02% methimazole in the drinking water for one month. Hematoxylin-eosin stained muscle sections were used to evaluate the fiber cross-sectional area (CSA) and the number of peripheral myonuclei per fiber. Immunohistochemistry was used to calculate the proportion of TR immunoreactive nuclei per fiber. Significant differences were considered at a P ≤ 0.05. RESULTS: As compared to control rabbits, hypothyroidism increased the averaged fiber CSA and the myonuclei per fiber in the Bsm. Although the myonuclei number per fiber was also increased in the Pcm, the effect concerning the fiber CSA was only observed in a fraction of the Pcm fibers. Both TRα and TRß were similarly expressed in the Pcm and Bsm. Hypothyroidism increased the expression of the TRα in the Bsm. Meanwhile, the expression of TR isoforms in the Pcm was not altered. CONCLUSION: Our findings support that the TR signaling is directly involved in morphometrical changes induced by hypothyroidism in the Pcm and Bsm. The effect of hypothyroidism on the Pcm and Bsm could be related to the different type of fiber and metabolism that these muscles have. Neurourol. Urodynam. 35:895-901, 2016. © 2015 Wiley Periodicals, Inc.

Differential damage and repair responses of pubococcygeus and bulbospongiosus muscles in multiparous rabbits.

AIM: To determine the extent of damage and regeneration associated with multiparity on the pubococcygeus and bulbospongiosus muscles. METHODS: Age-matched virgin nulliparous and multiparous rabbits that were killed at days 3 and 20 after the fourth delivery were used to harvest pubococcygeus and bulbospongiosus muscles. The activity of the lysosomal enzyme ß-glucuronidase was used as a muscle damage indicator. The number of immunoreactive myofiber-associated nuclei anti-Pax7, -MyoD, and -myogenin, as well as the anti-desmin immunoreactive area were measured in muscle sections to estimate some regenerative stages. Significant differences were considered at a P ≤ 0.05. RESULTS: The ß-glucuronidase activity was increased at postpartum day 20 in the pubococcygeus muscle. This variable was unaltered in the bulbospongiosus muscles of multiparas regardless of the postpartum day on which this was measured. The number of immunoreactive nuclei anti-Pax7 in the pubococcygeus muscle was similar between nulliparas and multiparas, whilst those of anti-MyoD and anti-myogenin were increased at postpartum days 3 and 20. The same was true for these latter three markers evaluated in the bulbospongiosus muscles, supporting an ongoing regeneration. The desmin-positive percentage of muscle area per field was increased at postpartum day 20 in the pubococcygeus muscle, whilst such an increment was seen at postpartum days 3 and 20 in the bulbospongiosus muscles. CONCLUSIONS: Damage and regeneration of the pubococcygeus and bulbospongiosus muscles are differently influenced by multiparity in rabbits. This could rely on the anatomical location, metabolism, myofiber composition, and muscle exertion during pregnancy and/or the delivery of each muscle.

Anatomic and functional properties of bulboglandularis striated muscle support its contribution as sphincter in female rabbit micturition.

PURPOSE: To determine anatomic and functional properties of the bulboglandularis muscle (Bgm) for clarifying its role in micturition in female rabbits. MATERIAL AND METHODS: Virgin female rabbits were used to describe the gross anatomy and innervation of the Bgm, to determine the effect of the Bgm contraction on urethral pressure, and to evaluate the Bgm activity during the induced-micturition. Both electromyogram and cystometrogram activity were simultaneously recorded in urethane-anesthetized rabbits. Bladder function was assessed measuring standard urodynamic variables before and after blocking the Bgm activity for approaching its contribution to micturition. The relevance of the Bgm activation for micturition was approached applying lidocaine injections. RESULTS: The Bgm was composed of circularly oriented striated fibers enveloping distal urethra and pelvic vagina. Both the venous plexus and urethra were comprised by the Bgm contraction induced by electrical stimulation. The Bgm showed bursts of tonic activity at the storage phase of micturition that gradually decreased until turning off as the onset of the voiding phase. The voided volume, the voiding efficiency, the threshold pressure, and the maximal pressure were decreased after lidocaine injection. Contrastingly, the threshold volume, the residual volume, the voiding duration, and the urethral resistance at voiding were increased. CONCLUSIONS: Present anatomical and physiological findings support that the Bgm acts as a sphincter during micturition of female rabbits. Neurourol. Urodynam. 35:689-695, 2016. © 2015 Wiley Periodicals, Inc.

Aromatase expression is linked to estrogenic sensitivity of periurethral muscles in female rabbits.

Beyond its role in the conversion of androgens to estrogens, the expression of aromatase could influence on the estrogenic signalling in targeted tissues. Considering the well-defined biochemical and physiological differences between the pubococcygeus (Pcm) and bulbospongiosus (Bsm) muscles in female rabbits, it is presently hypothesized that the aromatase expression is differentially linked to the estrogen sensitivity of each muscle. To this end, serum estradiol levels and the aromatase expression, presence of ERα and ERß and morphometry were evaluated in the Pcm and Bsm of female rabbits allocated in control, ovariectomized (OVX) and OVX treated with estradiol benzoate (OVX + EB) groups. Aromatase expression was high in the Pcm. Independently to serum estradiol, ovariectomy increased aromatase expression in the Pcm while decreased it in the Bsm. The EB treatment avoided the effect of ovariectomy only in the Pcm. The number of immunoreactive nuclei anti-ERα and anti-ERß was high in the Pcm of OVX and OVX + EB rabbits, while those in the Bsm remained unchanged. The number of peripheral nuclei per fibre and the cross-sectional area-to-myonucleus ratio were modified only in the Pcm. Our findings support aromatase expression in the Pcm, and Bsm of rabbits is differentially linked to estrogenic sensitivity of each muscle.

Differential metabolism of brown adipose tissue in newborn rabbits in relation to position in the litter huddle.

Competition for resources can contribute importantly to the early development of individual differences in behavioral and physiological phenotypes. In newborn rabbits, littermates compete for thermally favorable positions within the litter huddle. As brown adipose tissue (BAT) is the principal site of thermogenesis in such altricial young, we investigated differences in rabbit pups' growth and morphological differences in BAT associated with position within the huddle. We formed three treatment groups (7 litters/group): GI-birth (pups killed at birth); GII-chronic thermal challenge (pups killed after exposure to a moderately cold environmental during postnatal days 1-3); GIII-acute thermal challenge (as for GII but pups killed after an additional 30min exposure to a very cold environment on postnatal day 3). Interscapular BAT was removed at death for histological analysis, and triglyceride concentrations measured in serum. Pups occupying central positions in the huddle had higher skin temperatures, obtained more milk, and were more efficient at converting this into body mass, than pups occupying peripheral positions. There was no significant difference in BAT morphology or triglyceride concentrations between pups at birth, nor between central and peripheral pups chronically exposed to moderate cold until postnatal day 3. However, during acute cold exposure at this age, peripheral pups were less able to maintain their body temperature, they depleted BAT fat reserves almost completely, and they had lower serum concentrations of triglycerides than central pups. These findings confirm the contribution of early sibling relations to individual differences in growth and metabolic processes associated with thermoregulation in newborn rabbits.