Urethral regions with differential tissular composition may underlie urinary continence and voiding function in female rats.

AIMS: To analyze, in female rats, the anatomical and histological features of the urethra and its relationship with the vagina and clitoris, and its innervation. METHODS: Seventeen adult female Wistar rats were used. Gross anatomy and acetylcholinesterase (AchE) histochemistry were performed to describe the urethral features, adjacent structures, and innervation. The histomorphometric characteristics of the urethra were determined in transversal, longitudinal, or coronal sections stained with Masson's Trichrome. RESULTS: The female rat urethra is not a homogeneous tubular organ. The pre-pelvic and pelvic regions are firmly attached to the vagina with belt-like striated fibers forming a urethra-vaginal complex. The bulbar regions have curved segments and a narrow lumen. The clitoral region is characterized by a urethra-clitoral complex surrounded by a vascular plexus. The lumen area and thickness of the urethral layers significantly varied between regions (P < 0.05). Innervation of the urethra arrives from the major pelvic ganglion, the dorsal nerve of the clitoris (DNC), and the motor branch of the sacral plexus (MBSP). CONCLUSIONS: Differential tissular composition of the urethra may underlie urinary continence and voiding dysfunction through different physiological mechanisms. The urethra-vagina complex seems to be the main site controlling urinary continence through active muscular mechanisms, while the bulbar urethra provides passive mechanisms and the urethra-clitoris complex seems to be crucial for distal urethral closure by means of a periurethral vascular network.

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.

Coital Urinary Incontinence Induced by Impairment of the Dorsal Nerve of the Clitoris in Rats.

PURPOSE: We determined the effect of chronic bilateral neurectomy of the dorsal nerve of the clitoris on urinary parameters and sexual behavior of conscious female rats. MATERIALS AND METHODS: A total of 18 anesthetized virgin female Wistar rats were used in this study, including 11 that underwent bilateral neurectomy of the dorsal nerve of the clitoris and 7 that underwent sham surgery. Urinary parameters were determined in awake animals preoperatively, and 3 and 10 days postoperatively. Sexual behavior was tested 14 days postoperatively to determine whether the females expelled urine during sexual encounters. After male ejaculation the females were anesthetized with urethane to record external urethral sphincter electromyogram activity in response to clitoris, perigenital skin and vaginal stimulation. Neurectomy was corroborated anatomically. RESULTS: Sham surgery did not significantly modify urinary parameter values. However, bilateral neurectomy of the dorsal nerve of the clitoris significantly increased voiding frequency and voiding duration (p <0.05). It did not significantly affect the flow rate, voided volume or voiding interval. Of females that underwent bilateral neurectomy of the dorsal nerve of the clitoris 67% expelled urine just after male ejaculation. CONCLUSIONS: These results suggest that the pudendal nerve is an important neural pathway in the convergence and crosstalk of female urogenital neural circuits, and genital deafferentation may be a causal factor of coital urinary incontinence. Rats with bilateral transection of the dorsal nerve of the clitoris may serve as an animal model of coital incontinence.

Genitourinary dysfunction in male rats after bilateral neurectomy of the motor branch of the sacral plexus.

AIMS: To determine the contribution of the striated musculature anatomically related to the urethra on urinary continence in conscious male rats. We tested whether the bilateral neurectomy of the motor branch of the sacral plexus (MBSP), a nerve that innervates the bulbospongiosus, ischiocavernosus, and external urethral sphincter, is a reliable procedure to induce changes in voiding pattern that can be used as indicators of urinary incontinence in unanesthetized male rats. METHODS: Micturition behavior was videotaped and urinary parameters measured 24 h before and at day 2 and 10 after surgery. RESULTS: Intact animals have a stereotyped behavior of micturition consisting in urination in the corner of the cage. Neurectomized animals lost place preference for voiding demonstrated by leakage of urine throughout the cage while eating, walking, or sleeping. Voiding frequency was double and voiding duration was triple the amount before surgery. Urine flow rate and voiding volume were also significantly decreased. Necropsy showed that 10 days post-denervation semen material was accumulated in the urethra and in the bladder. CONCLUSION: In male rats the perineal striated muscles are crucial to maintaining normal urinary continence, preventing retrograde ejaculation, and to expelling urine and seminal secretions. Bilateral neurectomy of the MBSP may not be appropriate for long term survival urinary studies because effects on urinary parameters can be contaminated and/or masked by impaired seminal fluid expulsion, as a consequence of impairment of striated urethral muscle function.

Kinetic behavior of Fe(o,o-EDDHA)-humic substance mixtures in several soil components and in calcareous soils.

Ferric ethylenediamine- N, N'-bis-(o-hydroxyphenylacetic)acid chelate (Fe(o, o-EDDHA)) is one of the most effective Fe fertilizers in calcareous soils. However, humic substances are occasionally combined with iron chelates in drip irrigation systems in order to lower costs. The reactivity of iron chelate-humic substance mixtures in several soil components and in calcareous soils was investigated through interaction tests, and their behavior was compared to the application of iron chelates and humic substances separately. Two commercial humic substances and two Fe(o, o-EDDHA) chelates (one synthesized in the laboratory and one commercial) were used to prepare iron chelate-humic substance mixtures at 50% (w/w). Various soil components (calcium carbonate, gibbsite, amorphous iron oxide, hematite, tenorite, zincite, amorphous Mn oxide, and peat) and three calcareous soils were shaken for 15 days with the mixtures and with iron chelate and humic substance solutions. The kinetic behavior of Fe(o, o-EDDHA) and Fe non-(o,o-EDDHA) (Fe bonded to (o,p-EDDHA) and other polycondensated ligands) and of the different nutrients solubilized after the interaction assay was determined. The results showed that the mixtures did not significantly reduce the retention of Fe(o, o-EDDHA) and Fe non-(o,o-EDDHA) in the soil components and the calcareous soils compared to the iron chelate solutions, but they did produce changes in the retention rate. Moreover, the competition between humic substances and synthetic chelating agents for complexing metal cations limited the effectiveness of the mixtures to mobilize nutrients from the substrates. The presence of Fe(o, p-EDDHA) and other byproducts in the commercial iron chelate had an important effect on the evolution of Fe(o, o-EDDHA) and the nutrient solubilization process.

Fe uptake from meso and D,L-racemic Fe(o,o-EDDHA) isomers by strategy I and II plants.

One of the most efficient fertilizers to correct Fe deficiency in calcareous soils and waters with high bicarbonate content is based on ferric ethylenediamine-N,N'-bis(o-hydroxyphenylacetic) acid [Fe(o,o-EDDHA)]. Fe(o,o-EDDHA) forms two groups of geometric isomers known as meso and D,L-racemic. To determine the Fe uptake from meso and D,L-racemic Fe(o,o-EDDHA), four iron-efficient plants, two plants representative of strategy I (tomato and pepper) and two plants representative of strategy II (wheat and oats), were grown in hydroponic culture. Results indicated that strategy II plants took up iron from both Fe(o,o-EDDHA) isomers equally. However, strategy I plants took mainly the iron associated with the meso form (the lowest stability isomer).

Overlapping litters and reproductive performance in the domestic rabbit.

Rabbits (Oryctolagus cuniculus), like many small mammals, have a marked postpartum estrus, and during the breeding season, are often both pregnant and lactating. We examined reproductive performance and allocation of resources by rabbit mothers with overlapping litters under presumably optimal conditions of unrestricted food, standardized litter size, and young reproductive age. Even under these conditions, females raising overlapping litters incurred higher costs in terms of greatly increased food intake and pup mortality than females raising nonoverlapping litters. Despite such costs, females with overlapping litters raised a larger total number of young to weaning than females without the load of simultaneous lactation and pregnancy. By more than doubling food intake during lactation, females maintained a stable baseline body weight throughout the study, suggesting that this, in a species with low fat reserves, might have priority over the short-term raising of a maximum number of young. Contrary to the expectation that females with overlapping litters would allocate more resources to their senior young, no appreciable difference in number, growth, or survival between pups of senior and junior litters was found either at birth or weaning. While this might reflect a strategy in this opportunistic breeder of distributing reproductive chances similarly between senior and junior litters, it is now necessary to investigate females' breeding strategy when resources are limited.

Drought effects on fine-root and ectomycorrhizal-root biomass in managed Pinus oaxacana Mirov stands in Oaxaca, Mexico.

The effects of a severe drought on fine-root and ectomycorrhizal biomass were investigated in a forest ecosystem dominated by Pinus oaxacana located in Oaxaca, Mexico. Root cores were collected during both the wet and dry seasons of 1998 and 1999 from three sites subjected to different forest management treatments in 1990 and assessed for total fine-root biomass and ectomycorrhizal-root biomass. Additionally, a bioassay experiment with P. oaxacana seedlings was conducted to assess the ectomycorrhizal inoculum potential of the soil for each of the three stands. Results indicated that biomasses of both fine roots and ectomycorrhizal roots were reduced by almost 60% in the drought year compared to the nondrought year. There were no significant differences in ectomycorrhizal and fine-root biomass between the wet and dry seasons. Further, the proportion of total root biomass consisting of ectomycorrhizal roots did not vary between years or seasons. These results suggest that both total fine-root biomass and ectomycorrhizal-root biomass are strongly affected by severe drought in these high-elevation tropical pine forests, and that these responses outweigh seasonal effects. Forest management practices in these tropical pine forests should consider the effects of drought on the capacity of P. oaxacana to maintain sufficient levels of ectomycorrhizae especially when there is a potential for synergistic interactions between multiple disturbances that may lead to more severe stress in the host plant and subsequent reductions in ectomycorrhizal colonization.

Características anatómicas y fisiológicas de los músculos pélvicos en la coneja doméstica (Oryctolagus cuniculus) / Anatomical and physiological characteristics of pelvic muscles in the female rabbit (Oryctolagus cuniculus)

In mammals, the pelvic striated muscles have been linked to the regulation of urinary functions and little is known about the involvement of this muscle in reproductive functions. The objective of this study was to use surgical and electrophysiological techniques to determine the anatomical features and innervation of iliococcygeus and pubococcygeus muscles in adult female rabbits and characterize the reflex electromyographic (EMG) activity in response to genital stimulation. Results show that the iliococcygeus and pubococcygeus are long bilateral muscles with fibers attached to the ilium bone. The muscle fibers are not attached to the pelvic viscera but they run adjacent to the vagina and rectum to be inserted into the sacral vertebrae. The iliococcygeus and pubococcygeus muscles are innervated by branches arising from S3 and S4. The reflex EMG activity was obtained during stimulation of the vaginal orifice skin and the perineal and pelvic vagina. Abdominal vaginal stimulation did not cause an EMG response. Cervical stimulation produced a temporary inhibition in the activity of the iliococcygeus and pubococcygeus. These findings extend the poor descriptions of innervation and anatomy of the striated pelvic musculature shown in the textbooks and atlas of rabbits. They also suggest that the iliococcygeus and pubococcygeous muscles can be activated by reflex action during reproductive processes such as mating and parturition.

En mamíferos, la musculatura estriada pélvica se ha relacionado con la regulación de funciones urinarias y poco se sabe de su participación en funciones reproductivas. Los objetivos del presente estudio fueron determinar las características anatómicas y la inervación de los músculos iliococcígeo y pubococcígeo de la coneja adulta, y caracterizar la actividad electromiográfica (EMG) refleja en respuesta a la estimulación genital. Para ello se utilizaron técnicas quirúrgicas y electrofisiológicas. Los resultados muestran que el iliococcígeo y pubococcígeo son músculos bilaterales que se originan en el hueso iliaco; están inervados por ramas que emergen de S3 y S4; sus fibras musculares no se adhieren a las vísceras pélvicas, sino que discurren lateral a la vagina y al recto y se insertan en las vértebras sacras. Durante la estimulación de la piel del orificio vaginal y la vagina pélvica y perineal se presentó actividad EMG refleja en ambos músculos. La estimulación de la vagina abdominal no indujo respuesta EMG. La estimulación cervical produjo inhibición temporal en la actividad del iliococcígeo y pubococcígeo. Estos resultados contribuyen a las escasas descripciones anatómicas de la musculatura pélvica de la coneja que se encuentran en libros de texto y atlas; también sugieren que los músculos pélvicos iliococcígeo y pubococcígeo podrían activarse reflejamente durante procesos reproductivos, como la cópula y el parto.