Endocrine-paracrine cells of the male urogenital apparatus: a comparative histochemical and immunohistochemical study in some domestic ungulates

Topographic distribution of serotonin-immunoreactive urethral endocrine cells and their relationship with calcitonin gene-related peptide-immunoreactive nerves in male rats

We investigated the topographic distribution and morphology of serotonin (5-HT)-immunoreactive endocrine cells in the urethra of male rats, and focused on their relationship with peptidergic nerve fibers immunoreactive for calcitonin gene-related peptide (CGRP). Urethral endocrine cells immunoreactive for 5-HT were densely distributed in the epithelial layers of the prostatic part, but were sparsely distributed in the membranous and spongy parts of urethra. Distribution of urethral endocrine cells with 5-HT immunoreactivity in the prostatic part was restricted from the internal urethral orifice to the region of seminal colliculus. 5-HT-immunoreactive endocrine cells were also observed in the ductal epithelial layers of coagulating glands, prostatic glands, and seminal vesicles. 5-HT-immunoreactive endocrine cells were triangular or flask in shape and possessed an apical projection extending toward the urethral lumen, and basal or lateral protrusions intruding between other epithelial cells were also detected in some cells. Double immunolabeling for 5-HT and CGRP revealed that CGRP-immunoreactive nerve fibers attached to urethral endocrine cells with 5-HT immunoreactivity in the prostatic part. These results suggest that urethral endocrine cells may release 5-HT in response to luminal stimuli, and that these cells and CGRP-immunoreactive nerves may regulate each other by an axon reflex mechanism.

Experimental investigation of the biomechanics of urethral tissues and structures

NEW FINDINGS

What is the central question of this study? Prostheses for treatment of urinary incontinence elicit complications associated with an inadequate mechanical action. This investigation aimed to define a procedure addressed to urethral mechanical characterization. Experimental tests are the basis for constitutive formulation, with a view to numerical modelling for investigation of the interaction between the tissues and a prosthesis. What is the main finding and its importance? Horse urethra, selected for its histomorphometric similarity to human urethra, was characterized by integrated histological analysis and mechanical tests on the biological tissue and structure, leading to constitutive formulation. A non-linear, anisotropic and time-dependent response was found, representing a valid basis for development of a numerical model to interpret the functional behaviour of the urethra. Urinary dysfunction can lead to incontinence, with an impact on the quality of life. Severe dysfunction can be overcome surgically by the use of an artificial urinary sphincter. Nonetheless, several complications may result from inappropriate functioning of the prosthesis, in many instances resulting from an unsuitable mechanical action of the device on the urethral tissues. Computational models allow investigation of the mechanical interaction between biological tissues and biomedical devices, representing a potential support for surgical practice and prosthesis design. The development of such computational tools requires experimental data on the mechanics of biological tissues and structures, which are rarely reported in the literature. The aim of this study was to provide a procedure for the mechanical characterization of urethral tissues and structures. The experimental protocol included the morphometric and histological analysis of urethral tissues, the mechanical characterization of the response of tissues to tensile and stress-relaxation tests and evaluation of the behaviour of urethral structures by inflation tests. Results from the preliminary experiments were processed, adopting specific model formulations, and also providing the definition of parameters that characterize the elastic and viscous behaviour of the tissues. Different experimental protocols, leading to a comprehensive set of experimental data, allow for a reciprocal assessment of reliability of the investigation approach.

The urothelium: anatomy, review of the literature, perspectives for veterinary medicine

Over time, much knowledge has been accumulated about the active role of the urothelium, principally in rodents and human. Far from being a mere passive barrier, this specialized epithelium can alter the ion and protein composition of the urine, is able to sense and respond to mechanical stimuli such as pressure, and react to mechanical stimuli by epithelial cell communication with the nervous system. Most of the specialized functions of the urothelium are linked to a number of morpho-physiologic properties exhibited by the superficial umbrella cells, including specialized membrane lipids, asymmetric unit membrane particles and a plasmalemma with stiff plaques which function as a barrier to most substances found in urine, thus protecting the underlying tissues. Moreover, the entire mucosa lining the low urinary tract, composed of urothelium and sub-urothelium, forms a functional transduction unit, able to respond to eso- and endogenous physical and chemical stimuli in a manner assuring an adequate functional response. This review will summarize the available information on each area of inquiry from a morpho-functional point of view. Possible considerations pertaining to species of veterinary interest are reviewed as well. The review was prepared consulting the electronic databases PubMed and Cab Abstracts and retrieving all pertinent reports and the relative reference lists, in order to identify any potential additional studies that could be included. Full-length research articles and thematic reviews were considered. Information on the urothelium of some domestic animal species was also included.

Orexin expression in different prostate histopathologic examinations: Can it be a marker for prostate cancer? A preliminary result

OBJECTIVE

The aim of this study was to evaluate the expression of the orexin receptor in different prostate pathologies, including prostate adenocarcinoma, benign prostate hyperplasia and chronic prostatitis.

MATERIAL AND METHODS

A total of 90 patients (mean age 64.01±7.2 years) were enrolled in the study. The patients were divided into three groups of equal numbers based on their histopathologic findings: prostate cancer (Group 1), benign prostate hyperplasia (Group 2) and chronic prostatitis (Group 3). All the tissues were incubated with a primary antibody recognizing the Orexin receptor. The specific cytoplasmic immunoreactivity of the Orexin receptor was semiquantitatively scored for intensity and distribution based on a grading scale. The staining intensity and orexin expression were evaluated using Pearson χ(2) test.

RESULTS

A heterogeneous staining pattern of the Orexin receptor was observed between the groups. The expression rates were 90% (27/30) in Group 1, 53.3% (16/30) in Group 2 and 26.7% (8/30) in Group 3. While 5 patients (9.3%) in Group 1 showed strong staining, all samples from the other 2 groups showed only weak staining. There were significant differences in staining intensity between the three groups. The expression and distribution of the Orexin receptor was more widespread in Group 1 than in the other groups and was higher in patients with poorly differentiated malignancy. However, there was no significant difference based on Gleason score.

CONCLUSION

Orexin receptors are found in human prostate tissues and their expression is widespread in prostate cancer and in patients with a higher Gleason score. Therefore, we believe that Orexin immunoreactivity can be considered to be an indicator of poor prognosis and of poorly differentiated prostate cancer cases.

Evolving ideas about the male refractory period

The male refractory period (MRP) continues to be a topic of discussion and debate within the field of sexual medicine. To date explanations rely on central descending (efferent) influences involving specific neurotransmitter systems. Herein we explore the issue of the male refractory period, identifying problems with current explanations, specifying the parameters of an adequate model, and suggesting possible mechanisms mediating this phenomenon. We review the literature regarding existing explanations for the MRP and look to other systems of physiological regulation that might provide a model for the conceptualization of the MRP. Our approach differs from traditional explanations in that it emphasizes the possible roles of various peripheral, rather than central, feedback (afferent) systems that affect peripheral autonomic functioning and response. Yet our approach is consistent with other peripheral regulatory feedback systems controlling autonomic response related to such processes as heart rate, respiration, and gut motility. Although direct empirical research supporting our approach is lacking, sufficient evidence exists to support the idea that such processes are not only possible but likely with respect to the male refractory period. We suggest several lines of research that might provide empirical support for this approach.

Evidence of 5-HT components in human sperm: implications for protein tyrosine phosphorylation and the physiology of motility

Serotonin (5-hydroxytryptamine; C(10)H(12)N(2)O (5-HT)) is produced in the CNS and in some cells of peripheral tissues. In the mammalian male reproductive system, both 5-HT and tryptophan hydroxylase (TPH) have been described in Leydig cells of the testis and in principal cells of the caput epididymis. In capacitated hamster sperm, it has been shown that 5-HT promotes the acrosomal reaction. The aim of this work was to explore the existence of components of the serotoninergic system and their relevance in human sperm physiology. We used both immunocytochemistry and western blot to detect serotoninergic markers such as 5-HT, TPH1, MAO(A), 5-HT(1B), 5-HT(3), and 5HT(T); HPLC for TPH enzymatic activity; Computer Assisted Semen Analysis assays to measure sperm motility parameters and pharmacological approaches to show the effect of 5-HT in sperm motility and tyrosine phosphorylation was assessed by western blot. We found the presence of serotoninergic markers (5-HT, TPH1, MAO(A), 5-HT(1B), 5-HT(2A), 5-HT(3), 5-HT(T), and TPH enzymatic activity) in human sperm. In addition, we observed a significant increase in tyrosine phosphorylation and changes in sperm motility after 5-HT treatment. In conclusion, our data demonstrate the existence of components of a serotoninergic system in human sperm and support the notion for a functional role of 5-HT in mammalian sperm physiology, which can be modulated pharmacologically.

Comparative morphometric and glycohistochemical studies on the epididymal duct in the donkey (Equus asinus) and dromedary camel (Camelus dromedarius)

The present study was undertaken to compare morphometric and glycohistochemical differences in the epididymal duct of the donkey and the dromedary camel. Paraffin-embedded sections from the different regions of the duct (caput, corpus and cauda) of both species were stained conventionally for general histology and histomorphometry and also with fluorescein isothiocyanate (FITC) conjugated lectins for glycohistochemical mapping. Morphometric data (means ± SE) showed that the luminal diameter was widest (1029.76 ± 15.04 μm) in the donkey cauda and narrowest (179.80 ± 3.27 μm) in the camel corpus. The thickness of the peritubular muscle coat had the highest (74.32 ± 1.85 μm) and the lowest (24.32 ± 0.74 μm) values in the donkey cauda and corpus respectively. The greatest (94.44 ± 2.08 μm) and the least (21.48 ± 0.66 μm) values of epithelial height were reported respectively in the camel caput and in the donkey cauda. The length of stereocilia of principal cells in the camel was greatest (21.88 ± 0.57 μm) and lowest (6.68 ± 0.28 μm) in the caput and cauda. Binding sites for only six out of eight lectins could be found. The distribution pattern of binding sites of different lectins showed significant variations in both a species-specific and also region-specific manner. Distinct labeling was found in the Golgi zone, apical cytoplasm and on stereocilia of principal cells in the camel (WGA and DBA) and donkey (DBA) caput region, while other lectins exhibited variable reactivity in the other regions in both species. The basal cells showed variable binding to most of the lectins, however, they displayed distinct binding to WGA and PSA throughout the duct in camel and donkey respectively. In conclusion, both morphometric and glycohistochemical findings displayed regional species-specific and potentially functional relevant characteristics.

Expression of orexin A and its receptor 1 in the bovine urethroprostatic complex

Orexin A (oxA) and orexin B are recently discovered peptides derived from the proteolytic cleavage of the common precursor prepro-orexin. They bind two G protein-coupled receptors, defined orexin 1 (ox1R) and orexin 2 receptor. Both peptides are highly expressed in the lateral hypothalamic area of the brain and are involved in the regulation of many functions of the body, the best investigated of which is food intake. Recent data described the presence of orexins in peripheral organs such as the adrenal glands, stomach, bowel, pancreas, and testis. Here, we report the detection of oxA and ox1R in the exocrine and endocrine cytotypes of the cattle urethroprostatic complex by using immunohistochemistry. The expression of prepro-orexin and ox1R mRNA transcripts in the prostatic tissue was assessed by reverse-transcriptase polymerase chain reaction, while the presence of both the proteins in the tissue was confirmed by Western blotting analysis. Our findings provide the first evidence for the presence of oxA and ox1R in the urethroprostatic complex of the cattle and demonstrate that both proteins are locally synthesized, thus suggesting a role for oxA on both physiological and pathological functioning of the complex.

Immunohistochemical study of the pre- and postnatal innervation of the dog lower urinary tract: morphological aspects at the basis of the consolidation of the micturition reflex

Immunohistochemical studies were performed on male and female bladder and urethra collected from 4 adults dogs and 10 foetal specimens with crown-rump length from 53 to 155 mm (medium-sized breeds, presumptive 38 days of gestation to term). A panel of antisera was tested, including PGP 9.5 to describe the general intramural innervation, ChAT and TH to depict the cholinergic and nor-adrenergic components and NOS1, CGRP, SP, NPY, VIP, SOM, GAL, 5-HT to investigate the possible nitrergic, peptidergic and aminergic ones. A rich cholinergic innervation was present in adult bladder and urethra, along with a lesser number of adrenergic nerves and a small number of nitrergic ones. Either bladder or urethra received numerous CGRP-, SP-, NPY-, VIP-containing nerve fibres which were distributed throughout the muscle layers. All over the lower urinary tract strong to weak ChAT-, CGRP-, SP- and NPY-immunoreactivity was detected in intramural ganglia, in peripheral nerve bundles and around blood vessels. 5-HT-immunoreactive endocrine cells were present in the urethral epithelium. Early foetal organs were supplied only by cholinergic nerve fibres. Few NOS-, CGRP- and SP-ergic components appeared at the end of pregnancy. It can be guessed that sensory mediators such as CGRP and SP increase in postnatal ages while other neuropeptides, such as NPY and VIP, appear only after birth, as the urinary reflex consolidates.

Effects of castration on the expression of brain-derived neurotrophic factor (BDNF) in the vas deferens and male accessory genital glands of the rat

Brain-derived neurotrophic factor (BDNF) is a growth factor belonging to the family of neurotrophins. Although neurotrophins in the male genital organs have been well documented, their role in the biology of these organs is far from clear. In particular, little is known about the influence of sex hormones on neurotrophin expression. In the present study, using immunohistochemistry and enzyme-linked immunosorbent assay (ELISA), we investigated the distribution and tissue concentration of BDNF in the vas deferens and accessory male genital glands in normal and castrated rats. The expression of BDNF mRNA was also investigated. In normal rats, BDNF immunoreactivity was localized in the musculature of the vas deferens and vesicular gland and in the fibromuscular stromal cells of the prostate. In the ventral prostatic lobes, BDNF immunoreactivity was localized in basal, secretory and neuroendocrine epithelial cells. Innervating ganglia and nerves were immunoreactive in all the examined tracts. After castration, BDNF immunoreactivity increased in the musculature of the vesicular gland and in the fibromuscular stromal cells of both dorsal and ventral prostatic lobes. BDNF immunoreactivity also increased in the nerves. ELISA and reverse transcription/real-time polymerase chain reaction confirmed the findings of the immunohistochemical study. In the accessory glands, castration induced an increase of both BDNF tissue concentration and mRNA expression. These results suggest that BDNF is expressed in the internal male genital organs of the rat and that its expression is downregulated by androgen hormones. We hypothesize that the observed BDNF increases are related to the castration-induced regression of the sympathetic nerves.