Histological observations of the reproductive organs of the male dog from birth to sexual maturity

Cryptorchidism and testicular cancer in the dog: unresolved questions and challenges in translating insights from human studies†

Cryptorchidism, the failure of one or both testes to descend into the scrotum, and testicular cancer show a strong correlation in both dogs and humans. Yet, long-standing medical debates persist about whether the location of undescended testes directly causes testicular cancer in humans or if both conditions stem from a common origin. Although testicular cancer is a prevalent disease in dogs, even less is known about its cause and correlation with testicular descent in this species. This review investigates the relation between these two disorders in dogs, drawing insights from human studies, and examines key biomarkers identified thus far. In addition, it explores potential causal links, including the impact of temperature on maturing testicular cells and a potential shared genetic origin. Notably, this literature review reveals significant differences between men and dogs in reproductive development, histological and molecular features of testicular tumors, and the prevalence of specific tumor types, such as Sertoli cell tumors in cryptorchid dogs and germ cell tumors in humans. These disparities caution against using dogs as models for human testicular cancer research and underscore the limitations when drawing comparisons between species. The paper concludes by suggesting specific research initiatives to enhance our understanding of the complex interplay between cryptorchidism and testicular cancer in dogs.

Cryptorchidism: The dog as a study model

Cryptorchidism (CO) or undescended testicle is an abnormality of male gonadal development that can generate long-term repercussions in men, such as infertility and germ cell neoplasia in situ (GCNIS). The origin of these alterations in humans is not completely clear, due to the absence of an animal model with similar testicular development as in humans with CO. This work intends to describe the testicular histological development of dogs with congenital CO, and determine whether the species could adequately serve as a study model for this pathology in humans. The study was carried out with 36 dogs, equally distributed in two groups: healthy control (CTRL) and CO groups. The contralateral testis to the undescended one in CO group of the animals was considered and analyzed. Each group was subdivided in three stages of development: (1) peripubertal stage (6–8 months), (2) young adult (9–48 months) and (3) senile (49–130 months). Histological development, the presence of cells with gonocyte morphology, cell proliferation, testicular lipoperoxidation and hormonal concentrations of testosterone, estradiol, FSH and LH were evaluated and described. In the cryptorchid testes, the first histological alterations appeared from the first stage of development and were maintained until the senile stage. A pronounced testicular lipoperoxidation occurred only in the second stage of development. The histological alterations due to CO were markedly evident in the young adult stage. Testosterone concentrations witnessed a decrease starting from in the second stage and kept on until the last stage. The contralateral testes of the CO animals showed alterations that positioned them between the control and CO testes. Testicular development of dogs with CO is similar to that of humans. The results of the study suggest that this species could serve as a suitable model for the study of CO in humans.

A Review on Canine and Feline Prostate Pathology

Prostatic diseases are very common in male dogs, accounting for 3–10% of cases submitted to the veterinary practitioners. Commonly reported canine prostatic disorders include prostatic hyperplasia, prostatitis, prostatic cysts and prostatic carcinoma. However, clinical signs may be non-specific, or many cases are asymptomatic, thus leading to a difficult estimation of the actual prevalence of clinical cases. On the other side, because of the rare occurrence of prostate disease in cats, very little is known about pathogenesis, diagnostic approaches and treatment. The goal of this review is to provide detailed clinical and pathological overview of the feline and canine prostatic pathology, including the most up-to-date classification systems and histological findings. Emphasis is places on gross, cytological and histological features that are critical to reach a definitive diagnosis for a proper treatment and prognosis.

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Nonproliferative and Proliferative Lesions of the Dog

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions) Project (www.toxpath.org/inhand.asp) is a joint initiative of the societies of toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying lesions observed in most tissues and organs from the dog used in nonclinical safety studies. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions, lesions induced by exposure to test materials, and relevant infectious and parasitic lesions. A widely accepted and utilized international harmonization of nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.

Scientific and Regulatory Policy Committee Best Practices: Documentation of Sexual Maturity by Microscopic Evaluation in Nonclinical Safety Studies

The sexual maturity status of animals in nonclinical safety studies can have a significant impact on the microscopic assessment of the reproductive system, the interpretation of potential test article-related findings, and ultimately the assessment of potential risk to humans. However, the assessment and documentation of sexual maturity for animals in nonclinical safety studies is not conducted in a consistent manner across the pharmaceutical and chemical industries. The Scientific and Regulatory Policy Committee of the Society of Toxicologic Pathology convened an international working group of pathologists and nonclinical safety scientists with expertise in the reproductive system, pathology nomenclature, and Standard for Exchange of Nonclinical Data requirements. This article describes the best practices for documentation of the light microscopic assessment of sexual maturity in males and females for both rodent and nonrodent nonclinical safety studies. In addition, a review of the microscopic features of the immature, peripubertal, and mature male and female reproductive system and general considerations for study types and reporting are provided to aid the study pathologist tasked with documentation of sexual maturity.

Urodynamic and morphometric characteristics of the lower urogenital tract of male Beagle littermates from four months to two years of age

OBJECTIVE

To describe functional and anatomic changes of the lower urogenital tract of healthy male dogs during the sexually immature period and up to 2 years of age by urodynamic and morphometric assessment.

ANIMALS

6 sexually intact male Beagle littermates.

PROCEDURES

Dogs underwent electromyography-coupled urodynamic tests, CT-assisted retrograde urethrography, prostatic washes, and blood sampling monthly from 4 through 12 months of age and then at 3-month intervals. Urodynamic and morphometric variables and serum canine prostate-specific esterase concentrations were analyzed by statistical methods.

RESULTS

Integrated pressure of the urethra was significantly increased beginning at 8 months of age, compared with earlier time points. Urethral pressure peak amplitudes varied among anatomic regions. During bladder filling, few electromyographic signals were concurrent with urethral pressure peaks; these were most commonly detected in the penile portion of the urethra. Urethral length and prostate gland volume were significantly greater from 7 to 24 months of age than at younger ages. Urethral length was approximately 26 to 27 cm after 9 months, and prostate gland volume was approximately 11 to 12 cm³ after 11 months of age. Serum canine prostate-specific esterase concentrations correlated with prostate gland volume. Urinary bladder threshold volume was significantly increased at 6 months of age, compared with that at 4 months, with a maximum of 197.7 mL at 24 months.

CONCLUSIONS AND CLINICAL RELEVANCE

Urethral resistance was acquired at approximately 8 months of age, when growth of the lower urinary tract was incomplete. Electromyographic and integrated pressure measurement results and the distribution and amplitude of urethral pressure peaks highlighted the potential role of the prostate gland and possibly the bulbocavernosus muscles in control of continence.

Expression of claudin-11 in canine prepubertal testes, and in canine adult testes showing normal spermatogenesis, impaired spermatogenesis, or testicular neoplasia

The blood-testis barrier (BTB) consists of different cell-to-cell connections, including tight junction proteins like claudin-11 (CLDN11). For dogs, only limited data is published dealing with these proteins in general. Therefore, their physiological relevance, their postnatal expression, and their distribution pattern in pathological conditions, e.g. in altered spermatogenesis and testicular neoplasia were assessed. Canine testes from routine castrations, and those sent in for diagnostic purposes were investigated. Based on morphological evaluation, the dogs and testes were divided into groups: (1) dogs with normal spermatogenesis, (2) four months old prepubertal dogs, (3) intratubular seminoma, (4) diffuse seminoma, (5) Sertoli cell tumours (SCT), (6) Leydig cell tumours (LCT), and (7) dogs with impaired spermatogenesis (e.g. mixed atrophy). In order to examine possible alterations of the BTB components, immunohistochemistry (IHC) and immunofluorescence using a commercial antibody against CLDN11 was performed. Sertoli cell (SC) nuclei (SOX9) and peritubular myoid cells (smooth-muscle-actin, SMA) were also assessed using IHC. Additionally, semi-quantitative Western-blot (WB) and RT-PCR analyses of CLDN11 were conducted. In tubules with normal spermatogenesis, IHC of CLDN11 revealed a basolateral staining at BTB localisation. In prepubertal cords, CLDN11 was diffusely expressed along the cytoplasmic extensions of SCs supposing that the BTB was neither built up nor functional, yet. A shift from weakly expressed CLDN11 between/in residual SCs in intratubular seminoma to only small CLDN11 immunopositive stained spots in the cytoplasm of remaining SOX9-positive SCs in diffuse seminoma was detectable. Reduction or even loss of CLDN11 expression in diffuse seminoma was confirmed using RT-PCR and WB analyses, thus indicating that in seminoma, CLDN11 was downregulated at transcriptional level and completely lost its sealing function. Basal SCs in SCT still showed a CLDN11/SOX9 co-localisation, suggesting that luminal neoplastic SCs undergo de-differentiation during tumour progression. In LCT, no CLDN11 was detectable. Dogs with mixed atrophy showed an upregulation of CLDN11 in tubules with spermatogenic arrest on mRNA and protein level, leading to the conclusion that within these tubules regulatory mechanisms lost their equilibrium. For the first time, the spatial expression of CLDN11 in prepubertal canine testis, impaired spermatogenesis, intratubular seminoma and its absence in diffuse seminoma and LCT was shown. Since altered CLDN11 levels could be part of adaptive mechanisms to modify BTB integrity, further functional investigations to characterize the canine BTB need to be conducted.

Rhodesian Ridgebacks have an increased risk to develop benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is an age-dependent primarily non-inflammatory enlargement of the accessory gland in the intact dog. The aim of the present study was to control a previously raised suspicion of a breed-related higher incidence of BPH in dogs of the Rhodesian Ridgeback breed. For this, 18 Labrador Retrievers/LR and 20 Rhodesian Ridgebacks/RR were assigned to the age groups 18-24 months (n = 12), 25-48 months (n = 13) and 49-72 months (n = 13). Prostate gland status was determined by rectal palpation, B-mode ultrasound, calculation of the prostate gland volume and semen analysis regarding haemospermia and was classified according to blood plasma concentrations of canine prostate-specific arginine esterase (CPSE) (normal ≤ 60 ng/ml, increased ≥ 61 ng/ml; Pinheiro et al., 2017). Concentrations of testosterone, 5α-dihydrotestosterone and estradiol were analysed in peripheral blood serum or plasma for detecting breed-specific conditions regarding the endocrine metabolism. Prostatic volume was significantly larger in RR irrespective of the CPSE status. In RR, BPH occurred more frequently and started at an earlier age compared with the LR. Breed-related specificities in steroid metabolism in the RR were indicated by correlations of 5α-dihydrotestosterone and estradiol with age and of testosterone with prostate gland volume. Although the incidence of sonographic signs of BPH and haemospermia did not fit with normal and increased CPSE concentrations, a breed-specific higher incidence of BPH in the RR breed could be clearly verified.

Comparative Aspects of Pre- and Postnatal Development of the Male Reproductive System

This review describes pre- and postnatal development of the male reproductive system in humans and laboratory animals, and highlights species differences in the timing and control of hormonal and morphologic events. Major differences are that the fetal testis is dependent on gonadotropins in humans, but is independent of such in rats; humans have an extended postnatal quiescent period, whereas rats exhibit no quiescence; and events such as secretion by the prostate and seminal vesicles, testicular descent, and the appearance of spermatogonia are all prenatal events in humans, but are postnatal events in rats. Major differences in the timing of the developmental sequence between rats and humans include: gonocyte transformation period (rat: postnatal day 0-9; human: includes gestational week 22 to 9 months of age); masculinization programming window (rat: gestational day 15.5-17.5; human: gestational week 9-14); and mini-puberty (rat: 0-6 hr after birth; human: 3-6 months of age). Endocrine disruptors can cause unique lesions in the prenatal and early postnatal testis; therefore, it is important to consider the differences in the timing of the developmental sequence when designing preclinical studies as identification of windows of sensitivity for endocrine disruption or toxicants will aid in interpretation of results and provide clues to a mode of action. Birth Defects Research 110:190-227, 2018. © 2017 Wiley Periodicals, Inc.

Histological Development of Male Reproductive Organs in Microminipigs

Microminipigs are becoming increasingly attractive alternatives for various experimental applications, such as general toxicology studies, owing to their manageable size. However, there are limited studies on the male reproductive organs of microminipigs, particularly on the histological aspects of sexual maturity. To clarify the development of male reproductive organs, 35 male microminipigs, aged 0 to 12 months, were used in this study. Histological and histomorphological evaluation was performed based on spermatogenic development, measurement of tubular structure in testes and epididymides, and histological progress of accessory glands. In addition, spontaneous testicular changes were quantitatively assessed. Histologically, male microminipigs sexually matured around 4.5 months of age, when spermatogenesis in testes and structural development in genital organs were completed. Spontaneous testicular changes occurred in all the animals investigated. Multinucleated giant cell was most commonly observed, followed by hypospermatogenesis and tubular atrophy/hypoplasia. However, the number of affected tubules was less than 1% in testes after 4.5 months of age, suggesting that the influence of these changes on evaluation of toxicity studies may be minimal. It is preferable to use sexually mature animals in toxicology studies; therefore, the information obtained by the present study will be helpful for future toxicity evaluations in microminipigs.

Seasonal Changes in the Immunolocalization of Cytoskeletal Proteins and Laminin in the Testis of the Black-Backed Jackal (Canis mesomelas)

Manipulation of the reproductive activity of jackals is dependent on a thorough understanding of the reproductive biology of this species. This study describes seasonal morphological changes in the adult testis of the black-backed jackal in relation to the immunoexpression of the basement membrane marker, laminin and the cytoskeletal proteins, cytokeratin, smooth muscle actin and vimentin. Laminin was immunolocalized in basement membranes surrounding seminiferous tubules, as well as in basement membranes associated with Leydig, peritubular myoid and vascular smooth muscle cells. Scalloped basement membranes enclosed seminiferous tubules in regressing testes. The seminiferous epithelium and interstitial tissue in all animals studied were cytokeratin immunonegative. Smooth muscle actin was demonstrated in vascular smooth muscle cells, as well as in peritubular myoid cells encircling seminiferous tubules. Vimentin immunoreactivity was exhibited in the cytoplasm of Sertoli cells, Leydig cells, vascular endothelial cells, vascular smooth muscle cells and fibrocytes. Vimentin immunostaining in Sertoli, Leydig and peritubular myoid cells varied depending on the functional state of the testis. The results of the study have shown that dramatic seasonal histological changes occur in the testes of the jackal. In addition, the use of immunohistochemistry accentuates these morphological changes.

Expression and localization of epidermal growth factor, transforming growth factor-α and epidermal growth factor receptor in the canine testis

Gene expression of epidermal growth factor (EGF), transforming growth factor-α (TGF-α) and EGF receptor (EGF-R) and the localization of the corresponding proteins in the canine testis were studied. Levels of mRNA expressions were determined by semiquantitative reverse transcription polymerase chain reaction in the testes of the peripubertal (4–6 months), young adult (3–4 years), advanced adult (7–8 years) and senescent (11–16 years) groups. The EGF-R mRNA level in the testes of the peripubertal group was significantly higher than those in the other groups, whereas there was no difference in EGF and TGF-α mRNA levels among groups. Immunohistochemical stainings for EGF, TGF-α and EGF-R in the testis revealed that immunoreactivity in the seminiferous epithelium and Sertoli cell was weak and nonspecific for the stage of spermatogenesis, and distinct staining was found in Leydig cells. These results suggest that the EGF family of growth factors may be involved in testicular maturation and function in the dog.

Expression of CYP26b1 and related retinoic acid signalling molecules in young, peripubertal and adult dog testis

The objective of the study was to elucidate mRNA expression of CYP26b1 (cytochrome P450, family 26, subfamily B, polypeptide 1) and signalling molecules ALDH1 (aldehyde dehydrogenase 1), CRABPII (cellular retinoic acid-binding protein II), RARα (retinoic acid receptor alpha) and STRA8 (stimulated by retinoic acid gene 8) in dog testis from different post-natal developmental ages. Testicular tissue samples were collected from medium-sized mixed breed dogs at different ages such as young (<4 months; N = 4), peripubertal (4-8 months; N = 3) and adult (>8 months; N = 4) were used to evaluate relative mRNA expression. Genes of RA-degrading enzyme CYP26b1, ALDH1 involved in RA synthesis and genes of carrier protein CRABPII involved in RA metabolism were turned on during the post-natal testicular development in dogs. Their expression pattern differs at different developmental ages (p < 0.05), and the levels of mRNA expression were compensated towards a normal developmental response for the sexual maturity and continuous spermatogenesis. The mRNA expression of RARα, one of the RA receptors participates in RA signalling in connection to spermatogenesis, was recorded in young and adult stages at varying degree. STRA8 is one of the responsive genes with regard to meiosis, and this functional gene product was expressed in all ages with the changing level (p < 0.01). In summary, the expression pattern of RA signalling molecules differed from young to adult ages, and it is expected that these changes are to compensate towards a normal developmental response for the sexual maturity and continuous spermatogenesis.

Assessment of circulating hormones in regulatory toxicity studies II. Male reproductive hormones

When test article-related testicular toxicity or Leydig cell tumors are identified in nonclinical studies, the measurement of circulating hormones such as luteinizing hormone, follicle-stimulating hormone, inhibin, testosterone, or prolactin is often considered in order to aid mechanistic investigations or to identify potential biomarkers in man. Although some hormone levels are relatively constant, others are subject to wide variability owing to pulsatility of secretion, diurnal rhythms, and stress. To avoid being misled, it is important that this variation is factored into any study design that includes hormone measurements. Since all these possibilities start from the pathologist's reading of the tissue sections, we begin with a review of the morphologic changes that are tied to underlying alterations in hormones. We then provide the reader with basic information and representative hormone data, including coefficients of variation, for the major male reproductive hormones in the three main nonclinical species (rats, dogs, and cynomolgus monkeys). Power and probability tables for rats and dogs allow estimates of the number of animals or samples needed to provide a given likelihood of detecting a hormonal change of a given size. More importantly, we highlight the variability of this process and the real value in readers developing this information at their own site.

Development of semen quality following reversible downregulation of testicular function in male dogs with a GnRH agonist implant

Slow-release GnRH agonist implants have shown to be an effective and reversible alternative to surgical castration. Testicular function is downregulated with an arrest of spermatogenesis on the level of spermatogonia/primary spermatocytes but is fully restored after abolition of downregulation. Aim of this study was to assess the quality of ejaculates after active abolishment of downregulation by implant removal and to follow recrudescence of spermatogenesis. Five dogs - which served as their own controls - were treated with a slow-release implant containing the GnRH agonist azagly-nafarelin. Implants were removed during full downregulation (testosterone <0.1 ng/ml), and attempts to collect ejaculates started from week 4 onwards to week 29. First ejaculates could be obtained between weeks 8 and 12 with the first fully elongated spermatozoa observed in week 10. Volume, %motility and total sperm count increased and %pathomorphology decreased during the course of the study with all ejaculates being in the normal range by week 29. Our data indicate that onset of recrudescence of spermatogenesis coincides with the first testosterone increase after active abolishment of downregulation. Semen quality was fully regained with a significant improvement of %pathomorphology (p < 0.05) and a tendency of improved %motility. However, these observations on an improved semen quality need further validation and no final conclusions can be drawn yet.

Immunolocalisation and expression of Smad2 and Smad4 proteins in dog testis during postnatal development

The expression and localisation of downstream signalling molecules of transforming growth factor beta superfamily, Smad2 and Smad4 proteins, was investigated in immature and mature dog testis. Cellular localisation of Smad2 and Smad4 proteins was examined using immunohistochemistry. Quantitative analysis of immunostaining was determined by the image analysis system. The specificity of the antibodies was examined using Western blotting assay. Smad2 and Smad4 were widely expressed in the testes, mainly immunolocalised in the cytoplasm of gonocytes, Leydig cells and Sertoli cells of immature testes, and Leydig cells and Sertoli cells of mature testes. At the same time, the expression levels for both proteins were different between immature and mature age groups: the expression of Smad2 and Smad4 proteins in the Sertoli cells of mature testis was higher than in the immature group (P < 0.05), but the expression of these two proteins in Leydig cells of mature testis was weaker than that seen in immature stage (P < 0.05). The temporospatial distribution of Smad2 and Smad4 proteins in testicular cells suggests that these two signalling molecules may play an important role in specific stages of testicular development and spermatogenesis, thus providing direct evidences for transforming growth factor beta action in the dog testis.

Recrudescence of spermatogenesis in the dog following downregulation using a slow release GnRH agonist implant

The present study examined the degree to which downregulation with a GnRH agonist impaired spermatogenesis and the time course of morphological and hormonal changes that occurred during recrudescence of spermatogenesis. Using a control group (group 1, n = 5) of dogs, the effect of a removable slow release GnRH-agonist implant was investigated in beagle dogs (group 2, n = 30). The implant was removed after 5 months (week 0) and three to four dogs were castrated at weeks 0, 3, 6, 9, 12, 15, 18, 21 and 24. The degree of downregulation and recrudescence of spermatogenesis was assessed by evaluation of 200 tubular cross-sections, resulting in an assigning of dogs of group 2 to testis developmental groups (DG) according to the most developed germ cell observed: DG A, spermatocytes; DG B, round spermatids; DG C, elongating spermatids and DG D, elongated spermatids. Downregulation led to an arrest of spermatogenesis at the level of spermatogonia/primary spermatocytes. The time course of recrudescence showed high individual variations and the number of dogs falling into DG A, B, C and D was 4, 3, 6 and 17 respectively. Spermatogenesis in group 2, DG D was not different from group 1 (control). In DG A, mean area of Leydig-cell nuclei was lower (p < 0.001) than in the other DG and group 1 and resembled that of juvenile dogs (group 3, n = 3); nuclei of Sertoli cells had changed from more flat/polygonal (group 1, group 2, DG C and D) to round/ovoid and had moved to a more luminal position. As indicated by basal testosterone (T), luteinizing hormone (LH) and follicle stimulating hormone (FSH) concentrations at implant removal, full downregulation had been obtained. Testosterone, LH and FSH concentrations [X(g) (DF), ng/ml] increased (p < 0.05) from implant removal to DG B [T: 0.1 (1.24) vs 2.12 (2.31); LH: 0.2 (2.15) vs 1.11 (1.7); FSH: 0.37 (3.50) vs 6.37 (1.68)] and were more or less constant thereafter indicating that onset of spermatogenesis was related to an increase of plasma T occurring in a very narrow time window. Following GnRH implantation, the size of the testes and the prostate decreased by approximately 55% (p < 0.001), they increased to sizes similar to pre-treatment values following implant removal.

Aspectos histológicos e morfométricos dos testículos de gatos domésticos (Felis catus)

Nesta pesquisa foram obtidos dados histológicos e morfométricos comparativos sobre os testículos de gatos, pós-orquiectomia, divididos em dois grupos: Grupo 1, gatos com até 1 ano de idade e Grupo 2, animais acima de 1 ano. Verificou-se que: (1) aos 4 meses de idade os túbulos seminíferos apresentaram-se pouco desenvolvidos e com ausência de luz, epitélio seminífero baixo, células de Sertoli indiferenciadas e tecido intersticial escasso; (2) aos 5 meses os túbulos seminíferos começaram a se diferenciar com aumento do diâmetro e luz tubulares e as demais estruturas permaneceram semelhantes à observação anterior; (3) aos 6-7 meses ocorreu o início da espermatogênese e espermiogênese; as células de Leydig apareceram maiores, poliédricas com citoplasma vacuolizado e núcleo claro, e tecido intersticial esparso com poucos vasos sangüíneos; (4) os animais com 1 ano de idade apresentaram morfologia testicular igual à do animal adulto, com túbulos seminíferos de maior diâmetro, epitélio germinativo alto e luz tubular pequena, as células de Leydig aparecendo poliédricas, com dimensões variadas, citoplasma vacuolizado, núcleo claro e nucléolo evidente, e espaço intertubular seminífero variado com vasos sanguíneos, predominantemente evidentes; (5) no Grupo 1 o diâmetro médio dos túbulos seminíferos foi de 160,58µm e no Grupo 2 foi de 185,94µm, sendo os valores médios significantes entre si; (6) a altura média do epitélio seminífero foi de 49,51µm para o Grupo 1 e de 63,29µm para o Grupo 2, estaticamente significantes; (7) os maiores valores mensurados foram obtidos para os gatos do Grupo 2, por serem gatos adultos e portanto com os órgãos reprodutores funcionais.

Variability in Weight and Histological Appearance of the Prostate of Beagle Dogs Used in Toxicology Studies

This review was performed to assess variations in weight and histologic appearance of the prostate of untreated male beagle dogs between 23 and 108 weeks of age, from two breeding centers. Data from 125 control beagle dogs from twenty-seven regulatory toxicology studies were used. Age, terminal body weight, and prostate weight were analyzed. Prostate sections were examined microscopically, and histological changes—such as development of acini, amount of secretion, and patterns of dilation and inflammation—were recorded and graded when appropriate. The influence of age, terminal body weight, and source on the weight and histological appearance of the prostate, and the degree of interanimal variation were evaluated

Spontaneous and Age-Related Testicular Findings in Beagle Dogs

This study was conducted to characterize spontaneous testicular and epididymal microscopic findings in eighty control beagle dogs from toxicity studies. Hypospermatogenesis, characterized by randomly scattered missing spermatids and/or spermatocytes within seminiferous tubules, was observed in 75% of dogs six to seven months of age and declined to fewer than 10% in dogs over eleven months of age. Atrophy/hypoplasia of seminiferous tubules, characterized by subcapsular triangular clusters of tubules containing no germ cells, was observed in 25 to 40% of dogs under twelve months old, decreasing with age to 14 to 17% in dogs twelve to thirty-six months old. Retained spermatids, multinucleate giant cells, intracytoplasmic vacuoles (presumably in Sertoli cells), and swollen spermatocytes were common findings of minimal severity. Six- and seven-month-old dogs had lower testicular weights, less filling of the epididymal tails with sperm, and a two-fold higher incidence of abnormal epididymal content compared to dogs more than eight months of age. Most male beagles were histologically sexually mature by eight to nine months of age. This study confirms published reports that dogs at least ten months of age at necropsy usually are adequate for routine microscopic evaluation of the testes. If evaluation of spermatogenesis is critical, the incidental findings can be minimized by using males over twelve months of age.

Sequential expression of type IV collagen networks: testis as a model and relevance to spermatogenesis

The six alpha chains of type IV collagen are organized into three networks: alpha1/alpha2, alpha3/alpha4/alpha5, and alpha1/alpha2/alpha5/alpha6. A shift from the alpha1/alpha2 to the alpha3/alpha4/alpha5 network occurs in the developing glomerular basement membrane, but how the alpha1/alpha2/alpha5/alpha6 network fits into this sequence is less clear, because the three networks do not colocalize. Here, we studied the seminiferous tubule basement membrane of normal canine testis where all three networks do colocalize: the alpha1/alpha2 network is expressed from birth, the alpha1/alpha2/alpha5/alpha6 network by 5-6 weeks of age, and the alpha3/alpha4/alpha5 network by 2 months of age. A canine model of Alport syndrome allowed study of the absence of alpha3/alpha4/alpha5 and alpha1/alpha2/alpha5/alpha6 networks in testis. In Alport dogs, the seminiferous tubule basement membrane was thinner than in controls. Spermatogenesis began at the same time as with normal dogs; however, the number of mature sperm was significantly reduced in Alport dogs. Thus, it would appear that alpha3/alpha4/alpha5 and alpha1/alpha2/alpha5/alpha6 networks are not essential for onset of spermatogenesis, but long-term function may be compromised by the loss of one or both networks. This situation is analogous to the glomerular basement membrane in Alport syndrome. In conclusion, testis can serve as a model system to study the sequence of type IV collagen network expression.

Subchronic and chronic safety studies with genistein in dogs

Genistein is a phytoestrogen that occurs naturally in the diet, especially in soy-based foods. There is widespread interest in phytoestrogens as chemopreventive agents for a variety of diseases and cancers based on epidemiologic evidence. Although soy and its constituents, such as genistein, have been consumed at high levels in several Asian populations without apparent adverse effects, concern has been raised about potential adverse effects due to estrogenic and other activities. The subchronic and chronic safety of genistein were evaluated in the beagle dog including a 4-week study and a 52-week safety study with a 13 week interim sacrifice and a 4 week recovery period. In both studies at doses of 50, 150 and 500 mg/kg/day, genistein was well tolerated. In the 4 week study, except for an increase in uterine weights in female dogs at 500 mg/kg/day, there were no other treatment related findings. In the 52-week study, the primary effects of genistein were observed on the reproductive tract, which included for male dogs: reduced size and/or weight of the testes, epididymus and prostate of 2/2 dogs after 13 weeks of treatment and in 1/4 dogs after 52 weeks of treatment at 500 mg/kg/day. The histological changes observed in the affected dogs at 500 mg/kg/day indicated atrophy of the testes and prostate gland and absent spermatozoa in the epididymus. At the mid-dose of 150 mg/kg/day, although there was a reduction to a lesser extent in testes weight after 13, but not 52 weeks, there were no histopathological changes. In female dogs, the reproductive tract effects included increased uterine weight at 500 mg/kg/day after 13 weeks of treatment, but not after 52 weeks of treatment. There was also a small decrease in ovarian weights at 150 and 500 mg/kg/day after 13 weeks and at 500 mg/kg/day after 52 weeks of treatment. There were no histopathological correlates to the changes in organ weights in female dogs. In the 4-week recovery group dogs, no changes were observed in dogs previously treated for 52 weeks with 500 mg/kg/day of genistein. It is concluded that the administration of genistein to dogs for a period of 4-52 weeks was well tolerated and did not result in systemic toxicity. Effects of genistein on the reproductive tract at very high doses were functional in nature and are of a type that would be expected in view of the relatively weak estrogenic activity of genistein and were considered not adverse effects. In the 4-week study, the no observed adverse effect level (NOAEL) for genistein was considered to be >500 mg/kg/day and the no observed effect level (NOEL) was considered to be 150 mg/kg/day. For the 52-week study, the NOAEL is considered to be >500 mg/kg/day and the NOEL is considered to be 50 mg/kg/day.

Testicular compensatory hypertrophy related to hemicastration in prepubertal dogs

Several studies have reported that the plasma testosterone (T) level and semen volume are compensated after hemicastration (HEC) in adult dogs, but that the sperm count is not. Nevertheless, the effects of HEC in prepubertal dogs have not been reported. In this study, HEC was performed at 16 weeks of age in 8 male beagles, and the function of the residual testis was investigated until 48 weeks of age. The testis volume was consistently higher in the HEC group than the control (CON) group. After 40 weeks of age, compensatory hypertrophy was observed, with a mean testis volume of 125% of that in the CON group (p<0.05). Furthermore, the semen volume and plasma testosterone (T) level were similar to those in the CON group, suggesting functional compensation, but the sperm count was not compensated. These results showed that the testis volume, semen volume, and plasma T level were compensated after HEC in prepubertal dogs, but the spermatogenic function was not.

A quantitative study of seminiferous tubular cells in the developing Murrah buffalo testis

We report here a systematic quantitative study of the seminiferous tubular cells of Murrah buffaloes. The most advanced germ cell types in the different age groups (months) were A(0) spermatogonia (SG) (1 and 3), early pachytene (6 and 9), late pachytene (12), secondary spermatocytes (15 and 18), elongating spermatids (21 and 24), elongated spermatids attached to Sertoli cells (30), elongated spermatids detached from Sertoli cells (36) and spermatozoa (42 and 48). Central primitive Sertoli cells (CPSC) and basal primitive Sertoli cells (BPSC) were present in the sex cord of one-month-old calves, while Sertoli cells (SC) were first seen in nine-month-old calves. The number of gonocytes were maximal at six months but they were not seen after this time. Prespermatogonia (PSG) and SG were at a maximum at nine months of age but PSG were not seen after 36 months. The number of SG decreased significantly after nine months up to 36 months of age. Although spermatocytes and spermatids appeared in earlier developmental stages, a rapid increase in their number was recorded after 36 months. The number of SC was maximal in 18-month-old animals. BPSC predominated in the sex cord of animals aged one to six months, SG at 9-12 months of age, primary spermatocytes from 15-30 months and spermatids from 36 to 72 months and in older animals. We concluded that a decrease in the number of SG in buffalo calves after nine months of age might be responsible for a delay in sexual maturity. Moreover, the small number of spermatocytes and spermatids present before 36 months of age may be associated with the low yield of different germ cell divisions and with the cellular degeneration. A rapid increase in the number of spermatocytes and spermatids after 36 months resulted in sexual maturity between 42 and 48 months.

Evaluation of testicular toxicology: A synopsis and discussion of the recommendations proposed by the Society of Toxicologic Pathology

BACKGROUND

Detection of chemically induced effects on male fertility and on testicular spermatogenesis in particular, has become of increasing concern. More stringent regulatory guidelines, introduced by ICH, EPA and OECD (Table 1) have raised the awareness of toxicologists and pathologists for the need to conduct sensitive and careful evaluation of the male reproductive tract for potential toxic effects of administered compounds. With it has come confusion and in many cases, inappropriate procedures, often based on misunderstanding of what is required and on inadequate understanding of spermatogenesis. This article summarizes and discusses the main recommendations recently proposed by the Society of Toxicologic Pathology on recommended approaches for the evaluation of testicular and epididymal toxicity [Lanning LL, Creasy DM, Chapin RE, Mann PC, Barlow NJ, Regan KS, Goodman DG. Toxicologic Pathology 30:518-531, 2002]. The major recommendations are: Use sexually mature animals to evaluate effects on spermatogenesis. Sample left and right testes and epididymides and record organ weights. Use modified Davidson's fixative to fix testes from all species from studies of 13 wks duration and less. Examine transverse sections of the testes (including part of the rete), and longitudinal sections of the epididymides. Embed tissues in paraffin wax. For rodent studies up to 28 days, examine periodic acid-Schiff's-hematoxylin stained sections. For all other studies examine hematoxylin and eosin stained sections. Microscopic evaluation of the testis should be a qualitative evaluation carried out with an awareness of the spermatogenic cycle. Quantitative procedures are inappropriate for screening studies. Nomenclature and grading of findings for spermatogenic disturbances will vary on a case by case basis.

Changes in activities of enzymes related to energy metabolism in testicular tissues of dogs with seminoma

Changes in the activities of enzymes related to energy metabolism in the testicular tissues of dogs with seminoma were investigated. The testis was removed surgically from animals anaesthetized with halothane. Cytosolic and mitochondrial fractions were isolated and the total RNA was extracted from testicular homogenates. The activities of enzymes related to energy metabolism were measured and the mRNA of cytosolic malate dehydrogenase (MDH) was investigated by the reverse transcriptase-polymerase chain reaction (RT-PCR). The activities of the glycolytic enzymes glucose-6-phosphate dehydrogenase (G6PD) for the pentose phosphate pathway and malate dehydrogenase (MDH) for the malate-aspartate shuttle, and the expression of the mRNA of cytosolic MDH were significantly increased in the testicular tissues of dogs with seminoma. These enzymatic activities may be useful indicators with which to evaluate changes in the metabolic conditions in testicular tissues of dogs with seminoma.

Ultrastructural features in the epididymis of the dog (Canis familiaris, L.)

The ultrastructure of the epididymal duct of the dog is described in this paper. The epididymis was divided into three morphofunctional segments: initial, middle and terminal. The cellular population of the lining epithelium is formed from principal, apical, basal and clear cells. The peritubular stroma and the tubular interstitium surrounding the epithelium are also described. The outcome is compared to the description made in other species of mammals.

Spontaneous testicular lesions in purpose-bred beagle dogs

Spontaneous testicular lesions were assessed in 50 control purpose-bred male beagle dogs. They were selected from 13 toxicology studies conducted over the period 1988-1999. Age of the dogs at study termination varied from 8-20 months with an average age of 13 months. Regardless of age, the most significant finding was bilateral segmental hypospermatogenesis in 15/50 (30%) of the dogs. Cross sections of tubules with hypospermatogenesis were distributed randomly throughout the testes and were characterized by reduced proportions of germ cells, tubular shrinkage, and Sertoli cell prominence. These changes were occasionally associated with giant cells, with cellular debris, and in 6/15 (40%) with atrophic tubules devoid of germ cells, indicating a degenerative process. Focal subcapsular tubular atrophy or hypoplasia (tubules lined by Sertoli cells only) was also found in 9/35 (26%) of dogs without hypospermatogenesis. Inhibited spermiation with retention of mature sperm in tubules was seen in 6/50 dogs, 3 of which also showed hypospermatogenesis. Other findings of high incidence but low prevalence included tubules with multinucleated giant cells, swollen spermatocytes, or apoptotic germ cells. These latter changes are probably a constituent of normal spermatogenesis. In conclusion, about 30% of control beagle dogs show segmental hypospermatogenesis, which may be associated with degenerative changes, and an additional 18% of the dogs exhibit focal tubular atrophy/hypoplasia in otherwise normal testes. These changes have to be distinguished from compound-related toxic effects.

Chronic effects of the novel glucocorticosteroid RPR 106541 administered to beagle dogs by inhalation

The preclinical safety of RPR 106541, a novel 17-thiosteroid, was evaluated in young adult and mature dogs by inhalation exposure for 26 weeks and 52 weeks, respectively. A dry powder formulation of RPR 106541 in lactose was administered to young adult dogs (approximately 6 months of age at initiation) at doses of 0 (air and placebo controls), 10, 100, or 1,000 microg/kg/d for 26 weeks. A solution-based aerosol formulation was administered to mature dogs (approximately 10 months at initiation) from a pressurized metered dose inhaler at 0 (air and placebo controls), 10, 50, and 150 microg/kg/d for 52 weeks. Clinical evidence of glucocorticosteroid-induced immunosuppression was observed by weeks 20-26 following relatively high dose exposures (100 microg/kg/d and 1,000 microg/kg/d) in young dogs receiving the dry powder formulation for 26 weeks. Classic glucocorticosteroid effects were observed, including adrenocortical atrophy, reduced bone mass with retention of epiphyseal growth plates in long bones, prominence of stromal adipose tissue in bone marrow, and atrophy of lymphoid tissues. Inhalation administration of RPR 106541 to sexually mature dogs facilitated more definitive characterization of endocrine affects of RPR 106541 as compared with administration in younger, sexually immature animals. Significant effects in female reproductive organs included absence of corpora lutea in association with atresia of vesicular follicles within the ovaries, endometrial hyperplasia, and lobular development of mammary tissue. Discordant development of mammary tissue, accumulation of secretory material within hyperplastic endometrial glands, and hypertrophy of uterine lining epithelium in absence of ovulation were consistent with a secondary progestin effect by a potent glucocorticosteroid.