Aging effects in adrenal cortex of male Mongolian gerbil: A model for endocrine studies.

The adrenal gland produces steroid hormones that act in the homeostasis of organisms. During aging, alterations in the hormonal balance affect the adrenal glands, but these have not yet been fully described due to the lack of adequate animal models. The adrenal gland of the Mongolian gerbil has a morphology similar to the primate's adrenal gland, which makes it a possible animal model for endocrine studies. Therefore, the current study aimed to study the morphophysiology of the adrenal gland under the effect of aging. For this purpose, males Meriones unguiculatus, aged three, six, nine, twelve, and fifteen months were used. Morphometric, immunohistochemical, and hormonal analyses were performed. It was observed that during aging the adrenal gland presents hypertrophy of the fasciculata and reticularis zones. Lipofuscin accumulation was observed during aging, in addition to changes in proliferation, cell death, and cell receptors. The analyses also showed that the gerbil presents steroidogenic enzymes and the production of steroid hormones, such as DHEA, like that found in humans. The data provide the first comprehensive assessment of the morphophysiology of the Mongolian gerbil adrenal cortex during aging, indicating that this species is a possible experimental model for studies of the adrenal gland and aging.

Combined oral contraceptives promote androgen receptor and oestrogen receptor alpha upregulation in the female prostate (Skene's paraurethral glands) of adult gerbils (Meriones unguiculatus).

The aim of this study was to evaluate the effects of cyproterone acetate (CPA) and ethinyloestradiol (EE) alone or in combination on the female prostate of adult gerbils. Adult females were exposed for 21 days to daily oral doses of CPA (1mgkg-1), EE (10µgkg-1) or a combination of CPA and EE. Female prostatic complexes were removed, weighed and subjected to morphological, stereological, immunohistochemical and ultrastructural analyses. CPA treatment caused epithelial atrophy and decreased prostate secretory activity. The EE treatment group showed glandular hyperplasia, a high cell-proliferation index and an increase in androgen and oestrogen receptor α (AR and ERα) immunoreactivity. Combined treatment (CPA+EE) caused adverse effects, such as an increase in cell proliferation, higher AR and ERα immunoreactivity, prostatic intraepithelial neoplasia, cell degeneration and aging. In conclusion, the CPA-only treatment promoted antiandrogenic effects on the female gerbil prostate, whereas EE-only had a potent oestrogenic activity. However, when combined, EE overlapped the effects of CPA, changing the pattern of glandular hormonal regulation and stimulating the development of prostatic lesions in female gerbils.

Paracrine Signaling in the Prostatic Stroma: A Novel Role for the Telocytes Revealed in Rodents' Ventral Prostate.

The telocytes have recently been described in the prostate gland. In mature gland, they exist in close association with the acini and their telopodes form networks whose functions remain unclear. In this chapter, our group gives a brief introduction to telocytes and explores the history that led to such a concept and then discusses hypotheses and presents new evidences about the roles exerted by telocytes in the prostate. First is given emphasis on the role that these cells possibly play in paracrine signaling employed in the differentiation of smooth muscle periacinar are then discussed other roles potentially performed by telocytes in the prostate, such as the organizational, where these cells would act in order to delimit stromal microenvironments, thereby assisting the differentiation of the prostatic anatomical components. In addition, the pacemaker function of smooth muscle cells contraction, as evidenced by the presence of caveolae and gap-type junction and, finally, the role of telocytes in prostate remodeling and the possible action as adult progenitor cells. Generally speaking, the chapter reaffirms the existence of telocytes as distinct cells of other stromal cells and the importance of this new cell type for normal metabolism and prostate development.

Effects of exposure to estradiol and estradiol plus testosterone on the Mongolian gerbil (Meriones unguiculatus) female prostate.

The female prostate is a differentiated organ found in several mammal species, including humans and rodents. This gland has been related to important functions on female reproductive biology. Although the factors, which regulate prostate's development and activity are not well known, its functionality has been related to steroid hormones. It is well established that cyclic changes of estradiol and progesterone levels promote histophysiological adaptations of the whole female body. In contrast, only a few is found about those adaptations in female prostate. Thus, this study aimed to evaluate the effect of estradiol and estradiol + testosterone association on gerbil female prostate in order to verify, which hormonal associations are necessary to its homeostasis. For this, adult females had the ovaries surgically removed. After recovering, they received estradiol and estradiol + testosterone doses through 30 days, each 48 h. The prostatic tissue underwent morphological and morphometric-estereological analysis. Hormonal restriction caused great gland involution and decreased secretory activity, aspects that were reverted by exposure to estradiol and estradiol + testosterone. However, these hormones were not able to re-establish the normal prostate histoarchitecture. The immunoreaction of steroid receptors (ER-α, ER-ß, and AR) responded differently among the experimental and control groups, and PCNA assay showed a decrease in epithelial cell proliferation within groups that had hormone privation. Therefore, we conclude that estradiol and testosterone are able to influence prostate morphophysiology and the maintenance of gland homeostasis depends on a balance among these and other hormones.

Characterization of Mongolian gerbil chromatoid bodies and their correlation with nucleolar cycle during spermatogenesis.

The aims of the present study were to monitor the nucleolar cycle in Mongolian gerbil spermiogenesis, to verify the relationship between the nucleolar component and chromatoid body (CB) formation and to investigate the function of this cytoplasmic supramolecular structure in spermatogenic cells. Histological sections of adult seminiferous tubules were analysed cytochemically by light microscopy and ultrastructurally by transmission electron microscopy. The results reveal that in early spermatids, the CB was visualized in association with Golgi vesicles indicating that this structure may participate in the acrosome formation process as had been reported in other rodents. In late spermatids, the CB was observed near the axoneme region suggesting that this structure may support spermatozoon tail formation as happens in other species. Chromatoid body was joined with lipid droplets in this same cell type. This observation should be investigated to verify whether CB may be related to steroidal hormone metabolism. In conclusion, our data showed that there is disintegration of primary spermatocyte nucleoli at the beginning of prophase I and a fraction of this nucleolar material migrates to the cytoplasm, where a specific structure is formed, known as the 'chromatoid body', which apparently participates in some parts of the gerbil spermiogenesis process.

Morphological and histological effects on the medial pterygoid muscle after unilateral exodontia in gerbils.

Morphological effects on the medial pterygoid muscle were evaluated in 20 male gerbils (average weight, 55 g) after occlusal alterations induced by extraction of left side molar teeth. Controls were only submitted to surgical stress. Sixty days after surgery, the groups were divided into two subgroups for the following studies: (1) observation of macroscopic morphology and vessels distribution (n=10); (2) light microscopy histological analysis (n=10). Group results were statistically compared using the Wilcoxon and Mann-Whitney tests, with a significant value of p<0.05. Statistical differences in biometric data were found between the left and right sides of the experimental group (p=0.043), and between the left side of the control group when compared to the same side in the experimental group (p=0.044). Vessels supplied by bundles of the external carotid artery in the medial pterygoid muscle did not show distribution differences in group comparisons. Histological alterations were found in the ipsilateral side of the experimental group, with a central localization of the nucleus and degenerative aspect of the fibers, usually near to internal aponeurosis. Fiber diameters seemed reduced and the neuromuscular spindles were localized near internal aponeurosis and had a modified appearance. It is concluded that the medial pterygoid muscle in the gerbil is sensitive to alterations of the masticatory movements.

Lobe identity in the Mongolian gerbil prostatic complex: a new rodent model for prostate study.

Knowledge of structural and physiological differences among the prostatic lobes (PL) is the basis for development of experimental studies in traditional laboratory rodents. Although Mongolian gerbil reproductive organs have been increasingly investigated, its prostate structure is far from being properly known, and investigations of this organ focused on the ventral lobe (VL). Thus, the present study provides a thorough morphological description of prostatic complex in the male adult gerbil on the basis of topographic, histological, and ultrastructural analysis and ductal branching. Like other rodents, four pairs of PL were observed. However, in contrast to the rat and mouse, the VL is the least voluminous component and the dorsolateral lobe (DLL) is the most prominent and spatially isolated from remaining PL. The occurrence of a dorsal lobe (DL), hidden between bladder and insertion of seminal vesicles, has not been mentioned in previous reports with Mongolian gerbil. Collagenase digestion followed by microdissection revealed that, except for DL, which has a tubular-acinar organization, all PL exhibit tubular organization and variable ductal branching. Distinct histological and ultrastructural features such as secretory epithelium, aspect of luminal secretion and stromal organization are reported for each PL and are confirmed by morphometric and stereological methods. Histological sections showed at least three intralobar segments in VL and DL. Ultrastructural analysis evidenced that, although luminal epithelial cells of PL share typical features of exocrine secretory cells, there are striking lobe phenotypical variations. Both merocrine and apocrine pathways are observed in variable rates in all PL, with the predominance of the former in the DLL and the latter in the CG. The morphological observations presented herein point to distinct structural identities for each PL, which probably reflects specific functional compromise of seminal fluid secretion. These data also point to the gerbil as a good model for investigations concerning the regulation of prostate development and homeostasis, mainly with regard to the dorsal and dorsolateral PL.

Morphological features of the epididymal epithelium of gerbil, Meriones unguiculatus.

Principal cells of the ducts epididymis of the Mongolian gerbil showed ultrastructural characteristics of lining epithelium cells close related to processes of protein secretion, and transcytosis occurring between adjacent principal cells which were mainly verified in the initial segment. Principal cells also presented roles of fluid phase and adsorptive endocytoses, as well as autophagic and heterophagic lysosomal activities mainly observed in the caput epididymis. Columnar (principal) cells of the corpus epididymidis presented great number of variable vesicles and vacuoles distributed in all the cytoplasmic levels occurring a progressive coalescence pattern among them, which help to guarantee formation of cytoplasmic channels for fluid phase transport between the tubular lumen and epididymal interstitium. Clear cells were presented in the initial segment and predominately in the cauda epididymis epithelium of the gerbil and showed marked ultrastructural characteristics of endocytosis activities occurrence, perhaps directly related to the turnover of fluid phase of spermatozoa stored into the lumen of the distal tail. Other epididymal epithelium cells were verified and described such as basal, halo, apical and dark cells, but they did not presented special ultrastructural features.

Spermatogenic cycle length and spermatogenic efficiency in the gerbil (Meriones unguiculatus).

The gerbil (Meriones unguiculatus) is a rodent native of the arid regions of Mongolia and China. Because the gerbil can be easily bred in laboratory conditions, this species has been largely used as an experimental model in biomedical research. However, there is still little information concerning the testis structure and function in the gerbil. In this regard, we performed a detailed morpho-functional analysis of the gerbil testis and estimated the spermatogenic cycle length utilizing 3H-thymidine as a marker for germ cell progression during their evolution through the spermatogenic process. The stage frequencies of the XII stages characterized according to the acrosome formation and development were (I-XII) 13.8, 10.1, 8.1, 7.8, 4.0, 11.2, 7.5, 7.1, 5.9, 7.6, 8.1, and 8.9. The mean duration of each seminiferous epithelium cycle was determined to be 10.6 +/- 1.0 days and the total duration of spermatogenesis, based on 4.5 cycles, was approximately 47.5 days. The volume density of tubular and interstitial compartments was approximately 92% and 8%, respectively. Based on the volume occupied by seminiferous tubules in the testis and the tubular diameter, about 9 and 18 m of seminiferous tubules were found per testis and per gram of testis, respectively. Twelve primary spermatocytes were formed from each type A1 spermatogonia. The meiotic index was 2.8, indicating that 30% of cell loss occurs during meiosis. The number of Leydig and Sertoli cells per gram of the testis was 28 million and each Sertoli cell was able to support approximately 13 spermatids. The daily sperm production per gram of testis (spermatogenic efficiency) was 33 million. Taken together, these data indicate that, mainly due to the high seminiferous tubule volume density and Sertoli cell support capacity for germ cells, the gerbil presents high spermatogenic efficiency compared with other mammalian species already investigated. The data obtained in the present study might provide the basis for future research involving the reproductive biology in this species.

Structure, histochemistry, and ultrastructure of the epithelium and stroma in the gerbil (Meriones unguiculatus) female prostate.

The female prostate has aroused scientific interest because it is subjected to the same diseases compromising the male prostate during aging. The objective of this work was to characterize structurally, cytochemically, and ultrastructurally the tissue compartments of the normal adult female prostate of Meriones unguiculatus gerbils. The morphological analyses showed that the gerbil's female prostate is constituted of a cluster of glands and ducts inserted in a musculofibrous stroma. The alveolar epithelium is differentiated and consisted of basal proliferating cells, intermediary cells, and secretory cells. The secretory cells are the most numerous cell type and continuously secrete glycoproteins. The basal cells are the source of the secretory cells and they are then responsible for the alveolus renovation. The prostatic stroma is abundant and rich in elastic and collagen fibers, which are closely associated with smooth muscle cells and fibroblasts. The results showed that the gerbil's female prostate shows morphological and ultrastructural homology to the human female prostate (Skene's gland), and despite being a small organ, it is a mature and physiologically active gland.

Comparative study of inter- and intrahemispheric cortico-cortical connections in gerbil auditory cortex.

Topographic distributions and laminar pattern of cortico-cortical projections from the primary auditory field (AI), anterior auditory field (AAF), dorsoposterior field (DP), ventroposterior field (VP), dorsal field (D) and ventral field (V) were studied in relation to tonotopic maps in combined anatomical, electrophysiological and 2-deoxyfluoro-D-glucose (2DG) experiments. Distributions of axons were examined by means of retrogradely-transported fluorescent tracer Fast Blue (FB) injected in the primary (AI) and anterior (AAF) auditory field. Injections of fluorescent tracer were placed in electrophysiologically-identified locations of AI and AAF. Neurons in AAF, DP, VP and V project to AI in the ipsilateral hemisphere. This area also receives projections from AI, AAF and D from the contralateral hemisphere. In AI, DP and VP, neurons are connected with AAF in the ipsilateral hemisphere and AI and AAF in the opposite hemisphere. In all cases, patches of labeling are distributed along 2DG bands oriented parallel to the isofrequency line. Substantial numbers of retrogradedly labeled neurons with similar best frequencies (BFs) were observed in the ipsilateral and moderate to scant numbers in the contralateral hemisphere. In general, regions near the injection sites receive more densely-labeled projections than do more distant targets. In both hemispheres, the supragranular layer III contains the greatest concentration of cortico-cortical cells bodies; the granular and infragranular layer V contains a somewhat lower concentration.

Ultrastructure of the urethra of the Mongolian gerbil.

OBJECTIVE: The urethra is the main port of entry of sexually transmitted pathogens. However, papers on the morphology of the urethra are scarce. The Mongolian gerbil is a rodent native of the Mongolia and China and has been utilized as a laboratory animal since the 1960s. This work describes the ultrastructure of the urethra of the Mongolian gerbil to provide data for future experimental studies. METHODS: The urethra of ten adult male gerbils was studied by transmission electron microscopy. RESULTS: The epithelium of the pelvic urethra possesses two cell types: I and II, without the formation of cellular layers, while the penile urethra possesses cellular layers: basal, intermediate and superficial. The urethra presents neurosecretory cells belonging to the amine precursor uptake and decarboxylation system. CONCLUSIONS: The urethral epithelium of the gerbil is a neurosecretory epithelium, part of the amine precursor uptake and decarboxylation system.

Structure of the pelvic and penile urethra--relationship with the ducts of the sex accessory glands of the Mongolian gerbil (Meriones unguiculatus).

The urethra is the main place of entry for sexually transmitted pathogens. However, there is little literature on the morphology of the urogenital system, principally the urethra and ducts of the sex accessory glands. The Mongolian gerbil is an insectivorous, herbivorous and monogamous rodent with nocturnal habits; it has been used successfully as a laboratory animal since the 1960s. Therefore, the objective of the present paper was to describe the structure and ultrastructure of the urethra and its relations to the ducts of the accessory sex glands of the Mongolian gerbil (Meriones unguiculatus), contributing to the understanding of the reproductive biology of the rodent and aiming to provide data for future experimental studies. Conventional techniques of light and scanning electron microscopy were utilized. The urethra and ducts of the accessory sex glands are similar to those of the albino rat and the mouse. However, there is variation in drainage type among accessory sex glands for the inner urethra. The ducts of the seminal vesicle, the ductus deferens, drain their contents independently into the ampullary duct that opens in the urethra. The ducts of the prostate, coagulating and bulbourethral glands drain their contents independently into the urethra.

Kinetics of spermatogenesis in the Mongolian gerbil (Meriones unguiculatus).

The Mongolian gerbil (Meriones unguiculatus) is a small rodent native to the arid regions of Mongolia and Northeastern China. The present study provides descriptions of both the cellular associations of the seminiferous-epithelium cycle and relative frequencies of stages in the gerbil. Based on the development of the acrosomic system and the nuclear morphology changes using the PAS-H staining technique, the transformation of spermatids into spermatozoa was divided into 15 steps. The first 12 steps were used to identify 12 stages or cellular associations and the other three steps were spread among the first six stages of the cycle of the seminiferous epithelium. The relative frequencies found for stages I through XII were: 13.15; 8.06; 8.98; 6.48; 5.37; 6.71; 7.36; 7.45; 7.27; 5.83; 11.53 and 11.81, respectively. Stage I had the highest frequency while stage V proved the lowest frequency among the XII stages. The pattern of spermatogenesis is similar to those of rodents used as laboratory animals. The present description is the first for this rodent and provides the foundation for a variety of future studies of the testis in this animal.

Different patterns in the histology and autofluorescence of the Harderian glands of the Syrian Hamster, rat, mouse, Mongolian gerbil and guinea pig.

The purpose of this study was to compare the natural fluorescence in the Harderian glands of the Syrian hamster, rat, mouse, Mongolian gerbil and guinea pig (both sexes). For each species, 10 animals (five males and five females) were used. Histological autofluorescence studies were performed using a fluorescence microscope (450-490 nm filter). Two different types of fluorescent cells were observed in both hamster (type AFI high intensity and type AFII, low fluorescence) and rat (type AFI, low fluorescence and type AFII, high fluorescence) Harderian glands. The fluorescence was basally located in all mice cells, whereas it was observed near the epithelial cell nuclei in the Mongolian gerbil (occupying two-thirds and one-third of the cells in males and females, respectively). A high intensity of fluorescence was present throughout the acinar cells in the guinea pig. The patterns of fluorescence identified exhibited a sexual dimorphism in all species studied. These results demonstrate that the Harderian glands of the animal species examined exhibit a variety of histological autofluorescence patterns.

Morphology of the submandibular gland of the gerbil meriones unguiculatus: a macroscopic and light microscopy study

La morfología de la glándula submandibulardel gerbil fue estudiada macro y microscópicamente. Diez gerbiles fueron anestesiados, perfundidos e inyectados con formalina al 10 por ciento. La región cervical anterior de cada animal fue disecada para efectuar el análisis macroscópico de la glándula submandibular. Para el análisis histológico, las piezas fueron fijadas en la misma solución e incluidas en parafina para los procesos de rutina. Cortes seriados de 6-um fueron teñidos con hematoxilina-eosina y picrosirius, para análisis al microscopio de luz. Los resultados mostraron que la glándula submandibular de gerbil presentaba una forma ovoidea y localizada en la región submandibular, midiendo aproximadamente 9.0 mm de longitud y 5.9 mm de ancho. Histológicamente, cada acino estaba constituido por cuatro tipos de células dispuesta irregularmente. El sistema de ductos constaba de cuatro segmentos distintos: ductos intercalar, granuloso, estriado y excretor

Morphologic study of the masseter muscle of gerbil: meriones unguiculatus

El daño de los músculos masticadores relacionados con desórdenes cráneomandibulares son aspectos comunes en la clínica. Es importante contar con datos morfológicos de estos músculos en el sistema estomatognático. El propósito de este trábajo es mostrar la morfología del músculo masetero del gerbil Meriones unguiculatus, desde el nivel macroscópico hasta el de microscopía electrónica. En la observación macroscópica fueron utilizados 5 animales que fueron perfundidos con sulución de formalina al 100 por ciento. Las disecciones fueron fotografiadas. Posteriormente, los músculos fueron removidos e sumergidos en la solución de formalina, por unos pocos días. Las muestras fueron procesadas a través de técnicas histológicas convencionales y sumergidas en parafina. Cortes seriados de 6 um fueron teñidos con H. E. analizados y fotografiados con un fotomicroscopio JENAMED. Nuestros resultados mostraron que el músculo masetero presentaba 5 fascículos, los cuales se mezclaban en la porción media, y algunos husos estaban fusionados con la cápsula externa de ellos mismos, pareciendo husos gigantes

Angioarchitectural arrangements in corrosion cast of the nasal septum of the Mongolian gerbil.

The three-dimensional architecture of the vascular network of the nasal septum of the gerbil rat was studied using the corrosive resin cast technique. The angioarchitecture of the nasal septum observed with scanning electron microscopy (SEM) showed that a vascular network is disposed in the lamina propria. The capillaries, arterioles, venules and arteries were closely observed in different areas of the nasal septum mucosa.

Fine structure of the lining epithelium of the ductus deferens in gerbil: a segmental study

The cell types observed in the epithelium that lines the ductus deferens of the gerbil were principal, basal, narrow, and apical (mitochondria-rich) cells, whose cellular ultrastructure and segmental features were described. The morphological characteristics of the lining epithelium of the ductus in the three main tubular segments: adepididymic (proximal), funicular (middle) and adprostatic (distal) were presented. The cytophysiological role of the epithelial cell types in each segment was discussed on a comparative base. Resorption of seminiferous fluid and adsorptive endocytosis seem to be the main functions of the principal and apical cells. Moreover, secretory functions may occur in both cell types, mainly in principal cells in which ultrastructural characteristics of the Golgi-ER complex had been related to cellular secretion, perhaps of protein. Another ultrastructural feature of the supranuclear cytoplasm of principal cells was the presence of apical cytoplasmic expansions (apical protrusions), observed mainly in the epithelium of the distal ductus deferens segment, with suggestion of apocrine secretory process occurrence.

Características histológicas del meriones unguiculatus utilizado en experimentos / Histologic characteristics of Meriones unguiculatus used in experimental trials

Para determinar las caracterísiticas histológicas de Meriones unguiculatus sanos sometidos a las condiciones de animal de experimentación, se realizó el estudio de los órganos fundamentales de 50 especímenes sanos machos (encéfalo, corazón, pulmones, hígado, riñones, tractus gastrointestinal, bazo y testículos). Se procesaron los órganos en formol neutro al 10 por ciento. Se colorearon con hematoxilina-eosina y la coloración especial de Von Kossa para demostrar la presencia de calcio. Se encontró principalmente congestión visceral de diferentes grados en un 100 por ciento y un depósito de material homogéneoen los túbulos de composición cálcica, en el 16 por ciento. este último hallazgopuede ser de interés en estudios de insuficiencia renal crónica (AU)