Apoptosis of germ cells in the normal testis of the Japanese quail (Coturnix coturnix japonica)

Rate of spermatogenic cell apoptosis in the testis of domestic chicken (Gallus gallus domesticus) at different age groups

In both normal and pathological conditions, excess spermatogenic cells in the testicular tissue are known to be removed by the mechanism of apoptosis. There are a few studies on spermatogenic cell apoptosis in avian species. Therefore, the purpose of this study was to evaluate the rate of spermatogenic cell apoptosis in three different age groups of the local domestic chicken (Gallus gallus domesticus). Samples were collected from the testes of domestic chicken at three different reproductive stages; pre-pubertal, pubertal, and adult. The samples were subjected to transmission electron microscopy (TEM) and flow cytometry evaluations. TEM results revealed the morphological characteristics of apoptotic cells which included irregular nuclear and plasma membranes in the early stages of apoptosis, nuclear membrane rupture, nuclear material condensation, and fragments of apoptotic bodies in the later stages of apoptosis. The flow cytometry results revealed a significant difference between the mean percentage of apoptotic spermatogenic cells for the three age groups (P < 0.05). Post hoc analysis revealed a significant difference in the adult age group relative to the pre-pubertal age group. However, there was no significant difference between apoptotic spermatogenic cells of the pre-pubertal and the pubertal, and between the pubertal and the adult age groups. In conclusion, the present study revealed a gradual increase in the rate of apoptotic spermatogenic cells in the testes of domestic chicken during the pre-pubertal, pubertal, and adult age groups.

Ultrastructural changes in the spermatogenic cells of domestic chicken (Gallus gallus domesticus) observed at different reproductive stages

Spermatogenesis is a complex process. It is the modification of progenitor spermatogonia into mature spermatozoa. The stages are similar in all-male vertebrates, as well as avian species. However, studies on spermatogenesis in birds are fewer compared to mammals. The current study investigated the ultrastructural changes in the spermatogenic cells of domestic chickens in different reproductive stages. Thirty (30) male birds, ten (10) in each of the three reproductive stages: pre-pubertal, pubertal, and adult were used in the study. Testicular tissues from all age groups were processed for transmission electron microscopy (TEM). TEM results showed spermatogonia and primary spermatocytes in the pre-pubertal testis, and the seminiferous tubule lumen was wide and empty. Also, the nuclei of spermatogonia at this stage did not contain condensed chromatin material at the center nor scattered at the periphery of the nuclear membrane. There were slight differences between the spermatogenic cells in the pubertal and adult age groups. The spermatogonia, primary and secondary spermatocytes, and round spermatids with scanty chromatin material were observed in both age groups. In the adult age group, round and elongated spermatids with condensed chromatin materials were observed besides the other spermatogenic cells. Also, the seminiferous tubule lumen was filled with sperm cells and cellular debris, unlike in the pre-pubertal and pubertal age groups where they were wide and empty. The presence of numerous oval mitochondria were observed in all age groups. This signifies the active process of spermatogenesis in pre-pubertal, pubertal, and adult male domestic chickens.

Effect of di(n-butyl) phthalate on the blood-testis barrier during puberty onset

Di(n-butyl) phthalate (DBP) is considered a substance of serious concern because of its reproductive toxicity and endocrine-disrupting properties. Exposure to DBP causes morphological and functional changes in the male reproductive system of birds and mammals. However, there are no detailed reports on the effects of DBP on the Sertoli cell and junctional complexes of the blood-testis barrier (BTB) in birds. The present study investigated dose-related ultrastructural changes in Sertoli cells and junctional complexes of the BTB in adult Japanese quail (Coturnix coturnix japonica) exposed to DBP prior to puberty. A total of 25 Japanese quail were used for the study. Exposure to DBP doses of 50, 200 and 400 mg DBP/kg/d caused dose-related ultrastructural changes in junctional complexes including dilation and separation, while disruption of cytoplasmic membranes and mitochondria was observed in Sertoli cells. There was a significant difference in the sum of vacuoles, vacuole diameter, nuclear width, nuclear length, nuclear area, sum of damaged spherical mitochondria, width of elongated mitochondria and the sum of damaged elongated mitochondria among the five treatment groups (p ˂ 0.05). Prepubertal exposure to DBP at doses of 50, 200 and 400 mg DBP/kg/d for 30 days led to adverse effects in the adult male Japanese quail reproductive system by inducing structural changes in the Sertoli cells and junctional complexes. Such changes might disrupt the BTB and potentially interfere with spermatogenesis. Results indicated that the Sertoli cell is sensitive to DBP exposure and might be an important cellular target for DBP-induced testicular toxicity.

Junctional complexes of the blood-testis barrier in the Japanese quail (Coturnix Coturnix japonica)

This study investigated the developmental changes in the adherens junctions, gap junctions, as well as tight junctions forming the blood-testis barrier (BTB) in Japanese quail (Coturnix Coturnix japonica) testis. Testicular tissue from pre-pubertal, pubertal, adult, and aged Japanese quail were examined by immunohistochemistry and transmission electron microscopy (TEM). The tight junction proteins claudin-3, claudin-11, occludin and zonula occludens-1 (ZO-1), were generally localised in the cytoplasm of Sertoli cells, spermatogonia, and spermatocytes of pre-pubertal, pubertal, some adult birds. The adherens junction protein E-cadherin had a similar distribution pattern. During pre-pubertal development, the gap junction protein connexin-43 (Cx43) was only localised between Leydig cells in the testicular interstitium. However, TEM revealed the presence of gap junctions between cells of the seminiferous epithelium as early as the pre-pubertal stage. Furthermore, TEM confirmed the presence of tight and adherens junctions in the seminiferous epithelia of all age groups. The findings of this study document age-related differences in the immunolocalisation and intensity of the junctional proteins and the ultrastructure of the junctional complexes forming the BTB in quail testes. Additionally, the junctional complexes forming the BTB in the Japanese quail are well established prior to puberty. This study provides baseline information for the future evaluation of pathological changes in the BTB of avian species at different developmental stages.

Ontogeny of the testicular excurrent duct system of male Japanese quail (Coturnix japonica): A histological, ultrastructural, and histometric study

The testicular excurrent duct system undergoes several physiological and morphological changes during the reproductive stage or breeding season in mammals, birds, and reptiles. Studies on normal age-related histomorphological changes in the excurrent duct system of Japanese quails (Coturnix japonica) remain unreported, despite the extensive use of this bird as an avian model in research studies. The current study investigated the histological, ultrastructural, and histometric changes in the testicular excurrent duct system of the Japanese quail during three reproductive stages, namely prepubertal, pubertal, and adult. Simple squamous to low cuboidal cells formed the epithelia of the rete testis in prepubertal and pubertal birds, while in adult birds the lining was low cuboidal to cuboidal. In pubertal and adult birds, the nonciliated Type I epithelial cells of the proximal efferent duct displayed a subapical endocytotic apparatus comprising coated pits, coated apical tubules, and endosomes. There was a significant increase (p ≤ .001) in epithelial heights of all ducts of the excurrent duct system in the mature, sexually active, adult birds when compared to the other age groups. The luminal and tubular diameters, and the cross-sectional areas of efferent ducts and the epididymal duct unit increased significantly (p ≤ .001) with age. It is concluded that the morphology and morphometry of the excurrent ducts of the testis of the Japanese quail change as birds mature.

Structural observations on spermatogenic cells of Japanese quail (Coturnix coturnix japonica) pre-pubertally exposed to dibutyl phthalate: A light and transmission electron microscopy study

Exposure to dibutyl phthalate (DBP) induces testicular damage in mammals. However, studies on the effects of DBP on spermatogenic cells in birds are grossly lacking. Therefore, this study was designed to determine the effects of the pre-pubertal exposure to DBP on the histology and ultrastructure of spermatogenic cells in the testis of adult Japanese quail (Coturnix coturnix japonica). The birds were randomly divided into five dosage groups at the age of 4 weeks. The control group received a corn oil vehicle only (a dose of 1 mL/kg body weight), while the other four experimental groups received a daily dosage of 10, 50, 200, 400 mg/kg body weight of DBP (dissolved in corn oil), respectively with the aid of gastric lavage, for 30 days. Testicular samples were processed and examined by light microscopy and transmission electron microscopy. Histopathological evaluation revealed vacuole formation, germ cell degenerations, and the absence of spermatogenic cell series. Ultrastructurally, chromatin clumps in spermatocyte and degenerated spermatogonia with ruptured nuclear membranes resting on the distorted basement membranes were observed. Others were intracytoplasmic vacuoles in round spermatids and fragments of dense apoptotic bodies. In conclusion, the findings of the present study reveal that spermatogenic cells of Japanese quails seem to be more sensitive to DBP-induced degeneration compared to mammalian species studied. The Japanese quail could be used to monitor environmental contamination with low doses of DBP.

Age-related histomorphometric and ultrastructural changes in the Sertoli cells of Japanese quail (Coturnix Coturnix japonica)

Prepared sections from pre-pubertal, pubertal, adult, and aged Japanese quail testes were examined by light microscopy and transmission electron microscopy (TEM) and measurements of seminiferous tubular diameter (STD), luminal diameter (SLD), epithelial height (SEH) and cross-sectional area of the seminiferous tubules (AST) were taken using an image analyzer. Apoptotic Sertoli cells with features such as cell shrinkage and chromatin condensation were observed in pre-pubertal and aged quail. There was a significant difference between the mean Sertoli cell number (SCN), SLD, SEH, STD and AST among the four age groups (P < 0.001). The highest SCN (mean ± standard error) was recorded in the adult (30.53 ± 0.42), with the aged group displaying the lowest mean (11.80 ± 0.27) SCN. Spearman's rho correlation coefficients demonstrated a strong relationship between the SCN and SEH in the pubertal (ρ=0.915; P < 0.001), adult (ρ=0.878; P < 0.001), and aged (ρ=0.858; P < 0.001) groups, while a significant moderate correlation was observed in the pre-pubertal (ρ=0.606; P < 0.001) group. There were significant moderate correlations between the SCN and STD in the pre-pubertal (ρ=0.445; P < 0.001), pubertal (ρ=0.653; P < 0.001), adult (ρ=0.440; P < 0.001), and aged (ρ=0.514; P < 0.001) groups. Furthermore, significant moderate correlations were estimated between the SCN and AST in the pre-pubertal (ρ=0.453; P < 0.001), pubertal (ρ=0.661; P < 0.001), adult (ρ=0.393; P = 0.001), and aged (ρ=0.498; P < 0.001) groups. This study provides baseline data on the morphology and development of the Sertoli cell, as well as testicular morphometry in avian species during the pre-pubertal, pubertal, adult, and aged stages using the Japanese quail as a model.