Scanning electron microscopic study of the functional anatomy of the porcine oviductal mucosa

A three-dimensional model has not been clearly established for the porcine oviductal mucosa. The oviducts of 12 cyclic sows were examined by Scanning Electron Microscopy to study the structure and nature of the mucosal arrangement of the oviduct. Epithelial cyclic changes were also studied. The oviductal infundibulum is an asymmetric funnel-shaped structure surrounding the ostium, in which a wide and a narrow side can be distinguished. The mucosa is more complex in the narrow side, showing numerous and tortuous longitudinal primary folds, while the mucosa becomes simpler in the wide side. Around the ostium abdominale wide secondary folds form cul-de-sacs, with their opening pointing in ovarian direction. Areas between folds throughout the lumen of the oviduct show a high-degree of complexity. Inter-fold spaces are occupied by a system of irregular grooves and pockets, with the presence of basal crypts in the caudal oviduct. Marked variations were observed in the oviductal epithelium depending on the oviductal segment, basal or apical areas of the folds, and phase of the oestrous cycle. Cyclical changes were observed in the infundibulum and ampulla, so that prominent and numerous ciliated cells lined apical areas of the folds in the follicular phase; whereas secretary cells were predominant throughout all areas of epithelial surface in the luteal phase. The oestrous cycle phase appeared do not affect the epithelial population cells of the caudal segments of the oviduct: ciliated and secretory cells uniformly lined apical and basal areas of the folds. The topography of the oviduct provides a complex system of regulation, which may influence not only the passage of cells, but also movement of fluid within the oviductal canal.     

Morphometric and ultrastructural changes in ciliated cells of the oviductal epithelium in prolific Chinese Meishan and Large White pigs during the oestrous cycle.

There are some differences in reproductive features between the Chinese Meishan (CM) pig and Large White (LW) pig. The aim of the present study was to investigate the quantitative changes and ultrastructural features of ciliated cells in the various regions of the CM and LW pig oviduct during the follicular and luteal phases of the oestrous cycle. In the fimbrial and ampullar epithelia at the follicular phase, the ciliated cells were more plentiful than in the isthmic region in both pigs. In the CM pigs, there was a striking decrease in the percentage and cell height of ciliated cells in the luteal phase compared with the follicular phase. Although similar quantitative changes were observed in the LW pig oviduct, these changes were less dramatic than that in the CM pig oviduct. In both pigs, the percentage and cell height of ciliated cells in the isthmus were unchanged between the follicular and luteal phases. The ultrastructure of ciliogenic and ciliated cells was observed. In the fimbrial and ampullar epithelia during the follicular phase, most of the ciliated cells showed normal morphology, having many elongated cilia and mitochondria, but in the CM pig oviduct during the luteal phase many of the ciliated cells possessed immature cilia and swollen mitochondria. Cells undergoing ciliogenesis were frequently observed in the fimbriae and ampulla, and occasionally in the isthmus. Cytoplasmic protrusions containing variable numbers of ciliary axonemal complexes occurred in the fimbrial and ampullar epithelium in the CM pigs at the luteal phase, suggesting that deciliation of cells occurs by membrane-bound cilia packets forming at the apices of cells and pinching off. These results demonstrate that there are regional variations in the cyclic changes associated with the oviductal ciliated cells of the pigs, while there are marked morphometrical and ultrastructural changes in oviductal ciliated cells of the CM pigs compared with that of the LW pigs.     

Lysophosphatidic acid expression in theca cells depends on the type of bovine ovarian follicle

Lysophosphatidic acid (LPA) exerts various actions on the mammalian reproductive system. In cows, LPA stimulates the synthesis and secretion of luteotropic factors in the ovary, which affects the growth and development of ovarian follicles. The role of LPA in granulosa cells, oocyte and oocyte‐cumulus complex (COC) has previously been investigated; but its role in the theca layer, which is an important structural and functional component of the ovarian follicle, is still unclear. The goal of this study was to investigate the expression of LPA in theca cells originating from different bovine ovarian follicle types. Theca cells were separated from healthy, transitional and atretic ovarian follicles, based on intrafollicular estradiol: progesterone ratios. LPA concentration in the follicular fluid (FF) in different follicle types was measured, and expression of the enzymes responsible for LPA synthesis (autotaxin [AX], phospholipase A2 [PLA2]) and receptors for LPA (LPAR1‐4) were determined. The obtained results confirmed the follicle‐type dependent presence of LPA in the FF of the bovine ovarian follicles. The highest concentration of LPA was detected in follicles classified as healthy and dominant. LPAR1‐4, PLA2 and AX expression in theca cells in all of the types of follicles examined were detected at mRNA and protein level. These results suggest that theca cells can be a source of LPA synthesis other than granulosa cells and COCs, as well as the target for its action in the bovine ovarian follicle, with PLA2 and LPAR4 playing major roles in LPA synthesis and action.     

The localization and expression of epidermal growth factor and epidermal growth factor receptor in bovine ovary during oestrous cycle

Epidermal growth factor (EGF) is one of the important regulatory factors of EGF family. EGF has been indicated to effectively inhibit the apoptosis of follicular cells, to promote the proliferation of granulosa cells and the maturation of oocytes, and to induce ovulation process via binding to epidermal growth factor receptor (EGFR). However, little is known about the distribution and expression of EGF and EGFR in cattle ovary especially during oestrous cycle. In this study, the localization and expression rule of EGF and EGFR in cattle ovaries of follicular phase and luteal phase at different time points in oestrous cycle were investigated by using IHC and real-time qPCR. The results showed that EGF and EGFR in cattle ovary were mainly expressed in granulosa cells, cumulus cells, oocytes, zona pellucida, follicular fluid and theca folliculi externa of follicles. The protein and mRNA expression of EGF/EGFR in follicles changed regularly with the follicular growth wave both in follicular and in luteal phase ovaries. In follicular phase ovaries, the protein expression of EGF and EGFR was higher in antral follicles than that of those in other follicles during follicular growth stage, and the mRNA expression of EGFR was also increased in stage of dominant follicle selection. However, in luteal phase ovaries, the growth of follicles was impeded during corpus luteum development under the action of progesterone secreted by granular lutein cell. The mRNA and protein expressions of EGF and EGFR in ovarian follicles during oestrous cycle indicate that they play a role in promoting follicular development in follicular growth waves and mediating the selection process of dominant follicles.     

Regional and Cyclic Variations in the Ultrastructural Features of Secretory Cells in the Oviductal Epithelium of the Chinese Meishan Pig

The Chinese Meishan pig is prolific breed and it is considered that this pig has a capacity with higher rates of embryonic survival. The oviductal secretory cells may affect the embryonic development and survival. The aim of the present study was to investigate the ultrastructural features of secretory cells in the various regions of the Chinese Meishan pig oviduct during the follicular and luteal phases of the oestrous cycle. In the ampullar secretory cells, numerous secretory granules with moderately electron-dense matrices were present in the supranuclear cytoplasm and exocytosis of secretory granules was observed. The number of secretory granules was dramatically reduced in the ampullar secretory cells in the luteal phase. During the follicular phase in the fimbrial epithelium, the secretory cells contained rough endoplasmic reticulum and Golgi apparatus, but most cells had few small granules. In the luteal phase, the secretory cells in the ampullar and fimbrial epithelia extended beyond the luminal border of the ciliated cells. In the isthmus, many granules were present in the cytoplasm of secretory cells throughout the oestrous cycle, but the number of secretory granules was reduced in the luteal phase. The cytomorphometric data revealed that the height of ciliated cells decreased substantially in the fimbriae and ampulla at the luteal phase, while that of non-ciliated cells was less affected. These results suggest that the drastic reduction of cell height of ciliated cells cause the extrusion of most secretory cells beyond the ciliated cells in the fimbriae and ampulla during the luteal phase. In summary, our ultrastructural observations of Chinese Meishan pig oviduct revealed marked cyclic changes in the ultrastructural features of secretory cells. In particular, the ultrastructural features and the numbers of secretory granules were distinctive for each particular segment. These findings should provide insight into the regional and cellular differences in functions of secretory cells of the Chinese Meishan pig oviduct.     

Cyclic Related and Pathological Changes in the Lectin-binding Sites on the Swine Oviduct

This study was carried out to compare the lectin-binding pattern in the normal and pathological oviduct of sows during the ovarian cycle. Lectin-binding patterns showed differences between segments, phases of ovarian cycle and presence of morphologic lesions. In the infundibulum, it was observed that the cysts, in the follicular phase, reduced Ricinus communis-I (RCA-I) and Ulex europaeus-I (UEA-I) binding. Furthermore, in the pathological oviducts of the luteal-phase group, there is a reduction of Concanavalia ensiformis (Con-A) reactivity in this segment of the tube having wall cysts, adenomyosis and diverticulus. The Arachis hypogaea (PNA) binding in the infundibulum, during the luteal phase, decreased in the tube having adenomyosis. In animals with wall cysts, the Con-A, Triticum vulgaris (WGA) and RCA-I reactivity was minor in the glycocalyx of the isthmus epithelium during follicular phase. Con-A and Dolichos biflorus (DBA) binding pattern was minor in the luteal-phase isthmus of the tube having wall cysts, adenomyosis and diverticulus. In the ampulla, the wall cysts impaired the Con-A reaction only in the basal region of the epithelium, in the follicular phase. Binding with Con-A was decreased in the ampulla of animals in the luteal phase in the tube lesions with cysts and diverticulus. In addition, the diverticulus observed in the ampulla, during the luteal phase, reduced the PNA tubaric binding. The results of this study showed that the morphologic alterations modify the sugar pattern in the oviduct of sows. These modifications in glycoconjugates may be one of the reasons for the failure of fertility in sows.     

The expression of hypoxia-inducible factor-1 alpha in primary reproductive organs of the female yak (Bos grunniens) at different reproductive stages

The yak (Bos grunniens) is the most important livestock animal in high-altitude regions owing to its prominent adaptability to cold conditions, nutritional deficiencies and hypoxia. The reproductive organs exhibit different histological appearances and physiological processes at different reproductive stages. Hypoxia-inducible factor-1 alpha (HIF-1α) is the regulatory subunit of HIF-1 that crucially regulates the response to hypoxia in mammalian organisms. The goal of our study was to investigate the expression and distribution of HIF-1α in the primary yak reproductive organs at different reproductive stages. Samples of the ovary, oviduct and uterus of 15 adult female yaks were collected and used in the experiment. The expression and localization of HIF-1α proteins and mRNA were investigated using quantitative real-time polymerase chain reaction (qRT-PCR), Western blot (WB) and immunohistochemistry (IHC). The results indicated that the expression of HIF-1α protein in the ovary was higher during the luteal phase than during the follicular phase and gestation period (p < .05). In the oviduct, HIF-1α protein was also more highly expressed during the luteal phase than during the follicular phase and gestation period (p < .01). However, in the uterus, the HIF-1α protein had stronger expression during the gestation period than during the follicular phase (p < .01) and luteal phase (p < .05). The expression of HIF-1α mRNA was similar to that of its protein. Immunohistochemical analysis revealed intense immunostaining of HIF-1α proteins in the follicular granulosa cells, granular luteal cells, villous epithelial cells of the oviduct, endometrial glandular epithelium and luminal epithelium, foetal villous trophoblast, and epithelia of caruncular crypts. This study showed that the expression of HIF-1α in the ovary, oviduct and uterus varies according to the stage of the reproductive cycle. This implies that HIF-1α plays an important role in regulating the stage-specific physiological function of yak reproductive organs under hypoxic environments.     

Morphological Changes and Proliferative Activity in the Oviductal Epithelium during Hormonally Defined Stages of the Oestrous Cycle in the Bitch

The aim of the present study was to investigate morphological changes and proliferative activities in the epithelium of the canine oviduct with regard to the part of the oviduct – possibly indicating the existence of a locally restricted sperm reservoir – and the stage of the oestrous cycle. Nine healthy adult nulliparous bitches were submitted to ovariohysterectomy at three stages of the cycle: anoestrus (n = 3), late follicular phase (n = 3) and mid‐luteal phase (n = 3). The whole oviduct ranging from the utero‐tubal junction (UTJ) to the infundibulum (IN) was collected, divided into UTJ, IN plus six segments of equal length, i.e. eight oviductal specimens per animal were studied by light microscopy. Morphological characteristics of ovaries and endometrium were recorded macroscopically and verified histologically. The height of oviduct epithelial cells and percentage of ciliated cells (CC) were assessed and the respective data analysed statistically. Proliferative activity was immunohistochemically visualized by means of Ki‐67 antigen detection. Blood was collected and concentrations of oestradiol‐17β and progesterone (P₄) were measured. Within the IN and five of the six tissue samples collected from the ampulla and isthmus in anoestrous bitches, the oviductal surface epithelium consisted of low cuboidal cells demonstrating a uniform dark staining intensity. Only a very few scattered lighter staining CC could be detected. Under the influence of oestrogens during late follicular phase, the oviductal epithelium was highly differentiated. Lighter stained CC with apically located nuclei were easily distinguishable from basophilic secretory cells with apical cytoplasmic protrusions. Cell height and percentage of CC were significantly higher than in anoestrus (p ≤ 0.05). During mid‐luteal phase, high levels of P₄ were associated with differentiated and dedifferentiated cells as well as cells in regression seen in the mucosal folds of all samples. The percentage of CC and cell height were significantly lower than during late follicular phase (p ≤ 0.05). Further signs of dedifferentiation consisted of a loss of cilia, a pinching off of the apical cytoplasm as well as the presence of debris and macrophages within the oviductal lumen. In the oviductal part of UTJ and the caudal isthmus hormone‐dependent variations in cellular morphology were less distinct. Changes in cell height were minimal and did not differ significantly throughout the oestrous cycle. Hypertrophic cells with large nuclei were predominantly present at these sites, but did not consistently demonstrate signs of ciliation or secretion. Sporadic proliferating activity, visualized by means of Ki‐67 antigen, was mainly seen in some cells of the late follicular phase samples. Thus, overall proliferative activity is generally very low or may occur within a relatively short period of time. It therefore cannot be excluded, that periods exhibiting higher mitotic rates are not included in the present study. It should, however, be mentioned that cells demonstrating morphological signs of apoptosis can only be seen very sporadically within a few specimens during mid‐luteal phase, thus, reflecting low proliferative capacities and minimal cellular turnover found during this study. The results of the present study strongly indicate that oestrogens cause hypertrophy and differentiation, whereas P₄ induces gradual dedifferentiation or regression of the oviductal epithelium. Furthermore, they reveal clearly visible changes in the morphology of the tubal epithelium during the oestrous cycle. Depending on the tubal segment, these are, however, variably expressed. Whether the low degree of cellular variation of the UTJ and caudal isthmus is caused by specific hormone concentrations at these sites or specific regulatory mechanisms and may be associated with specific functional properties such as the formation of a locally restricted sperm reservoir needs further investigations.     

Light and Scanning Electron Microscopic Studies of Oviductal Epithelium in Thai Swamp Buffalo (Bubalus bubalis) at the Follicular and Luteal Phases

The purpose of this study was to investigate the morphological changes in the epithelium of Thai swamp buffalo oviducts at the follicular and luteal phases by histological technique and scanning electron microscopy. The samples from the infundibulum, ampulla, isthmus and uterotubal junction (UTJ) of the oviduct were taken immediately after slaughter at the local abattoir. Noticeable cyclic changes were observed on the epithelial surface of the infundibulum and ampulla, but few changes were present in the isthmus and UTJ. At the follicular phase, the epithelium of infundibulum and ampulla were densely covered with ciliated cells whose cilia concealed the apical processes of the secretory cells. In contrast, the secretory cells dominated in the epithelium at the luteal phase and most of the ciliated cells were hidden by the bulbous processes of these cells. In the isthmus and UTJ at the follicular and luteal phases, the secretory cells were almost flat or gently rounded and covered with numerous microvilli at their apical surface. In conclusion, the histological and ultrastructural observation of Thai swamp oviduct epithelium revealed marked cyclic changes in the cellular differences associated with the main functions of segmental variations.     

促性腺激素受体在雌性水牛生殖器官的表达定位研究

为研究促性腺激素受体(FSHR、LHR)在广西雌性水牛生殖器官中的分布情况,运用免疫组化SABC法对处于不同发情周期(卵泡期、黄体期)成年水牛的卵巢、子宫、输卵管中FSHR、LHR分别进行染色定位。结果表明,FSHR/LHR阳性细胞在卵巢主要见于卵巢内膜细胞及卵泡颗粒细胞;子宫主要见于子宫内膜上皮细胞和腺体细胞;输卵管主要见于柱状上皮纤毛细胞。其中,随着发情周期不同,FSHR、LHR的表达量也有所差异,卵巢中卵泡期FSHR、LHR的表达量均高于黄体期;子宫中FSHR的表达量卵泡期高于黄体期,LHR的表达量黄体期高于卵泡期;而输卵管并没有显著差异。     

Changes in the mast cell distribution in the canine ovary and uterus throughout the oestrous cycle

This is the first study describing the relation between the phase of the oestrous cycle and the number of mast cells (MCs) in the canine ovaries and uterine horns. The total number of MCs was counted in cortex ovarii, medulla ovarii, endometrium and myometrium. The number of MCs was compared in all of these areas among the bitches in the early follicular phase, luteal phase and anoestrus. MCs were the most numerous in the early follicular phase and in the luteal phase; however, they were significantly less numerous during anoestrus. Based on the results, it was concluded that the number of MCs in ovaries and uterine horns fluctuates during the oestrous cycle. The results of this study may contribute to clarifying the role of MCs in the reproductive organs of bitches.     

Quantitative unbiased estimates of endometrial gland surface area and volume in cycling cows and heifers

Entire reproductive tracts were removed from seven normal healthy heifers and qualitative unbiased estimates made of endometrial gland volume density and glandular surface density. After examining approximately 55 microscopic fields of endometrium from each tract, a mean glandular surface density value of 10.2 mm(2)/mm(3) (CE 3.1%) was obtained. The stereological method was then employed in optimising the design of the main study. The endometrial height was measured for 17 healthy cycling heifers and 19 similar cows. Subsequently, unbiased estimates were made of intercaruncular endometrial gland volume per unit surface for all cattle were investigated; differences between heifers and cows generally, and the possible effect of the follicular and luteal phases of the oestrous cycle were compared. The mean surface area of glands per unit area of endometrium at the intercaruncular site in heifers and cows was approximately 18 mm(2)/mm(2) in the follicular phase and 26 mm(2)/mm(2) in the luteal phase, figures similar to the gland area found in women. The intercaruncular gland volume increased significantly, by about 30% during the luteal phase of the bovine oestrous cycle in heifers, from 0.01 to 0.13 per mm(3). The differences in endometrial anatomy between site of sampling and either follicular or luteal phases of the oestrous cycle were always more significant in heifers than cows. The endometrial thickness in cows was always greater than for heifers, irrespective of the site of sampling. It was concluded that the intercaruncular endometrium of cattle was far more active physiologically than recognised previously.     

Integrated analysis of miRNA–mRNA interaction in ovaries of Turpan Black Sheep during follicular and luteal phases

To investigate the regulatory mechanism of the follicular–luteal phase transition in Turpan black sheep (Ovis aries), the genome-wide expression patterns of microRNAs (miRNAs) and genes were investigated in ovaries of six sheep (3 years and single lamb with 3 consecutive births) during follicular and luteal phases of the oestrous cycle. Bioinformatic analysis was used to screen potential miRNAs and genes related to Turpan black sheep ovarian function. RT-qPCR was used to validate the sequencing results. In total, we identified 139 known and 71 novel miRNAs in the two phases with miRNA-seq, and a total of 19 miRNAs were significantly differentially expressed, of which 7 were up-regulated and 12 were down-regulated in the follicular phase compared with luteal phase. A total of 150 genes were significantly differentially expressed, including 63 up-regulated and 87 down-regulated in the follicular phase compared with the luteal phase by RNA-seq data analysis. Those DEGs were significantly enriched in 103 GO terms and several KEGG pathways, including metabolic pathway, ovarian steroidogenesis, steroid hormone biosynthesis and oestrogen signalling pathway. In addition, we created a miRNA–mRNA regulatory network to further elucidate the mechanism of follicular–luteal transition. Finally, we identified key miRNAs and genes including miR-143, miR-99a, miR-150, miR-27a, miR-125b, STAR, STAT1, which might play crucial roles in reproductive hormone biosynthesis and follicular development. The miRNA–mRNA interactive network clearly illustrates molecular basis involving in follicular–luteal transition.     

Dynamics of apoptosis-related gene expression during follicular development in yak

The potential reproduction power of domestic animals is limited by a complicated follicular atresia process. P53, caspase-9 (Casp9), Bax, Bcl-2 and Fas play a crucial role in the ovarian mitochondrion-dependent apoptosis and death receptor pathway. In accordance with this study, the expression levels of Casp9, Bax, Bcl-2 and Fas were analysed in ovaries and oviducts of yak by immunohistochemistry (IHC). P53 and the above in ovarian granulosa cells (GCs) from atretic (3–6 mm) to healthy follicles (6–8 mm) and in oviducts were examined from the luteal phase to the follicular phase during the oestrous circle by Western blot (WB) and real-time PCR (RT-PCR). Results demonstrated that typical classic apoptotic factors Casp9, Bax, Bcl-2 and Fas were expressed in the cytoplasm and zonal pellucida of oocytes, primordial follicles, primary follicles, ovarian surface epithelium, ovarian GCs, granular lutein cells, surface epithelia in oviduct uterotubal junction and oviduct ampulla during the luteal phase. RT-PCR and WB revealed that P53 and Fas significantly increased in GCs of atretic follicles. P53 and Casp9 increased in oviduct epithelium during the luteal phase, but Fas was unchanged. A contrary tendency was noted in Bcl-2 and Bax expression. Overall, P53 and Fas play an essential role in inducing GC apoptosis, and Bax, Bcl-2, Casp9 and P53 are involved in oviduct epithelial regeneration in yak.     

神经生长因子(NGF)在母牛性腺及性腺外生殖器官中的表达研究

本研究旨在探讨神经生长因子(nerve growth factor,NGF)在母牛卵泡期及黄体期子宫、卵巢、输卵管3种组织中的表达情况。采用FQ-PCR方法和Western blotting技术对成年母牛卵泡期及黄体期的子宫、卵巢、输卵管中的NGF mRNA和蛋白质表达进行了检测。结果表明,NGF mRNA和蛋白质在卵泡期和黄体期的子宫、卵巢、输卵管中均有表达,且卵泡期子宫中NGF mRNA表达量显著高于卵泡期卵巢和黄体期输卵管中NGF mRNA表达量(P0.05),其它组织间无显著差异。     

Light and electron microscopic studies on mast cells of the bovine oviduct

This study was conducted to determine the staining properties, the light and electron microscopic appearance and numerical distribution of mast cells from different regions of the bovine oviduct during the estrous phase and luteal phase. Ten oviducts from bovines in the estrous phase, and 10 from bovines in the luteal phase were used as study samples. In three regions of the oviduct (infundibulum, ampulla, isthmus), mast cells that showed metachromasia with toluidin blue and Ab(+), SO(-) with the combined Ab/SO stains were encountered. Electron microscopic studies of the mast cells showed them to contain two types of granules; a dense homogeneous type and a tiny particulate type. In all three regions of the oviduct, the luteal phase was observed to have a higher number of mast cells per mm2 area than the estrual phase with the isthmus having the most dense population.     

雌性牦牛主要生殖器官中DBI的表达与定位分析

为加深对DBI基因功能的探究,揭示其在牦牛生殖生理过程中的作用.本试验采集健康母牦牛(3～6岁)繁殖周期不同阶段(卵泡期、黄体期和妊娠期)的卵巢、输卵管和子宫组织,共分为9组,每组设置3个生物学重复.采用实时荧光定量PCR (qRT-PCR)和蛋白免疫印迹技术(Western blotting,WB)检测牦牛DBI在繁...     

Endometrial glycogen, protein, nucleic acids and phosphatases during oestrous cycle in buffaloes (Bubalus bubalis).

Distinct cyclic variations were observed in the concentrations of endometrial glycogen, protein, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) and activities of acid phosphatase (ACP) and alkaline phosphatase (AKP) during the follicular and luteal phases of the oestrous cycle in buffaloes. Glycogen, protein, DNA and RNA concentrations were significantly (P less than 0.01) higher in buffalo endometrium during the follicular phase than the luteal phase of the oestrous cycle whereas ACP and AKP activities were significantly (P less than 0.01) elevated during the luteal phase compared with the follicular phase. These results are discussed in relation to the nourishment of the blastocyst during the pre-implantation period.     

Ultrastructural and ultracytochemical cyclic changes in the bovine uterine tube (oviduct) epithelium.

Ultrastructural and ultracytochemical features of the uterine tube (oviduct) infundibulum were studied in 8 Hereford cows, which were slaughtered in pairs on days 1 (estrus), 3, 9 or 10, and 18 of the estrous cycle. Fibrous granules (60 to 80 nm), which are supposedly related to basal body replication, were observed in the apical cytoplasm of ciliated cells. Close association between basal bodies and fibrous granules was apparent, especially during the follicular phase. Cilia were observed throughout of estrous cycle, although degeneration of cilia was not observed at any phase of the cycle. Prominent, striated rootlets were observed during both the follicular and luteal phases of the cycle. Maximum secretory cell differentiation was apparent during the follicular phase, at which time these cells were characterized by having a well-developed, rough endoplasmic reticulum with dilated cisternae, numerous ribosomes, and secretory granules of varied size and density. A prominent feature of the secretory granules was their membranous structure, consisting of concentric lamellae of equal dimensions. During the luteal phase, cytoplasmic protrusions were prominent, and extruded nuclei along with other cytoplasmic organelles were present in the tubal lumen. The presence of a well-developed, rough endoplasmic reticulum and numerous secretory granules during the follicular phase indicates that secretory activity of the uterine tube infundibulum may be stimulated by estrogen. During estrus, the cytoplasm of the stromal cells displayed abundant, rough endoplasmic reticulum with dilated cisternae. The increased and extensively dilated rough endoplasmic reticulum at the time of estrus probably indicates increased protein synthesis by the stromal cells. The presence of adenosine triphosphatase activity on the membrane of cilia suggests that this enzyme is involved in energy-forming reactions related to the vigorous action of cilia. The presence of acid phosphatase activity on the cell membrane of the epithelium, microvilli, and secretory granules may indicate involvement in the secretory mechanism of the cell.