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1.
Data from 34 yearling Hereford or Angus bulls were used to investigate relationships of testicular size, quantitative rates of sperm production, Sertoli cell numbers, numbers of germ cells supported per Sertoli cell, and the efficiency of spermatogenesis to daily sperm output and seminal quality. Two ejaculates were collected by electroejaculation from each bull on each of 2 days/week throughout the study. The percentage of progressively motile sperm and the percentage of morphologically normal sperm were determined from aliquots of fresh semen. Additional aliquots of semen were frozen in glass ampules or plastic straws and subsequently evaluated for postthaw motility and percentage of sperm with intact acrosomes. Sertoli cell numbers, the numbers of germ-cells per Sertoli cell, and the efficiency of spermatogenesis were unrelated to the quality of fresh or frozen semen (P greater than 0.05). In first ejaculates, the numbers of sperm and motile sperm were related (P less than 0.05) to testicular parenchymal weight (r = 0.38 and 0.50), daily sperm production (r = 0.45 and 0.53), and spermatids per gram of testicular parenchyma (r = 0.35 and 0.34). Testicular parenchymal weight and daily sperm production also were related to daily sperm output and to the average daily motile sperm output of these bulls (P less than 0.05), but could account for less than 25% of the variability in these end points among bulls. 相似文献
2.
Kuriyama K Kitamura T Yokoi R Hayashi M Kobayashi K Kuroda J Tsujii H 《The Journal of reproduction and development》2005,51(5):657-667
Methyl methanesulphonate (MMS), a potent alkylating agent and testicular toxicant, was orally administered to rats for 5 days at 40 mg/kg. During the recovery period of up to 5 weeks, males were evaluated for testicular toxicity and sperm morphology. The 5-week recovery period were designated as follows: Day 1 (the day after final treatment); Week 1, Week 2, Week 3, Week 4 and Week 5 (1, 2, 3, 4 and 5 weeks after final treatment). Morphologically abnormal sperm increased beginning in Week 3, peaked in Week 4 and declined slightly in Week 5. Histopathological examinations indicated retention of step 19 spermatids at stage IX from Day 1 through Week 3. Quantitative evaluation of spermatogenic cells indicated a decrease in the number of late pachytene spermatocytes and early spermatids on Day 1. TUNEL examination showed a significantly high frequency of apoptosis in the meiosis cells in Week 1. In the present study, genetic damage induced by treatment with MMS affected spermatogenesis and a wide variety of spermatogenic cells in the testis. Apoptosis in the course of meiosis seemed to be involved in the elimination process of genetically insulted germ cells, and this process seems to play an important role in eliminating and/or decreasing the germ cells with retention of spermatids and the potential to express morphologically abnormal spermatozoa. 相似文献
3.
S Romagnoli P Bonaccini C Stelletta A Garolla M Menegazzo C Foresta A Mollo C Milani D Gelli 《Reproduction in domestic animals》2009,44(S2):329-333
Clinical investigation of canine testicular function is complicated by the difficulty in the evaluation of seminiferous tubules. Until recently, testicular biopsy was the only diagnostic option for dogs with persistent oligo/azoospermia. In human andrology, testicular fine needle aspiration (TFNA) is currently considered a useful method in the evaluation of azoospermia and severe oligozoospermia, and has long replaced classical biopsy to evaluate spermatogenesis. In order to verify its diagnostic efficacy for the clinical approach to canine oligo- or azoospermia, TFNA was performed in seven adult (two oligozoospermic and five azoospermic) dogs. After sedation, a fine (21–23 gauge) butterfly needle connected to a 50-ml syringe was inserted into each testicle; strong suction was applied and the aspirated fluid squirted on a glass slide, smeared out, air-dried and stained with a modified May–Grunwald–Giemsa. Under light microscopy, Sertoli cells (all those found in each investigated field) and spermatogenic cells (n = 100) were counted on each smear in order to differentiate spermatogonia, primary spermatocytes, secondary spermatocytes, early spermatids, late spermatids and spermatozoa, and calculate their relative percentages. Cytological analysis showed the following testicular pictures: normal spermatogenesis (compatible with obstruction of the seminal ducts), hypospermatogenesis, maturative disturbances and Sertoli cell-only syndrome. Two dogs with an obstructive lesion were treated with corticosteroids; one of them recovered and sired two litters of puppies. 相似文献
4.
Lucile Bodet Olivier Albaric Emmanuel Topie Elie Dagher Florian Chocteau Anne Gogny 《Reproduction in domestic animals》2020,55(10):1343-1354
In cats, assessment of the testicular function is mainly based on sperm evaluation. Whatever the technique used, the volume of collected sperm is often small, which may lead to technical difficulties to achieve the semen evaluation in routine practice. Fine-needle aspiration (FNA) biopsy of the testicular parenchyma is one of the other methods used to assess testicular function. The aim of this study was to explore the relevance of FNA in the assessment of testicular cells in sexually mature cats. Eighteen cats over one year of age were recruited among animals presented for surgical neutering. Semen was collected by electroejaculation before it was evaluated. FNA biopsies of the testicles were taken using a 21-gauge needle. After castration, histological analysis of the testes was performed. Semen evaluation and histological analysis showed no anomalies, which confirmed normal spermatogenesis in all the cats and allowed a proper interpretation of the cytological findings. The cells identified through cytological examination were spermatogonia (1.99 ± 0.17%), primary spermatocytes (10.49 ± 0.74%), round spermatids (34.80 ± 1.57%), elongated spermatids (23.59 ± 2.02%), spermatozoa (21.56 ± 1.86%), Sertoli cells (7.53 ± 1.23%) and Leydig cells (0.04 ± 0.03%). However, spermatocytes II were not identified. This is due to the low proportions of these cells, related to their very short lifespan. Likewise, the very low number of Leydig cells observed is probably due to the damage caused during the aspiration stage. This study showed that fine-needle aspiration is an efficient method to describe cytologically normal testicular populations, a cornerstone for future research aimed to study abnormal spermatogenesis and to correlate it to cytological proportion of germ cells. 相似文献
5.
The objective of this study was to investigate reproductive characteristics of stallions at a tropical zone in the breeding and non-breeding seasons. The following parameters were assessed: testicular volume; semen quality; and serum concentrations of LH, FSH, and testosterone; in addition to the percentages of germ cells and proportions of germ cells/Sertoli cells by testicular cytology in stallions. Semen was collected from eight adult stallions twice a week during a 12-week period in both seasons (6?weeks before and 6?weeks after the summer and winter solstices). Jugular blood samples were collected periodically for hormone analysis by radioimmunoassay during the same periods. Testicular measures and cytological samples were taken at the end of each period. Mean concentration of testosterone was significantly higher (P?=?0.04) during the breeding season and the proportion of Sertoli cells/100 germ cells in cytological smears was significantly lower during the breeding season (P?=?0.0001). Effects of season were not significant either for testicular volume or for any semen parameter (P?>?0.05). Seasonal changes in the mean concentrations of LH and FSH were not observed (P?>?0.05). There were also no significant differences in the mean percentages of germ cell types between both seasons (P?>?0.05). Lack of seasonal differences in the testicular volume and semen parameters of tropical stallions are probably due to the small variation in duration of natural light between the observed periods, slightly under 3?h. 相似文献
6.
The removal of endogenous germ cells of recipient stallions is a key step to produce donor germ cell-derived sperm using the germ cell transplantation technique. Six Thoroughbred stallions were divided into a treatment (n = 3) and a control group (n = 3), and 70% glycerin (1, 2, 3-trihydroxypropane, 40 mL per testis) or phosphate-buffered saline, respectively, was locally injected into testes. General semen evaluation, libido, and testicular volume were performed weekly from 3 weeks before to 10 weeks after treatment. The number of round germ cells in the ejaculate was counted using a hemocytometer. The hematoxylin and eosin staining was performed on the cross sections of testicular tissue obtained 11th week of treatment. Plasma testosterone levels in blood collected weekly were measured using a colorimetric competitive enzyme immunoassay kit. The sperm number was significantly lower than that of the control group at 5 and 10 weeks after glycerin injection. No differences in the status of spermatogenesis in the cross sections of seminiferous tubules and testicular volume were found between the two groups. The 70% glycerin-treated stallions had reduced total and progressively motile sperm and exhibited a significantly higher population of round germ cells in the ejaculate. Testosterone levels, testicular volumes, and libido of stallions were not significantly different between the groups. In conclusion, although intratesticular injection of 70% glycerin may have caused disassociation of some germ cells in the seminiferous tubules for several weeks, it did not significantly ablate germ cells in the tubules at 11 week in stallions. 相似文献
7.
VASA (DDX4) is a Putative Marker for Spermatogonia,Spermatocytes and Round Spermatids in Stallions 
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下载免费PDF全文 Expression of the protein DDX4/MVH, or VASA, has been reported in germ cells of several species. The main objectives of this study were to (i) investigate VASA expression patterns in testicular cells of stallions at two different reproductive stages (pre‐pubertal and post‐pubertal) and (ii) evaluate the use of VASA antibody as a molecular marker for single germ cells from stallions. Testicular tissues were obtained from stallions and categorized as pre‐pubertal and post‐pubertal based on the formation of lumen and status of spermatogenesis on the cross section of seminiferous tubules. The results of Western blot showed a VASA protein band located at 76 kDa, indicating that the rabbit antibody has a cross‐reactivity with horse testicular tissues. The result of immunolabelling showed that VASA was expressed in the cytoplasm of spermatogonia at both reproductive stages and in spermatocytes and round spermatids at the post‐pubertal stage. GATA4‐positive Sertoli cells and Leydig cells located in the interstitial space were not immunolabelled with VASA. These results suggest that VASA can be utilized as a molecular marker for germ cells of stallions at pre‐pubertal and post‐pubertal stages. Interestingly, immunolabelling intensity was significantly higher in pachytene spermatocytes compared to spermatogonia and round spermatid. VASA antibody was also effective for staining of single germ cell preparations. In conclusion, VASA protein expression can be used as a marker for identification of spermatogonia, spermatocytes and round spermatids in testicular tissues of stallions. 相似文献
8.
Masamichi Kurohmaru Toshiyasu Matsui Hitomi Igarashi Shosaku Hattori Yoshihiro Hayashi 《Anatomia, histologia, embryologia》2021,50(2):417-421
The postnatal testicular development and actin distribution in the seminiferous epithelium were examined by light microscopy, using the testes of the Habu (Trimeresurus flavoviridis; snake) from 0-year-old to 3-year-old. At 0-year-old (about 1 month after birth), the testis was quite small in size, and the seminiferous epithelium was composed of only Sertoli cells and large spermatogonia. Actin immunoreactivity was observed in the peritubular myoid cells, but could not be detected in the seminiferous epithelium. At 1-year-old (about 10 months after birth), the testicular size increased to a great degree. In the seminiferous epithelium, spermatocytes newly appeared. Actin could still not be detected in the seminiferous epithelium. At 2-year-old (about 1 year and 10 months after birth), the testes continued to develop in size. In the seminiferous epithelium, elongate spermatids and round spermatids were frequently seen, in addition to Sertoli cells, spermatogonia and spermatocytes. Thus, active spermatogenesis was clearly recognized at this age. Moreover, the actin distribution in the seminiferous epithelium was observed at the site between Sertoli cells and spermatids, as well as that at adult stage. The immunoreactivity of actin in the peritubular myoid cells gradually increased from 0-year-old to 2-year-old. Conclusively, it seems likely that spermatogenesis in the Habu initiates at 2-year-old, accompanying with the appearance of actin in the seminiferous epithelium. 相似文献
9.
Fifteen stallions of different breeds, age 3-11 years, had their right testicles evaluated by fine needle aspiration cytology (FNAC). Cytological analysis showed the following spermatogenic cell types: spermatogonia (1.6% +/- 1.1); spermatocyte I (3.4% +/- 2.2); spermatocyte II (0.8% +/- 0.7); early spermatids (25.5% +/- 9.5); late spermatids (37.0% +/- 9.3). Spermatozoal numbers were expressed as the spermatic index (SI = 31.5% +/- 8.5) and Sertoli cells were expressed as the Sertoli cell index (SEI = 20.9% +/- 17.0) (means +/- s.d). Identification of cell types was relatively easy and no immediate adverse effects of aspiration were noted. The results suggest that FNAC of testis may assist clinical diagnosis in the study of male equine infertility. 相似文献
10.
In spite of widespread application of flutamide in the endocrine therapies of young and adult patients, the side effects of this antiandrogen on spermatogenesis and germ‐cell morphology remain unclear. This study evaluates the short‐term androgen blockage effect induced by the administration of flutamide to the testes of pubertal (30‐day old) and adult (65‐ and 135‐day old) guinea pigs, with an emphasis on ultrastructural alterations of main cell types. The testes removed after 10 days of treatment with either a non‐steroidal antiandrogen, flutamide (10 mg/kg of body weight) or a pharmacological vehicle alone were processed for histological, quantitative and ultrastructural analysis. In pubertal animals, flutamide androgenic blockage induces spermatogonial differentiation and accelerates testes maturation, causing degeneration and detachment of primary spermatocytes and round spermatids, which are subsequently found in great quantities in the epididymis caput. In post‐pubertal and adult guinea pigs, in addition to causing germ‐cell degeneration, especially in primary spermatocytes, and leading to the premature detachment of spherical spermatids, the antiandrogen treatment increased the relative volume of Leydig cells. In addition, ultrastructural evaluation indicated that irrespective of age antiandrogen treatment causes an increase in frequency of organelles involved with steroid hormone synthesis in the Leydig cells and a dramatic accumulation of myelin figures in their cytoplasm and, to a larger degree, in Sertoli cells. In conclusion, the transient exposition of the guinea pigs to flutamide, at all postnatal ages causes some degenerative lesions including severe premature detachment of spermatids and accumulation of myelin bodies in Leydig and Sertoli cells, compromising, at least temporarily, the spermatogenesis. 相似文献
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Kawakami E Hori T Tsutsui T 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2000,62(2):203-206
Three dogs diagnosed as having asthenozoospermia were given three intramuscular injections of 50 mg testosterone(T)-depot plus 250 IU pregnant mare serum gonadotropin (PMSG) at 2-week intervals, and their plasma T and testicular transferrin (Tf) concentrations, testicular histology, and semen quality were examined during the period of hormone therapy. Plasma T concentrations temporarily increased, and there was a slight improvement in spermatogenesis. Increased Tf concentrations suggested that Sertoli cell function in all three dogs was promoted by hormone treatment. The results showed that semen quality, especially the percentages of motile sperm and abnormal sperm, were improved between 1 and 5 weeks after the start of T-depot plus PMSG treatment. 相似文献
14.
An experiment involving a total of 61 crossbred boars evaluated the effects of dietary Se and vitamin E on spermatogenic development at various stages of sexual development and the prostaglandin F2alpha (PGF2alpha) content in the seminal vesicle and prostate glands at 18 mo of age. The experiment from 5.4 to 9 mo of age was conducted as a 2 x 2 factorial in a randomized complete block design. Dietary Se at 0 or .5 ppm was the first factor and vitamin E at 0 or 220 IU/kg diet was the second. From 9 to 18 mo of age, a group of sexually active and inactive boars was a third factor. Treatment diets were fed from weaning (28 d of age) to the end of the experiment. Three boars per treatment group at 5.4 (105 kg BW), 6.2 (130 kg BW), and 9.0 (150 kg BW) mo of age were killed and the testes collected. From 9 to 18 mo of age, three boars from each dietary treatment group were used for semen collection, and another set of three to four boars from each treatment group remained sexually inactive. At 18 mo, both sets of boars were killed and their testes, prostates, and seminal vesicles were collected. The testis at each age was evaluated for sperm reserve numbers and germ and Sertoli cell populations. At 5.4 or 6.2 mo of age, testicular sperm reserves were not affected by dietary Se (P > .15), at 9.0 mo of age there was a trend for a higher (P < .10) number of sperm reserves, and by 18 mo of age the Se-fed boars had higher (P < .01) numbers of sperm reserves. Vitamin E had no effect (P > .15) on testicular sperm reserves at any age period. Boars fed dietary Se had a greater number of Sertoli cells (P < .01) and round spermatids (P < .01) at 6.2 mo of age, but by 18 mo of age the boars fed Se had more Sertoli cells (P < .05), more secondary spermatocytes (P < .01), and more round spermatids (P < .05). Vitamin E did not affect Sertoli or germ cell populations at the various ages. Boars at 18 mo of age had lower PGF2alpha concentrations in the prostate (P < .05) and seminal vesicles (P < .01) when vitamin E was fed, whereas Se had no effect. Sexually active boars had lower PGF2alpha concentrations in the seminal vesicles (P < .01) than sexually inactive boars, but there was no effect (P > .15) of sexual activity on the number of Sertoli cells, primary or secondary spermatocytes, or round spermatids. Our results indicate that Se has a role in establishing the number of boar spermatozoal reserves and Sertoli cells, whereas supplemental vitamin E did not affect these criteria. 相似文献
15.
Azoospermia is described in two sibling Labrador Retriever dogs. Clinical investigations following failure to sire pups after normal matings revealed testicular hypoplasia and degeneration. Sperm were absent on repeated ejaculate examination in both dogs. Histopathological examination of testicular needle aspirate biopsy and whole testicle of the first dog displayed an absence of spermatids and spermatocytes. Seminiferous tubules containing Sertoli cells with or without primary spermatogonia were present in the second dog. Peritubular lymphocyte accumulation was also present in both dogs. The dogs had been conceived using frozen-thawed semen. 相似文献
16.
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. 相似文献
17.
Junaidi A Williamson PE Trigg TE Cummins JM Martin GB 《Reproduction in domestic animals》2009,44(5):757-763
The present study is part of a programme of research designed to evaluate the efficacy of the GnRH superagonist,deslorelin (D-Trp6-Pro9-des-Gly10-LHRH ethylamide), as a contraceptive for male dogs. Adult dogs were assigned to a completely randomized design comprising six groups of four animals. Each dog in the control group received a blank implant (placebo) and each dog in the other five groups received a 6 mg deslorelin implant. One group of deslorelin treated dogs was sacrificed on each of days 16, 26, 41, 101 and 620, and testicular and prostate tissues were collected for study by light and electron microscopy. On days 16 and 26 after implantation, we observed partial disruption of the seminiferous tubules, with early spermatids shed into the lumen. On days 41 and 101 after implantation, 90–100% of the seminiferous tubules were atrophic and aspermatogenic.On day 101 after implantation, 99% of all sections showed atrophy of the epithelium and shrinkage of epithelial height in the ductus epididymides. On days 41 and 101 after implantation, prostate tissue showed complete atrophy of the glandular epithelium (100% of sections) and an apparent increase in the relative proportion of connective tissue. At the electron microscopic level, in dogs treated with deslorelin for 41 and 101 days, the Sertoli cells were smaller and their nucleoli appeared smaller than in the control dogs. The nucleoli of the Leydig cells were atrophied and prostate glandular epithelium showed reduced epithelial height, a trophy of the nucleolus and an absence of secretory granules.Tissues collected during the recovery phase revealed a complete recovery of spermatogenesis. In conclusion, slow release implants containing deslorelin induce a striking a trophy of the testes and prostate gland by 26 days after implantation, explaining the previously reported loss of ejaculate and arrest of sperm output. At histological level,the entire process appears to be completely reversible, in accordance with data on endocrine variables and semen production. 相似文献
18.
The current study evaluated effects of quinestrol on oxidative stress and abnormal spermatogenesis for male Mongolian gerbils. Gerbils were randomly divided into multi-dose treated, single-dose treated, control groups. At 15 days after treatment antioxidant enzymes (SOD, GSH-Px) activities and T-AOC were decreased whereas the MDA concentration was significantly increased, testicular weight and seminiferous tubular areas decreased, germ cells were rarefied and showed irregular distribution in seminiferous tubules, apoptosis was pronounced among spermatocytes and spermatids, the number of dead and abnormal acrosomes of spermatozoa increased significantly in quinestrol treated groups. At 30 days following treatment the testicular histopathological changes were more severe, sperm quality and antioxidant capacity continued to decline, and multi-dose treatment produced more damage to gerbils testes compared with single-dose treatment. The physiological indicators were recovered by 60 days of treatment withdrawal. The results showed oxidative stress induced by quinestrol in relation to abnormal spermatogenesis. 相似文献
19.
Okano T Murase T Tsubota T 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2003,65(10):1093-1099
Twenty-one wild male Japanese black bears (Ursus thibetanus japonicus) were captured in the summer-autumn of 1998-2000 in the vicinity of Neo Village, Gifu Prefecture. Testes were measured, and testicular samples were biopsied and observed histologically. Four steroidogenic enzymes, i.e., cholesterol side-chain cleavage cytochrome P450 (P450scc), 3beta-hydroxysteroid dehydrogenase (3betaHSD), 17-alpha hydroxylase cytochrome P450 (P450c17), and aromatase cytochrome P450 (P450arom) were immunolocalized. Serum testosterone concentrations were measured by radioimmunoassay. Testis size changed little from 1-3 years of age, increased rapidly at 4 years, and attained its peak at 5 years. Serum testosterone concentrations ranged from 0.05 to 1.78 ng/m l, and the mean +/- standard deviation was 0.43 +/- 0.48 ng/ml. Age of sexual maturation in wild male Japanese black bears was estimated to be 3-4 years. Seasonal changes in spermatogenesis were obvious; active in June, July and August, degenerated by September. Leydig cells, Sertoli cells and germ cells have the capability of synthesizing androgen, and Leydig cells, Sertoli cells, spermatids and spermatogonia have the capability of synthesizing estrogen in Japanese black bears. 相似文献
20.
Expression of retinoic acid‐metabolizing enzymes,ALDH1A1, ALDH1A2, ALDH1A3, CYP26A1, CYP26B1 and CYP26C1 in canine testis during post‐natal development 下载免费PDF全文
下载免费PDF全文 VR Kasimanickam 《Reproduction in domestic animals》2016,51(6):901-909
Mammalian spermatogenesis involves highly regulated temporal and spatial dynamics, carefully controlled by several signalling processes. Retinoic acid (RA) signalling could have a critical role in spermatogenesis by promoting spermatogonia differentiation, adhesion of germ cells to Sertoli cells, and release of mature spermatids. An optimal testicular RA concentration is maintained by retinaldehyde dehydrogenases (ALDHs), which oxidize RA precursors to produce RA, whereas the CYP26 class of enzymes catabolizes (oxidize) RA into inactive metabolites. The objective was to elucidate gene expression of these RA‐metabolizing enzymes (ALDH1A1, ALDH1A2, ALDH1A3, CYP26A1, CYP26B1 and CYP26C1) and their protein presence in testes of young, peripubertal and adult dogs. Genes encoding RA‐synthesizing isozymes ALDH1A1, ALDH1A2 and ALDH1A3 and RA‐catabolizing isomers CYP26A1, CYP26B1 and CYP26C1 were expressed in testis at varying levels during testicular development from birth to adulthood in dogs. Based on detailed analyses of mRNA expression patterns, ALDH1A2 was regarded as a primary RA‐synthesizing enzyme and CYP26B1 as a critical RA‐hydrolysing enzyme; presumably, these genes have vital roles in maintaining RA homeostasis, which is imperative to spermatogenesis and other testicular functions in post‐natal canine testis. 相似文献