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ABSTRACT. To study the role of estrogen in the testes, testosterone and testicular steroidogenic enzyme mRNA levels were investigated in male Sprague-Dawley rats 24 hr after intramuscular administration of a single dose of estradiol-3-benzoate (EB). EB administration resulted in a greater decrease in intra-testicular and serum testosterone in 10-week-old rats than in 3-or 5-week-old rats. A dose of 2 µg EB/kg had the lowest observed effect. The level of serum luteinizing hormone (LH) was unchanged at any dose. Semiquantitative RT-PCR analysis revealed that, of the four major testicular steroidogenic enzymes, mRNA levels of cytochrome P450 side-chain cleavage and 17β-hydroxysteroid dehydrogenase type-III were significantly reduced, and mRNA levels of cytochrome P450 17α-hydroxylase/ C 17-20 lyase (P450c17) were reduced severely and significantly, by EB administration. However, the level of 3β-hydroxysteroid dehydrogenase type-I mRNA was not changed. In addition, the P450c17 mRNA level in EB-treated rats was much lower than that in the testes of hypophysectomized rats, with the level in the latter being equal to that in control rats. LH is secreted into blood periodically, the effects of estrogen on the LH secretion pattern of the pituitary gland, for example, in frequency and amplitude of LH pulse, were difficult to detect with the methods of the present study. The results indicated, at least, that EB administration down-regulates P450c17 gene expression predominantly, resulting in the inhibition of testosterone production. From the differences in the steroidogenic enzyme expressions between hypophysectomized and EB-treated rats, it was suggested that EB acts on the testis directly or indirectly though not via alteration of LH secretion and induces reduction of P450c17 mRNA level. KEY WORDS: estrogen, rat, steroidogenic enzyme, testis, testosterone.J. Vet. Med. Sci. 64(2): 107-113, 2002 It has been documented that estrogen receptor (ER) α is expressed in Leydig cells, rete testes, and efferent ducts [6], and that ERβ is expressed in Sertoli cells and spermatogenic cells [32]. Eddy et al. found that testes in knockout mice lacking a functional ERα (ERKO) were atrophic with disruptions to the seminiferous epithelium and had gross dilations of the seminiferous tubule lumen in adulthood [5].Further studies on ERKO mice demonstrated that the disruption to spermatogenesis in this line was caused by a back pressure of fluid accumulating in the seminiferous tubules due to a lack of reabsorption of fluid in the efferent ductules, which were stimulated by estrogen in the normal male mouse [9]. These reports suggest that estrogen plays important roles in the male reproductive system.Testosterone plays a fundamental role in spermatogenesis and is synthesized by Leydig cells in the testicular interstitium. Estrogen inhibits testosterone production in the testes of many vertebrates, human [18], rat, frog [23], and fish [8]. Both 17β-estradiol (E 2 ) and estradiol-3-benzoate (EB), a synthetic estrogen agonist, are known to h...

The mixed infection of Cucumber mosaic virus (CMV) and a potyvirus has been known to increase CMV titer in Nicotiana benthamiana plants, resulting in synergistic viral symptoms. We found that among three potyviruses--Potato virus Y (PVY), Turnip mosaic virus (TuMV), and Clover yellow vein virus (C1YVV)--synergistic effects on CMV (or a recombinant CMV vector) titers were most efficiently induced by a co-infection with PVY in N. benthamiana plants. In addition, the helper component-proteinase (HC-Pro) gene of PVY expressed by transgenic plants, which is a viral RNA silencing suppressor, was sufficient to cancel the cycling pattern of CMV titer, resulting in increased levels of overall CMV accumulation. Surprisingly, we found that the levels of CMV and the foreign protein expressed from the CMV vector were much higher in the HC-Pro-transgenic plants than the levels detected in the plants mixed-infected with CMV and PVY. The mechanism for canceling the cyclic infection of CMV by the HC-Pro protein alone is discussed in view of the interaction between RNA silencing and HC-Pro, as well as the possible involvement of the 3a protein.

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TCDD (2,3,7,8-tetrachlorodebenzo-p-dioxin) requires the presence of the aryl hydrocarbon receptor (Ahr) gene for its toxic effects, such as reproductive disorders in male offspring of maternally exposed rats and mice. To study the involvement of the Ahr gene in producing the toxic phenotype with respect to testicular development, we administered a relatively high dose of TCDD to mice with three different maternally derived Ahr genotypic traits, and then compared several Ahr-dependent alterations among male reproductive systems on Postnatal Day 14. Reduction in anogenital distance and expression of prostatic epithelial genes in the urogenital complex (UGC) were detected in Ahr(+/+) and Ahr(+/-) mice exposed to TCDD, whereas no difference was observed in Ahr(-/-) mice. In situ hybridization revealed the absence of probasin mRNA expression in the prostate epithelium, despite the obvious development of prostatic lobes in TCDD-exposed mice. In contrast to obvious prostatic dysfunction and induction of cytochrome P450 (CYP) family genes in the UGC by TCDD, no alterations in testicular functions were observed in germ cell/Sertoli cell/interstitial cell marker gene expression or CYP family induction. No histopathological changes were observed among the three genotypes and between control and TCDD-exposed mice. Therefore, mouse external genitalia and prostatic development are much more sensitive to TCDD treatment than testis. Further, the Ahr gene, analyzed in this study, does not significantly contribute to testicular function during perinatal and immature stages, and the developing mouse testis appears to be quite resistant to TCDD exposure.

Salicylic acid (SA), an essential secondary messenger for plant defence responses, plays a role in maintaining a balance (trade‐off) between plant growth and resistance induction, but the detailed mechanism has not been explored. Because the SA mimic benzothiadiazole (BTH) is a more stable inducer of plant defence than SA after exogenous application, we analysed expression profiles of defence genes after BTH treatment to better understand SA‐mediated immune induction. Transcript levels of the salicylic acid glucosyltransferase (SAGT) gene were significantly lower in BTH‐treated Nicotiana tabacum (Nt) plants than in SA‐treated Nt control plants, suggesting that SAGT may play an important role in SA‐related host defence responses. Treatment with BTH followed by SA suppressed SAGT transcription, indicating that the inhibitory effect of BTH is not reversible. In addition, in BTH‐treated Nt and Nicotiana benthamiana (Nb) plants, an early high accumulation of SA and SA 2‐O‐β‐d‐glucoside was only transient compared to the control. This observation agreed well with the finding that SAGT‐overexpressing (OE) Nb lines contained less SA and jasmonic acid (JA) than in the Nb plants. When inoculated with a virus, the OE Nb plants showed more severe symptoms and accumulated higher levels of virus, while resistance increased in SAGT‐silenced (IR) Nb plants. In addition, the IR plants restricted bacterial spread to the inoculated leaves. After the BTH treatment, OE Nb plants were slightly larger than the Nb plants. These results together indicate that SAGT has a pivotal role in the balance between plant growth and SA/JA‐mediated defence for optimum plant fitness.

SummaryA plant viral vector has the potential to efficiently produce recombinant proteins at a low cost in a short period. Although recombinant proteins can be also produced by transgenic plants, a plant viral vector, if available, may be more convenient when urgent scale-up in production is needed. However, it is difficult to use a viral vector in open fields because of the risk of escape to the environment. In this study, we constructed a novel viral vector system using a movement-defective Cucumber mosaic virus (CMV) vector, which is theoretically localized in the inoculated cells but infects systemically only with the aid of the transgenic helper plant that complements viral movement, diminishing the risk of viral proliferation. Interestingly, the helper plant systemically infected with the vector gave strong cross-protection against challenge inoculation with wild-type CMVs. Using CMV strains belonging to two discrete CMV groups (subgroups I and II), we also improved the system to prevent recombination between the vector and the transgene transcript in the helper plant. We here demonstrate the expression of an anti-dioxin single chain variable fragment (DxscFv) and interleukin-1 receptor antagonist (IL1-Ra) in Nicotiana benthamiana by this viral vector confinement system, which is applicable for many useful high-quality recombinant proteins.