Pathway of testosterone biosynthesis in the testis of the marmoset Saguinus oedipus

These studies were undertaken to determine the principal pathway of androgen biosynthesis by the testis of the marmoset $\text{Saguinus oedipus}$. Testicular fragments (25 mg) were incubated at 37°C in Krebs-Ringer bicarbonate buffer, pH 7.4, containing pregnenolone-7-³H (3β-hydroxy-5-pregnen-20-one) or progesterone-7-³H. Duplicate fragments were incubated with each substrate for 30 min, one hr, three hr, or five hr, for a total of 16 separate incubations. Metabolites were separated by paper and thin-layer chromatography, with identity established by recrystallization to constant specific activities and ³H/¹⁴C ratios. Pregnenolone was readily metabolized to progesterone, 17α-hydroxyprogesterone, androstenedione (4-androstene-3, 17-dione) and testosterone. Progesterone was converted to 17α-hydroxyprogesterone, androstenedione and testosterone. 17α-hydroxyprogesterone was the predominant metabolite obtained from both substrates at one, three and five hrs of incubation. Neither 17α-hydroxypregnenolone (3β-17-dihydroxy-5-pregnen-20-one) nor dehydroepiandrosterone (3β-hydroxy-5-androsten17-one) was detected in the incubates. These data suggest a predominant Δ⁴ pathway with accumulation of 17α-hydroxyprogesterone in the testis of this primate specie.     

Adrenal glands of mouse and rat do not synthesize androgens.

Human adrenal glands produce considerable amounts of the C-19 steroids dehydroepiandrosterone (DHEA) and androstenedione. To investigate the capability of rodent adrenals to produce these steroids, cell suspensions of mouse and rat adrenal glands were incubated in the absence and presence of adrenocorticotropic hormone (ACTH). Corticosterone levels in the incubation medium increased dramatically in the presence of ACTH, but no significant amounts of 17-hydroxyprogesterone or androstenedione could be detected. This indicates that the adrenals of rat and mouse lack the enzyme 17 alpha-hydroxylase. Absence of plasma cortisol in the presence of high levels of corticosterone confirmed these data. Plasma levels of androstenedione were significantly decreased in castrated male rats as compared to levels observed in intact males, showing the contribution of the testes to the plasma content of androstenedione. Very low levels of androstenedione were observed in female, male and castrated male mice. Plasma concentrations of DHEA were not detectable in intact and castrated male mice and rats. It is concluded that rat and mouse lack the enzyme necessary to synthesize adrenal C-19 steroids and that the adrenals in these animals, therefore, do not contribute to plasma levels of androstenedione and DHEA.     

Steroid hormones as bactericidal agents to Helicobacter pylori

Helicobacter pylori is a unique bacterial species that assimilates various steroids as membrane lipid components. Our group has recently found, however, that certain steroids may impair the viability of H. pylori. In this study, we go on to reveal that estradiol, androstenedione, and progesterone (PS) all have the potential to inhibit the growth of H. pylori. Of these three steroid hormones, progesterone demonstrated the most effective anti-H. pylori action. 17α-hydroxyprogesterone caproate (17αPSCE), a synthetic progesterone derivative, had a much stronger anti-H. pylori action than progesterone, whereas 17α-hydroxyprogesterone, a natural progesterone derivative, completely failed to inhibit the growth of the organism. Progesterone and 17αPSCE were both found to kill H. pylori through their bacteriolytic action. Among five bacterial species investigated, H. pylori was the only species susceptible to the bactericidal action of progesterone and 17αPSCE. The other four species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epiderimidis, all resisted this action. Progesterone and free-cholesterol (FC) obstructed each other's effects against the H. pylori cell. Taken in sum, these results suggest that progesterone and FC may bind to the identical region on the H. pylori cell surface. We expect these findings to contribute to the development of a novel anti-H. pylori steroidal agent.     

Endocrine correlates of pregnancy in the ring-tailed lemur (Lemur catta): implications for the masculinization of daughters

Female ring-tailed lemurs (Lemur catta) are Malagasy primates that are size monomorphic with males, socially dominate males, and exhibit a long, pendulous clitoris, channeled by the urethra. These masculine traits evoke certain attributes of female spotted hyenas (Crocuta crocuta) and draw attention to the potential role of androgens in lemur sexual differentiation. Here, hormonal correlates of prenatal development were assessed to explore the possibility that maternal androgens may shape the masculine morphological and behavioral features of developing female lemurs. Maternal serum 17α-hydroxyprogesterone, dehydroepiandrosterone sulphate (DHEA-S), ?⁴ androstenedione (androst-4-ene-3,17,dione), testosterone, and 17β-estradiol were charted throughout the 19 pregnancies of 11 ring-tailed lemurs. As in spotted hyenas, lemur pregnancies were associated with an immediate increase in androgen concentrations (implicating early maternal derivation), followed by continued increases across stages of gestation. Pregnancies that produced singleton males, twin males, or mixed-sex twins were marked by greater androgen and estrogen concentrations than were pregnancies that produced singleton or twin females, especially in the third trimester, implicating the fetal testes in late-term steroid profiles. Concentrations of DHEA-S were mostly below detectable limits, suggesting a minor role for the adrenals in androgen biosynthesis. Androgen concentrations of pregnant lemurs bearing female fetuses, although less than those of pregnant hyenas, exceeded preconception and postpartum values and peaked in the third trimester. Although a maternal (and, on occasion, fraternal) source of androgen may exist for fetal lemurs, further research is required to confirm that these steroids would reach the developing female and contribute to her masculinization.     

Steroid hormone formation in bovine ovarian follicles.

In an attempt to assess histophysiological implication of the follicular compartment of the bovine ovary in steroid hormone formation and the effect of human chorionic gonadotropin (hCG) in vitro on follicular steroidogenesis, minces of follicular tissues from non-gravid bovine ovaries were incubated with radioactive testosterone or acetate in the presence and absence of hCG. Significant amounts of estrone and estradiol-17beta were formed on incubation with testosterone-4-14C; hCG decreased the conversion approximately by 30%. The major radioactive products formed from acetate-l-14C were androstenedione and testosterone with lesser amounts of dehydroepiandrosterone and 17-hydroxyprogesterone. In addition, small amounts of progesterone, 17-hydroxypregnenolone, estrone and estradiol-17beta were formed. Histology of the dissected follicle specimens was characterized by dominant theca cells undergoing luteinization with small amounts of granulosa cells, which showed neither proliferation nor luteinization. The pattern of distribution of radioactivity among the steroids formed from acetate-14C was considered to represent steroidogenic profile of bovine atretic follicles. The addition of hCG in vitro increased the overall incorporation of radioactive acetate into the steroids approximately by 50%, although the range of increase was not uniform in the individual steroids under the exprimental conditions.     

Developmental changes of serum steroids produced by cytochrome P450c17 in rat

Serum levels of 17-hydroxypregnenolone, dehydroepiandrosterone, 17-hydroxyprogesterone, and androstenedione were measured during the postnatal development of rats 1-14 weeks of age. A significant decrease in the serum levels of these steroids with increasing age was observed, using multiple regression analysis: 17-hydroxypregnenolone (beta= -1.56, S.E.= 0.25, P < 0.00001), dehydroepiandrosterone (beta= -0.43, S.E.= 0.07, P < 0.00001), 17-hydroxyprogesterone (beta= -2.51, S.E.= 0.45, P < 0.00001), and androstenedione (beta= -1.63, S.E.= 0.33, P < 0.00001). A sex-related difference was not found. The observed decline in the serum levels of the steroids was directly proportional to the previously reported decrease in mRNA expression and enzyme activity of cytochrome P450c17 in the rat liver. Yet, despite this decrease to undetectable levels in liver after 7-8 weeks, significant amounts of 17-hydroxypregnenolone, 17-hydroxyprogesterone, dehydroepiandrosterone, and androstenedione were still observed in the rat serum. This may partly be due to the mRNA expression of cytochrome P450c17 in tissues other than the liver, such as the testis and/or duodenum, after 4 weeks of age. Serum levels of pregnenolone, progesterone, and corticosterone in the developing rats were also examined.     

Effects of 17-hydroxyprogesterone caproate (17-OHPC) administration to pregnant squirrel monkeys (Saimiri boliviensis boliviensis)

Poor reproductive performance of the squirrel monkey (Saimiri boliviensis boliviensis) in captivity and a relative progesterone (P) deficiency in pregnancy have been reported. Since premature births may contribute to pregnancy wastage, we attempted to measure the effectiveness of 17-hydroxyprogesterone caproate (17-OHPC) treatment of pregnant squirrel monkeys to prevent early deliveries. Based on clearance studies of nonpregnant animals, 25 mg of 17-OHPC was administered at 6-day intervals to a test group of 31 pregnant monkeys while the control group of 29 received saline. Venous blood was obtained at 6- to 12-day intervals for measurement of 17-hydroxyprogesterone (17-OHP), P, 17-B estradiol (E), and androstenedione (A), and dihydroepiandrosterone (DHEA) levels by radioimmunoassays. The treated group had a significant increase in serum 17-OHP (P < 0.001), P (P < 0.01), and DHEA (P < 0.05) levels compared to controls. The numbers of live births, stillbirths, or neonatal deaths did not differ significantly between groups. Although 17-OHPC administration appeared to increase P and 17-OHP levels, this did not alter the duration of pregnancy nor delay the onset of labor. A significant fall in 17-OHP, P, and E levels was observed 6–12 days before delivery.     

Evidence for the secondary sexual development of the anal fin in female kokanee salmon Oncorhynchus nerka

This study examines whether the anal fin undergoes secondary sexual development similar to other reproductive traits in salmonids. This hypothesis was tested by comparing the anal‐fin size of female kokanee salmon Oncorhynchus nerka that were in the early and late stages of sexual development. Females in an advanced stage of maturation had significantly larger anal fins relative to females in an early state of maturation (+4–7%), indicating that the anal fin undergoes secondary sexual development. The magnitude of this secondary growth was comparable with snout length (+9–10%), which is known to undergo secondary sexual development in female salmonids. When morphological trait dimensions were compared between the sexes, the anal fin was the only morphological trait found to have a female‐biased sexual size dimorphism. This is the first study to show that the anal fin of female salmonids undergoes secondary sexual development.     

Developmental patterns of serum luteinizing hormone, gonadal and adrenal steroids in the sooty mangabey (Cercocebus atys)

Serum levels of luteinizing hormone (LH), testosterone, dehydroepiandrosterone sulfate (DHAS), androstenedione and cortisol were determined in multiple samples from 86 sooty mangabeys of varying ages (0-17 years). Testosterone, androstenedione, DHAS and cortisol were measured by radioimmunoassay; LH was determined by in vitro bioassay. Serum LH concentrations were elevated in neonates (less than 6 months) and in animals older than 72 months of age. The higher LH levels were associated with increased circulating concentrations of testosterone in males but not females. The pubertal rise in serum testosterone at approximately 55-60 months of age in males was coincident with rapid body growth. No pubertal growth spurt was observed in females. Serum levels of androstenedione and DHAS were highest during early postnatal life (less than 6 months) with androstenedione exceeding 600 ng/dl in males and 250 micrograms/dl in females, but declined rapidly in both sexes to a baseline of 150 ng/dl by 19 months of age. Serum androstenedione did not fluctuate significantly in adult animals. The pattern of age-related changes in serum DHAS paralleled those of serum androstenedione, whereas serum cortisol values did not change significantly with age. Developmental changes in serum LH, testosterone and body weight suggest that the sooty mangabey matures substantially later than the rhesus monkey. The pattern of serum gonadal and adrenal steroids during sexual maturation is similar to that seen in the baboon with no evidence of an adrenarche.     

Effect of acute ACTH administration on plasma steroid levels in the dog

Production of adrenal steroids in intact and castrated dogs is stimulated acutely by ACTH. While the increase in plasma cortisol, 17-hydroxypregnenolone and 17-hydroxyprogesterone is not affected by castration, the increment of dehydroepiandrosterone is totally abolished. On the other hand, administration of 17-hydroxypregnenolone in adrenalectomized dogs caused an increase in plasma C-19 steroids such as dehydroepiandrosterone, androstenedione and testosterone indicating that this C-21 progestin in plasma is rapidly converted. The site of this conversion is likely the testis. Furthermore, acute hCG administration in adrenalectomized dogs resulted in a marked increase in the levels of plasma 17-hydroxypregnenolone and dehydroepiandrosterone. However, our data show an ACTH-induced rise in 5-androstene-3 beta. 17 beta-diol in intact and castrated dogs, thus suggesting that this steroid is a good parameter to assess in the stimulation of adrenal steroidogenesis by ACTH.     

Effects of cadmium in vitro on microsomal steroid metabolism in the inner and outer zones of the guinea pig adrenal cortex

Studies were carried out to evaluate the effects of cadmium in vitro on microsomal steroid metabolism in the inner (zona reticularis) and outer (zona fasciculata and zona glomerulosa) zones of the guinea pig adrenal cortex. Microsomes from the inner zone have greater 21-hydroxylase than 17α-hydroxylase activity, resulting in the conversion of progesterone primarily to 11-deoxycorticosterone and of 17α-hydroxy progesterone principally to its 21-hydroxylated metabolite, 11-deoxycortisol. Microsomes from the outer zones, by contrast, have far greater 17α-hydroxylase and C_17,20-lyase activities than 21-hydroxylase activity. As a result, progesterone is converted primarily to its 17-hydroxylated metabolite, 17α-hydroxyprogesterone; and 17α-hydroxyprogesterone is converted principally to δ⁴-androstenedione, with only small amounts of 21-hydroxylated metabolites being produced. Addition of cadmium to incubations with inner zone microsomes causes concentration-dependent decreases in 21-hydroxylation and increases in 17α-hydroxylase and C_17,20-lyase activities, resulting in a pattern of steroid metabolism similar to that in normal outer zone microsomes. Cadmium similarly decreases 21-hydroxylation by outer zone microsomes but has no effect on the formation of 17-hydroxylated metabolites or on androgen (Δ⁴-androstenedione) production. In neither inner nor outer zone microsomes did cadmium affect cytochrome P-450 concentrations, steroid interactions with cytochrome(s) P-450, or NADPH–cytochrome P-450 reductase activities. The results indicate that cadmium produces both quantitative and qualitative changes in adrenal microsomal steroid metabolism and that the nature of the changes differs in the inner and outer adrenocortical zones. In inner zone microsomes, there appears to be a reciprocal relationship between 21-hydroxylase and 17α-hydroxylase/C_17,20-lyase activities which may influence the physiological function(s) of that zone.     

Female Preference for Male Lateral Projection Area in the Shortfin Molly, Poecilia mexicana: Evidence for a Pre-existing Bias in Sexual Selection

Sailfin molly (Poecilia latipinna) males possess a large dorsal fin (sailfin) and perform an elaborate courtship display. Females prefer to associate and mate with males of greater body and sailfin size. Evidence supports a single origin for the sailfin species complex from a shortfin ancestor. Unlike sailfin species, males of the shortfin species complex are sexually monomorphic in fin size and exhibit little or no courtship behavior. In this study, we tested the pre‐existing bias and lateral projection area (LPA) hypotheses for sexual selection by examining female mating preferences in the shortfin molly, P. mexicana. Specifically, we presented females with pairs of dummy males differing in: (1) dorsal fin and body size together (holding fin:body size ratio constant); (2) body size (holding dorsal fin size constant); (3) dorsal fin size (holding body size constant); and dorsal fin:body size ratio (holding total LPA constant). Females spent more time near dummies of greater body and dorsal fin size. The preference functions based on the first three sets of stimuli showed a similar pattern: the greater the LPA difference between paired dummies, the stronger the preference for the larger of the two. However, in the fourth experiment, neither fin size, body size, nor any particular dorsal fin + body size combination was preferred. These findings support the LPA hypothesis suggesting that increased LPA is more stimulating to sexually receptive females and that females consequently prefer larger males. Moreover, these data are consistent with results obtained in an identical series of experiments conducted on P. latipinna. The preference for increased male dorsal fin size/LPA by both female P. latipinna and P. mexicana supports the pre‐existing bias hypothesis. Thus, a bias for increased male LPA and consequent selection for enlarged dorsal fins may have preceded the appearance of the sailfin trait within the Molliensia lineage.     

Biosynthesis and metabolism of testosterone by sertoli cell-enriched seminiferous tubules

Sertoli cell-enriched tubules isolated from rats which had been treated with 1,4-dimethyl sulfonyloxybutane were incubated with either [¹⁴C] progesterone or [¹⁴C] testosterone for 2 hours. Tubules of normal rats and fragments of Sertoli cell-enriched testes were incubated under the same conditions. Sertoli cell-enriched tubules converted progesterone to 20α-dihydroprogesterone, 17α-hydroxyprogesterone, androstenedione and testosterone. The major metabolite was 20α-dihydroprogesterone. The percentage conversion of progesterone into testosterone corresponded to a production of 10–20 ng testosterone. Sertoli cell-enriched tubules converted testosterone to dihydrotestosterone, androstenedione, 3α-androstanediol and 3β-androstanediol. Under our experimental conditions, dihydrotestosterone was the major 5α-reduced metabolite. Normal tubules converted progesterone and testosterone to the same metabolites as Sertoli cell-enriched tubules. Fragments of Sertoli cell-enriched testes were much more active than isolated tubules in metabolizing progesterone. They produced the same amounts of 5α-reduced metabolites of testosterone.     

A new species of electric knifefish,genus Compsaraia (Gymnotiformes: Apteronotidae) from the Amazon River,with extreme sexual dimorphism in snout and jaw length

Abstract

A new species of the neotropical electric fish genus Compsaraia is described from the western Amazon of Peru and Brazil. Compsaraia samueli is distinguishable from all other apteronotids by sexual dimorphism in which mature males exhibit extreme elongation and slenderness of the snout and jaws. Compsaraia samueli is readily distinguishable from its only congener, C. compsa, by more caudal‐fin rays (17–18 vs. 13–16), a shorter caudal peduncle (mean length 9% vs. 34% body length to end of anal fin), a less tapering body shape in lateral profile (mean ratio of body depth at origins of anal fin and dorsal organ 93% vs. 75%), and a smaller maximum adult body size (230 vs. 305 mm). The genus Compsaraia is readily separated from other apteronotids by a pale antorbital stripe and a pale L‐shaped patch over the supra‐temporal canal. The phylogenetic position of C. samueliis estimated by inclusion in a previously published data matrixof osteological and other morphological characters. Comparisons of the cranial bones in apteronotids shows the derived morphology of C. samueli to be a composite of three developmentally and phylogenetically discrete characters: (1) positive allometric growth before sexual maturity in both sexes of the pre‐orbital region of the neurocranium, (2) positive allometric growth of the (oral) jaws, and (3) secondary sexual dimorphism of snout and jaw morphology. The genus Compsaraia represents one of at least three phylogenetically independent cases of snout elongation and one of at least four cases of jaw elongation within the Apteronotidae. Compsaraia samueli also represents one of at least four cases of secondary sexual dimorphism in snout and jaw length within the Apteronotidae. The phylogenetic distribution of snout and jaw characters within the Apteronotidae suggests the influence of both sexual and trophic functional influences on the evolution of head morphology.     

The novel mutant scl of the medaka fish, Oryzias latipes, shows no secondary sex characters

A new mutant that has neither male nor female secondary sex characters was found in the medaka, Oryzias latipes. Both XX and XY mature mutants had gonads with many spermatozoa, but spawning did not occur when the mutants were paired with normal males or normal females. F1 progeny were successfully obtained by artificial insemination using unfertilized eggs from wild-type females and spermatozoa of the XY mutant. The mutant phenotype did not occur in the F1 progeny from this cross. Incrossing among the F1 progeny produced 17 mutant offspring out of 68 progeny (25%), demonstrating that the mutant phenotype is caused by a single recessive mutation. This mutant was named scl (sex character-less). Because papillary processes, a male secondary sex character, were induced in the XY mutants by androgen administration, it seems that the androgen receptor is functioning normally. We found a loss-of-function type mutation in the P450c17 gene of the mutant; this gene encodes a steroidogenic enzyme required for the production of estrogen and androgen. The scl phenotype was completely linked to the mutant genotype of P450c17, strongly suggesting that mutation at the P450c17 locus is responsible for the scl mutant phenotype.     

Early steroid metabolism by chick blastoderm invitro

Yolk free blastoderms of chick embryo were incubated 3 or 22 hours with labeled pregnenolone, progesterone, 17-hydroxyprogesterone, dehydro-epiandrosterone, androstenedione, testosterone and estradiol-17β. Metabolites and unconverted substrates were found both in the incubation medium and in the cells. Enzymes responsible for identified conversions were: 17α-hydroxylase, 17-20-desmolase, Δ⁵3β- and 3α-hydroxysteroid dehydrogenase, 17β-hydroxysteroid dehydrogenase and 5α- and 5β-reductase. The results suggest that the steroid metabolizing enzyme activities found may reflect a more general ability of early embryonic cells.     

Effect of Actinomycin D and Cycloheximide on Gonadotropin-Induced 17α, 20β-Dihydroxy-4-pregnen-3-one Production by Intact Ovarian Follicles and Granulosa Cells of the Amago Salmon,Oncorhynchus rhodurus*

The effect of actinomycin D and cycloheximide on gonadotropin (partially purified chum salmon gonadotropin, SGA)-induced 17α, 20β-dihydroxy-4-pregnen-3-one (17α, 20β-diOHprog, a maturation-inducing steroid in amago salmon) production was examined in intact ovarian follicles and granulosa cells of postvitellogenic amago salmon, Oncorhynchus rhodurus. Both actinomycin D and cycloheximide blocked gonadotropin-induced 17α, 20β-diOHprog production by intact follicles. In contrast, gonadotropin-induced 17α-hydroxyprogesterone production by intact follicles was not abolished by actinomycin D, but was abolished by cycloheximide, suggesting that postvitellogenic amago salmon ovarian follicles already contain the RNAs necessary for the synthesis of 17α-hydroxyprogesterone. In isolated granulosa cells, chum salmon gonadotropin was able to stimulate 17α, 20β-diOHprog production only when a precursor, 17α-hydroxyprogesterone was provided in the incubation medium, indicating that gonadotropin acts directly on granulosa cells to enhance the activity of 20β-hydroxysteroid dehyrogenase (20β-HSD). Total inhibition of 20β-HSD enhancement in granulosa cells, judged by 17α, 20β-diOHprog production, was achieved when actinomycin D was added between 1 hr before the start of incubation with 17α-hydroxyprogesterone and gonadotropin to 6 hr after. With cycloheximide total inhibition was observed when added in the period of 1 hr before to 9 hr after the start of the incubation. These results suggest that chum salmon gonadotropin acts on granulosa cells to enhance the de novo synthesis of 20β-HSD by a mechanism involving RNA synthesis.     

Sexually dimorphic male horns and their use in agonistic behaviors in the horn-headed cricket <Emphasis Type="Italic">Loxoblemmus doenitzi</Emphasis> (Orthoptera: Gryllidae)

Sexual dimorphism, the difference between the sexes in secondary sexual characters, is in general driven by processes of sexual selection. The horn-headed cricket, Loxoblemmus doenitzi, exhibits sexual dimorphism in head shape. Males have flat heads and triangular horns on both sides of their heads, whereas females have rounded heads and no horns. We hypothesized that male horns have evolved due to intra-sexual selection, in which males use these horns as weapons in aggressive interactions. We tested two predictions of this hypothesis by conducting agonistic trials with field-caught males of L. doenitzi: (1) the horns should be used in agonistic interactions between males, and (2) the asymmetry in horn size or horn use may determine contest outcome. Horn length was significantly correlated with thorax length and hind femur length. During agonistic interactions, males aggressively used their horns by beating the opponent’s horns with their own or by poking the opponent’s body. However, logistic regression analysis revealed that neither horn length nor horn use were significant factors for contest outcome. Instead, body size was significant for determining contest outcome. We discuss possible scenarios for evolution of male horns in L. doenitzi.     

Effects of chronic ethanol ingestion on steroid profiles in the rat testis

Testosterone, seven of its potential precursors, three of its metabolites and estradiol were analyzed in testes from rats given ethanol for 23 days in a nutritionally adequate liquid diet. The results were compared to those obtained with pair-fed control rats. The concentrations of pregnenolone, progesterone, 17-hydroxyprogesterone, androstenedione and testosterone were markedly lowered in four of the five rats given ethanol. The concentrations of the other 3 beta-hydroxy-delta 5 steroids and estradiol were unchanged, resulting in significantly increased ratios between 17-hydroxypregnenolone and 17-hydroxyprogesterone (P less than 0.025) and between androstenediol and testosterone (P less than 0.025) in the ethanol-treated rats. The results indicate that chronic ethanol administration reduces formation of testosterone by affecting a step prior to pregnenolone. There may also be an effect on the conversion of some 3 beta-hydroxy-delta 5 to the corresponding 3-oxo-delta 4 steroids. The levels of testosterone and three other steroids in testes of rats given the liquid diet were significantly lower than those in testes of animals fed a standard rat chow. This indicates a dietary influence on testicular steroid concentrations.     

17α-甲基睾酮对剑尾鱼的影响

目的研究17α-甲基睾酮暴露对产后雌性剑尾鱼(Xiphophorus helleri)性逆转组织形态学变化的影响,探讨剑尾鱼第二性征变化作为水环境风险评价(ERA)的有效生物学标记的可能性。方法使用浸浴法以10μg/L 17α-甲基睾酮为剑尾鱼染毒持续7周,对实验鱼的体形、腹鳍、臀鳍、尾鳍及性腺等组织器官的变化进行观察;同时对幼鱼在实验室养殖条件下的性别分化进行统计。结果 17α-甲基睾酮对产后雌鱼有明显的影响,受诱导后出现性逆转,逐渐发育形成雄性第二性征:体形变纤细;腹鳍第1鳍条变短、第2和第3鳍条延长,臀鳍第3、4、5鳍条末端钩状化且第3鳍条变粗壮,尾鳍上下缘出现增生;体内与臀鳍相连的骨骼合并生长;受诱导的雌鱼性腺呈现退化趋势并伴有卵细胞坏死现象,生殖能力受到负面影响。结论剑尾鱼臀鳍和尾鳍变化可作为水环境雄激素物质污染监测的有效生物学标记。