Steroidogenic capacity of Trypanosoma cruzi trypomastigotes

American Trypanosomiasis is caused by the hemoflagellate Trypanosoma cruzi (T. cruzi) and affects millions of persons causing variable degrees of digestive and heart disturbances. As far as we concerned, T. cruzi capacity to synthesize steroid hormones has not been investigated. Therefore, the aim of this work was to investigate the capacity of T. cruzi trypomastigotes to transform tritiated steroid precursors into androgens and estrogens. The T. cruzi Tulahuén strain was obtained from mice blood. The trypomastigotes were cultured for 6 and 24h in Dulbbeco's modified Eagle's medium plus FCS and antibiotics. Tritiated dehydroepiandrosterone or androstendione were added to the culture media and parasites were incubated for 6 or 24h. The cultures were centrifuged and ether extracted. The steroids were analyzed by thin layer chromatography (TLC) in two solvent systems. After incubation with (3)H-androstenedione, T. cruzi trypomastigotes synthesized (3)H-testosterone (T), (3)H-17beta-estradiol (E(2)) and (3)H-estrone (E(1)). Metabolism of (3)H-DHEA by the parasites yielded (3)H-androstendione and (3)H-androstendiol at 6h of incubation. The recrystallization procedure further demonstrated the (3)H-androstendiol and (3)H-17beta-estradiol syntheses. Results indicate for the first time that T. cruzi trypomastigotes produce androgens and estrogens when incubated in the presence of steroid precursors and suggest the presence of active parasite steroidogenic enzymes.     

Minimum requirements of hydrophobic and hydrophilic features in cationic peptide antibiotics (CPAs): pharmacophore generation and validation with cationic steroid antibiotics (CSAs)

Cationic peptide antibiotics (CPAs) are known to possess amphiphilic structure, by virtue of which they display lytic activity against bacterial cell membranes. Naturally occurring antimicrobial peptides contain a large number of amino acid residues, which limits their clinical applicability. Recent studies indicate that it is possible to decrease the chain-length of these peptides without loss of activity, and suggest that a minimum of two positive ionizable (hydrophilic) and two bulky groups (hydrophobic) are required for antimicrobial activity. By employing the HipHop module of the software package CATALYST, we have translated these experimental findings into 3-D pharmacophore models by finding common features among active peptides. Positively ionizable (PI) and hydrophobic (HYD) features are the important characteristics of compounds used for pharmacophore model development. Based on the highest score and the presence of amphiphilic structure, two separate hypothesis, Ec-2 and Sa-6 for Escherichia coli and Staphylococcus aureus, respectively, were selected for mapping analysis of active and inactive peptides against these organisms. The resulting models not only provided information on the minimum requirement of PI and HYD features but also indicated the importance of their relative arrangement in space. The minimum requirement for PI features was two in both cases but the number of HYD features required in the case of E. coli was four while for S. aureus it was found to be three. These hypotheses were able to differentiate between active and inactive CPAs against both organisms and were able to explain the experimental results. The hypotheses were further validated using cationic steroid antibiotics (CSAs), a different class of facial amphiphiles with same mechanism of antimicrobial action as that of CPAs. The results showed that CSAs also require similar minimum features to be active against both E. coli and S. aureus. These studies also indicate that the minimum feature requirements may be conserved for different strains of the same organism. Figure shows the mapping of an active cationic peptide antibiotic (CPA) mapped to the most acceptable hypothesis Sa6 against S. aureus     

Flavaglines and triterpenoids from the leaves of Aglaia forbesii

Three structurally complex flavaglines of the cyclopenta[bc]benzopyran type, named desacetylpyramidaglains A, C, D (1-3), and the triterpene 23, 24, 25-trihydroxycycloartan-3-one (4) were isolated from the leaves of Aglaia forbesii together with the two rare pregnane steroids 2beta,3beta-dihydroxy-5alpha-pregn-17(Z)-en-16-one and 2beta,3beta-dihydroxy-5alpha-pregn-17(E)-en-16-one, as well as the bisamide pyramidatine, the sesquiterpene spathulenol, and the widespread triterpenoids lupeol, lupenone, and a mixture of beta-sitosterol and stigmasterol. Their structures were elucidated by 1D and 2D NMR spectroscopy and mass spectrometry. Compounds 3, 4, 5, and 6 were tested for antituberculosis and antiviral activity.     

Reproductive endocrine responses to photoperiod and exogenous gonadotropins in the pallas' cat (Otocolobus manul)

Fecal samples were collected for 14–26 months from three male and six female Pallas' cats (Otocolobus manul) to examine gonadal steroidogenic activity in response to changes in photoperiod and treatment with exogenous gonadotropins. Females exhibited a seasonal anestrus from May–December, excreting consistently low concentrations of fecal estrogens (overall mean, 50.2±8.5 ng/g). During the breeding season (January–April), baseline fecal estrogen concentrations were higher, averaging 128.4±18.9 ng/g, with peak concentrations ranging from 455.8–909.6 ng/g. Interpeak intervals in estrogen excretion ranged between 7 and 21 days, with an average estrous cycle length of 14.3±1.7 days. Two females became pregnant after natural mating, with overall luteal progestogen concentrations averaging ～40 μg/g throughout gestation. Fecal estrogens increased in mid‐gestation, peaking just before birth. Induction of follicular development with eCG (100–300 IU, i.m.) resulted in an increase in fecal estrogens (peak range, 263.1–1198.1 ng/g), followed by a postovulatory increase in fecal progestogens (overall mean, 41.1±11.9 μg/g) after hCG (75–150 IU, i.m.). Despite apparently normal ovarian responses, none of the females conceived after artificial insemination (AI). The gonadotropin‐induced nonpregnant luteal phase lasted 49.8±5.3 days (range, 30–60 days), whereas gestation lasted ～70 days. In the male Pallas' cat, fecal androgens were elevated from November–April (overall mean, 352.3±30.3 ng/g) compared with nadir concentrations during the rest of the year (82.1±3.3 ng/g). Entrainment of seasonality to photoperiod was demonstrated by stimulation of gonadal steroidogenic activity in cats exposed to increasing artificial light during natural (nonbreeding season) and artificially induced short‐day photoperiods. In summary, reproduction in Pallas' cats is highly seasonal and photoperiod‐dependent. Females exhibit elevated baseline and peak fecal estrogen concentrations for 3–4 months during late winter/early spring. Testicular steroidogenic activity precedes the rise in female estrogen excretion by about 2 months, presumably to ensure maximal sperm production during the breeding season. Zoo Biol 21:347–364, 2002. Published 2002 Wiley‐Liss, Inc.     

Endocrine Correlates of Reproductive Status in Breeding and Nonbreeding Wild Female Moustached Tamarins

In callitrichid primates, reproduction is usually restricted to a single female per group. Reproductive rate is high and the occurrence of a postpartum estrus can lead to simultaneous lactation and pregnancy. In contrast, nonreproductive females often show ovarian inactivity. However, most studies on callitrichid reproductive physiology have been conducted in captivity, where conditions differ considerably from those in the wild, so that reproductive conditions may be strongly modified. Using fecal estrogen and progestogen measurements to monitor female reproductive status in 2 groups of wild moustached tamarins (Saguinus mystax), we examined 1) whether reproductive females in free-ranging groups also show postpartum estrus and 2) whether nonreproductive females demonstrate signs of ovarian activity. In both reproductive females, clear changes in the excretion pattern of progestogen and estrogen metabolites over time in combination with information on parturition dates allowed us to differentiate between pregnancy, a period of postpartum ovarian inactivity lasting for 54 and 64–82 days, and a period of ovarian activity before conception. Nonreproductive females demonstrated temporal fluctuations in hormone concentrations and absolute hormone levels that were similar to ones in the breeding females during the phase of ovarian activity. The results suggest that, in contrast to most captive female tamarins, reproductive females in wild groups of moustached tamarins do not have a postpartum estrus and that nonreproductive females show ovarian activity despite the presence of a breeding female. We therefore conclude that findings from captivity should be only carefully compared to the situation in the wild.     

Effects of constant short and long photoperiod regimes on the spawning performance and sex steroid levels of female and male sea bass

Under constant short photoperiod, the spawning time of 2-year-old sea bass Dicentrarchus labrax was advanced as compared to controls, whereas spawnings were delayed under constant long photoperiod. High plasma levels of 17β-oestradiol (E_2/) and testosterone (T) in females were coincident with the appearance of vitellogenic oocytes in the ovary, while high levels of 11-ketotestosterone (11-KT) and T in males were coincident with the presence of spermiating males. Although plasma levels of E₂ in females and 11-KT in males were low during the remainder of the cycle, levels of T were always >1 ng ml⁻¹ in both sexes, suggesting that T could play an important role during the initial stages of gonadal development. The profiles of E₂ and T in females and 11-KT and T in males exposed to constant short days were similar to those in the control group, but fish which were maintained under constant long photoperiods showed a bimodal pattern of these steroids. The results obtained from fish exposed to constant photoperiod regimes provide further evidence that an endogenous process could be operating to control the reproduction of sea bass.     

纳木错裸鲤性腺发育的组织学研究

采用常规的组织切片方法,对西藏特有鱼类纳木错裸鲤的性腺发育进行了组织学研究,系统地描述了各期精巢和卵巢的形态结构、特征及其变化.尤其论述了其卵巢中卵细胞的卵黄核破碎与分解的特点、卵膜的结构、核仁排出物在卵黄形成过程中的作用,以及卵粒重吸收的过程.根据各期卵巢中卵母细胞的组成情况,认为纳木错裸鲤已达性成熟的个体并不是每年都参与繁殖活动是对高原极端、多变气候环境的一种生态适应;阐明了纳木错裸鲤属于分批同步产卵鱼类.       

养殖鲥鱼性腺发育的研究

经激素处理和生态调控的养殖鲥鱼,能完成性腺发育的全过程,其可分为６个时期,卵细胞发育可相应分为６个时相。与其它鱼类不同,细胞中液泡最早出现在胞质的内缘而不是外缘。大、小核仁数随卵母细胞的发育而变化。成熟卵巢成熟系数为８５４％～１２６４％。成熟期卵径为６２８５～８３５３μｍ、精子头径为０７４～１５５μｍ。达性成熟的鲥鱼,冬季卵巢为Ⅱ期、精巢为Ⅱ～Ⅲ期。精、卵巢发育呈现出明显的不同步现象。前者５月底开始进入成熟期,后者７月初进入成熟期。初级卵母细胞由Ⅱ时相发育到Ⅳ时相基本上是同步的。第Ⅳ期卵巢卵径的频率仅出现１个高峰。养殖鲥鱼属１年１次产卵类型。     

塔里木河叶尔羌高原鳅繁殖生物学研究

2010年7月至2011年12月,在塔里木河阿拉尔段采集叶尔羌高原鳅Triplophysa (Hedinichthys) yar-kandensis (Day)940尾(除性别未辨个体外)用于繁殖生物学研究。种群雌雄比为0.85︰1,最小性成熟,雌性个体体长为8.2 cm,体重为7.4 g,年龄为3龄;雄性个体体长为6.5 cm,体重为3.4 g,年龄为2龄。叶尔羌高原鳅卵径分布呈单峰形,推测应属于同步产卵类型。计算了88尾Ⅳ-Ⅴ期雌鱼的怀卵量,其体长范围30-195 mm,体重范围3.59-114.04 g,绝对繁殖力为1101-56320(9944±5487)粒,相对繁殖力为824-1140(982±158);塔里木河阿拉尔段叶尔羌高原鳅种群繁殖力(Fp)为403.46万粒。