骨髓间充质干细胞对环磷酰胺诱导卵巢损伤的保护作用

目的:研究骨髓间充质干细胞(MBSc)对注射环磷酰胺(CTX)引起的大鼠卵巢损伤的保护作用。方法:将30只SD大鼠按随机数字表随机分为三组,即对照组,模型组及细胞移植组,分别经尾静脉接受生理盐水,CTX和CTX+MBSc移植。监测大鼠体重,动情周期的变化,用药结束后一周处死大鼠,测定血清雌二醇(E2),卵泡刺激素(FSH),黄体生成素(LH)的变化,观察各组大鼠卵巢形态学及卵泡数量变化,并利用原位细胞凋亡TUNEL法检测3组大鼠卵巢中细胞凋亡指数(AI)。结果:与对照组比较,模型组大鼠体重下降,动情周期延长,卵泡数量下降,E2下降,FSH及LH升高,组织细胞AI增加。与模型组比较,细胞移植组大鼠体重增加,动情周期缩短,卵泡数量增加,尤其是中大卵泡数增加,E2上升,LH下降,FSH接近正常。结论:MBSc移植能通过减少卵巢组织AI而在一定程度上减少环磷酰胺引起的卵巢功能损伤。     

微囊化胰岛B细胞系体外生长和分泌功能的研究

目的：研究海藻酸钠－多聚赖氨酸－海澡酸钠（APA）微囊化胰岛B细胞系BTC6－F7的生长和分泌规律,探索其作为生物人工胰岛的可能性。方法：以微囊静电液滴发生器制作APA微囊化BTC6－F7细胞,体外培养并定期测定微囊化细胞的生长和胰岛素分泌。结果：在实验观察的90d内,BTC6－F7细胞可在微囊内以细胞团的形式生长、存活。囊内细胞总数随培养时间的延长而增加,但细胞活率呈下降趋势,胰岛素分泌与囊内活细胞数的变化规律一致,最初呈上升趋势,然后较长时间维持在相对恒定的水平。结论：本研究所制备的APA微囊化胰岛B细胞可在较长时间内保持生长、存活和分泌功能,为进一步发展生物型人工胰岛奠定了基础,并可用于糖尿病的发病机理和治疗研究。     

SGA微囊制备及其与大鼠胰岛生物相容性的体外观测

目的:制备硫酸酯化葡甘聚糖-海藻酸钡(SGA)微囊,包裹大鼠胰岛,对比观测SGA微囊的体外生物相容性.方法:溶液共混法制备硫酸酯化葡甘聚糖-海藻酸盐混合凝胶液,改良Omer法制作SGA微囊.X射线衍射分析SGA二元共混膜结构;SGA微囊化SD大鼠胰岛,体外培养14d后,胰岛素刺激释放实验对比SGA微囊和APA、ABa(海藻酸钡)微囊对大鼠胰岛的影响.结果:衍射图谱显示硫酸酯化葡甘聚糖-海藻酸钡共混膜在原属于海藻酸钡的2θ 11°、20.3°结晶峰变小,在20 29.8.出现新结晶峰,说明SGA二元共混膜相互作用强烈,融合较好;胰岛素刺激释放实验显示,体外培养后SGA微囊对大鼠胰岛的影响与APA、ABa微囊无差别(P＞0.05).结论:SGA微囊膜结构稳定,融合度较好,对大鼠胰岛体外生物相容性较高,可以为下一步体内移植所应用.     

用微囊化转基因细胞治疗PD猴的初步研究

用海藻酸钠／多聚赖氨酸（ＡＬＧ／ＰＬＬ）方法制备了包裹转 酪氨酸羟化酶基因的大鼠在肌细胞微囊。在在体外,微囊内的细胞能长时间存活及生长,并能产生ＴＨ蛋白。将这种微囊移植于正常猴的纹状体,１个月后仍能在微囊内观察到活细胞,而且移植处凶胶质细胞明显增生,在此基础上,将这种微囊移植于患帕金森病（ＰＤ）的模型猴的纹状体,初步观察到的其病理性旋转行为有明显改善。     

新生小鼠卵巢组织的玻璃化冻存、移植及分离卵泡的体外成熟培养初步研究

目的:系统地探索新生小鼠卵巢组织的玻璃化冻存建立卵巢库,移植和分离卵泡以及体外成熟培养的实验方法。方法:对1日龄小鼠卵巢组织进行冻存,解冻复苏和同种肾包膜下移植,从卵巢移植物种中进行卵泡分离和体外成熟培养。结果:①采用平衡液(ES)处理25min,玻璃化液(VS)处理3min方案冻存的卵巢组织具有更高比例的形态完整卵泡,其完整原始卵泡率均值达96.6%,显著性高于实验中其它四组方案(P0.05);②在分别移植2周和4周后回收卵巢移植物,发现二者的卵巢回收率无显著差异(P0.05),但移植4周组的卵泡回收数目要明显高于2周组(P0.05);③在培养基中添加适量的自体血清(10%,V/V)能显著提高卵子的体外成熟率,培养12h后对照组中生发泡破裂(GVBD)发生率为(34.74±4.26)%,添加血清后提高至(54.60±3.37)%,成熟的MⅡ期卵子获得率从(43.17±1.31)%升高至(57.75±5.31)%,有显著性差异(P0.05)。结论:通过该实验较好地建立了卵巢组织的玻璃化冻存、移植和卵泡分离以及体外成熟培养的实验方法。     

绿色荧光蛋白标记人脐带间充质干细胞大鼠卵巢移植的实验观察

目的观察人脐带间充质干细胞(MSCs)移植于大鼠卵巢后存活的情况,为MSCs参与动物实验提供实验依据。方法以腺病毒介导绿色荧光蛋白(GFP)基因体外转染MSCs 48 h,于大鼠腹腔卵巢注射移植,于注射移植后1h及移植后3、7、21 d取材并在荧光显微镜下观察MSCs的存活情况。取材石蜡切片行苏木精-伊红(HE)染色观察移植细胞部位组织病理图像。结果 MSCs注射移植后3 d、7 d时GFP荧光表达较强,细胞轮廓清晰,与注射后1h平均吸光度值比较,移植后3、7 d检测荧光吸光度值差异均无统计学意义(P0.05);移植后21 d时GFP荧光表达较弱,吸光度值差异有统计学意义(P0.05)。术后大鼠组织切片光镜下移植的MSCs细胞清晰可见,无急性排斥反应特征出现。结论 MSCs在大鼠腹腔卵巢移植,其与异种个体组织相容性较好。     

左归丸上调雷公藤多苷诱导卵巢功能低下大鼠卵巢PLGF及Flt-1水平

目的观察左归丸对雷公藤多苷致卵巢功能低下(diminished ovarianresev,DOR)大鼠卵巢胎盘生长因子(placental growth factor,PLGF)及其受体(FMS-like tyrosine kinasel,FLT-1)表达的影响,进一步了解左归丸促进血管生成的作用机制。方法雷公藤多苷灌胃造成大鼠卵巢功能低下,造模成功后,分别给予蒸馏水20g/kg、左归丸11g/kg、左归丸33g/kg、结合雌激素65μg/kg灌胃治疗后,观察各组动情周期变化,计算卵巢、子宫指数,采用免疫组织化学法及Western blot法检测大鼠PLGF及其受体Flt-1水平。结果造模后大鼠动情周期延长,治疗后大鼠动情周期逐渐恢复至正常。与模型组比,各治疗组的卵巢、子宫指数增高;各治疗组PLGF、Flt-1水平明显增高。结论左归丸可以通过上调雷公藤多苷模型大鼠卵巢组织PLGF,FLT-1水平,促进卵巢血管的生成,从而改善卵巢储备功能。     

卵巢组织异体移植对去势模型大鼠骨质疏松的治疗作用

目的:研究卵巢组织异体移植对去势模型大鼠骨质疏松的治疗作用及其机制。方法:将40只SD雌性大鼠随机分为假手术组、去卵巢模型组,雌激素组和卵巢组织块移植组。采用背部定位切除双侧卵巢,建立去势大鼠模型。造模的同时,将同种异体卵巢组织块植入去卵巢大鼠背部肌肉层以建立卵巢移植模型。雌激素组大鼠按雌激素0.06 mg/kg灌胃进行替代治疗3个月,其他各组均给予等量生理盐水。实验结束后,称量体重和子宫湿重,计算子宫重量指数;HE染色光镜观察大鼠阴道上皮细胞和股骨细胞形态;骨密度仪法检测大鼠全身、股骨和胫骨近端的骨密度;放射免疫法检测血清雌激素(E2)水平。结果:与假手术组相比,模型组大鼠子宫重量指数明显下降(P0.01);血清雌激素水平显著降低(P0.01);阴道上皮细胞较小,无角质化;股骨中的骨小梁数目显著减少,骨吸收明显,呈典型的"岛屿状",骨髓腔增大,髓腔中基质细胞极少;双能X线显示,模型大鼠全身、股骨和胫骨的骨密度均显著减少(P均0.01);与模型组相比,雌激素组和移植组大鼠的子宫重量指数增加明显(P0.01,P0.01);两组大鼠的血清雌激素水平上升显著(P0.01,P0.01);病理切片显示,雌激素组和移植组大鼠的阴道上皮细胞大多呈角质化;雌激素组大鼠皮质骨增厚,骨小梁粗壮,数量多,排列较整齐,骨小梁间距较小,且骨髓腔缩小,骨基质细胞明显增多;移植组大鼠皮质骨面积较大,骨小梁数量和面积增加明显,骨小梁间距小,排列规则,连接增多,骨基质细胞分布均匀。结论:卵巢组织移植可能是通过与靶肌肉组织产生新生血管连接,不断分泌内源性雌激素,后者通过结合子宫、阴道和股骨组织中靶受体-雌激素受体,进而维持子宫和阴道等靶组织的形态与功能,并抑制骨质组织矿物质的丢失,从而达到改善或促进雌性大鼠内分泌功能的目的。     

玉竹提取物对大鼠多囊卵巢综合症的疗效研究

目的 观察玉竹提取物（POD）对多囊卵巢综合症（PCOS）模型大鼠卵巢功能及炎症的影响。方法 本研究选择3周龄雌性SD大鼠,采用来曲唑进行灌胃21 d复制PCOS模型,造模成功后,采用不同浓度POD对PCOS模型大鼠进行灌胃处理。记录大鼠每日饮水及摄食量、体重变化情况及动情周期,检测血液相关指标、测定血清睾酮水平,检测大鼠糖耐量,采用苏木素-伊红（HE）染色观察卵巢组织形态学变化,通过蛋白质免疫印迹法（WB）、实时荧光定量反转录聚合酶链反应（qRT-PCR）及免疫组织化学法（IHC）检测卵巢组织内抗苗勒激素（AMH）、炎性细胞因子白介素-1β (IL-1β)、肿瘤坏死因子α (TNF-α)的表达。结果 与对照组相比,PCOS模型大鼠动情周期紊乱、卵巢呈多囊样改变,血清睾酮水平显著上升、卵巢AMH表达上调、糖耐量异常（P<0.01）,IL-1β和TNF-α表达增加（P<0.01）;不同浓度POD处理PCOS模型大鼠后,大鼠动情周期逐渐恢复正常、卵巢中黄体数量增加、囊性卵泡数量减少、血清睾酮水平下调、糖耐量异常缓解（P<0.01）,卵巢组织炎性细胞因子IL-1β、TNF-...     

脉络丛细胞微囊脑内移植前后的物理及生化性能研究

通过测定脉络丛细胞海藻酸盐微囊在大鼠脑内移植前及移植后的物理及生化性能变化,以探讨其应用于移植治疗神经系统疾病的可行性.用海藻酸盐多聚鸟氨酸微囊包裹猪脉络膜细胞,移植至大鼠黑质-纹状体通道,移植前、移植后4个月及6个月分别测定微囊的大小、形态及细胞的活力、分泌蛋白质及神经营养因子的能力、蛋白质组学的变化.脉络膜细胞微囊在移植前、后大小、细胞活力、蛋白质组学分析、分泌蛋白质及神经营养因子的能力无显著变化.海藻酸盐-多聚鸟氨酸CP微囊能有效地防止脉络膜细胞被受体免疫系统所攻击,使得它们能在大鼠的大脑存活6个月以上并不引起不良作用.     

Effect of prenatal stress and gonadal hormone condition on depressive behaviors of female and male rats

Whether prenatal stress (PNS) and gonadal hormones may influence depressive behavior of rats in the forced swim test was investigated. In Experiment I, adult diestrous female rats had increased immobility, which is indicative of depression, but did not show any significant difference in the duration of struggling compared to intact adult males. In Experiment 2, the behavior of adult intact, castrated, or castrated dihydrotestosterone (DHT)- or estrogen (E2)-replaced offspring of dams that were restrained under lights for 45 min on gestational day 18 (PNS) or were not subjected to gestational stress (non-PNS, control condition) were compared. There were no effects of PNS, but DHT and E2 produced anti-depressant effects on behavior of male rats. Castration decreased struggling and increased immobility compared to intact rats. DHT or E2 replacement was able to partially reinstate struggling and immobility behavior but not to levels of intact males. In Experiment 3, behavior of PNS or control rats that were in proestrus or were ovariectomized and DHT, E2, or vehicle-replaced were compared. Ovariectomy decreased struggling and increased immobility compared to that of proestrous rats. E2 or DHT to control females increased anti-depressant struggling behavior compared to ovariectomized control or PNS rats administered vehicle, which demonstrated greater duration of struggling than did E2-primed, PNS rats. E2 or DHT administration decreased immobility of PNS and control females. These findings suggest that E2 and DHT have some anti-depressant effects but that modest PNS may alter E2's ability to alleviate some depressive behavior in female, but not male rats.     

Effect of oestrogen on Pasteurella pneumotropica in rat vagina

The effects of ovarian hormones on the vaginal population of Pasteurella pneumotropica in rats were investigated. Specified-pathogen-free adult female Wistar-Imamichi rats with a 4 day oestrous cycle were inoculated with P. pneumotropica in the vagina. Cyclic changes in the vaginal population of P. pneumotropica were not observed in ovariectomized rats and the bacterial population was at a similar level to that at normal dioestrus. Administration of oestrogen to ovariectomized rats caused an increase in the numbers of P. pneumotropica and total bacteria in the vagina nearly equal to that at oestrus in intact rats. The numbers of these organisms in the vagina of ovariectomized rats treated with progesterone did not change and were similar to those of control ovariectomized rats treated with sesame oil. Vaginal smears of ovariectomized rats treated with oestrogen were characterized by abundant cornified non-nucleated epithelial cells with many adherent Gram-negative coccobacilli and were similar to smears from intact rats at oestrus. These findings suggest that the proliferation of P. pneumotropica at oestrus in rat vagina may be primarily due to the environment provided by the degeneration of vaginal epithelial cells promoted by oestrogen secretion from the ovaries.     

Hypothalamic receptors of sex hormones in the mechanism of the sexual differentiation of the brain in rats

Studies have been made on the content of receptors of estradiol (E2) and testosterone (T) in cytoplasmic and nuclear fractions of the hypothalamus of male and female rats during neonatal development, as well as in adult females after androgenization in neonatal period and adult males castrated within 3 days of postnatal life. It was shown that both E2 and T are present in the blood serum of male and female newborn rats. In female hypothalamus, only E2 receptors were found, whereas in males both types of receptors were revealed, their content being higher than in females. In adult animals subjected to changes in the level of sex hormones in the blood during early neonatal period, changes in concentration of the receptors in the hypothalamic centres of regulation of tonic and cyclic secretion of gonadotropins were found. The data obtained presumably reveal the role of receptors of sex hormones in sex differentiation of the brain.     

Metabolism of [4-14C]estrone in hamster and rat hepatic and renal microsomes: species-, sex- and age-specific differences.

The metabolism of [4-14C]estrone (E1) was examined in liver and kidney microsomes of adult castrated male and ovariectomized female hamsters and rats and in neonatal and immature hamster renal microsomes. In castrated male hamster liver microsomes, E1 was metabolized extensively to six major metabolites; 15 beta-hydroxyestrone, 7 alpha-hydroxyestrone, 6 alpha-hydroxyestrone, 6 beta-hydroxyestrone, 2-hydroxyestrone, and delta(9,11)-dehydroestrone, and a nonpolar fraction. Six minor metabolites of E1 were also detected. In contrast, kidney microsomes derived from castrated male hamsters metabolized E1 to mainly 17 beta-estradiol, 2- and 4-hydroxyestrone, 6 alpha-hydroxyestrone, 6 beta-hydroxyestrone and one monohydroxyestradiol metabolite. However, 16 alpha-hydroxyestrone was not detected. A variable, but low amount of estriol was also found. Interestingly, the quantity of 2-hydroxyestrone found in kidney microsomes of the hamster represented 26% of the total amount of metabolites formed, whereas in liver microsomes, only 9% of the overall metabolism resulted in the formation of 2-hydroxyestrone. The ability of kidney microsomes of female ovariectomized hamsters and two different rat strains to metabolize E1 was 5.9- and 9.4-fold lower, respectively, compared to renal microsomes of male castrated hamsters. The onset of oxidative metabolism in newborn hamster kidneys during development was also assessed. The results indicate that the oxidative metabolism of [14C]E1 in renal microsomes of newborn hamsters was 20-fold less than in kidney microsomes of adult hamsters. While catechol E1 metabolites were essentially negligible in hamster kidneys of these ages, it was evident that the conversion of E1 to estradiol via 17 beta-hydroxysteroid dehydrogenase resembles levels seen in the adult animals. Between the age of one and two months, the male hamster kidney exhibited the capacity to metabolize E1 at levels seen in fully mature adult hamsters.     

Factors involved in the testicular development from fetal mouse ovaries following transplantation

We have previously shown that fetal mouse ovaries develop testicular structures after transplantation into adult male mice. The mechanisms of gonadal sex reversal is poorly understood. In the present study, we examined how a host environment is involved in the induction of testicular development in ovarian grafts. Fetal ovaries on the twelfth day of gestation were microencapsulated with semipermeable membranes, transplanted beneath the kidney capsules of adult male mice, and fixed for histological examinations between the sixteenth and twenty-second day after transplantation. Fifteen of forty-seven ovarian grafts were found to be completely enclosed in microcapsules, whereas the microcapsule membranes of other grafts were partly broken or had been lost. These differences of microencapsulation conditions made it possible to study the role of host factors in gonadal sex reversal. All ovarian grafts surrounded by microcapsule membranes developed ovarian structures. In contrast, most ovarian grafts which had lost the microcapsules developed testicular structures in addition to ovarian structures. When ovarian grafts were partially enclosed in microcapsule membranes, testicular structures developed only in the area in contract with the host kidney. These results suggest that direct interaction between the ovarian graft and cells or large macromolecules from the host is involved in the development of testicular structures in ovarian grafts.     

小鼠卵巢冷冻移植后卵泡发育和卵母细胞成熟的研究

本研究探讨了冷冻保存的1日龄小鼠卵巢异体异位移植后,其原始卵泡重新启动生长发育的能力。一日龄B6C2F．小鼠卵巢分离冷冻后置液氮中保存,保存1周。6个月后解冻,并将卵巢移植到8-12周龄B6C2F．受体鼠。肾脏包膜下,移植至少14d。每侧肾囊移植2枚卵巢的40只受体鼠中卵巢的回收率为45．00％（72／160）,而每侧。肾囊移植l枚卵巢的20只受体鼠的回收率为82．50％（33／40）。移植卵巢上卵泡的发育基本与体外自然生长鼠的卵巢卵泡发育情况一致。对卵巢移植19d的受体鼠用孕马血清促性腺激素（pregnant mare serum gonadotrophin,PMSG）处理后,从移植卵巢上发育成熟卵泡中获得的卵母细胞在MEM0c培养基中培养16-17h,有40．90％的卵母细胞发生生发泡破裂（germinal vesicle breakdown,GVBD）,其中89．02％的卵母细胞发育到第二次减数分裂中期（metaphaseⅡ,MⅡ）。将剩余的卵母细胞继续培养到20～21h,又有50．83％的卵母细胞发生生发泡破裂,但其中只有21．40％的卵母细胞能够发育到MII期。以上结果说明,小鼠早期卵巢经过冷冻．解冻并异体异位移植后,其原始卵泡能够重新启动生长发育,发育后的卵泡卵母细胞能够在体外培养成熟。这些结果意味着原始卵泡或卵巢冷冻一移植技术有可能充分利用雌性生殖细胞用于濒危动物保种、建立动物基因库和人类辅助生殖等。     

Male-induced puberty acceleration in young female wild mice: hormonal regulation and source of pheromonal cue

Experiments were designed to examine the influence of adult males on the rate of sexual maturation in young female wild mice. In one experiment, young females were raised in presence of adult males, adult females and in absence of any individual, while in another, they were exposed to urines of: (1) castrated males, (2) spayed females, (3) castrated and TP-treated males, (4) castrated and placebo-injected males. Female maturation as measured by age at vaginal opening and first vaginal oestrus was accelerated by presence of adult males, whereas presence of adult females considerably delayed the vaginal opening and the appearance of first oestrus in young females. In the other set of the experiments, urine from castrated or castrated and placebo-injected males was ineffective in inducing early puberty while urine from spayed females highly delayed the sexual maturation. By contrast, urine from castrated and TP-treated males accelerated the puberty more or less like normal males. The results indicate that male's chemosignal accelerating puberty in young females is present in urine and its production is under the control of androgens. However, the female-originating urinary pheromone which delays the puberty in young females is not regulated by ovarian hormones.     

Modulation of hepatic glucose-6-phosphate dehydrogenase activity in male and female rats by estrogen

The effect of estradiol-17 beta on the activity of glucose-6-phosphate dehydrogenase was studied in both male and female rats to further characterize the sex differences in the activity of this enzyme. Four groups of intact and castrated rats were implanted subcutaneously with graded doses (2.4, 4.8 and 7.2 micrograms/day) of pelleted estradiol in a physiologically relevant experimental system. After fourteen days the rats were sacrificed and their livers were assayed for G6PD activities. The result indicated that: (i) the enzyme activity was 3-fold higher in normal adult female than in male rats, (ii) low doses of E2 (2.4, 4.8 and 7.2 micrograms/day) increased the activity of G6PD 6-fold in castrated males and over 2-fold in female castrates as well as intact rats (iii) E2 stimulation of G6PD activity appears to be more effective in castrated males than in female rats (IV) sex difference in the activity of G6PD disappeared after treatment with E2 in castrated rats. It is concluded that the activity of G6PD in rats is markedly enhanced by low doses of E2, which appears to be largely responsible for the sex differences in the activity of this enzyme in rats.     

Effect of thyroid hormone on initiation of persistent oestrus in the rat.

When rats are exposed to continuous illumination persistent oestrus and polyfollicular ovaries develop. Thyroidectomy at 24 days of age (juvenile rats) prevents the onset of persistent oestrus and polyfollicular ovaries under exposure to constant light, and irregular ovulation continues to occur. Replacement with 1.75 microng L-thyroxine in these rats produces a prolonged oestrus. However, in adult persistent-oestrous rats (90 days after exposure to continous illumination) thyroidectomy does not interrupt persistent vaginal cornification. In rats receiving 100 microng of testosterone propionate subcutaneously at 5 days of age, persistent oestrus and polyfollicular ovaries develop. Thyroidectomy at 24 days of age (juvenile) prevents the onset of persistent oestrus and the development of polyfollicular ovaries, however, ovulation is not observed. Replacement treatment with 1.75 microng L-thyroxine in these rats produces a prolonged oestrus and polyfollicular ovaries. However, in adult persistent oestrus rats, thyroidectomy at 130 days does not interrup persistent vaginal cornification. From these facts, it may be inferred that circulation of a physiological level of thyroid hormone in juvenile rats is necessary for the development of oestrogen binding receptors in the hypothalamus. Therefore, a hypothyroid state during the juvenile stage interferes with the development and maturation of hypothalamic controlled pituitary ovarian function.     

Neonatal castration of male and female rats affects luteinizing hormone responses to estrogen during adulthood

We examined the positive and negative feedback effects of estradiol (E2) on luteinizing hormone (LH) and prolactin (Prl) secretion in adult male and female rats which were gonadectomized within 24 h after birth (long-term castrates) and compared these responses to those elicited by E2 in short-term castrated (7 days) adult males and females. The high serum E2 did not reduce the elevated serum LH concentrations in long-term castrates until 4 days of treatment. Also, only after negative feedback was established were the positive feedback actions of E2 observed. In contrast, Prl surges were observed after 2 days of E2, and baseline Prl serum levels were elevated by Day 3 of E2 in long-term castrated male and female rats. Some long-term castrates lacked both LH and Prl surges, and E2 was ineffective in altering basal gonadotropin secretion in these animals. Short-term castrated males had elevated serum Prl levels but no Prl surges. Seemingly, when the hypothalamus is deprived of estrogen or androgen from birth to adulthood, an equal percentage of males and females become refractory to the positive feedback effects of estrogen during adulthood. Thus, it is difficult to separate castration effects from those which may be produced by the endogenous androgen secreted during the first 26 h of life.