NEURAL AND ENDOCRINE EFFECTS OF ENVIRONMENTAL EXPOSURE TO CHEMICALS

流行病学研究表明，雄配子和复合体， 生殖细胞的增殖、发育、 和生存受到控制，可能受到威胁。 由于长期 生物半衰期，镉（Cd）的痕量环境 具有累积毒性的污染物。 虽然 精子发生对镉毒性非常敏感，这可能是 与血睾屏障通透性增加和高 金属硫蛋白（Mt）的组成型表达，试图确定 敏感的阶段，细胞类型和作用机制受到阻碍， 普通实验室哺乳动物复杂的睾丸组织 一 技术上有利的替代方案是鲨鱼睾丸， 在体内逐阶段分析精子发生， 生殖单位（精囊），包括阶段同步的生殖细胞 细胞/Sertoli细胞克隆，分离用于实验和分析 体外 初步研究表明，镉增加渗透性， 减数分裂和减数分裂后阶段的功能障碍，但优先 在减数分裂前阶段集中在组织中，在那里它增加了合成 Mt样蛋白的表达，增加了germ克隆的百分比， 经历程序性细胞死亡（凋亡），并增加 SGP-2是体细胞凋亡的常见标志物。 我们建议 检查镉在早期直接进入生殖细胞的假设， 发育阶段，采取了积极的镉积累机制 通过增强的MT表达进一步放大， 通过扰乱正常的控制机制。 Cd介导缺陷 早期的发展将对随后的所有发展产生深远的影响。 阶段和成熟精子的最终数量。 利用鲨鱼睾丸 模型和在体内和体外的方法，我们将（1）定义动力学 镉的吸收和滞留分阶段进行，并确定细胞和细胞核 与累积的胞质位点;（2）将Cd暴露与 细胞内水平和镉对屏障通透性的影响，Mt和SGP- 2的表达，以及凋亡的程度和时间;（3）阐明 细胞凋亡与DNA复制/修复的关系 生殖/激素状态对镉的反应;（4）启动研究， 确定镉激活茎细胞凋亡的途径 细胞/精原生殖细胞群;和（5）评估 用于鉴定生精毒物的培养的减数分裂前精囊 影响男性程序性（凋亡）与非调节性（坏死）死亡 生殖细胞

Epidemiological studies indicate that male gametes and the complex, hormone-regulated processes by which germ cell proliferation, development and survival are controlled, may be threatened. By virtue of a long biological half-life, cadmium (Cd) exemplifies a trace environmental pollutant with potential as a cumulative toxicant. Although spermatogenesis is exquisitely sensitive to Cd toxicity, which may be related to increased permeability of the blood-testis barrier and high constitutive expression of metallothionein (Mt), attempts to pinpoint sensitive stages, cell-types and mechanisms of action have been hampered by the complex testicular organization of common laboratory mammals. A technically advantageous alternative is the shark testis, which facilitates analysis of spermatogenesis stage-by-stage in vivo and allows intact germinal units (spermatocysts), comprising stage-synchronized germ cell/Sertoli cell clones, to be isolated for experimentation and analysis in vitro. Initial studies indicate that Cd increases permeability of a functional barrier in meiotic and postmeiotic stages but is preferentially concentrated in tissues at premeiotic stages, where it increases synthesis of a Mt-like protein, increases the percentage of germinal clones undergoing programmed cell death (apoptosis), and increases secretion of SGP-2, a frequent marker of apoptosis in somatic cells. We propose to examine the hypothesis that Cd has direct access to germ cells in early developmental st ages, is taken up by an active Cd-accumulating mechanisms that is further amplified by enhanced mt expression, and activates a cell death program by perturbing normal control mechanisms. Cd-mediated defects early in development would have profound consequences for all subsequent stages and the final number of mature spermatozoa. Using the shark testis model and in vivo and in vitro approaches, we will (1) define kinetics of Cd uptake and retention stage-by-stage and identify cellular and nuclear vs. cytosolic sites of accumulation; (2) relate Cd exposure to intracellular levels and to Cd effects on barrier permeability, Mt and SGP- 2 expression, and to the extent and timing of apoptosis; (3) elucidate the relationship between apoptosis and DNA replication/repair and reproductive/hormonal status in response to Cd; (4) initiate studies to determine pathways by which Cd activates apoptosis in the stem cell/spermatogonial germ cell population; and (5) evaluate the utility of cultured premeiotic spermatocysts for identifying spermatogenic toxicants that affect programmed (apoptotic) vs. unregulated (necrotic) death of male germ cells.