NEURAL AND ENDOCRINE EFFECTS OF ENVIRONMENTAL EXPOSURE TO CHEMICALS

流行病学研究表明，雄性配子和复合体， 荷尔蒙调节的生殖细胞增殖、发育过程 生存受到控制，可能会受到威胁。凭借长时间的 生物半衰期，镉(Cd)是一种痕量环境 有可能成为累积毒物的污染物。虽然 精子发生对镉毒性非常敏感，这可能是 与血-睾丸屏障通透性增加和高 金属硫蛋白(MT)的结构性表达，试图精确定位 敏感阶段、细胞类型和作用机制受到以下因素的阻碍 普通实验哺乳动物的复杂的睾丸组织。一个 另一种具有技术优势的选择是鲨鱼睾丸，它有助于 分析活体内精子发生的阶段性和完整性 生发单位(精囊)，由阶段同步化的生殖细胞组成 细胞/支持细胞克隆，分离用于实验和分析 在试管中。初步研究表明，镉增加了细胞的渗透性 减数分裂和减数分裂后的功能障碍，但优先 集中在减数分裂前的组织中，在那里它增加了合成 类mt蛋白，增加生发克隆的百分比 经历细胞程序性死亡(细胞凋亡)，并增加分泌 SGP-2，体细胞凋亡的常见标记物。我们建议 检验CD在早期直接接触生殖细胞的假设 发育阶段，由活跃的镉积累机制占据 它被增强的mt表达进一步放大，并激活细胞 通过扰乱正常的控制机制来执行死亡程序。Cd介导的缺陷 早期的开发将对随后的所有 成熟精子的分期和最终数量。用鲨鱼的睾丸 模型、体内和体外方法，我们将(1)定义 分阶段摄取和滞留Cd，并鉴定细胞和细胞核 与胞浆堆积部位的比较；(2)与镉暴露有关 细胞内水平及对Cd对屏障通透性、mt和sgp的影响 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/修复的关系及意义 生殖/荷尔蒙状况对镉的反应；(4)启动研究以 确定镉激活茎中细胞凋亡的途径 细胞/精原生殖细胞群体；以及(5)评估 培养的减数分裂前精囊鉴定生精毒物 会影响男性的程序性(凋亡性)与非调节性(坏死性)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.