Photoperiodic Regulation of a Circannual Rhythm

几乎所有动物的身体结构、功能和行为都发生了显著的变化，使它们能够适应并生存在随季节变化的自然环境的艰苦环境中。卡施博士的研究目标是了解季节变化调节季节性繁殖的方式，这是一个可逆生育和不育的自然过程。他选择了家养母羊作为示范系统。在该物种中，季节性繁殖过程是由自我维持的神经内分泌活动的内源性节律自发产生的。白天长度的变化提供了时间线索，允许这种内生节奏随着环境的周期性变化而适当调整。Karsch博士将确定在发情期给出的短日光周期信号是否有效，以及在繁殖季节给出的长日光周期信号是否无效。通过将褪黑激素注射到松果体摘除的绵羊体内，特定的光周期信息将被恢复。褪黑激素是一种只在夜间由松果体分泌的荷尔蒙，它使动物能够知道黑夜有多长，从而知道一天的持续时间。这项研究的结果应该会导致对一个具有巨大生物学意义和实践重要性的基本问题的新见解：生育力的调节。这些结果也将更广泛地适用于各种生理、代谢和行为节律，这些节律构成了许多动物适应机制的组成部分。对这些过程的理解应该对季节性繁殖的濒危物种的生殖生物学产生深远的影响。由于这些研究将在家羊身上进行，因此研究结果将直接影响食品和纤维行业的生产。

Virtually all animals undergo marked changes in body structure, function and behavior which enable them to adapt to, and survive, the hardships of a seasonally changing natural environment. The goal of Dr. Karsch's research is to understand the means by which the changing seasons regulate seasonal reproduction, a natural process of reversible fertility and infertility. He has selected domestic female sheep as the model system. In this species, the process of seasonal reproduction is generated spontaneously by a self-sustained endogenous rhythm of neuroendocrine activity. Changes in day length provide time cues which permit appropriate phasing of this endogenous rhythm with cyclic changes in the environment. Dr. Karsch will determine whether a short day photoperiodic cue is effective when given during anestrus, and whether a long day photoperiodic cue is ineffective when given during the breeding season. The specific photoperiodic messages will be restored by infusion of melatonin into pinelectomized sheep. Melatonin is a hormone secreted by the pineal gland only at night, and it enables the animal to tell how long the night is and thus the duration of the day. The outcome of this research should lead to new insights into a fundamental problem of enormous biological significance and practical importance: the regulation of fertility. The results will also be more broadly applicable to a wide variety of physiological, metabolic and behavioral rhythms which form an integral part of the adaptive mechanisms in many animals. An understanding of these processes should have profound implications to the reproductive biology of endangered species that are seasonal breeding. Since the studies will be done in domestic sheep, the findings will have a direct bearing on production in the food and fiber industries.