RAPID: Elevated in Utero Temperature: A Suppressor of Fetal Development and Ruminant Fitness?

最近完成了一系列以小牛犊为模型的研究，以验证宫内热应激对出生后即刻反刍动物健康的影响。研究表明，经历宫内热应激的小牛在出生和断奶时体型较小，被动免疫转移减少，天然免疫功能受到抑制。一个旨在进一步检查在妊娠最后60天经历热应激的奶牛的健康和表现的项目目前正在进行中。在妊娠晚期在这样的特定条件下经历宫内热应激的小牛的可用性为进一步了解改变新生儿健康和发育的环境因素提供了一个独特的机会，并可能导致改变健康的免疫功能的终身差异。这项应用的快速资金对于利用这一独特的机会洞察热应激的基本生物学至关重要。第一个被提议的目标是梳理导致观察到的免疫球蛋白摄取差异的细胞机制，并确定在子宫和早期生命中免疫状态的差异是否在以后的生活中持续存在。子宫内热应激可降低肠道吸收免疫球蛋白的能力。这一假说将通过测量在妊娠后期经历热应激或降温的母牛的组织和细胞中的免疫球蛋白吸收水平以及相对的细胞凋亡水平来验证。为了更全面地评估子宫内热应激的长期影响，将比较热应激和冷却水坝对小牛的功能免疫终点和生长情况。在热应激奶牛和/或其小牛中观察到的免疫抑制也可能是由于它们的免疫细胞亚群与冷却的免疫细胞亚群不同所致。为了解决这一可能性，将用流式细胞仪检测奶牛产前和产后8周的外周血以及为实现上述第一个目标而牺牲的小牛的外周血、脾和胸腺，以检测不同类型的免疫细胞的频率，包括B细胞、T细胞、单核细胞、巨噬细胞和粒细胞。因此，作为整体健康状况的指标，该项目将对子宫热应激后免疫功能的细胞机制以及对青春期生长和存活的影响有更广泛的理解。拟议研究的更广泛影响包括加强对热应激生物学的了解，以及为提高饲养和圈养反刍动物在较高环境温度下茁壮成长的能力制定管理干预措施的可能性。为了实现这些目标，持续的研究生教育支持是必要的。还需要扩大在动物生物学领域接受培训的人员的多样性，以更好地代表一般人口。两位杰出的西班牙裔年轻女科学家将作为研究生参与这一项目。佛罗里达大学也有相当多的西班牙裔本科生，其中两名学生被招募来向他们介绍基本的研究方法、免疫学技术以及数据汇总和呈现。本科生将协助动物护理、样本采集和免疫功能检测的方方面面。因此，这项提议将大大增加佛罗里达大学动物生物学专业学生的能力和多样性。

A series of studies using the bovine calf as a model was recently completed to exame the impact of in utero heat stress on ruminant fitness during the immediate post-natal period. The studies indicate that calves that experience in utero heat stress are smaller at birth and weaning, have reduced passive immune transfer, and depressed innate immune function. A project designed to further examine the health and performance of cows that experience heat stress during the final 60 days of gestation is currently underway. The availability of calves that experience in utero heat stress under such defined conditions during late gestation presents a unique opportunity to gain further insight into environmental factors that alter neonatal health and development, and possibly induce life-long differences in immune function that alter fitness. RAPID funding of this application is essential to capitalize on this unique opportunity to gain insight into the fundamental biology of heat stress. The first proposed objective is to tease apart the cellular mechanisms responsible for the observed differences in immunoglobulin uptake, and to determine if in utero and early-life differences in immune status persist in later life. Intestinal capacity for immunoglobulin absorption could be reduced by heat stress in utero. That hypothesis will be tested by measuring tissue and cellular levels of IgG absorption and relative levels of apoptosis in neonatal calves from dams that experience heat stress or cooling during late gestation. To more fully assess the long-term impact of in utero heat stress, functional immune endpoints and growth in calves from heat stressed and cooled dams will be compared. Immune suppression observed in heat-stressed cows and/or their calves may also result from differences in their immune cell subsets compared to those that are cooled. To address this possibility, peripheral blood of cows 8 weeks pre- and post-partum and peripheral blood, spleen and thymus of calves sacrificed to address the first objective above will be evaluated by flow cytometry for the frequency of different types of immune cells including B cells, T cells, monocytes, macrophages and granulocytes. A broad understanding of the cellular mechanisms of immune function following in utero heat stress, and the impact on growth and survival to puberty, as an indicator of overall fitness will therefore be developed as a result of this project. The broader impacts of the proposed study include enhanced understanding of heat stress biology, and the potential to develop management interventions for farmed and captive ruminants with improved capacity to thrive under higher ambient temperatures. To accomplish these goals, continued graduate educational support is necessary. There is also a need to expand the diversity of those trained in the field of animal biology to better represent the general population. Two outstanding young women scientists of Hispanic ethnicity will work on this project as graduate students. The University of Florida also has a significant population of undergraduate students of Hispanic descent and two of those students have been recruited to introduce them to basic research methods, techniques in immunology, and data summary and presentation. The undergraduates will assist with all aspects of the animal care, sample collection, and conduct of immune function assays. Thus the proposal will add significantly to the capacity and diversity of students trained in animal biology at the University of Florida.