Use of thyrotropin receptor (TSHR) mutants to detect stimulating TSHR antibodies in hypothyroid patients with idiopathic myxedema, who have blocking TSHR antibodies

Deletions of residues 295-306, 299-301, and 387-395 of the TSH receptor, as well as point mutations of cysteine 301 or 390 to serine, and tyrosine 385 to phenylalanine or alanine, markedly diminish the ability of a transfected receptor to measure the activity of blocking TSH receptor autoantibodies (TSHRAbs) in patients with idiopathic myxedema and hypothyroidism, but not stimulating TSHRAbs in Graves' patients. This has allowed us to use these mutants to detect stimulating TSHRAb activity in the sera of hypothyroid patients with idiopathic myxedema who have blocking TSHRAbs. In 7 such patients, we show that 50% or more have significant stimulatory activity in cells transfected with mutant receptors, as evidenced by the ability of the immunoglobulin G to directly increase cAMP levels or to enhance the ability of TSH or a Graves' stimulating TSHRAb to increase cAMP levels. Three of the TSH receptor mutants, deletions of residues 295-306 and 387-395 and the point mutation of cysteine 301 to serine, are shown to be particularly useful in these assays and may be useful to clarify the pathogenetic role and clinical significance of stimulating TSHRAbs in patients with autoimmune thyroid disease who also have blocking TSHRAbs.

Ultrastructural evaluation of the oocytes and spermatozoa of the scleractinian coral Mussismilia harttii

Global coverage of living coral has declined by half since 1950s. Reef-building species have been severely impacted in this climate crisis scenario, compromising the future of coral reefs. Despite their importance, there is a lack of knowledge regarding the reproductive biology of scleractinian corals. In the present study, we evaluated through electron microscopy approaches, the gametes of the endemic Southwestern Atlantic coral Mussismilia harttii. We observed spherical oocytes with microvilli throughout the outer membrane. Fine granular material dispersed in cytoplasm, lipid granules, numerous yolk bodies, and mitochondria were identified in the oocytes. In addition, small Symbiodinium-like cells were observed, suggesting a vertical transmission from parental coral to oocytes. The spherical-head sperm presents a 9.3 ± 2.1 μm flagellum. The nucleus is located centrally in the head, and the centrioles are positioned between the nuclear base and the flagellar insertion, which is connected to the axoneme. This axoneme has a microtubular arrangement (9+2). Vesicles, underlining the inner plasma membrane, presented the same electron-dense pattern as the Golgi complex, and mitochondria positioned surrounding the axoneme. The vesicles present in the sperm may have a role as an acrosome since the oocytes do not develop any cell specialization for fertilization.

Simulated climate change and atrazine contamination can synergistically impair zebrafish testicular function

Elements that interfere with reproductive processes can have profound impacts on population and the equilibrium of ecosystems. Global warming represents the major environmental challenge of the 21st century, as it will affect all forms of life in the coming decades. Another coexisting concern is the persistent pollution by pesticides, particularly the herbicide Atrazine (ATZ), which is responsible for a significant number of contamination incidents in surface waters worldwide. While it is hypothesized that climate changes will significantly enhance the toxic effects of pesticides, the actual impact of these phenomena remain largely unexplored. Here, we conducted a climate-controlled room experiment to assess the interactive effects of the projected 2100 climate scenario and environmentally realistic ATZ exposures on the reproductive function of male zebrafish. The gonadosomatic index significantly decreased in fish kept in the extreme scenario. Cellular alterations across spermatogenesis phases led to synergic decreased sperm production and increased germ cell sloughing and death. ATZ exposure alone or combined with climate change effects, disrupted the transcription levels of key genes involved in steroidogenesis, hormone signaling and spermatogenesis regulation. An additive modulation with decreased 11-KT production and increased E2 levels was also evidenced, intensifying the effects of androgen/estrogen imbalance. Moreover, climate change and ATZ independently induced oxidative stress, upregulation of proapoptotic gene and DNA damage in post-meiotic germ cell, but the negative effects of ATZ were greater at extreme scenario. Ultimately, exposure to simulated climate changes severely impaired fertilization capacity, due to a drastic reduction in sperm motility and/or viability. These findings indicate that the future climate conditions have the potential to considerably enhance the toxicity of ATZ at low concentrations, leading to significant deleterious consequences for fish reproductive function and fertility. These may provide relevant information to supporting healthcare and environmental managers in decision-making related to climate changes and herbicide regulation.