The flagellar apparatus of spermatozoa in fish. Ultrastructure and evolution

Chondrichthyes possess an evolved type of spermatozoa. Their flagellar apparatus is characterized by the presence of flagellar roots which form the axis of the midpiece, and the existence of one or two lateral elements associated with the axoneme. Osteichthyes, mainly teleosteans, show a great diversity of spermatic forms. The primitive spermatozoon with a 9 + 2 pattern flagellum is common. The primitive spermatozoon has evolved along different lines. The spermatic diversity which results from this is mainly evident in the structure of the flagellar apparatus. In the animal kingdom the primitive spermatozoon with a 9 + 2 pattern flagellum, present in primitive metazoa, is retained in phyla where external fertilization is maintained. The main evolutionary tendencies--elongation, aflagellarity or biflagellarity--are generally connected with the acquisition of internal fertilization. These evolutionary tendencies are found in teleosteans. It is not possible to link aflagellarity or biflagellarity of the gamete in certain fishes to this method of fertilization. Only the elongation of the spermatozoon is connected, in certain cases, with internal fertilization, but this cannot be taken as general.     

Lessons learned through listening to biology students during a transition to online learning in the wake of the COVID‐19 pandemic

During the Spring Semester of 2020, an outbreak of a novel coronavirus (SARS‐CoV‐2) and the illnesses it caused (COVID‐19) led to widespread cancelling of on‐campus instruction at colleges and universities in the United States and other countries around the world. Response to the pandemic in university settings included a rapid and unexpected shift to online learning for faculty and students. The transition to teaching and learning online posed many challenges, and the experiences of students during this crisis may inform future planning for distance learning experiences during the ongoing pandemic and beyond. Herein, we discuss the experiences of first‐ and second‐year university students enrolled in a biology seminar course as their classes migrated to online environments. Drawing on reported student experiences and prior research and resources, we discuss the ways we will adjust our own teaching for future iterations of the course while offering recommendations for instructors tasked with teaching in online environments.     

Polymorphisms in the nucleotide excision repair gene ERCC2/XPD and risk of non-Hodgkin lymphoma

Non-Hodgkin lymphoma (NHL) represents a complex group of B- and T-cell malignancies characterised by chromosomal translocations. Since defects in DNA repair result in an increased frequency of chromosomal aberrations it has been hypothesised that genetic variation in DNA repair may be associated with risk of NHL. To investigate the relationship between DNA repair and NHL we analysed polymorphisms in XPD (R156R, D312N, K751Q) using DNA collected in a UK population-based case-control study of lymphoma. We observed no association between genetic variation in XPD and risk of NHL. However, the XPD 751 Gln allele was associated with a two-fold decreased risk of diffuse large B-cell lymphoma (OR 0.56, 95% CI 0.34–0.92, p = 0.02), the major subtype of NHL. Overall, our study identifies that XPD polymorphisms may be important in the aetiology of NHL although analysis of additional polymorphisms and extended haplotype studies are required to clarify their role.     

Toll-Like Receptor 9 in Plasmacytoid Dendritic Cells Fails To Detect Parvoviruses

Toll-like receptor 9 (TLR9) recognizes genomes of double-stranded DNA (dsDNA) viruses in the endosome to stimulate plasmacytoid dendritic cells (pDCs). However, how and if viruses with single-stranded DNA (ssDNA) genomes are detected by pDCs remain unclear. Here we have shown that despite the ability of purified genomic DNA to stimulate TLR9 and despite the ability to enter TLR9 endosomes, ssDNA viruses of the Parvoviridae family failed to elicit an interferon (IFN) response in pDCs.     

Oleate and linoleate stimulate degradation of β-casein in prolactin-treated HC11 mouse mammary epithelial cells

Although virtually all cells store neutral lipids as cytoplasmic lipid droplets, mammary epithelial cells have developed a specialized function to secrete them as milk fat globules. We have used the mammary epithelial cell line HC11 to evaluate the potential connections between the lipid and protein synthetic pathways. We show that unsaturated fatty acids induce a pronounced proliferation of cytoplasmic lipid droplets and stimulate the synthesis of adipose differentiation-related protein. Unexpectedly, the cellular level of β-casein, accumulated under lactogenic hormone treatment, decreases following treatment of the cells with unsaturated fatty acids. In contrast, saturated fatty acids have no significant effect on either cytoplasmic lipid droplet proliferation or cellular β-casein levels. We demonstrate that the action of unsaturated fatty acids on the level of β-casein is post-translational and requires protein synthesis. We have also observed that proteasome inhibitors potentiate β-casein degradation, indicating that proteasomal activity can destroy some cytosolic protein(s) involved in the process that negatively controls β-casein levels. Finally, lysosome inhibitors block the effect of unsaturated fatty acids on the cellular level of β-casein. Our data thus suggest that the degradation of β-casein occurs via the microautophagic pathway.