Sperm chemotaxis is driven by the slope of the chemoattractant concentration field
Spermatozoa of marine invertebrates are attracted to their conspecific female gamete by diffusive molecules, called chemoattractants, released from the egg investments in a process known as chemotaxis. The information from the egg chemoattractant concentration field is decoded into intracellular Ca2+ concentration ([Ca2+]i) changes that regulate the internal motors that shape the flagellum as it beats. By studying sea urchin species-specific differences in sperm chemoattractant-receptor characteristics we show that receptor density constrains the steepness of the chemoattractant concentration gradient detectable by spermatozoa. Through analyzing different chemoattractant gradient forms, we demonstrate for the first time thatStrongylocentrotus purpuratus sperm are chemotactic and this response is consistent with frequency entrainment of two coupled physiological oscillators: i) the stimulus function and ii) the [Ca2+]i changes. We demonstrate that the slope of the chemoattractant gradients provides the coupling force between both oscillators, arising as a fundamental requirement for sperm chemotaxis.
Authors: Zhylkaidarova A, Kaidarova D, Batyrbekov K, Shatkovskaya O, Begimbetova D Abstract We carried out an analysis of the total incidence of colon cancer throughout Kazakhstan. Retrospectively, according to the regional reports on endoscopic screening, the study showed an increase in the age-related incidence of colorectal cancer (CRC) cases from 2004-2008 to 2009-2014. The peak of morbidity in both periods was noted in the age category of>70 years. The indicators of the territorial distribution of CRC incidence make it possible to divide the regions into areas with low or high rates of CRC. Specific indicat...
Conclusions: The transduodenal approach for obtaining samples from solid lesions using a 19-G flexible needle seems feasible and accurate. PMID: 32447874 [PubMed - as supplied by publisher]