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How do human eggs stay dormant and reproductively healthy for decades in the ovaries?

<p>Human eggs form before birth and can remain reproductively viable for up to 50 years before they are fertilised. But how can they remain dormant and healthy in the ovaries for so long?</p> <p>According to a new study published in Nature, the answer lies in their altered metabolic activity – skipping the use of a key protein and enzyme complex (respiratory complex I).</p> <p>To generate energy in their dormant state and avoid creating harmful molecules that can damage DNA and cause cell death, human eggs instead use alternative metabolic pathways never before seen in other animal cell types.</p> <p>“Humans are born with all the supply of egg cells they have in life. As humans are also the longest-lived terrestrial mammal, egg cells have to maintain pristine conditions while avoiding decades of wear-and-tear,” explains lead author Aida Rodriguez-Nuevo, a postdoctoral researcher at the Centre for Genomic Regulation (CRG), Spain.</p> <p>“We show this problem is solved by skipping a fundamental metabolic reaction that is also the main source of damage for the cell. As a long-term maintenance strategy, it’s like putting batteries on standby mode,” she adds.</p> <p>“This represents a brand new paradigm never before seen in animal cells.”</p> <h2>Altered metabolism in oocytes</h2> <p>Human eggs first form in the ovaries during foetal development. During the early stages of maturation, immature egg cells (known as oocytes) are put into cellular arrest and can remain dormant for decades.</p> <p>During this period, the oocyte’s mitochondria – kind of like the batteries of the cell – still generate just enough energy to fulfill the cell’s needs.</p> <p>To investigate how they do this, researchers used a combination of live imaging and proteomic (large-scale study of proteins) and biochemistry techniques to investigate this energy generation in human and Xenopus (aquatic frog) oocytes.</p> <p>Interestingly, they found that the oocytes do not use a fundamental protein, known as complex I, that initiates the reactions that generate energy in the mitochondria of most other cells.</p> <p>In fact, complex I is virtually absent in oocytes.</p> <p>This allows oocytes to avoid creating molecules known as reactive oxygen species (ROS) – molecules containing oxygen that readily react with other chemicals. ROS are normal by-products of cellular metabolism but are harmful when they accumulate, damaging the normal function of DNA, proteins, and other cellular components, and eventually causing cell death.</p> <p>They are also associated with lower rates of fertilisation and embryo survival.</p> <p>Live imaging showed that neither Xenopus nor human early oocytes showed any detectable ROS signal.</p> <h2>Implications for preserving ovarian reserves</h2> <p>According to the authors of the study, this finding explains why some individuals with mitochondrial conditions linked to complex I don’t experience reduced fertility, compared to those with conditions affecting other mitochondrial respiratory complexes.</p> <p>This finding could also lead to new strategies to help preserve the human egg cell reserves of patients undergoing cancer treatment.</p> <p>“Complex I inhibitors have previously been proposed as a cancer treatment. If these inhibitors show promise in future studies, they could potentially target cancerous cells while sparing oocytes,” explains senior author Dr Elvan Böke, group leader in the Cell &amp; Developmental Biology program at the CRG.</p> <p>The team plan to continue this research to discover the exact energy source that human egg cells use instead of complex I.</p> <p>“One in four cases of female infertility are unexplained – pointing to a huge gap of knowledge in our understanding of female reproduction. Our ambition is to discover the strategies (such as the lack of complex I) oocytes employ to stay healthy for many years in order to find out why these strategies eventually fail with advanced age,” concludes Böke.</p> <p><strong>This article originally appeared on <a href="https://cosmosmagazine.com/science/human-eggs-oocytes-dormant-metabolism/" target="_blank" rel="noopener">cosmosmagazine.com</a> and was written by Imma Perfetto.</strong></p> <p><em>Image: Shutterstock</em></p>

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AI-system promises better art reproductions – but not yet

<div> <div class="copy"> <p>A team from the Computer Science and Artificial Intelligence Laboratory at the Massachusetts Institute of Technology in the US is developing a new, deep learning-assisted system to reproduce art with a 3D printer to make more accurate, convincing reproductions.</p> <p>The system combines a process known as halftoning, which uses little dots of ink, and a layering technique that has 10 different colours, rather than the usual cyan, magenta, yellow, and black of 2D printers. This keeps the ink from blotting, which happens when too much is deposited on the printing surface, and it allows the printer to produce a wider range of tones.</p> <p>The technique, combined with a “deep learning model to predict the optimal stack of different inks”, results in “unprecedented spectral accuracy”, the team writes in a new paper, being presented this month at a <a rel="noopener" href="https://sa2018.siggraph.org/en/" target="_blank">computer graphics conference in Tokyo</a>.</p> <p>“If you just reproduce the colour of a painting as it looks in the gallery, it might look different in your home,” says Changil Kim, one of the paper’s authors. “Our system works under any lighting condition, which shows a far greater colour reproduction capability than almost any other previous work.”{%recommended 6743%}</p> <p>The researchers they hope the project will eventually make art more available, since “our reliance on museums to exhibit original paintings and sculpture inherently limits access and leaves those precious originals vulnerable to deterioration and damage”.</p> <p>“The value of fine art has rapidly increased in recent years, so there’s an increased tendency for it to be locked up in warehouses away from the public eye,” notes mechanical engineer Mike Foshey.</p> <p>“We’re building the technology to reverse this trend, and to create inexpensive and accurate reproductions that can be enjoyed by all.”</p> <p>The developers concede that there is still work to be done on the system, which they named RePaint, to truly render a van Gogh simulacrum. For starters, images like Starry Night use a cobalt blue that the ink library isn’t able to “faithfully reproduce”.</p> <p>But paintings – particularly oil paintings – are three-dimensional works. The brush strokes leave ridges and bumps that can reflect light, throwing off the rendering. Right now, the printer reads glossy reflections as white highlights, but the team has plans to incorporate recognition of “the rich spatially-varying gloss and translucency found in many paintings”. The system will learn to use surface reflection, rather than less colour, to reproduce the gloss.</p> <p>One other issue? Those glorious Monet water lilies look more like postage stamps, since the system’s reproductions are only a few centimetres across. The engineers are hoping to bring down the costs and time printing to accommodate larger reproductions.</p> <em>Image credit: Shutterstock            <!-- Start of tracking content syndication. Please do not remove this section as it allows us to keep track of republished articles --> <img id="cosmos-post-tracker" style="opacity: 0; height: 1px!important; width: 1px!important; border: 0!important; position: absolute!important; z-index: -1!important;" src="https://syndication.cosmosmagazine.com/?id=23508&amp;title=AI-system+promises+better+art+reproductions+%E2%80%93+but+not+yet" alt="" width="1" height="1" /> <!-- End of tracking content syndication -->          </em></div> <div id="contributors"> <p><em>This article was originally published on <a rel="noopener" href="https://cosmosmagazine.com/technology/ai-system-promises-better-art-reproductions-but-not-yet/" target="_blank">cosmosmagazine.com</a> and was written by Samantha Page. </em></p> </div> </div>

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