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Ballooning by xkcd
"Time to dance in front of Mary Jane! If I’m lucky, she’ll turn out not to practice pre-copulatory sexual cannibalism!"
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Researchers reveal how the alteration of a single nucleotide—the basic building block of DNA—could initiate fragile X syndrome, the most common inherited form of intellectual disability. The study appears in The Journal of Cell Biology.
Fragile X syndrome is caused by a defect in a gene on the X chromosome called fragile X mental retardation 1 (FMR1). Around 1 in 230 women and 1 in 360 men carry a so-called premutation, in which a series of DNA repeats at one end of the FMR1 gene is slightly longer than normal. These repeats are prone to even further expansion when FMR1 is passed from mother to child, causing the gene to switch off and stop producing a protein that is important for some cognitive functions.
A group of researchers from Albert Einstein College of Medicine of Yeshiva University in New York previously found that a certain site that initiates DNA replication, located near to the FMR1 gene, is inactivated in fragile X embryonic stem cells. This inactivation changes the way that the FMR1 gene is copied during cell division, which could pose problems that lead to expansion of the DNA repeats within the gene.
Intriguingly, a specific alteration in the DNA sequence near the FMR1 gene—a “single-nucleotide polymorphism” or SNP— has been linked to an increased risk of repeat expansion in some premutation carriers. These researchers discovered that this SNP overlaps with the inactive replication origin in fragile X embryonic stem cells.
Nucleotides in DNA include one of four bases (cytosine, thymine, adenine, or guanine). The researchers found that normal embryonic stem cells had a thymine base at the SNP site and an active replication origin. Fragile X cells, in contrast, had a cytosine base and an inactive origin. The researchers also derived embryonic stem cells from mothers carrying the fragile X premutation. These cells had a thymine base and a normal replication pattern and, accordingly, showed no tendency to expand their repeat numbers over time.
The findings show that the substitution of cytosine for thymine might inactivate the DNA replication origin when the FMR1 gene is passed from mother to child, increasing the risk of DNA repeat expansions that can lead to fragile X syndrome.
Gerhardt, J., et al. 2014. J. Cell Biol. doi:10.1083/jcb.201404157
Caption: Researchers used genetic mapping to determine that stem cells derived from mothers carrying a fragile X premutation (above) show a normal pattern of DNA replication when a nearby DNA sequence is similar to normal stem cells. Credit: Gerhardt et al., 2014
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Trees’re always a relief, after people.
This year’s Longitude Prize is focused on the growing problem of antibiotic resistant bacteria. They’ve put together a nice image, shown here, which showcases what they term ‘the ten most dangerous antibiotic resistant bacteria’. You can read more detail on each of them here:http://www.nesta.org.uk/news/antibiotic-resistant-bacteria
The prize offers a £10 million prize fund for the development of a cheap, accurate, and easy to use bacterial infection test kit, which will allow doctors to prescribe the correct antibiotics at the correct time for patients, to try to help minimise the development of antibiotic resistance.
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A fast-sensitive “electronic-nose” for sniffing the highly infectious bacteria C. diff, that causes diarrhoea, temperature and stomach cramps, has been developed by a team at the University of Leicester.
The team have measured the Volatile Organic Compounds (VOCs) given out by different of strains of Clostridium difficile and have shown that many of them have a unique “smell”. In particular, different strains show different chemical fingerprints which are detected by a mass spectrometer.
Identifying the unique ‘smell’ of C. diff which would lead to rapid diagnosis of the condition.
The research is published on-line in the journal Metabolomics.
Caption: This is an image of Clostridium difficile or C-diff. Credit: University of Leicester
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Seth Magle, who directs the Urban Wildlife Institute in Chicago, suspects that most of the species of bats found in cities are using cemeteries as habitat, or to forage for food. But cemeteries aren’t just great places for spooky things like bats.
Like parks, golf courses and other urban green spaces, cemeteries can provide a refuge for all sorts of wildlife, including red foxes, skunks, woodchucks, opossums, white-tailed deer and beaver, Magle says, as well as fox squirrels, gray squirrels and “all the sort of usual urban residents that you would expect — rats and house mice and things of that nature.”
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Steven Davis of the University of California, Irvine, and Robert Socolow of Princeton (best known for his work dividing the climate challenge into carbon “wedges”) have written “Commitment accounting of CO2 emissions,” a valuable new paper in Environmental Research Letters showing the value of shifting from tracking annual emissions of carbon dioxide from power plants to weighing the full amount of carbon dioxide that such plants, burning coal or gas, could emit during their time in service.
Credit Jason Lee/Reuters
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Human articular cartilage defects can be treated with nasal septum cells. Researchers at the University and the University Hospital of Basel report that cells taken from the nasal septum are able to adapt to the environment of the knee joint and can thus repair articular cartilage defects. The nasal cartilage cells’ ability to self-renew and adapt to the joint environment is associated with the expression of so-called HOX genes. The scientific journal Science Translational Medicine has published the research results together with the report of the first treated patients.
K. Pelttari, B. Pippenger, M. Mumme, S. Feliciano, C. Scotti, P. Mainil-Varlet, A. Procino, B. von Rechenberg, T. Schwamborn, M. Jakob, C. Cillo, A. Barbero, I. Martin. Adult human neural crest-derived cells for articular cartilage repair. Science Translational Medicine, 2014; 6 (251): 251ra119 DOI: 10.1126/scitranslmed.3009688
Articular cartilage replaced: MRI of defect tissue site before (left) and four months after (right) transplantation. Credit: University of Basel, Department of Biomedicine
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Language of Life : Mycoplasma
Mycoplasma refers to a genus of bacteria that lack a cell wall. Without a cell wall, they are unaffected by many common antibiotics, such as penicillin, that target cell wall synthesis.
The first strains of mycoplasma were isolated at the Pasteur Institute in 1898. Mycoplasmas are the smallest free-living organisms and considered the simplest of bacteria. Owing to their extremely basic genomes, they are like parasites exploiting host cells to fulfill their energy requirements and biosynthesis of their components.
Several species are pathogenic in humans, including M. pneumoniae, which is an important cause of atypical pneumonia and other respiratory disorders, and M. genitalium, which is believed to be involved in pelvic inflammatory diseases. Mycoplasma are the smallest living cells yet discovered,can survive without oxygen, and are usually about 0.1 µm in diameter.
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