cell nuclei

anonymous asked:

To the person who you said is by definition a feminist: it is very much like when a person who is a male by definition, which is someone who is a "person bearing an X and Y chromosome pair in the cell nuclei and normally having a penis, scrotum, and testicles, and developing hair on the face at adolescence; a boy or man." They are a male by definition even if they don't idenify with the definition that they fall under.

That’s an interesting point, but I think that may also be a false equivalency.

Visualizing the genome: First 3D structures of active DNA created

Scientists have determined the first 3D structures of intact mammalian genomes from individual cells, showing how the DNA from all the chromosomes intricately folds to fit together inside the cell nuclei.

Researchers from the University of Cambridge and the MRC Laboratory of Molecular Biology used a combination of imaging and up to 100,000 measurements of where different parts of the DNA are close to each other to examine the genome in a mouse embryonic stem cell. Stem cells are ‘master cells’, which can develop – or 'differentiate’ – into almost any type of cell within the body.

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Scientists Keep a Molecule from Moving Inside Nerve Cells to Prevent Cell Death

Amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease) is a progressive disorder that devastates motor nerve cells. People diagnosed with ALS slowly lose the ability to control muscle movement, and are ultimately unable to speak, eat, move, or breathe. The cellular mechanisms behind ALS are also found in certain types of dementia.

A groundbreaking scientific study published in Nature Medicine has found one way an RNA binding protein may contribute to ALS disease progression. Cells make RNA to carry instructions for making proteins from DNA to protein-constructing machinery.

The culprit protein, TDP-43, normally binds to small pieces of newly read RNA and helps shuttle the fragments around inside nerve cell nuclei. The study describes for the first time the molecular consequences of misplaced TDP-43 inside nerve cells, and demonstrates that correcting its location can restore nerve cell function. Misplacement of TDP-43 in nerve cells is a hallmark of ALS and other neurological disorders including frontotemporal dementia (FTD), Alzheimer’s, Parkinson’s, and Huntington’s diseases. Studies that characterize common mechanisms behind these diseases could have widespread implications and may also accelerate development of broad-based therapies.

To find the misplaced TDP-43, the researchers viewed nerve cells donated by people who died from ALS or FTD under high powered microscopes. They discovered TDP-43 accumulates in nerve cell mitochondria, critical structures responsible for generating the enormous amount of energy nerve cells require. By physically isolating the affected mitochondria the researchers were able to pinpoint TDP-43’s exact location inside the subcellular structures. They were also able to characterize variations of the protein most likely to get misplaced.

This important work was led by Xinglong Wang, PhD, from the department of pathology at Case Western Reserve University School of Medicine and a team of scientists from his laboratory.

“By multiple approaches, we have identified the mitochondrial inner membrane facing matrix as the major site for mitochondrial TDP-43,” explained Wang. “Mitochondria might be major accumulation sites of TDP-43 in dying neurons in various major neurodegenerative diseases.”

The researchers discovered that once inside the mitochondria, TDP-43 resumes its RNA binding role and attaches itself to mitochondrial genetic material. This disrupts the mitochondria’s ability to generate energy for the cell. Wang’s team was able to precisely identify the RNA in mitochondria that was bound by TDP-43 and observe the resultant disassembly of mitochondrial protein complexes. This finding provides much needed clarity on the consequences of TDP-43 misplacement inside nerve cells and opens the door for deeper studies involving a range of neurological disorders. Although the study focused on ALS and FTD, according to Wang “mislocalization of TDP-43 represents a key pathological feature correlating strongly with symptoms in more than half of Alzheimer’s disease patients.”

Mutations in the gene encoding TDP-43 have long been linked to neurodegenerative diseases like ALS and FTD. Wang’s team found that disease-associated mutations in TDP-43 enhance its misplacement inside nerve cells. The researchers also identified sections of TDP-43 that are recognized by mitochondria and serve as signals to let it inside. These sections could serve as therapeutic targets, as the study found blocking them prevents TDP-43 from localizing inside mitochondria. Importantly, Wang’s team was able to keep TDP-43 out of nerve cell mitochondria in mice using small proteins which “almost completely” prevented nerve cell toxicity and disease progression.

“We, for the first time, provide the novel concept that the inhibition of TDP-43 mitochondrial localization is sufficient to prevent TDP-43-linked neurodegeneration,” said Wang. “Targeting mitochondrial TDP-43 could be a novel therapeutic approach for ALS, FTD and other TDP-43-linked neurodegenerative diseases.”

Wang has begun to develop small proteins that prevent TDP-43 from reaching mitochondria in human nerve cells, and has a patent pending for the therapeutic molecule used in the study.

There is no treatment currently available for ALS or FTD. The average life expectancy for people newly diagnosed with ALS is just three years, according to The ALS Association.

NIH3T3 cells were pre-loaded with a green fluorescent cell tracker dye prior to co-culture and prior to imaging, all cell nuclei were labelled with the DNA specific Hoechst 33342. This approach allowed to positively identify individual cells as either NIH3T3 or MDCK. Imaging reveals that even in the presence of a co-culture, the majority of cells continued to display a clear preference for growing on the ridges or in the grooves. Phase contrast and fluorescence imaging reveals that after 48 h of co-culture on 100µm wide grooves, NIH3T3 cells display a clear preference to migrate and grow on the ridge surfaces.

Leclerc et al., Biomaterials 2013

Red areas are cells that line capillaries feeding the heart muscle (the dark background area). The blue dots are cell nuclei.
Visualised using confocal microscopy (to see the colours) superimposed with differential interference contrast microscopy (to see the tissue structure) by Dr Paul Monaghan, Dr Tracey Hinton, Di Green and Dr Kim Wark, CSIRO.
Size: this piece of tissue is 260 micrometres wide

This is part of a project by CSIRO scientists to look at innovative ways to deliver new kinds of RNA-based treatments to tissues that may have been infected with viruses or have particular genetic problems.

Lynn Margulis (1938-2011) was an evolutionary theorist and science author, the first modern proponent of the significance of symbiosis in evolution. Her research fundamentally transformed and established the understanding of the evolution of cells with nuclei. Her work was seen as controversial and was widely rejected for years, until genetic evidence proved it definitively.

Her 1966 paper, “On the Origin of Mitosing Cells”, was rejected for publication by 15 scientific journals initially, but today it is considered a landmark in endosymbiotic theory. She also proposed the Gaia theory, which sees Earth as a self-regulating system.

This is a patch of nanoscopic needles that was built to inject DNA and other nucleic acids directly into individual cells. 

The technique, developed by scientists at Imperial College London and Houston Methodist Research Institute, constructs tiny porous groups of needles out of biodegradable silicon. Each needle is 1,000 times thinner than a human hair. The team showed that their innovation could be used to deliver therapeutic nucleic acids inside human and animal cells. 

[The image (above) shows human cells (green) on the nanoneedles (orange). The nanoneedles have injected DNA into the cells’ nuclei (Blue). The image was taken by the researchers using optical microscopy. Image courtesy Chiappini et al./ICL.]

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BIG NEWS IN LIFE SCIENCE:

Under the Sea, a Missing Link in the Evolution of Complex Cells

by Carl Zimmer

Unlike bacteria, humans have big, complex cells, packed with nuclei containing DNA and mitochondria that produce energy. All so-called eukaryotes share our cellular complexity: animals, plants, fungi, even single-celled protozoans like amoebae.

Scientists estimate that the first eukaryotes evolved about 2 billion years ago, in one of the greatest transitions in the history of life. But there is little evidence of this momentous event, no missing link that helps researchers trace the evolution of life from bacteria to eukaryotes.

On Wednesday, a team of scientists announced the discovery of just such a transitional form. At the bottom of the Arctic Ocean, they found microbes that have many — but not all — of the features previously only found in eukaryotes. These microbes may show us what the progenitors of complex cellular organisms looked like…

(read more: NY Times)

photo: R.B. Pedersen/Centre for Geobiology/University of Bergen