Is DNA Repair a Substitute For Sex?

Bdelloid rotifers seem to get along just fine without sex. What’s more, they have done so over millions of years of evolution, resulting in at least 370 species. These hardy creatures somehow escape the usual drawback of asexuality – extinction!

Bdelloid rotifers have been able to give up sex and survive because they have evolved an extraordinary efficient mechanism for repairing harmful mutations to their DNA.

In animals that do have sex, DNA repair is accomplished during meiosis, when chromosomes pair up (one from the father, one from the mother) and “fit” genes on one chromosome can serve as templates to repair damaged genes on the other chromosome. The bdelloid, though, always seems to reproduce asexually, by making a clone of itself. How then, does it cope with deleterious mutations?

Scientists demonstrated the enormous DNA repair capacity of bdelloid rotifers by zapping them with ionizing radiation (gamma rays), which has the effect of shattering its DNA into many pieces. “We kept exposing them to more and more radiation, and they didn’t die and they didn’t die and they didn’t die,” says Mark Welch. Even at five times the levels of radiation that all other animals are known to endure, the bdelloids were able to continue reproducing.

Philodina roseola

The bdelloids’ DNA repair capacity probably evolved due to a different environmental adaptation – tolerance of extreme dryness. Bdelloids, which live in ephemeral aquatic habitats such as temporary freshwater pools and on mosses, are able to survive complete desiccation (drying out) at any stage of their life cycle. They just curl up and go dormant for weeks, months, or years, and when water becomes available, they spring back to life. Desiccation, like ionizing radiation, breaks up the rotifers’ DNA into many pieces. Presumably, the same mechanisms they use to survive desiccation as part of their life cycle also protect them from ionizing radiation.

Extreme Resistance of Bdelloid Rotifers to Ionizing Radiation.2008. Gladyshev, E., and M. Meselson . Proc. Natl. Acad. Sci. 105 (13): 5139-5144.

Evidence for degenerate tetraploidy in bdelloid rotifers. 2008. Mark Welch, D.B., J.L. Mark Welch and M. Meselson. Proc. Natl. Acad. Sci. 105 (13): 5145-5149.

Died This Day: Hermann Rorschach

Watchmen & Rorschach © DC Comics

Rorschach (Nov. 8, 1884 - April 2, 1922) was a Swiss psychiatrist who devised the inkblot test that bears his name and that is widely used clinically for diagnosing psychopathology. His secondary-school nickname was Kleck, meaning "inkblot," because of his interest in sketching.

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In 1917, he learned of Szyman Hens, who had studied the fantasies of his subjects using inkblot cards. Rorschach began in 1918 using 15 accidental inkblots, asking patients, "What might this be?" He knew the human tendency to project interpretations and feelings onto ambiguous stimuli. The subjective responses of his subjects enabled him to distinguish among them on the basis of their perceptive abilities, intelligence, and emotional characteristics. His published results (1921) drew little interest until after his death. link

Jack Kirby Explains The Origin of Mankind

The Eternals created by Jack Kirby & © Marvel Comics

Jack Kirby retold the origin of the Earth and the evolution of Mankind more than once in his career as he introduced his wild new concepts to the comic book reading world. Here’s his take from ‘The Eternals’:

CLICK TO ENLARGE & READ

Jack explains what it's all about:

Read it all in the next issue of, "THE ETERNALS!"

Read Jack's "Origin of Homo mermanus"

The Hardness of Squid Beaks

Abstract: The beak of the Humboldt squid Dosidicus gigas represents one of the hardest and stiffest wholly organic materials known. As it is deeply embedded within the soft buccal envelope, the manner in which impact forces are transmitted between beak and envelope is a matter of considerable scientific interest

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Challengers of the Unknown © DC Comics

Here, we show that the hydrated beak exhibits a large stiffness gradient, spanning two orders of magnitude from the tip to the base. This gradient is correlated with a chemical gradient involving mixtures of chitin, water, and His-rich proteins that contain 3,4-dihydroxyphenyl-L-alanine (dopa) and undergo extensive stabilization by histidyl-dopa cross-link formation.

These findings may serve as a foundation for identifying design principles for attaching mechanically mismatched materials in engineering and biological applications.

The Transition from Stiff to Compliant Materials in Squid Beaks. 2008. Ali Miserez et al. Science 319: 1816-1819.

Living Upside-Down Shapes Spiders for Energy Saving

Art by Frank Cho

Researchers investigating spider species which live, feed, breed and ‘walk’ in an upside-down hanging position have found that their lifestyle drives a shape in spiders that confers high energy efficiency, as in oscillatory pendulums.

The great majority of land animals evolved legs capable of supporting the weight of their whole bodies, enabling them to move around with their heads above their feet. However, many spider species found it more convenient to literally turn their world upside down. They spend most of their lives hanging suspended by their legs, and ‘walk’ by swinging under the influence of gravity.

One of the focal questions was the evolutionary importance of ‘bridging’ – the technique many spiders use to move between remote plants by building their own silk bridges, which they cross by ‘walking’ suspended upside-down from them. Earlier research by other authors indicated that for monkeys this suspensory way of locomotion might be a more energetically efficient way of transportation than ‘regular’ walking on the ground.

“We discovered that spiders that live upside-down have evolved disproportionately longer legs relative to ‘normal’ spiders, which enables them to move faster while bridging than while ‘normally walking’ on the ground. Particularly ‘clumsy’ walkers are larger spiders, because their long legs – otherwise so convenient for bridging – do not allow an easy lifting of their relatively large body mass” says Dr. Jordi Moya-Laraño from Spain, the principal investigator on this project.





These results have implications for the evolution and ecology of spiders. For example, small spiders that hang from their webs should be able to leave their webs in search for prey by walking on the ground, as found in some tiny spiders, something that large spiders will be unable to do efficiently. link

Ref: Morphological Evolution of Spiders Predicted by Pendulum Mechanics. 2008. Jordi Moya-Laraño et al. PLOS One e1841.

New Organic Molecule Discovered in Space

Art by Vaughn Bode and Larry Todd

Researchers from the Max Planck Institute for Radio Astronomy in Bonn have detected for the first time a molecule closely related to an amino acid: amino acetonitrile. The organic molecule was found in the "Large Molecule Heimat", a giant gas cloud near the galactic centre in the constellation Sagittarius.

The « Large Molecule Heimat » is a very dense, hot gas clump within the star forming region Sagittarius B2. In this source of only 0.3 light-year diameter, which is heated by a deeply embedded newly formed star, most of the interstellar molecules known to date have been found, including the most complex ones such as ethyl alcohol, formaldehyde, formic acid, acetic acid, glycol aldehyde (a basic sugar), and ethylene glycol.

Starting from 1965, more than 140 molecular species have been detected in space, in interstellar clouds as well as in circumstellar envelopes. A large fraction of these molecules is organic or carbon-based. A lot of attention is given to the quest for so-called "bio"-molecules, especially interstellar amino acids. Amino acids, the building blocks of proteins and therefore key ingredients for the origin of life, have been found in meteorites on Earth, but not yet in interstellar space.

Amino acetonitrile (NH2CH2CN)

The simplest amino acid, glycine (NH2CH2COOH), has long been searched for in the interstellar medium but has so far not been unambiguously detected. Since the search for glycine has turned out to be extremely difficult, a chemically related molecule was searched for, amino acetonitrile (NH₂CH₂CN), probably a direct precursor of glycine.

"Finding amino acetonitrile has greatly extended our insight into the chemistry of dense, hot star-forming regions. I am sure we will be able to identify in the future many new, even more complex organic molecules in the interstellar gas. We already have several candidates!" says Karl Menten, director at the Max Planck Institute for Radioastronomy. link

Just as long as they don't find, "The Green Slime"....!

Fear that Freezes the Blood in Your Veins

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"The blood froze in my veins" or "My blood curdled" – these common figures of speech can be taken literally, according to the latest studies. For it turns out that intense fear and panic attacks can really make our blood clot and increase the risk of thrombosis or heart attack.

Earlier studies showed that stress and anxiety can influence coagulation.A Bonn-based research team around Franziska Geiser (from the Clinic and Policlinic for Psychosomatic Medicine and Psychotherapy) and Ursula Harbrecht (from the Institute of Experimental Haematology and Transfusion Medicine) have been the first to conduct a very careful examination of coagulation in patients with anxiety disorders.

In the coagulation system two mechanisms operate that are indispensable to life and normally work in opposite directions, each counterbalancing the other. First, coagulation involves a thickening of the blood so that a plug can form and prevent excessive bleeding from damaged vessels. Second, there is "fibrinolysis", a process that keeps the blood fluid and breaks down clots. In the case of the anxiety-disorder patients, however, the researchers observed through close analysis of the blood an activation of coagulation accompanied by an inhibition of fibrinolysis. For these types of patients, the coagulation system goes out of balance as the coagulation tendency rises – possibly with dangerous consequences. In extreme cases the imbalance can lead to blockage of a coronary artery.

The increased coagulation tendency could, says Franziska Geiser, be the "missing link" that explains why anxiety patients have a statistically higher risk of dying from heart disease by a factor of 3 or 4. link