A Molecular Camouflage to Evade Innate Immunity

Innate immunity is the first line of defense employed by our body to fight against pathogens in general. Phagocytic killing of pathogens is an important aspect of innate immunity. The phagocytic cells of the innate immune mechanism such as the neutrophils and macrophages, are capable of discriminating between self and non-self and selectively kill the foreign (non-self) pathogens.

How do phagocytic cells do not kill our own cells?

All our cells have a glycoprotein attached to our cell membrane that is designated as CD47. Macrophages have a receptor for CD47, called as SIRPα (Signal Regulatory Protein-Alpha). Binding of a CD47 on our cell surface to the receptor SIRPα present on a phagocytic cell, prevents the phagocytes from the phagocytic killing of such cells.

CD47
http://www.rcsb.org/pdb/explore/explore.do?structureId=2jjs

Thus CD47 molecule provides a “self” signal to phagocytes and spares cells carrying this signal molecule from being destructed by phagocytes. The gene for this CD47 is located in the long arm of Chromosome number 3 (3q13.1-q13.2).

In essence, any foreign particle or cell tagged with the CD47 peptide act as a passport, stay in the body without triggering any inflammatory responses and evade from being destructed by phagocytic cells of the innate immune system.

Dennis Discher from the Molecular and Cell Biophysics and NanoBioPolymers Laboratory (University of Pennsylvania, Philadelphia) and associates, made use of this idea. They chemically synthesized a peptide similar to but smaller than CD47. This synthetic peptide with only 21 aminoacid residues can exactly fall into the groove of the (CD47 receptor) SIRPα and thus can prevent an inflammatory response. The researchers attached these ‘molecular mimic’ of the ‘self-peptide’ (CD47 mimic) to nanobeads and then injected them into hosts and successfully found out that such tagged nanobeads were indeed recognized as ‘self structures’ and phagocytic cells spared them from destruction!

In future, this ‘immune-evading’ strategy could help in the diagnosis and therapy of cancers.

-      Dr. P. Kumarasamy

Further Reading:

http://www.sciencemag.org/content/339/6122/971.abstract

http://blogs.nature.com/spoonful/2013/02/nanoparticles-engineered-to-shuttle-cancer-drug-past-immune-system.html

http://www.youtube.com/watch?v=dmaeaS6uRLA
http://cen.acs.org/articles/91/i8/Peptide-Fools-Immune-System-Allowing.html

Why don't hybrids of an interspecies mating survive?

Every individual species is characteristically different and are reproductively isolated and mating between species, even if it occurs,  the embryonic development of such hybrids is arrested even at an very early stage.

The questions that still remain are:
What really happens? 
What factors block the embryonic development in such interspecies mating? 

The answer comes from a recent publication from the PLoS Genetics an online free journal. 

Mitochondrial genome cannot make many of the proteins that the organelle need and most of such proteins are synthesized in the cytoplasm that are encoded in the nuclear genome. Mitochondria, the power house of the cell cannot function properly without proteins that are encoded by nuclear genome. Thus, the interactions of mitochondrial and nuclear DNA are critical to cellular life. The interactions of nuclear genome and mitochondrial genome are essential not only for the mitochondrial transcription, translation, and cellular respiration (oxidative phosphorylation) but also for the phenotypic variation and fitness of the organism as a whole . 

In the new study, Colin Meiklejohn from Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, USA and colleagues artificially introduced mutations in certain nuclear genes and mitochondrial genes of two different species of the fruitfly, Drosophila melanogaster and Drosophila simulans and have ‘genetically dissected’ and found out that a mitochondrial-nuclear incompatibility is indeed one of the main factors that hinders the embryonic development of hybrids. 

- Dr. P. Kumarasamy

Further reading:

http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1003238 http://www.the-scientist.com//?articles.view/articleNo/34398/title/Mitochondria-Versus-Nucleus/

Eat while you eat to have a cut in your fat

Our physiology as a whole is well coordinated and timed by an internal clock mechanism. Disturbing the ‘physiological timing’ may result in various pathological consequences.

Our heart rate shows a rhythmic fluctuation with a high at day time and low at night when we sleep so does the blood pressure. So, for checking your heart rate or blood pressure, the time at which you measure is important.

Different drugs are metabolized (degraded) at different rates that depends on the time of day.

For example, Alcohol is degraded slowly during day time and faster during night. That is why you experience ‘more kick’ for a lesser dose of alcohol when you drink during day time. Since the alcohol is degraded slowly during the day, more alcohol is retained and accumulated in your circulation for a longer time.

Blood clots faster during day but takes relatively a longer time at night. Hence, you tend to bleed more of a cut injury during night rather than during day! Therefore, safe time for men to have a shave is during day time!!

There are many more to add to this list of events showing rhythmic fluctuations under the purview  of our biological clock.

A recent study shows that mouse when allowed to feed freely at any time of the day (ad libitum) became obese and soon developed other complications. Whereas mouse fed with the same calorie food but fed only at restricted timings remained healthy. 


The moral of the study:
Follow a “restricted time” for eating.

Avoid continuous eating or eating at irregular timings or wide spread eating times.

This may result in

·         Increased Adiposity

·         Increased Glucose Intolerance

·         Increased Leptin Resistance

·         Increased Liver Pathology

·         Increased Inflammation and

·         Decreased Motor Coordination

-Dr. P. Kumarasamy

Further reading:

https://www.cell.com/cell-metabolism/abstract/S1550-4131%2812%2900189-1

CHELYABINSK METEOR EXPLOSION

The Chelyabinsk meteor of 15^th February 2013:

We all know that a massive asteroid the “2012 AH14 meteor” just passed some 27000 km from Earth on 16^th Feb 2013. Coincidently, a  day before this, another asteroid, a 10-ton meteor entered the Earth,  lit up the sky over the Russian region, exploded and hit the ground at Chelyabinsk on 15^th Feb 2013.

This ‘Chelyabinsk meteor’ entered the atmosphere at a hypersonic speed of at least 54,000 kilometers per hour and shattered into pieces about 30-50 kilometers above the ground level. NASA estimates the meteor to be at least 55 feet across and possibly weighed about 10,000 tons. The impact made a crater on the outskirts of Chelyabinsk.

Video links:

http://www.youtube.com/watch?v=XZEXNZwqnpU

http://www.youtube.com/watch?v=jQkr6zPujNI

http://www.youtube.com/watch?v=uBb1hXQZGbc

What are Asteroids, Meteors and Meteorites?

Asteroids are rocky objects wandering in space. They vary in their size from a few meters to about hundreds of kilometers wide. The bigger asteroids are also called as minor planets or dwarf planets (if the asteroids are quite big) or planetoids. The famous asteroids are seen as a belt of 750,000 rocky chunks lying between the orbits of Mars and Jupiter. There are more than millions of asteroids orbiting the sun.

When an asteroid enters Earth’s atmosphere (or any other planet), the asteroid begins to burn, light up due to the frictional heat. Now it is called as a shooting star or meteor.

Many asteroids are completely burnt up into ash before reaching the ground and some do reach the ground and these are called as meteorites.

There are more than 165 terrestrial meteor impact craters on the Earth’s surface. The structure of such Meteor Impact craters that appears like a scar on the Earth’s surface is often referred to as an Astrobleme.

The following 10 are the most amazing Impact Craters on Earth

http://www.youtube.com/watch?v=XlUILcsRDbg

1.              The Kaali Craters (a group of 9 meteorite craters) located in the village of Kaali on the Estonian island of Saaremaa (West Estonian archipelago) in the Baltic Sea. The crater is about 4000 – 8000 years old. The crater has a depth of 22 meters and a diameter of 110 meters.

2.              The Tenoumer Crater is located in the western Sahara Desert, Mauritania (North West Africa). It is 1.9 km in diameter and the edges of the crater rise up to 110 meters high above the base of the crater. The crater is estimated to be approximately 21000 years old.

3.              The Lonar Crater can now be seen as a saline soda lake located at Lonar in Buldana district of Maharashtra, India. The crater is about 1.2 km in diameter with a depth of about 137 meters. The age of this crater is estimated to be about 570,000 years.

4.              The Monturaqui Crater is located south of the Salar de Atacama, in the Antofagasta region of Chile (South Western part of South America). The crater is about 370 meters in diameter and approximately 34 meters deep. The crater is estimated to have been created some 660,000 years ago.

5.              The Roter Kamm Crater is located in the Namib Desert in the Karas Region of South West Africa. The crater is 2.5 km in diameter and 130 meters deep. The age is estimated to be between 4 and 5 million years.

6.              The Tswaing crater also located in South Africa some 40 km north of Pretoria is formed into a salt lake. The crater lake is about 1.13 km in diameter and 100 meters deep and the age is estimated to be some  220,000 years. There is a Museum with a memorial to the Astro-geologist Eugene Merle Shoemaker who showed that craters such as Tswaing are formed by impact. He is better known for the discovery of the Comet Shoemaker-Levy 9 which crashed into the Jupiter atmosphere between July 16 and July 22, 1994.

7.              The Pingualuit Crater is a perfectly round, water-filled crater located in the Ungava Peninsula of Quebec, in the Canadian Arctic region. This crater was formerly called as the Chubb Crater and later came to known as the New Quebec Crater. The edge of the crater is elevated by about 160 meters above the surrounding tundra and the crater is about 400 meter deep with a lake depth of about 267 meters. The crater is estimated to be about 1.4 million years old.

8.              The Amguid Crater located  in Algeria (North Africa), is approximately 530 meters in diameter and approximately 65 meters deep. The age of this crater is estimated to be less than 100,000 years.

9.              The Wolfe Creek Crater is the world’s second largest meteor impact Crater located in the Western Australia. The crater measures about 875 meters in diameter and 60 meters deep from the rim to the crater floor with the age is estimated to be less than 300,000 years.

10.          The Barringer Crater, the world’s largest crater is located in the northern Arizona   desert of the United States. It was formerly known as the Canyon Diablo Crater. This carter is named in honor of Daniel Barringer who first suggested that it was produced by the impact of a meteorite that was later named as Canyon Diablo Meteorite. The edge of this crater is elevated by about 45 meters above its surrounding plains. The crater is about 1,200 meters in diameter and about 170 meters deep and believed to be 50,000 years old.

 -Dr. P. Kumarasamy

A RAIN OF WEB SITES

Erick Reis, a twenty year old web-designer from the town of Santo Antonio da Platina, Brazil reported about thousands of spiders hanging along power lines near his friend’s house.
Ever since Reis posted the video on the Net on 7^th Feb 2013, over a million have watched so far this spectacular, giant network of ‘web-sites” raining from the sky!
Have a look at this to believe!
Initially these spiders were thought to be Anelosimus eximius. Arachnologist Deborah Smith, from the University of Kansas soon identified these spider species really belong to Parawixia bistriata.

Further reading:

http://www.wired.com/wiredscience/2013/02/thousands-of-spiders/

The dangerous POP culture!

Many organic pollutants are released by man that are previously unknown in nature. These organic compounds are highly persistent in the environment (because of their very slow degradation) and by virtue of this property these organic pollutants slowly enter food chain and accumulate (bioaccumulation) and get magnified through the food web (biomagnification). Such organic compounds are called POPs (Persistent organic pollutants) or PBTs (Persistent, Bioaccumulative and Toxic-pollutants).

I have classified POPs into two main groups:

1.     Polyhalogenated compounds (PHCs)

Per fluorinated compounds or perfluoro carbons (PFCs) - Bisphenol A (BPA)

Poly brominated diphenyl ethers or PBDEs

Poly chlorinated biphenyl (PCB)

Poly chlorinated dibenzo dioxins (PCDDs)

polychlorinated dibenzo furans (PCDFs)

     2.     Polycyclic aromatic hydrocarbons (PAHs)

For a list of PAHs – visit this site

Now the Poly Iso Butene (PIB), joins this list! – read the news below

The new entrant PIB 

Lyme Bay near Weymouth, Dorset (Southern part of UK), is internationally important for seabirds.

Recently, within a short span of time, over 4,000 seabird were found dead possibly affected by a mysterious sticky substance from mineral oil.  The sticky, colorless substance seems to act like glue on the birds’ feathers preventing them from flying and also interfered with their thermoregulation.

Chris Rowland and his team at Plymouth University have found that the ‘sticky substance’ is indeed a form of Poly Iso Butene (PIB), a lubricant additive that is used to improve the quality of lubricating oils.

- Dr. P. Kumarasamy