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Date: 12.13.2012

12.13.2012

platelets confer resistance to parasites

Platelets prevent parasitic infestation. Image from Sciencemag.org

From Science magazine this week, a report on how platelets express genes to help kill parasites. An excerpt from the perspective:

The six Plasmodium parasite species that cause disease in humans (P. falciparum, P. vivax, P. malariae, P. ovale wallickerie, P. ovale curtisii, and P. knowlesi) appear to have independently colonized hominids and influenced the genetic composition of different human populations (3). For example, the genes responsible for sickle cell anemia, thalassemia, and glucose-6-phosphate dehydrogenase deficiency have a higher frequency in populations where malaria is, or was once, endemic. These genes provide protection against severe malaria syndromes and likely evolved in response to the disease by providing a survival advantage (4). Another of these genes encodes the Duffy-antigen receptor for chemokines (DARC/Fy glycoprotein/CD234) found on red blood cells. This protein also acts as a receptor for P. vivax (5), and human red blood cells lacking this receptor are resistant to invasion by this species and by P. knowlesi (6, 7). The impact of this genetic selection can be seen in the geographical distribution of P. vivax. This parasite is spread throughout tropical regions of the world, but is rare in large areas of central and western Africa where many individuals lack Duffy-antigen receptor expression on red blood cells. Thus, this “Duffy-negative” phenotype appears to have evolved as an innate resistance mechanism to P. vivax infection.

McMorran et al. extend previous work that demonstrated an important role for platelets in resistance to malaria (8) by identifying platelet factor 4 (PF4) as a key molecule in platelet-mediated killing of P. falciparum. PF4 is released from α granules in activated platelets to promote blood coagulation (9). It binds the Duffy-antigen receptor, along with several other chemokines (10). McMorran et al. found that a functional Duffy-antigen receptor is required for the antiparasitic activity of PF4.

Also check out the scientific research paper here [subscription required].

12.13.2012

massachusetts eighth graders score well in science & math

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We are often told that American students aren’t excelling at science and math. What we never hear is that some school systems are in fact doing an excellent job in education our future generations. Massachusetts happens to be on state that excels. The new results from the Trends in Mathematics & Science Study, or TIMSS, reveal that Massachusetts students score highly in math and science. Only Singapore scored higher than Massachusetts in Science. And five countries scored higher than Massachusetts in math. The state performance was higher than any other in the U.S. It should be noted that not all countries participate this assesment.  See the excerpt from WBUR for links to the test results:

Massachusetts eighth-graders are among the smartest in the world when it comes to math and science, according to a new study of academic performance.

The state’s eighth-graders ranked second in science and sixth in math, respectively, in theTrends in International Mathematics and Science Study (TIMSS). More than half a million students from 63 countries participated in the test.

Only Singapore outscored the state’s eighth-graders on the science (PDF) part of the exam.

In the math section (PDF), Massachusetts students were outscored by test-takers from South Korea, Singapore, Chinese Taipei (Taiwan), Hong Kong and Japan.

12.13.2012

zinc cures jellyfish stings

 

jellyfish

A jellyfish. Image from blogs@ Cape Breton University

Looks like scientists may have stumbled upon a new cure for jellyfish stings. Scientists at the University of Hawaii found zinc gluconate inhibits the action of jellyfish venom. From Scientific American:

Yanagihara used electron microscopy to visualize the venom’s affects on blood cells, and as suspected, found that venom porins create holes that lead to cell rupture. But as previous clinical research had shown, the cells bursting wasn’t the real issue; Yanagihara found that instead, for several minutes before they break apart, red blood cells leaked potassium. Animal models confirmed that this sudden spike of potassium in the blood stream, termed hyperkalemia, is what leads to rapid changes in heart rate and function and, ultimately, the cardiovascular collapse that causes death by jellyfish. With the physiology of stings revealed, Yanagihara could finally start the laborious task of finding a way to stop the venom in its tracks.

Jellies aren’t the only animals that create porins. “The structural motif of the cubozoan porin reminded me of the bacterial porins,” said Yanagihara. “I scoured that literature to look for inhibitors of the self assembly of those pore forming toxins and discovered studies from the 1940s even as far back as the 1890′s citing zinc ion as useful in the inhibition of bacterial driven lytic reactions.” Yanagihara tested over 100 compounds to see if they inhibited jellyfish venom, and found that one of the safest—zinc gluconate—worked well.

Scientists aren’t 100% sure how zinc compounds inhibit the porins, but they believe that the zinc disrupts the binding domains necessary for the proteins to assemble to form pores. In in vitro models, Yanagihara found that a low dose of zinc gluconate completely prevented the venom’s blood cell busting effect. She then tested the compound in animal models, and found it worked better than the commercially available antivenom for box jelly stings, keeping the mice alive more than twice as long as the antivenom.

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