X-Message-Number: 28146
From: "Basie" <>
Subject: You can have your anti freez and eat it.
Date: Thu, 29 Jun 2006 13:50:13 -0400

Jokes aside. I wonder if one eats these  fish whether the anti freeze 
proteins will be  would be absorbed by the human gut.

Basie
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>


Researchers Discover Which Organs In Antarctic Fish Produce Antifreeze
Thirty-five years ago Arthur DeVries of the University of Illinois at 
Urbana-Champaign first documented antifreeze glycoproteins (AFGPs) in 
Antarctic notothenioid fishes. This month three colleagues report they've 
solved the ensuing, long-running mystery of where these AFGPs, which allow 
the fish to survive in icy waters, are produced.
Chi-Hing 'Christina' C. Cheng, a professor of animal biology at Illinois, 
and colleagues have discovered that antifreeze glycoproteins originate in 
the exocrine pancreas and the stomach of Antarctic fish, not the liver as 
long presumed.
"Ever since the discovery of these antifreeze proteins, it was assumed they 
had to be produced in the liver, since the vertebrate liver is well known as 
a source of secreted plasma protein, so there was no reason to think 
otherwise" said Chi-Hing "Christina" C. Cheng, a professor of animal 
biology. "It turns out that the liver has no role in the freezing avoidance 
in these fishes at all."
Instead, antifreeze glycoproteins (AFGP) originate primarily from the 
exocrine pancreas and the stomach, say Cheng, Paul A. Cziko and Clive W. 
Evans in a paper appearing online this week ahead of regular publication in 
the Proceedings of the National Academy of Sciences. Cziko is a research 
specialist at Illinois. Evans is a professor of molecular genetics and 
development at the University of Auckland in New Zealand.
The liver-synthesis mindset dominated earlier studies even though results 
appeared to be at odds, Cheng said. The first radioactive-tracer 
characterization of liver AFGP biosynthesis, in fact, suggested another 
source of production was possible. Later on, Northern-blot studies had shown 
very low expression levels of antifreeze messenger RNA in the liver, but 
this was inconsistent with high levels of production of the protein, the 
researchers noted.
Cheng and colleagues used Northern blots of total RNA from various tissues 
to hybridize with an AFGP gene probe. A clear picture of strong AFGP mRNA 
expression came into focus in the pancreatic tissues in all notothenioids 
tested. The use of cDNA cloning and sequencing showed that the mRNA all 
encode secreted AFGPs.
An RNA analysis from tissues of a single notothenioid unveiled the anterior 
portion of the stomach, next to the esophagus-stomach junction, as being the 
only other site with strong AFGP mRNA expression. Using antibodies, the 
researchers found the absence of liver synthesis and strong pancreas 
expression in newly hatched fish larvae and young juveniles.
The exocrine pancreas is the larger of the two parts that make up the 
pancreas. It consists of tubuloacinar glands that primarily manufacture and 
secrete digestive enzymes that break down food in the intestine so it can be 
absorbed.
In this case, AFGPs are secreted into the intestinal lumen where they 
protect the intestinal fluid from being frozen by ice crystals that come in 
with seawater and food. Internal fluids in notothenioids are about one-half 
as salty as seawater. While seawater reaches its freezing point at -1.91 
degrees Celsius, fish fluids freeze at about -1 degree Celsius. These 
species dwell in water that rarely rises above the freezing point and is 
regularly filled with ice crystals.
From the intestine, the AFGPs are, apparently, absorbed into the blood. This 
hypothesis is based on the near-identical composition and abundance of AFGPs 
found in the fish serum.
"In this comprehensive study, we confirm that the exocrine pancreas is the 
major AFGP synthesis site in Antarctic notothenioid fishes from hatching 
through adulthood, while the liver is AFGP-expression null in all life 
stages," the researchers conclude. "Because the notothenioids are confined 
to chronically icy Antarctic waters, and face high risks of ice inoculation 
from frequent seawater drinking, the evolution of AFGPs in these fishes was 
probably driven first and foremost by the need to prevent the hyposmotic 
intestinal fluid from freezing."
The researchers also studied a variety of fishes from Arctic waters that 
have liver expression of AFGPs, and found that all of them also express 
antifreeze in the pancreas.
The findings, they wrote, bring a new perspective to teleost 
freeze-avoidance physiology and "reveals that the long-held paradigm of 
hepatic-based AF synthesis and secretion is no longer universally 
applicable." Instead, pancreatic antifreeze expression is universal.
The National Science Foundation funded the research through two grants 
Cheng, while Evans received funding from the University of Auckland Research 
Committee.

Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=28146