Loss of the SKI proto-oncogene in individuals affected with 1p36 deletion syndrome is predicted by strain-dependent defects in Ski-/- mice.

Experiments involving overexpression of Ski have suggested that this gene is involved in neural tube development and muscle differentiation. In agreement with these findings, Ski-/- mice display a cranial neural tube defect that results in exencephaly and a marked reduction in skeletal muscle mass. Here we show that the penetrance and expressivity of the phenotype changes when the null mutation is backcrossed into the C57BL6/J background, with the principal change involving a switch from a neural tube defect to midline facial clefting. Other defects, including depressed nasal bridge, eye abnormalities, skeletal muscle defects and digit abnormalities, show increased penetrance in the C57BL6/J background. These phenotypes are interesting because they resemble some of the features observed in individuals diagnosed with 1p36 deletion syndrome, a disorder caused by monosomy of the short arm of human chromosome 1p (refs. 6-9). These similarities prompted us to re-examine the chromosomal location of human SKI and to determine whether SKI is included in the deletions of 1p36. We found that human SKI is located at distal 1p36.3 and is deleted in all of the individuals tested so far who have this syndrome. Thus, SKI may contribute to some of the phenotypes common in 1p36 deletion syndrome, and particularly to facial clefting.     

Chromosomal variation and heterochromatin polymorphisms inPeromyscus maniculatus

Summary Evidence is presented that chromosomal variation inPeromyscus results from 1. addition of heterochromatic short arms to acrocentric chromosomes, and 2. pericentric inversions. Constitutive heterochromatin polymorphisms contribute to variation in the amount of heterochromatin inPeromyscus populations.Submitted in partial fulfilment of the requirements of Master of Science degree in Zoology at the University of Wyoming.Supported in part by Public Health Service Grant No. GM-20491 from the National Institute of Health and by grants from the U. Wyoming Division of Basic Research and Research Coordination.     

Effects of loading density on cafish blood

Summary Results from this study indicate that a fish density stress syndrome exists for red blood cell morphology. Smaller (by 3.5%) and rounder (by 0.6%) red blood cells were consistently found in intensive fish cultures.Acknowledgments. This work was conducted as part of the Federal Interagency Energy/Environmental Research and Development Program with funds administered through the Environmental Protection Agency (EPA Contract No. EPA-IAG-D8-E721-DR, TVA Contract No. TV-41967A). Dr Ralph H. Brooks and Billy G. Isom are acknowledged for making this study possible. The data were kindly donated by Dr R.W. Williams and W.E. Barksdale, both formerly with the Department of Biology, University of North Alabama, Florence, Alabama.     

Evidence from the Mars Express High Resolution Stereo Camera for a frozen sea close to Mars' equator

It is thought that the Cerberus Fossae fissures on Mars were the source of both lava and water floods two to ten million years ago. Evidence for the resulting lava plains has been identified in eastern Elysium, but seas and lakes from these fissures and previous water flooding events were presumed to have evaporated and sublimed away. Here we present High Resolution Stereo Camera images from the European Space Agency Mars Express spacecraft that indicate that such lakes may still exist. We infer that the evidence is consistent with a frozen body of water, with surface pack-ice, around 5 degrees north latitude and 150 degrees east longitude in southern Elysium. The frozen lake measures about 800 x 900 km in lateral extent and may be up to 45 metres deep--similar in size and depth to the North Sea. From crater counts, we determined its age to be 5 +/- 2 million years old. If our interpretation is confirmed, this is a place that might preserve evidence of primitive life, if it has ever developed on Mars.     

Plasma membrane phosphoinositide organization by protein electrostatics

Phosphatidylinositol 4,5-bisphosphate (PIP2), which comprises only about 1% of the phospholipids in the cytoplasmic leaflet of the plasma membrane, is the source of three second messengers, activates many ion channels and enzymes, is involved in both endocytosis and exocytosis, anchors proteins to the membrane through several structured domains and has other roles. How can a single lipid in a fluid bilayer regulate so many distinct physiological processes? Spatial organization might be the key to this. Recent studies suggest that membrane proteins concentrate PIP2 and, in response to local increases in intracellular calcium concentration, release it to interact with other biologically important molecules.