PubMed Health⌕ Search

Biomedical subjects

K M Towe

Publications and source records attributed to K M Towe.

12 recordsLinked to original sources
PubMed1990

Aerobic respiration in the Archaean?

The Earth's atmosphere during the Archaean era (3,800-2,500 Myr ago) is generally thought to have been anoxic, with the partial pressure of atmospheric oxygen about 10(-12) times the present value. In the absence of aerobic consumption of oxygen produced by photosynthesis in the ocean, the major sink for this oxygen would have been oxidation of dissolved Fe(II). Atmospheric oxygen would also be removed by the oxidation of biogenic methane. But even very low estimates of global primary productivity, obtained from the amounts of organic carbon preserved in Archaean rocks, seem to require the sedimentation of an unrealistically large amount of iron and the oxidation of too much methane if global anoxia was to be maintained. I therefore suggest that aerobic respiration must have developed early in the Archaean to prevent a build-up of atmospheric oxygen before the Proterozoic. An atmosphere that contained a low (0.2-0.4%) but stable proportion of oxygen is required.

Aerobiosis↗
PubMed1981

Structural distinction between ferritin and iron-dextran (imferon). An electron diffraction comparison.

Electron diffraction data from ferritin, iron-dextran (Imferon), ferrihydrite, and beta-FeOOH support earlier suggestions that ferritin iron and ferrihydrite are structurally the same and totally different from Imferon and beta-FeOOH, which are closely related. The conclusion that ferritin and Imferon are uniquely similar is not confirmed. Ferrihydrite-dextran complexes should make a better analog than existing iron-dextrans for the study of ferritin iron-protein interactions.

Ferritins↗
PubMed1970

Oxygen-collagen priority and the early metazoan fossil record.

The thesis is developed that a low oxygen level Precambrian atmosphere presented early-evolving metazoan organisms with physiological connective tissue priorities resulting from the important molecular oxygen requirements in the biosynthesis of collagen hydroxyproline. Shells, cuticles, and carapaces which are not mandatory metazoan prerequisites but which directly or indirectly demand substantial connective tissue collagen are oxygen expensive, low priority features. A marked increase in atmospheric oxygen level near the beginning of the Paleozoic would eliminate oxygen-collagen priorities simultaneously and on a world-wide basis in all metazoan stocks providing evolutionary pressure for enlarged musculatures and associated "hard parts." This could explain the sudden presence in the fossil record of the early Cambrian of advanced and diversified metazoans, the earlier forms of which were essentially unpreservable.

Animals↗
PubMed1967

Echinoderm calcite: single crystal or polycrystalline aggregate.

Electron microscopy of natural and broken surfaces of echinoid skeletal plates reveals that the interior portions have the morphology of a single crystal, whereas the exterior is a polycrystalline aggregate with preferred orientation. These data help to resolve earlier contradictory x-ray and optical evidence.

Animals↗