Search results for "Oxygen transport"
showing 10 items of 63 documents
Human Brain Neuroglobin Structure Reveals a Distinct Mode of Controlling Oxygen Affinity
2003
Neuroglobin, mainly expressed in vertebrate brain and retina, is a recently identified member of the globin superfamily. Augmenting O(2) supply, neuroglobin promotes survival of neurons upon hypoxic injury, potentially limiting brain damage. In the absence of exogenous ligands, neuroglobin displays a hexacoordinated heme. O(2) and CO bind to the heme iron, displacing the endogenous HisE7 heme distal ligand. Hexacoordinated human neuroglobin displays a classical globin fold adapted to host the reversible bis-histidyl heme complex and an elongated protein matrix cavity, held to facilitate O(2) diffusion to the heme. The neuroglobin structure suggests that the classical globin fold is endowed …
A vertebrate globin expressed in the brain.
2000
Haemoglobins and myoglobins constitute related protein families that function in oxygen transport and storage in humans and other vertebrates. Here we report the identification of a third globin type in man and mouse. This protein is predominantly expressed in the brain, and therefore we have called it neuroglobin. Mouse neuroglobin is a monomer with a high oxygen affinity (half saturation pressure, P50 approximately 2 torr). Analogous to myoglobin, neuroglobin may increase the availability of oxygen to brain tissue. The human neuroglobin gene (NGB), located on chromosome 14q24, has a unique exon-intron structure. Neuroglobin represents a distinct protein family that diverged early in metaz…
Oxygen Consuming Regions in EMT60/Ro Multicellular Tumour Spheroids Determined by Nonlinear Regression Analysis of Experimental PO2 Profiles
1987
Malignant cells can be studied in vitro, in a tumour-like microenvironment, by growing multicellular tumour spheroids in culture (Sutherland, McCredie and Inch, 1971). Franko and Sutherland (1979) utilized diffusion theory to explain the viable rim thicknesses of spheroids measured histologically. Without PO2 profiles, however, an unequivocal interpretation of their results was not possible. Systematic studies of the PO2 profiles in spheroids have since been made with oxygen microelectrodes by several groups (Carlsson et al., 1979; Kaufman et al., 1981; Mueller-Klieser and Sutherland, 1982a,b). Based on these measurements, new analyses utilizing diffusion theory are being developed to chara…
A Contribution Concerning the Unsettled Problem of Intrasplenic Microcirculation
1973
From morphological studies it is well known that the vascular bed of the spleen consists of at least two different compartments. Figure one schematically shows how the splenic microcirculation can be subdivided. One compartment corresponds to the white pulp (pathways number 1 and 2), the other compartment to the red pulp, for which the existance of either an open or a closed type of terminal vascular bed is discussed. Futhermore there are references that the microcirculation in the red pulp is not homogeneous but composed of both types, as illustrated by the pathways marked by number 3 and 4.
Water Influences on the Copper Active Site in Hemocyanin
2010
Active metal sites play a key role in the biochemistry of oxygen transport by hemocyanins. Observing the changes in the local electronic structure of the copper sites upon oxygenation is thus essen...
The diversity and evolution of chelicerate hemocyanins
2012
Abstract Background Oxygen transport in the hemolymph of many arthropod species is facilitated by large copper-proteins referred to as hemocyanins. Arthropod hemocyanins are hexamers or oligomers of hexamers, which are characterized by a high O2 transport capacity and a high cooperativity, thereby enhancing O2 supply. Hemocyanin subunit sequences had been available from horseshoe crabs (Xiphosura) and various spiders (Araneae), but not from any other chelicerate taxon. To trace the evolution of hemocyanins and the emergence of the large hemocyanin oligomers, hemocyanin cDNA sequences were obtained from representatives of selected chelicerate classes. Results Hemocyanin subunits from a sea s…
Globin genes are present in Ciona intestinalis.
2003
The key position of the Ciona intestinalis basal to the vertebrate phylogenetic tree brings up the question of which respiratory proteins are used by the tunicate to facilitate oxygen transport and storage. The publication of the Ciona draft genome sequence suggests that globin genes are completely missing and that-like some molluscs and arthropods-the sea squirt uses hemocyanin instead of hemoglobin for respiration. However, we report here the presence and expression of at least four distinct globin gene/protein sequences in Ciona. This finding is in agreement with the ancestral phylogeny of the vertebrate globins. Moreover, it seems likely that the Ciona hemocyanin-like sequences have enz…
Characterization of DrosophilaHemoglobin
2002
In contrast to previous assumptions, the fruit fly Drosophila melanogaster possesses hemoglobin. This respiratory protein forms a monomer of about 17 kDa that is not exported into the hemolymph. Recombinant Drosophila hemoglobin displays a typical hexacoordinated deoxy spectrum and binds oxygen with an affinity of 0.12 torr. Four different hemoglobin transcripts have been identified, which are generated by two distinct promoters of the hemoglobin (glob1) gene but are identical in their coding regions. Putative binding sites for hypoxia-regulated transcription factors have been identified in the gene. Hemoglobin synthesis in Drosophila is mainly associated with the tracheal system and the fa…
The Influence of Oxygen Affinity of Blood and Cerebral Blood Flow on Cerebral Oxygen Supply
1969
The quantity of oxygen transported, per unit of time, by the blood to the brain, is determined by the blood flow, the oxygen capacity, and the oxygen affinity of the blood. The O2-exchange between the blood and the tissue cells depends mainly on the oxygen transport characteristics of the blood and the O2 diffusion conditions in the blood and tissue.
Basic Mechanisms of Diffusive and Diffusion-Related Oxygen Transport in Biological Systems: A Review
1992
In mammals, energy metabolism of active tissues requires permanent availability of oxygen. Because cessation of O 2 supply results in loss of organ function within seconds or minutes, continual feed of adequate amounts of O 2 to tissue is the most vital task for living organisms. For many years, it therefore has been one of the greatest challenges to physiologists to understand the mechanisms provided by nature to satisfy this need for oxygen.