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Abstract: The red blood cells of the neonatal brushtailed possum exhibit unusually strong cooperativity at high levels of oxygen saturation (n =5.4) which appear to arise from a concentration dependent aggregation of one of the neonatal hemoglobin isoforms. Red blood cells from neonatal pouched young exhibit a Bohr factor of −0.36. Stripped hemolysate is sensitive to added 2,3-bisphosphoglycerate (BPG) (apparent binding constant K =35 μmol L−1) and ATP (K =180 μmol L−1), but is largely insensitive towards chloride ions. Five isoforms of non-adult hemoglobin were identified using isoelectric focusing. Mass spectrometry indicated that two early isoforms contain alpha chains identical to the adult alpha chain. The remaining three isoforms are composed of identical alpha type and beta type gene products, but differ in their isoelectric points due to differential post-translational modification. [Copyright &y& Elsevier]

Abstract: The hemoglobins contained within the red blood cells of the adult brushtail possum exhibited cooperative (n =2.6) oxygen binding curves with an associated p50 of 38 mm Hg at pH 7.4 and a large Bohr effect (−0.60). Stripped hemolysate showed a Bohr effect of −0.27, and was sensitive to added DPG (K =56 μmol L−1), ATP (K =130 μmol L−1), and chloride ions. Four isoforms of hemoglobin were identified using isoelectric focusing. Mass spectrometry indicated that all four isoforms most likely represent the same gene products which have differentially undergone post-translational deamidation and glutathionylation. The oxygen binding characteristics of three isolated isohemoglobins have been determined. [Copyright &y& Elsevier]

This study reports the identification and characterization of markers of Alzheimer's disease (AD) in aged sheep ( Ovis aries ) as a preliminary step toward making a genetically modified large animal model of AD. Importantly, the sequences of key proteins involved in AD pathogenesis are highly conserved between sheep and human. The processing of the amyloid-β (Aβ) protein is conserved between sheep and human, and sheep Aβ 1–42 /Aβ 1–40 ratios in cerebrospinal fluid (CSF) are also very similar to human. In addition, total tau and neurofilament light levels in CSF are comparable with those found in human. The presence of neurofibrillary tangles in aged sheep brain has previously been established; here, we report for the first time that plaques, the other pathologic hallmark of AD, are also present in the aged sheep brain. In summary, the biological machinery to generate the key neuropathologic features of AD is conserved between the human and sheep, making the sheep a good candidate for future genetic manipulation to accelerate the condition for use in pathophysiological discovery and therapeutic testing. [ABSTRACT FROM AUTHOR]

Over the past decade, following the discovery of the human heme protein neuroglobin, many studies have searched for evidence for this protein's mechanism of action. Much data has accrued showing that high levels of neuroglobin will protect cells from apoptotic cell death, following a wide range of challenges. Various explanations of its actions, based on measured reactivity with oxygen, nitric oxide, or free radicals, have been proposed, but none have, as yet, been substantiated in vivo. Following preliminary experiments, it was previously hypothesised that 'the central role of neuroglobin in highly metabolically active cells and retinal and brain neurons is to reset the trigger level of mitochondrial cytochrome c release necessary to commit the cells to apoptosis' (I.U.M.B.M. Life (2008) 60, 398). In this article, we review the evidence, which has accumulated to support this hypothesised mechanism of action of neuroglobin and integrate this data, with other reported intracellular functions of neuroglobin, to suggest a plausible central role for neuroglobin in the control of apoptosis. © IUBMB IUBMB Life, 62(12): 878-885, 2010. [ABSTRACT FROM AUTHOR]

Abstract: We examined for the first time the hemoglobin components of the blood of the Australian lungfish, Neoceratodus forsteri and their functional responses to pH and the allosteric modulators adenosine triphosphate (ATP), guanosine triphosphate (GTP), 2,3-bisphosphoglyceric acid (BPG) and inositol hexaphosphate (IHP) at 25 °C. Lysates prepared from stripped, unfractionated hemolysate produced sigmoidal oxygen equilibrium curves with high oxygen affinity (oxygen partial pressure required for 50% hemoglobin saturation, p 50 =5.3 mmHg) and a Hill coefficient of 1.9 at pH 7.5. p 50 was 8.3 and 4.5 mmHg at pH 6 and 8, respectively, which corresponded to a modest Bohr coefficient (Δlog p50/ΔpH) of −0.13. GTP increased the pH sensitivity of oxygen binding more than ATP, such that the Bohr coefficient was −0.77 in the presence of 2 mmol L−1 GTP. GTP was the most potent regulator of hemoglobin affinity, with concentrations of 5 mmol L−1 causing an increase in p50 from 5 to 19 mm Hg at pH 7.5, while the order of potency of the other phosphates was IHP>ATP>BPG. Three hemoglobin isoforms were present and each contained both α and β chains with distinct molecular weights. Oxygen affinity and pH-dependence of isoforms I and II were essentially identical, while isoform III had a lower affinity and increased pH-dependence. The functional properties of the hemoglobin system of Neoceratodus appeared consistent with an active aquatic breather adapted for periodic hypoxic episodes. [Copyright &y& Elsevier]

Neuroglobin has been identified to protect brain neurons from apoptotic stress. Hydrogen sulphide has a role in the brain as a neuromodulator, involving NMDA receptor activation. Here we report on studies of the in vitro interaction of ferric neuroglobin with hydrogen sulphide. Hydrogen sulphide binds very tightly to the heme group of neuroglobin in a biphasic reaction. The faster of the two reaction processes is concentration dependent whilst the slower process is not. The rate of hydrogen sulphide binding is pH sensitive and as the pH is reduced over the physiological range the rate of reaction increases by a factor of ∼10. This change in reactivity appears to reflect the ionisation of the heme distal His ligand rather than a preference for the binding of H2S. We discuss the potential role of neuroglobin in the modulation of hydrogen sulphide sensitivity of neurons in the brain. © 2008 IUBMB IUBMB Life, 60(2): 135–138, 2008 [ABSTRACT FROM AUTHOR]

Milk is composed of a complex mixture of lipids, proteins, carbohydrates and various vitamins and minerals as a source of nutrition for young mammals. The composition of milk varies between individuals, with lipid composition in particular being highly heritable. Recent reports have highlighted a region of bovine chromosome 27 harbouring variants affecting milk fat percentage and fatty acid content. We aimed to further investigate this locus in two independent cattle populations, consisting of a Holstein-Friesian x Jersey crossbreed pedigree of 711 F2 cows, and a collection of 32,530 mixed ancestry Bos taurus cows. Bayesian genome-wide association mapping using markers imputed from the Illumina BovineHD chip revealed a large quantitative trait locus (QTL) for milk fat percentage on chromosome 27, present in both populations. We also investigated a range of other milk composition phenotypes, and report additional associations at this locus for fat yield, protein percentage and yield, lactose percentage and yield, milk volume, and the proportions of numerous milk fatty acids. We then used mammary RNA sequence data from 212 lactating cows to assess the transcript abundance of genes located in the milk fat percentage QTL interval. This analysis revealed a strong eQTL for AGPAT6, demonstrating that high milk fat percentage genotype is also additively associated with increased expression of the AGPAT6 gene. Finally, we used whole genome sequence data from six F1 sires to target a panel of novel AGPAT6 locus variants for genotyping in the F2 crossbreed population. Association analysis of 58 of these variants revealed highly significant association for polymorphisms mapping to the 5′UTR exons and intron 1 of AGPAT6. Taken together, these data suggest that variants affecting the expression of AGPAT6 are causally involved in differential milk fat synthesis, with pleiotropic consequences for a diverse range of other milk components. [ABSTRACT FROM AUTHOR]