pH titration study of cytochrome c peroxidase and apocytochrome c peroxidase.

A pH titration study of cytochrome c peroxidase and apocytochrome c peroxidase was carried out at 25 degrees C and 0.1 M ionic strength. The net charge on cytochrome c peroxidase due to proton association and dissociation varies from +32 at pH 2 to --50.2 at pH 12, while that of apocytochrome c peroxidase varies between +24.5 at pH 3 to --48 at pH 12. The apoprotein tented to aggregate below pH 3. Between pH 4 and 8, the titration behavior of both the native enzyme and the apoenzyme are consistent with the semi-empirical Linderstr?m-Lang theory. Between pH 9 and 12, the titration behavior of both the holo- and apoproteins suggest they assume a more extended conformation which reduces the electrostatic interaction charged groups on the surface. In the acid region, between pH 4 and 3, a similar transition occurs in which the protein expands 40% based on the electrostatic factor of the Linderstr?m-Lang theory.     

Some observations on enamel thickness and enamel prism packing in the miocene hominoid Otavipithecus namibiensis

Otavipithecus namibiensis is currently the sole representative of a Miocene hominoid radiation in subequatorial Africa. Several nondestructive techniques, such as computed tomography (CT) and confocal microscopy (CFM), can provide useful information about dental characteristics in this southern African Miocene hominoid. Our studies suggest that the molars of Otavipithecus are characterized by (1) thin enamel and (2) a predominance of pattern 1 enamel prism. Together, these findings provide little support for the recent suggestion of an Afropithecini clade consisting of Otavipithecus, Heliopithecus, and Afropithecus. Instead, they lend some (though not conclusive) support to the suggestion of an Otavipithecus/African ape clade distinct from Afropithecus. © 1995 Wiley-Liss, Inc.     

Sphingosine kinase 1 expression is regulated by signaling through PI3K, AKT2, and mTOR in human coronary artery smooth muscle cells

Sphingosine kinase 1 (SphK1) is a lipid kinase implicated in mitogenic signaling pathways in vascular smooth muscle cells. We demonstrate that human coronary artery smooth muscle (HCASM) cells require SphK1 for growth and that SphK1 mRNA and protein levels are elevated in PDGF stimulated HCASM cells. To determine the mechanism of PDGF-induced SphK1 expression, we used pharmacological inhibitors of the PI3K/AKT/mTOR signaling pathway. Wortmannin, SH-5, and rapamycin significantly blocked PDGF-stimulated induction of SphK1 mRNA and protein expression, indicating a regulatory role of the PI3K/AKT/mTOR pathway in SphK1 expression. To determine which isoform of AKT regulates SphK1 mRNA and protein levels, siRNAs specific for AKT1, AKT2, and AKT3 were used. We show that AKT2 siRNA significantly blocked PDGF-stimulated increases in SphK1 mRNA and protein expression levels as well as SphK1 enzymatic activity levels. In contrast, AKT1 or AKT3 siRNA did not have an effect. Together, these results demonstrate that the PI3K/AKT/mTOR signaling pathway is involved in regulation of SphK1, with AKT2 playing a key role in PDGF-induced SphK1 expression in HCASM cells.     

A new candling procedure for thick and opaque eggs and its application to avian conservation management

The ability to monitor developing avian embryos and their associated vascular system via candling enables the application of important reproductive management techniques. Egg candling facilitates the confirmation of egg viability throughout the incubation process and identification of a precise position on a vein for the safe extraction of blood. Blood samples may then be analysed to retrieve vital health and genetic information to assist in conservation management. However, the thick or opaque egg shell characteristics of some avian species prevents the observation of egg contents using traditional candling methods, thus limiting management options. This paper tests a novel method of preparing thick-shelled or opaque eggs so that traditional egg candling and blood extraction methods may be applied. Eggs from captive emu (Dromaius novaehollandiae, Latham 1790) and southern cassowary (Casuarius casuarius johnsonii, Linnaeus 1758) were obtained, and partial fenestration was performed on two areas of shell either before incubation or at ⅓ of incubation. Hatchability and weight loss were examined as a measure of effect of the fenestration process on the developing embryo. Clear observation of vascular development was successful in 97% of viable fenestrated eggs, without affecting hatchability or weight loss. Blood samples were taken from developing embryos and DNA was successfully extracted for proof of concept of this new technique. The ability to observe vascular development and monitor the developing embryo in thick and opaque eggs will significantly improve both in situ and ex situ population management options such as in ovo sexing in species of concern.     

Measurement error in the Hawksley random zero sphygmomanometer: what damage has been done and what can we learn?

The Hawksley random zero sphygmomanometer is used in all aspects of blood pressure research, from clinical trials to evaluation of new blood pressure recorders. It is designed to reduce observer bias in blood pressure measurement. The problem is that it also underestimates blood pressure. Furthermore, this was first reported more than two decades ago. In this paper Rónán Conroy and colleagues explore the consequences of using an inaccurate instrument for important research and why prestigious organisations like the World Health Organisation continue to use it.