638 research outputs found
Simulated biomechanical performance of morphologically disparate ant mandibles under bite loading
Augmented laminography, a correlative 3D imaging method for revealing the inner structure of compressed fossils
Non-destructive imaging techniques can be extremely useful tools for the investigation and the assessment of palaeontological objects, as mechanical preparation of rare and valuable fossils is precluded in most cases. However, palaeontologists are often faced with the problem of choosing a method among a wide range of available techniques. In this case study, we employ x-ray computed tomography (CT) and computed laminography (CL) to study the first fossil xiphosuran from the Muschelkalk (Middle Triassic) of the Netherlands. The fossil is embedded in micritic limestone, with the taxonomically important dorsal shield invisible, and only the outline of its ventral part traceable. We demonstrate the complementarity of CT and CL which offers an excellent option to visualize characteristic diagnostic features. We introduce augmented laminography to correlate complementary information of the two methods in Fourier space, allowing to combine their advantages and finally providing increased anatomical information about the fossil. This method of augmented laminography enabled us to identify the xiphosuran as a representative of the genus Limulitella
Human plasma phospholipid transfer protein increases the antiatherogenic potential of high density lipoproteins in transgenic mice
Plasma phospholipid transfer protein (PLTP) transfers phospholipids
between lipoprotein particles and alters high density lipoprotein (HDL)
subfraction patterns in vitro, but its physiological function is poorly
understood. Transgenic mice that overexpress human PLTP were generated.
Compared with wild-type mice, these mice show a 2.5- to 4.5-fold increase
in PLTP activity in plasma. This results in a 30% to 40% decrease of
plasma levels of HDL cholesterol. Incubation of plasma from transgenic
animals at 37 degrees C reveals a 2- to 3-fold increase in the formation
of pre-beta-HDL compared with plasma from wild-type mice. Although
pre-beta-HDL is normally a minor subfraction of HDL, it is known to be a
very efficient acceptor of peripheral cell cholesterol and a key mediator
in reverse cholesterol transport. Further experiments show that plasma
from transgenic animals is much more efficient in preventing the
accumulation of intracellular cholesterol in macrophages than plasma from
wild-type mice, despite lower total HDL concentrations. It is concluded
that PLTP can act as an antiatherogenic factor preventing cellular
cholesterol overload by generation of pre-beta-HDL
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