Deep muscles in the lower leg of the opossum

Abstract

the dopaminergic character of any of these progenitor cells. Double immunostaining for TH and the markers for young cells may reveal the possible dopaminergic character of the progenitors. P2 Segmental and quantitative differences between lamina I-thalamic and lamina I-periaqueductal grey projecting neurons in the cat Lamina I projections to either thalamus or periaque-ductal grey (PAG) have been described in different species, but the differences in number and distribution of these lamina I cells in each segment of the spinal cord (C1-Coc2) have not been studied before. In the cat, large WGA-HRP injections were made in the thalamus, and the results were compared with those from earlier studies of this laboratory on the spinal projections to the PAG (Mouton & Holstege, 1998, 2000), using the same materials and methods. Throughout the length of the spinal cord, at least twice as many lamina I cells were labeled after PAG injections as after thalamus injections. This difference was strongest for the lower lumbar and sacral cord, where many more labeled lamina I-PAG than lamina I-thalamic cells were found. In the thalamus injected cases most labeled lamina I neurons were found in the C7 segment, while in the PAG injected cases they were most numerous in C5-C6 and the upper thoracic segments. The present findings suggest that the lamina I-PAG pathway plays a more important role in nociception than the lamina I-thalamic pathway. The great difference between the number of lamina I cells projecting to the thalamus and PAG in the lumbosacral region may reflect the relay of specific non-nociceptive urogenital information to the PAG. P3 Developmental changes in endocardial expression of shear stress responsive genes KLF-2, ET-1 and NOS-3 in chicken embryos Hemodynamics play an important role in normal cardiogenesis and changes in blood flow can cause congenital heart malformations (Hogers et al., 1999). Since shear stress is positively correlated to flow it is also important in cardiac development. Endothelin-1 (ET-1) is a growth hormone and vasoconstrictor. The gene contains a shear stress response element (SSRE) in its promoter region, like the gene for endothelial nitric oxide synthase (NOS-3). NOS-3 produces NO, which is the functional counterpart of ET-1, a vasodilator. Expression of Lung Krü ppel-like factor (KLF-2) has been related to shear stress as it is expressed in the endothelium of the adult human aorta at sites of high shear stress. From in vitro experiments it is known that KLF-2 and NOS-3 are upregulated by high shear stress, whereas ET-1 is downregulated. In this study the expression patterns of these shear responsive genes KLF-2, ET-1 and NOS-3 were investigated during chicken cardiovascular development from stage HH16 to HH30. According to the in vitro studies ET-1 was expected to be low or absent and NOS-3 to be high at sites where KLF-2 expression is high. Using radioactive in situ hybridisation, it was shown that in the early stages expression patterns are mostly not shear-related, whereas during development this correlation becomes stronger. Patterns of KLF-2 and NOS-3 overlap in the endocardium at lumen constrictions in the heart, such as the sino-atrial transition, the atrioventricular canal and the outflow tract. In these regions KLF-2 and NOS-3 mRNA exclude that of ET-1. In the early stages the aortic sac and the pharyngeal arch arteries show KLF-2 and NOS-3 expression, where ET-1 is negative. Our results suggest that in the embryonic cardiovas-cular system KLF-2 is expressed in regions of highest shear stress, and that ET-1 and NOS-3 are, at least in the later stages, related to shear stress. REFERENCE Hogers B, DeRuiter MC, Gittenberger-de Groot AC, Poelmann RE. 1999. Extraembryonic venous obstructions lead to cardiovascular malformations and can be embryolethal. Cardiovasc Res 41:87-99. P4 Deep muscles in the lower leg of the opossum