Candida tropicalis ATCC 20336 can grow on fatty acids or alkanes as its sole source of carbon and energy, but strains blocked in ␤-oxidation convert these substrates to long-chain ␣,-dicarboxylic acids (diacids), compounds of potential commercial value (Picataggio et al., Biotechnology 10:894-898, 1992). The initial step in the formation of these diacids, which is thought to be rate limiting, is -hydroxylation by a cytochrome P450 (CYP) monooxygenase. C. tropicalis ATCC 20336 contains a family of CYP genes, and when ATCC 20336 or its derivatives are exposed to oleic acid (C 18:1 ), two cytochrome P450s, CYP52A13 and CYP52A17, are consistently strongly induced (Craft et al., this issue). To determine the relative activity of each of these enzymes and their contribution to diacid formation, both cytochrome P450s were expressed separately in insect cells in conjunction with the C. tropicalis cytochrome P450 reductase (NCP). Microsomes prepared from these cells were analyzed for their ability to oxidize fatty acids. CYP52A13 preferentially oxidized oleic acid and other unsaturated acids to -hydroxy acids. CYP52A17 also oxidized oleic acid efficiently but converted shorter, saturated fatty acids such as myristic acid (C 14:0 ) much more effectively. Both enzymes, in particular CYP52A17, also oxidized -hydroxy fatty acids, ultimately generating the ␣,-diacid. Consideration of these different specificities and selectivities will help determine which enzymes to amplify in strains blocked for ␤-oxidation to enhance the production of dicarboxylic acids. The activity spectrum also identified other potential oxidation targets for commercial development.

Separation of cell types and developmental stages in the Arabidopsis root and subsequent expression profiling have yielded a valuable dataset that can be used to select candidate genes for detailed study and to start probing the complexities of gene regulation in plant development. The electronic version of this article is the complete one and can be found online at

ABSTRACT. The elastic laminae in a vessel provide resilience to its wall. In perinatal and adult rats, we used in situ hybridization to localize the mRNA for tropoelastin (TE) in endothelial cells, medial smooth muscle cells, and adventitial fibroblasts of pulmonary arteries and veins to determine the contribution of these cells to laminae formation. We found that 1 ) all three cell types are elastogenic but for each the ontogenic pattern is different, 2) signal in the artery is strongest in the late fetal lung, 3) postnatally TE expression decreases first in the outer medial smooth muscle cells, and 4) the pattern of expression in arteries differs from that in veins. In the d 19 fetus, the signal for TE mRNA was higher in arteries than in veins. In the immediate postnatal period, the arterial signal declined, whereas the signal in veins increased. By postnatal d 21, the arterial TE signal per cell had significantly decreased to an intensity lower than that in veins. In the adult rat lung, no TE mRNA was detected by in situ hybridization. The reciprocal alterations in TE expression in pulmonary arteries and veins may suggest a response to the postnatal change in pulmonary blood pressure. We speculate that because all three cell types are potentially elastogenic they may all play a role in the remodeling that occurs after vascular injury. (Pediatr Res 31: 280-285, 1992) Abbreviations ISH, in situ hybridization TE, tropoelastin SSC, sodium chloride sodium citrate buffer RT, room temperature PA, pulmonary artery PV, pulmonary vein TGF-B, transforming growth factor+The resilience of the vascular wall is attributed largely to its elastic laminae. Synthesis of the elastin pro-protein, TE, by vascular smooth muscle cells has been demonstrated in tissues ( 1-4) and isolated cells (3,5,6). We have recently demonstrated the specificity of the TE complementary RNA probe and identified, by ISH, TE mRNA in endothelial cells of the rat preacinar PA in perinatal lung tissue (7). Although elastogenesis in pulmonary vascular cells is developmentally regulated (8) as in other tissues, the dramatic changes of pulmonary blood pressure and oxygenation at birth may be significant regulatory factors. Prosser et al. (9) have shown by ISH that there is increased TE mRNA in the medial smooth muscle cells of the hypoxia-induced pulmonary hypertensive calf compared with normotensive controls. With the physiologic postnatal drop in pulmonary arteriolar resistance, PA pressure decreases and PV pressure and flow rise concomitantly. To study the relative contribution of endothelial cells, smooth muscle cells, and adventitial fibroblasts to the formation of elastic laminae during normal perinatal pulmonary vascular adaptation and growth, we evaluated in perinatal rat pups TE mRNA distribution in the main PA, in preacinar and intraacinar arteries, and in postacinar and lobular PV. We found that TE expression decreases in the PA and increases in the PV postnatally and that endothelial cells, smooth muscle cells, and adventitial fibroblasts all...