In birds, differentiation of embryonic gonads is not as strictly determined by the genetic sex as it is in mammals, and can be influenced by early manipulation with a sex steroid hormone. Thus administration of an aromatase inhibitor induces testis development in the genetic female, and administration of estrogen induces a left ovotestis in the genetic male embryo. Another feature of avian gonadogenesis is that only the left ovary develops in most species. Molecular mechanisms underlying these features at the level of gene expression have not been elucidated. In this paper, we present evidence that a gene for aromatase cytochrome P-450, an enzyme required for the last step in the synthesis of estradiol-17 , is expressed in medullae of the left and right gonads of a female chicken embryo, but not in those of a male chicken embryo, and that an estrogen receptor gene is expressed only in epithelium (and cortex later, in the female) of the left, not the right, gonad of both sexes, but the expression in the male left gonad is temporary and restricted to an early stage of development. Differential expression of these two genes serves well to explain the above features of gonadal development in birds. Furthermore, in ovo administration of estradiol-17 from the 5th to the 14th day of incubation does not cause expression of the estrogen receptor gene in the right gonad of chicken embryos of either sex, suggesting that the absence of expression of the estrogen receptor gene in the right gonad is not the result of down-regulation, but may be regarded as an important cause of the unilateral ovarian development.

Enzymatic ring-opening polymerization of a 16-membered lactone, 1Epentadecanolide (PDL), has been carried out in bulk using various lipases of different origin as catalyst. The polymerization with Pseudomonasfluorescens lipase (lipase PF) catalyst afforded the corresponding polyester in high yields.The rate of the polymerization catalyzed by lipase PF at a temperature lower than 45°C was very small, whereas the polymerization at higher polymerization temperature (260°C) proceeded much faster. Lipase derived from Pseudomonas cepacia was also active for the polymerization of PDL.The polymerization catalyzed by Candida cylindracea lipase at high temperature (75°C) afforded the polymer with molecularweight up to 2.0 x lo'. The polymerization behavior of PDL through lipase catalysis has been compared with that of e-caprolactone (8-CL). PDL showed an enzymatically higher polymerizability than e-CL, despite the smaller ring-strain of PDL, which is due to the stronger recognition of PDL by lipase. Enzymatic copolymerization of PDL with other lactones using lipase PF catalyst produced copolymers with molecular weight of several thousands. From 13C NMR analysis, the diad sequence distributions were determined.' Without enzyme.

An immobilized lipase derived from Candida antarctica was used as catalyst for the ring opening polymerization of lactones. A small amount of the immobilized enzyme showed the extremely efficient catalysis in the lactone polymerization. The polymerization in the presence of 1-octanol enhanced the rate of reaction.

Enantioselective copolymerization of racemic substituted lactones with achiral lactones has been examined by using Candida antarctica lipase as catalyst. In the copolymerization of racemic β-butyrolactone with 12-dodecanolide, the (S)-isomer was preferentially reacted to give the (S)-enriched optically active copolymer with enantiomeric excess of β-butyrolactone unit = 69%, which is much larger than that of the homopolymerization under similar reaction conditions. The absolute configuration of β-butyrolactone unit in the copolymer was confirmed by the acid-catalyzed methanolysis to methyl 3-hydroxybutyrate. δ-Caprolactone was also enantioselectively copolymerized by the lipase catalyst to give the optically active polyester. The highest ee value (76%) was achieved by the copolymerization of δ-caprolactone and 12-dodecanolide in diisopropyl ether.

Enzymatic ring-opening polymerization of a 6-membered cyclic carbonate, 1,3dioxan-2-one, was investigated by using lipase as catalyst in bulk. Supported lipase derived from Cundidu antarcticu catalyzed the polymerization to give the corresponding aliphatic polycarbonate. Unchanged monomer was recovered in the absence of the enzyme or using an inactivated enzyme, indicating that the present polymerization proceeds through enzymatic catalysis.