Polarized light propagation in corneal lamellae.

The propagation of polarized light through the cornea is affected by the orientations of the corneal lamellae and by the refractive imbalance between the collagen fibrils and the ground substance. Thus, well-designed measurements and analyses of polarized light propagation through the cornea can be used to obtain information regarding the cornea's lamellar and fibrillar structures. This paper shows that, for the rabbit, measured values of the optical parameters strongly suggest that the distribution of lamellae orientations is not random, but has one (or two) preferred orientation directions. Also, there is considerable evidence that collagen is intrinsically anisotropic. The Weiner formula gives the effective birefringence of an assembly of parallel isotropic fibrils and its generalization to the case of anisotropic fibrils is presented. Finally, calculations based on preferred orientation models having lamellae composed of anisotropic fibrils show that comparison with experimental values can yield structural information.

Prostate cancer metastasis-suppressor genes: a current perspective.

Prostate cancers account for 43% of all cancers diagnosed in American men. It is estimated that in 1996, 317,000 new cases of prostate cancer were diagnosed and 41,000 men died of the disease. The challenge of treating prostate cancer lies in accurately distinguishing those histologically-localized cancers which will complete metastatic progression from those that will remain indolent. At this time, we lack appropriate histological markers to make such distinctions, therefore, it is often difficult to accurately predict the clinical course of an individual patient's disease. There is growing evidence that a critical event in the progression of a tumor cell from a non-metastatic to metastatic phenotype is the loss of function of metastasis-suppressor genes. These genes specifically suppress the ability of a cell to metastasize. Work from several groups has demonstrated that human chromosomes 8, 10, 11 and 17 encode prostate cancer metastasis suppressor activities. As a result of these efforts the first prostate cancer metastasis-suppressor gene, KAI1, was identified and mapped to the p11-2 region of chromosome 11. In subsequent studies, an additional gene encoded by the same region, CD44 was also determined to have metastasis-suppressor activity. Recent studies have shown a correlation between decreased expression of KAI1 and CD44 and an increased malignant potential of prostate cancers. It is anticipated that the identification of other metastasis suppressor genes may allow for the development of diagnostic markers useful in the clinical substaging of individual tumors. This manuscript is intended to present our perspective on the importance of these genes in the understanding of prostate cancer progression. More importantly, we present new findings from our laboratory's effort to identify the metastasis-suppressor genes encoded by human chromosome 17. Specifically we report the strategy currently being used to evaluate a series of candidate genes and the approach being utilized to pinpoint the metastasis-suppressor region on human chromosome 17.

Development of a high-efficiency method for gene marking of Dunning prostate cancer cell lines with the enzyme beta-galactosidase.

Although the bacterial enzyme beta-galactosidase has been used as a reporter gene in a variety of mammalian systems; the variability and instability of its expression has limited its use. Transfection of Dunning rat prostatic cell lines with beta-galactosidase expression plasmids resulted in 5-10% of cells expressing the enzyme transiently, and < 5% of G418-resistant clones showing any level of expression. To address this problem, we developed a labeling protocol using a replication defective retrovirus containing a beta-galactosidase expression cassette. Between 30-50% of cells transduced expressed high levels of this enzyme. Homogeneous cell populations were isolated by subsequent fluorescence-activated cell sorting, using a fluorescent beta-galactosidase substrate. Using a modification of standard staining procedures, small metastatic foci of cells expressing beta-galactosidase in mouse lung tissue were detected with high sensitivity. This method has several advantages over standard transfection protocols, including the expedient and efficient transfer of the beta-galactosidase gene and the stability of its expression in a variety of Dunning sublines.