Stable transformation of papaya via microprojectile bombardment

Summary Stable transformation of papaya (Carica papaya L.) has been achieved following DNA delivery via high velocity microprojectiles. Three types of embryogenic tissues, including immature zygotic embryos, freshly explanted hypocotyl sections, and somatic embryos derived from both, were bombarded with tungsten particles carrying chimeric NPTII and GUS genes. All tissue types were cultured prior to and following bombardment on half-strength MS medium supplemented with 10 mg 1^–1 2,4-D, 400 mg 1^–1 glutamine, and 6% sucrose. Upon transfer to 2,4-D-free medium containing 150 mg 1^–1 kanamycin sulfate, ten putative transgenic isolates produced somatic embryos and five regenerated leafy shoots. Leafy shoots were produced six to nine months following bombardment. Tissues from 13 of these isolates were assayed for NPTII activity, and 10 were positive. Six out of 15 isolates assayed for GUS expression were positive. Three isolates were positive for both NPTII and GUS,Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - GUS -glucuronidase - X-gluc 5-Br-4-Cl-3-indolyl--D-glucuronic acid - CaMV cauliflower mosaic virus - NOS nopaline synthase - NPTII neomycin phosphotransferase II Journal Series no. 3448 of the Hawaii Institute of Tropical Agriculture and Human Resources     

Tracking metastatic tumor cell extravasation with quantum dot nanocrystals and fluorescence emission-scanning microscopy

Metastasis is an impediment to the development of effective cancer therapies. Our understanding of metastasis is limited by our inability to follow this process in vivo. Fluorescence microscopy offers the potential to follow cells at high resolution in living animals. Semiconductor nanocrystals, quantum dots (QDs), offer considerable advantages over organic fluorophores for this purpose. We used QDs and emission spectrum scanning multiphoton microscopy to develop a means to study extravasation in vivo. Although QD labeling shows no deleterious effects on cultured cells, concern over their potential toxicity in vivo has caused resistance toward their application to such studies. To test if effects of QD labeling emerge in vivo, tumor cells labeled with QDs were intravenously injected into mice and followed as they extravasated into lung tissue. The behavior of QD-labeled tumor cells in vivo was indistinguishable from that of unlabeled cells. QDs and spectral imaging allowed the simultaneous identification of five different populations of cells using multiphoton laser excitation. Besides establishing the safety of QDs for in vivo studies, our approach permits the study of multicellular interactions in vivo.     

IN VITRO CULTURE OF FLORAL BUDS OF AQUILEGIA

Tepfer, S. S., R. I. Greyson, W. R. Craig, and J. L. Hindman. (U. Oregon, Eugene.) In vitro culture of floral buds of Aquilegia. Amer. Jour. Bot. 50(10): 1035–1045. Illus. 1963.—Floral buds at various stages of development, from early stages before sepal initiation to late stages with young carpel primordia present, were grown in culture on various agar media. A basic medium containing White's minerals, Nitsch's trace elements, coconut milk, sucrose, and assorted water-soluble vitamins was developed for growth of the buds. The addition of indoleacetic acid, gibberellic acid, and kinetin to the basic medium extended the developmental limits of buds at nearly all stages and decidedly improved the continued development of carpels. On this medium buds produce all of their organ primordia, growing from early stages to about the size of flowers at anthesis, but will not develop unless the sepals are removed. This inhibiting effect of sepals is not understood at this time. Stamen development is consistently poor beyond the point of differentiation of anther and filament, even with the addition of hormones. The development of buds in culture is illustrated and compared with development in intact plants. With further improvement of the medium, it is hoped that these buds may be used for experiments testing theories of floral morphogenesis.     

Proliferative response of human diploid fibroblasts to intermittent light exposure

Three- to four-hour exposure to fluorescnt light, one to three times weekly, reproducibly enhanced the proliferation rate of human diploid fibroblasts. This enhancement was observed in WI-38 and a line from whole embryo mince at late population doubling level (PDL) as well as in a line from adult skin at early PDL. Single or multiple exposures of short duration stimulated proliferation, whereas exposures of long duration were cytotoxic. This proliferative response is reversible, and is mediated through the culture medium, Dulbecco Vogt's supplemented with 10% fetal bovine serum. Apparently light produces some mitogenic substance(s) in the culture medium that accumulates in the cells and is toxic or growth-stimulatory depending on its concentration per cell. Another possibility is that light produces in the medium both cytotoxic and growth-stimulatory substances.     

Topography of nucleic acid helices in solutions. XXIV. Intercalation specificities of DNA and their possible role in the recognition process

Through the use of reporter molecules, I, it is shown that more than one type of intercalating site must exist in DNA. Although this finding is completely consistent with the DNA structure it has not yet been demonstrated. The significance of the presence of different intercalating sites in DNA may be of extreme importance in the recognition of nucleic acid-protein systems.