Agronomic evaluation of prospective new crop species. V.Jarilla chocola—A proteinase source

Jarilla chocola (Caricaceae) was evaluated at two locations as a potential new crop. The fruits and tuberous roots of this dioecious, perennial plant contain proteinase. Results show limited potential because of intolerance to freezing, susceptibility to soil-borne pathogens, and only moderate fruit production. Partial shade and moist, well drained soils are required for adequate vegetative development. Seed require an after-ripening period for good germination. There were more male than female plants in small seedling populations, and these bloomed more profusely than female plants.     

A reversible multi-well chamber for incubation of cultured cells with small volumes: application to screening of hybridoma fusions using immunofluorescence microscopy

Immunofluorescence microscopy is a powerful technique for detecting the location of surface and intracellular antigens in individual cells. However, using standard methods, processing large numbers of samples for immunofluorescence is cumbersome and difficult. To simplify greatly this process, we have developed a chamber that reversibly creates multiple small wells in a large (150 mm) tissue culture dish. This device allows the rapid and convenient processing of hundreds of samples each of 100 microliters volume. Each sample is examined using a short working distance, high numerical aperture immersion objective for maximum sensitivity and resolution. This apparatus makes immunofluorescence a practical method for the primary screening of hybridoma clones.     

Antitumor activity of a thioether-linked immunotoxin: OVB3-PE

A thioether-linked immunotoxin was made between Pseudomonas exotoxin and the monoclonal antibody OVB3. This conjugate, OVB3-PE, was cytotoxic for the human ovarium cancer cell line OVCAR-3 (ID of 2.5 x 10(-12) M) and it was therefore tested for antitumor activity in a nude mouse model of ovarian cancer. This model employs the injection of a lethal number of OVCAR-3 cells into the peritoneal cavity of nude mice. When 0.2-1 micrograms of OVB3-PE was injected intraperitoneally on three successive days beginning 3-5 days after OVCAR-3 cell implantation, the survival of the tumor-bearing mice was increased 2-4-fold compared to that of untreated control mice. Median survival times for control mice ranged from 44 to 50 days while survival times of 150 days or greater were seen in mice treated with OVB3-PE. When OVB3-PE administration was delayed until 2-4 weeks after tumor cell implantation, OVB3-PE treatment also showed antitumor activity, but the duration of survival was less than with the early treatments. OVB3-PE was also cytotoxic for MCF-7 breast carcinoma cells, HT-29 colon carcinoma cells, and A431 epidermoid carcinoma cells.     

Collection of insulin, EGF and alpha2-macroglobulin in the same patches on the surface of cultured fibroblasts and common internalization.

We have used video intensification microscopy to observe fluorescent derivatives of insulin, epidermal growth factor and alpha2-macroglobulin added to Swiss 3T3-4 cells. At 4 degrees C, each of these polypeptides binds diffusely to specific receptors on the cell surface. When the cells are warmed to 23 or 37 degrees C, the bound insulin epidermal growth factor or alpha2-macroglobulin rapidly forms patches on the cell surface and is internalized. Using fluorescein-labeled alpha2-macroglobulin and rhodamine-labeled derivatives of insulin and epidermal growth factor, we show that all three polypeptides are internalized within the same vesicles by a common pathway. The mechanism for the internalization of these molecules is discussed.     

Ultrastructural immunocytochemical localization of the phosphomannosyl receptor in Chinese hamster ovary (CHO) cells

Using ultrastructural immunocytochemistry and antibodies directed against bovine liver phosphomannosyl (PM) receptor, we have localized the receptor in Chinese hamster ovary (CHO) cells. The majority of the receptor was found within the cell. Only a small fraction of the receptor was found on the surface and most of it was clustered in coated pits. Because these cells contain endogenous ligands for the receptor, it was not possible to determine if this clustered state was dependent on occupancy of the receptor. The bulk of the cell's receptor was found in the endoplasmic reticulum, nuclear envelope, and in the Golgi system. Most of the Golgi localization was associated with peripheral Golgi elements, suggesting a possible concentration of receptor in GERL. Very little receptor was found associated with mature lysosomes. PM receptor was also localized in structures that were identified as receptosomes by the presence of alpha 2-macroglobulin (alpha 2M)-gold, a ligand previously shown to enter CHO cells by the coated pit-receptosome pathway. This finding is consistent with the notion that during receptor-mediated endocytosis, receptors accompany ligand from the coated pit into the receptosome. The observation that the majority of the receptor was found in the endoplasmic reticulum and structures similar to GERL raises the possibility that the PM receptor plays an important role in compartmentalization of lysosomal enzymes in the GERL system.