Development and characterization of a human cell line from an ovarian mixed mullerian tumor (carcinosarcoma)

Summary A cell line derived from a human ovarian carcinosarcoma was established in tissue culture and in nude mice. Two sublines, LDF and HDF, separated by discontinuous density centrifugation were also established from the parent line JoN. The cloning efficiency of the JoN line was 21%. Morphologic features of adenocarcinoma cells characteristic of the parent JoN cells were retained in the sublines and clones; all lines showed the same karyotype and DNA content (pseudodiploid and pseudotetraploid). Keratin, as demonstrated immunohistochemically, was strongly expressed in the parent line JoN and the xenograft tumor, but not at all in the LDF sublines and only moderately in the HDF sublines. Vimentin, however, was expressed in neither the parent line JoN nor the xenograft tumor, but was present in both sublines. Transglutaminase and plasminogen activator activity was high in the parent line JoN. Neither, sublines nor clones showed the same high enzyme activity as the parent line. It is concluded that this human tumor line JoN is comprised of epithelial cells, capable of multidirectional differentiation.     

Dissociating Two Stages of Preparation in the Stop Signal Task Using fMRI

Often we must balance being prepared to act quickly with being prepared to suddenly stop. The stop signal task (SST) is widely used to study inhibitory control, and provides a measure of the speed of the stop process that is robust to changes in subjects’ response strategy. Previous studies have shown that preparation affects inhibition. We used fMRI to separate activity that occurs after a brief (500 ms) warning stimulus (warning-phase) from activity that occurs during responses that follow (response-phase). Both of these phases could contribute to the preparedness to stop because they both precede stop signals. Warning stimuli activated posterior networks that signal the need for top-down control, whereas response phases engaged prefrontal and subcortical networks that implement top-down control. Regression analyses revealed that both of these phases affect inhibitory control in different ways. Warning-phase activity in the cerebellum and posterior cingulate predicted stop latency and accuracy, respectively. By contrast, response-phase activity in fronto-temporal areas and left striatum predicted go speed and stop accuracy, in pre-supplementary motor area affected stop accuracy, and in right striatum predicted stop latency and accuracy. The ability to separate hidden contributions to inhibitory control during warning-phases from those during response-phases can aid in the study of models of preparation and inhibitory control, and of disorders marked by poor top-down control.     

Sperm cell surface characteristics of Plumbago zeylanica L. in relation to transport in the embryo sac

Myosin associated with the male germ cells of angiosperms interacts with actin, promoting transport of the non-motile generative and later sperm cells in the pollen tube. Myosin localizing on the sperm cell plasma membrane seems negligible in Plumbago, as reflected by the absence of: (i) anti-myosin labeling using immunoelectron microscopy, (ii) sperm motility on actin matrices, and (iii) electrophoretic movement changes after addition of antibody. Sperm cells injected directly into actively streaming Nitella internodal cells, however, follow actin bundles and their movement is sensitive to ATP and Mg²⁺. This may be based on simple charge binding since negatively charged latex beads also migrate on actin, whereas neutral or positively-charged latex beads do not. Sperm cells are negatively charged according to capillary microelectrophoresis, whereas killed sperm cells, which are positively charged do not migrate. The sperm cell that normally fertilizes the egg has a higher calculated charge (8.277 × 10³ esu/cm²) compared with the sperm cell that fuses with the central cell (6.120 × 10³ esu/cm²). Received: 15 December 1998 / Accepted: 21 January 1999