Chromogenic Assay Method of Lipopolysaccharide (LPS) for Evaluating Bacterial Standing Crop in Seawater

A chromogenic method, based on amoebocyte lysate of horseshoe crab and amino acids- para -nitroanilide substrate was employed to quantify lipopolysaccharide (LPS) as a measure of the bacterial standing crop in seawater. The range over which LPS could be reliably determined by this method was from 0.2 to 10 ng/ml of sample, and the method reported here could have several advantages compared with the turbidity determination method.
Vertical distributions of total and particulate LPS were parallel in seawater column. Particulate LPS was not shown to be related to the biomass of total bacteria in some cases, but correlated with the numbers of large bacterial cells whose size was greater than 1 fan in length.
In most of the profiles investigated in the shallow sea there was no parallel relationship between LPS and chlorophyll-a whereas in some cases the profiles were similar.
In growing cultures of Vibrio anguillarum the content of cellular LPS as a percentage of the total cellular carbon during the 3 d growth ranged from 6–15% (w/w).     

Dual Effects of cAMP on the Stability of Prespore Vesicles and 8-bromo cAMP-enhanced Maturation of Spore and Stalk Cells of Dictyostelium discoideum

It is well known that interconversion between prestalk and prespore cells occurs in 3-dimensional (3–D) isolates of Dictyostelium. The present work was undertaken to examine whether or not the interconversion occurs even in monolayer sheets. The results suggested that in monolayer sheets of either prespore or prestalk cells, the interconversion does not occur. Furthermore, effects of cAMP were examined in relation to the formation or loss of prespore vesicles (PSVs). In monolayer sheets, prespore cells retain their PSVs in the presence of cAMP, though they lose them in its absence. In 3–D masses, however, cAMP induces the conversion into stalk cells, stimulating PSV loss. In the case of prestalk cells, cAMP induces the maturation of prestalk cells to stalk cells in 3–D masses, but it does not induce stalk differentiation in monolayer sheets.
8-Bromo cAMP stimulates the maturation of prespore and prestalk cells into spore and stalk cells, respectively. However, the vegetative and the aggregative cells remain amoeboid even in its presence. These observations suggest that 8-bromo cAMP stimulates the maturation rather than inducing prespore and prestalk differentiation.     

Melanocyte-Stimulating Properties of Arachidonic Acid Metabolites: Possible Role in Postinflammatory Pigmentation

Normal human epidermal melanocytes became swollen and more dendritic with an increase in the amount of tyrosinase and immunoreactive b-locus protein when they were cultured for 2 days with the following arachidonic acid metabolites: prostaglandin (PG) D₂, leukotriene (LT) B₄, LTC₄, LTD₄, LTE₄, thromboxane (TX) B₂ and 12-hydroxy eicosatetraenoic acid (12-HETE). The effect of LTC₄ was particularly strong compared to that of PGE₂, about which we have previously reported. On the other hand, PGE₁, PGF_2α and 6-ketoPGF_1α did not show any significant stimulatory effect. These data suggest that arachidonate-derived chemical mediators, especially LTC₄, may be responsible for the induction of post-inflammatory hyperpigmentation of the skin.     

Establishment of a Murine Model for Metastasis of Cytokine-Producing Tumor to the Brain

The A375 cell line, derived from human malignant melanoma, has characteristics of interleukin-6 (IL-6) production. By using this cell line, we have investigated a murine metastasis model of IL-6-producing tumors to the brain by injecting A375 cells directly into the left cardiac ventricle. Nude mice were anesthetized with intraperitoneal injection of pentobarbital sodium. Next, A375 cells suspended in phosphate-buffered saline (PBS) were injected into the left cardiac ventricle of mice. An intracardiac injection of 10⁵ cells developed tumor colonies in the brain after 4 to 6 weeks. Metastatic cells were found in every lobe of the brain. An immunocytochemical study revealed IL-6 production by A375 cells at the metastatic sites in the brain. By the transfection of genes encoding proteins into A375 cells, a novel model of protein expression in the brain in vivo could be constructed. Our system does not require great skill. Our experimental model will facilitate future studies of the local effects of proteins in the brain.     

Implications of Differential Chemotaxis and Cohesiveness for Cell Sorting in the Development of Dictyostelium discoideum

Cell sorting behavior was observed during the development of Dictyostelium discoideum Ax-2, between cells grown with [G(+) cells] and without [G(−) cells] glucose. Development of the G(−) cells was about 2-3 hr faster, as reflected by differences in chemotactic sensitivity of the cells and cell cohesiveness. Among various mixing combinations of G(−) and G(+) cells, the most clear sorting occured when vegetative G(+) cells were mixed with G(−) cells which had been allowed to develop for 3 hr, the G(−) cells being located in the anterior prestalk region of a migrating slug. In contrast, vegetative G(−) cells moved to the posterior prespore region of a slug when mixed with G(+) cells which had developed for 6 hr. These findings indicate a close relationship of the cellular developmental stage to the sorting behavior. Possible implications of the differential chemotactic ability and cohesiveness for the sorting mechanism are disscussed.     

Ultrastructural Changes of the Two Types of Differentiated Cells during the Migration and Early Culmination Stages of Dictyostelium discoideum

Changes of fine structure during prolonged migration of Dictyostelium discoideum slugs were studied by electronmicroscopy. Prespore specific vacuoles of cells located near the substratum gradually degenerated and the prespore antigen contained in them was lost. During the process, mitochondria in the prespore cells were transformed dramatically: as the mitochondrion elongates, its central part becomes thinner and the cristae become localized at its two ends. Then it bends and its two ends fuse to segregate part of the cytoplasm. The cristae then accumulate in the original ends. Similar mitochondrial transformation was observed in prespore cells of cell masses induced to culminate after a long period of migration.