Incubation

About: Incubation is a research topic. Over the lifetime, 5748 publications have been published within this topic receiving 126541 citations.

Improved culturability of SAR11 strains in dilution‐to‐extinction culturing from the East Sea, West Pacific Ocean

Abstract: Although the SAR11 clade of the Alphaproteobacteria represents the most abundant and ubiquitous bacterioplankton in the ocean, very few laboratories have successfully cultured SAR11 cells. All of the SAR11 strains isolated thus far have been retrieved from the Oregon coast and the Sargasso Sea. In this study, a modified dilution-to-extinction culturing with prolonged incubation at low temperature was applied in an effort to cultivate major bacterioplankton lineages in the East Sea, Western Pacific Ocean. Five to 10 cells were inoculated into each well of 48-well plates, followed by the incubation of the plates at 10 degrees C for 4, 8, 20, and 24 weeks. Among a total of 35 isolated strains, 18 strains assigned to the SAR11 clade were isolated after 8, 20, and 24 weeks of incubation, whereas no SAR11 cells were detected in the samples after 4 weeks of incubation. The SAR11 isolates, noticeably, comprised 64-82% of the total isolates from the plates incubated for 20 and 24 weeks. Extinction cultures belonging to the Roseobacter, OM43, and SAR92 clades were also cultivated. The results of this study suggest that long-term incubation at low temperatures might prove an alternative for the efficient cultivation of new variants of the members of the SAR11 clade.

Estrogen sulfates: biological and ultrastructural responses and metabolism in MCF-7 human breast cancer cells.

Abstract: The biological effects and ultrastructural alterations by different estrogen-3-sulfates (E1-3-S and E2-3-S) and estradiol-17-sulfate (E2-17-S) were studied in the MCF-7 mammary cancer cell line in culture. The estrogen-3-sulfates very significantly stimulated the progesterone receptor (PR). The values (in pmoles/mg DNA ± SE) were: control, 0.46 ± 0.09; E1-3-S, 2.24 ± 0.30, and E2-3-S, 2.56 ± 0.45. The value of PR after E2-17-S incubation (0.56 ± 0.24) was similar to the non-treated cells. The PR values obtained by the incubation of unconjugated estrone and estradiol were: 2.63 ± 0.45 and 2.27 ± 0.36, respectively. Analysis of the unconjugated estrogens in the medium indicated significant hydrolysis of estrogen-3-sulfates but not of E2-17-S. Using [3H]-E1-3-S, an important transformation was observed inside the cells, a great part being converted to estradiol (>60% in the nuclear fraction). Electron microscopic examination indicated alterations in the secretory system after incubation with estrogen-3-sulfates similar to those obtained with unconjugated estradiol. The effect provoked by E2-17-S was significantly less than for the other sulfates.

Activation of the complement system by Cryptococcus neoformans leads to binding of iC3b to the yeast.

Abstract: The complement system plays a key role in resistance to cryptococcosis. In the present study, we examined several factors that influence the binding of C3 cleavage fragments to Cryptococcus neoformans. Binding of C3 was determined by using normal human serum supplemented with 125I-labeled C3. Incubation of encapsulated cryptococci in 20% serum led to the binding of approximately 3.2 X 10(6) molecules of C3 to each cell. The binding of C3 was markedly inhibited by heating the serum at 56 degrees C for 30 min or by chelation of the serum with EDTA. Chelation of the serum with EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] reduced binding of C3 by 37%. These results indicated that activation of C3 cleavage fragments and their binding to C. neoformans was primarily dependent upon the alternative pathway. Bound C3 could be removed by incubation with 1.0 M hydroxylamine (pH 10) but not by incubation with 3.5 M NaSCN or with phosphate-buffered saline containing 0.1% sodium dodecyl sulfate. These results suggested that C3 fragments were bound to C. neoformans by ester bonds. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of C3 fragments eluted from the yeast showed the presence of protein bands consistent with the presence of iC3b. C3b was not detected on the yeast after incubation with serum for time intervals as short as 2.5 min, indicating a rapid conversion of cell-bound C3b to iC3b. These results indicate that iC3b is the ligand which most likely interacts with the phagocyte C3 receptors involved in the phagocytosis of C. neoformans.