Role of ethylene in postharvest quality of cut oriental lily ‘Stargazer’

The effects of endogenous and exogenous C₂H₄ and C₂H₄ inhibitors on the postharvest leaf and flower quality of Oriental lily Stargazer were investigated. Endogenous C₂H₄ was not produced by freshly harvested excised leaves or flowers. Treatment of freshly harvested excised flowers, buds, leaves, and intact cut stems with C₂H₄ concentrations as high as 10 µl·l^–1 did not affect bud opening or longevity or the development of leaf yellowing. Therefore, treatment with anti-C₂H₄ compounds, such as silver thiosulfate (STS) and 1-methylcyclopropene (1-MCP), did not improve the quality of the flowers. Data thus indicate that freshly harvested Stargazer were not sensitive to C₂H₄. Sensitivity of Stargazer to C₂H₄, however, increased dramatically following cold storage, as exposure of cold-stored stems to C₂H₄ concentrations as low as 0.3 µl·l^–1 significantly affected bud opening. The development of leaf yellowing on cold-stored stems was not affected by the exogenous C₂H₄. Pretreating cold-stored stems with 1-MCP significantly reduced blasting of small buds that failed to develop due to carbohydrate depletion and reduced the percentage of buds that did not fully open. Concurrently, 1-MCP did not affect the quality of the leaves. These data indicate that sensitivity of cut lilies to C₂H₄ differs following cold storage and that 1-MCP is a more suitable anti-C₂H₄ compound than STS. Furthermore, studies on endogenous C₂H₄ production revealed that, while C₂H₄ was not detected in freshly harvested buds and leaves, it was produced by both following cold storage. The latter produced C₂H₄ at a higher rate than the former. Results of this study clearly indicate that there are two situations in which lilies will benefit from pretreatment with an anti-C₂H₄ compound (1) when cut stems contain buds that are marginally small for opening and (2) when cut stems will be cold stored before marketing.     

Distribution of turbidity detection times produced by single cell-generated bacterial populations

The distributions of the times to turbidity for wells inoculated with single cells of Listeria innocua were determined in different environmental conditions (pH 4.5 to 7 and with 0.5% to 8% of NaCl at 30 degrees C). It was established by statistical analysis that the main source of the variability of the detection times, T, is the variability of individual lag times. A linear relation dev(T) approximately T was observed between the detection times and their standard deviation. At slow growth, other sources of variability became increasingly significant.     

The effects of a mutant connexin 26 on epidermal differentiation

To elucidate the mode of action of dominant mutant connexins in causing inherited skin diseases, transgenic mice were produced that express the true Vohwinkel syndrome-associated mutant Cx26 (D66H), from a keratin 10 promoter, specifically in the suprabasal epidermal keratinocytes. Following birth, the transgenic mice developed keratoderma similar to that of human carriers of Cx26 (D66H). Expression of the transgene resulted in a loss of Cx26 and Cx30 at intercellular junctions of epidermal keratinocytes and accumulation of these connexins in the cytoplasm. Injection of primary mouse keratinocytes with Lucifer Yellow showed no difference in terms of dye spreading between transgenic and non transgenic keratinocytes in vitro. Expression of the mutant Cx26 (D66H) did not interfere with the formation of the epidermal water barrier during late embryonic development. Attempts to produce transgenic mice expressing the wild type form of Cx26 from the K10 promoter failed to produce viable animals although transgenic embryos were recovered at days 9 and 12 of gestation, suggesting that the transgene might be embryonic lethal.     

Reduced accumulation of specific microRNAs in colorectal neoplasia

Short non-coding RNAs are known to regulate cellular processes including development, heterochromatin formation, and genomic stability in eukaryotes. Given the impact of these processes on cellular identity, a study was undertaken to investigate possible changes in microRNA (miRNA) levels during tumorigenesis. A total of 28 different miRNA sequences was identified in a colonic adenocarcinoma and normal mucosa, including 3 novel sequences and a further 7 that had previously been cloned only from mice. Human homologues of murine miRNA sequences, miR-143 and miR-145, consistently display reduced steady-state levels of the mature miRNA at the adenomatous and cancer stages of colorectal neoplasia.     

Quartz crystal microbalance study of endothelial cell number dependent differences in initial adhesion and steady-state behavior: evidence for cell-cell cooperativity in initial adhesion and spreading

The quartz crystal microbalance (QCM) technique has been applied to the real time monitoring of endothelial cell (EC) adhesion and spreading on the QCM gold surface. We previously showed that the measured QCM Deltaf and DeltaR shifts were due to cells adhering to the gold crystal surface, requiring proteolytic enzyme treatment to be removed from the surface, in order for the Deltaf and DeltaR shifts to return to zero. In the present report, we demonstrate the quantitative dependence and saturation of the measured Deltaf and DeltaR shifts on the number of firmly attached ECs as measured by electronic counting of the cells. We demonstrate through a light microscope simulation experiment that the different Deltaf and DeltaR regions of the QCM temporal response curve correspond to the incident ECs contacting the surface, followed by their adhesion and spreading, which reflect cellular mass distribution and cytoskeletal viscoelasticity changes. Also, we demonstrate that the dose response curve of Deltaf and DeltaR values versus attached EC number is more sensitive and possesses less scatter for the hydrophilically treated surface compared to the native gold surface of the QCM. For both surfaces, a Deltaf and DeltaR versus trypsinized, attached EC number plot 1 h post-seeding exhibits a sigmoid curve shape whereas a similar plot 24 h post-seeding exhibits a hyperbolic curve shape. This number dependence suggests cell-cell cooperativity in the initial cell adhesion and spreading processes. These QCM data and our interpretation are corroborated by differences in cell appearance and spreading behavior we observed for ECs in a light microscope fluorescence simulation experiment of the cell density effect. For a stably attached EC monolayer at 24 h post-addition, steady-state Deltaf and DeltaR values are higher and exhibit saturation behavior for both the hydrophilically treated gold surface as compared to the untreated surface. The steady-state 24 h Deltaf and DeltaR values of stably attached ECs are shifted from the 1 h attached ECs. The 24 h values are characteristic of a more energy-dissipative structure. This is consistent with the time-dependent elaboration of surface contacts in anchorage-dependent ECs via the attachment of intregrins to underlying extracellular matrix. It is also in agreement with the known energy dissipation function of the ECs that cover the interior of blood vessels and are exposed to continuous pulsatile blood flow.     

Glutathione (GSH) concentrations vary with the cell cycle in maturing hamster oocytes,zygotes, and pre-implantation stage embryos

Glutathione (GSH) is thought to play critical roles in oocyte function including spindle maintenance and provision of reducing power needed to initiate sperm chromatin decondensation. Previous observations that GSH concentrations are higher in mature than immature oocytes and decline after fertilization, suggest that GSH synthesis may be associated with cell cycle events. To explore this possibility, we measured the concentrations of GSH in Golden Hamster oocytes and zygotes at specific stages of oocyte maturation and at intervals during the first complete embryonic cell cycle. Between 2 and 4 hr after the hormonal induction of oocyte maturation, GSH concentrations increased significantly (approximately doubling) in both oocytes and their associated cumulus cells. This increase was concurrent with germinal vesicle breakdown and the condensation of metaphase I chromosomes in the oocyte. GSH remained high in ovulated, metaphase II (MII) oocytes, but then declined significantly, by about 50%, shortly after fertilization, as the zygote progressed back into interphase (the pronucleus stage). GSH concentrations then plummeted by the two-cell embryo stage and remained at only 10% of those in MII oocytes throughout pre-implantation development. These results demonstrate that oocyte GSH concentrations fluctuate with the cell cycle, being highest during meiotic metaphase, the critical period for spindle growth and development and for sperm chromatin remodeling. These observations raise the possibility that GSH synthesis in maturing oocytes is regulated by gonadotropins, and suggest that GSH is more important during fertilization than during pre-implantation embryo development.     

Nanoparticulate DNA packaging using terpolymers of poly(lysine-g-(lactide-b-ethylene glycol))

Terpolymers of poly(lysine-g-(lactide-b-ethylene glycol)) (pK-pLL-pEG) were synthesized by using ring-opening polymerization and functional end-group grafting. Synthesis was characterized with gel permeation chromatography, proton nuclear magnetic resonance spectroscopy, and a trinitrobenzene sulfonic acid binding assay. Polymer association behavior with DNA was investigated using an ethidium bromide exclusion assay, static light scattering, and scanning electron microscopy. Polylactide molecular weight was varied to investigate its impact on DNA association and resulting complex characteristics. Polylysine ( = 8800, DP = 42) modified with either 7400 or 10 870 pLL-pEG reduced the minimum amount of primary amines necessary for complete condensation by 23% and 48%, respectively, compared to unmodified polylysine (pK42). Complexes formed with the highest molecular weight terpolymer demonstrated significantly (p < 0.1) greater resistance to DNase I than lyophilized pK42-DNA particles. This study suggests that modification of pK42 with pLL-pEG diblock copolymers impacts polylysine's associative and binding behavior to DNA and resulting particle characteristics. Modulation of terpolymer composition in complexes can enable control over intracellular plasmid dissociation rates to improve transfection efficiency.