55 research outputs found
Hyperbaric oxygen preconditioning ameliorates blood-brain barrier damage induced by hypoxia through modulation of tight junction proteins in an in vitro model
Aim To explore the effects of hyperbaric oxygen preconditioning
(HBOP) on the permeability of blood-brain barrier
(BBB) and expression of tight junction proteins under hypoxic
conditions in vitro.
Methods A BBB in vitro model was constructed using the
hCMEC/D3 cell line and used when its trans-endothelial
electrical resistance (TEER) reached 80-120 Ω · cm2 (tested
by Millicell-Electrical Resistance System). The cells were
randomly divided into the control group cultured under
normal conditions, the group cultured under hypoxic conditions
(2%O2) for 24 h (hypoxia group), and the group
first subjected to HBOP for 2 h and then to hypoxia (HBOP
group). Occludin and ZO-1 expression were analyzed by
immunofluorescence assay.
Results Normal hCMEC/D3 was spindle-shaped and
tightly integrated. TEER was significantly reduced in the
hypoxia (P = 0.001) and HBOP group (P = 0.014) compared
to control group, with a greater decrease in the hypoxia
group. Occludin membranous expression was significantly
decreased in the hypoxia group (P = 0.001) compared to
the control group, but there was no change in the HBOP
group. ZO-1 membranous expression was significantly decreased
(P = 0.002) and cytoplasmic expression was significantly
increased (P = 0.001) in the hypoxia group compared
to the control group, although overall expression
levels did not change. In the HBOP group, there was no
significant change in ZO-1 expression compared to the
control group.
Conclusion Hyperbaric oxygen preconditioning protected
the integrity of BBB in an in vitro model through modulation
of occludin and ZO-1 expression under hypoxic conditions
Redundant Mechanisms Prevent Mitotic Entry Following Replication Arrest in the Absence of Cdc25 Hyper-Phosphorylation in Fission Yeast
Following replication arrest the Cdc25 phosphatase is phosphorylated and inhibited by Cds1. It has previously been reported that expressing Cdc25 where 9 putative amino-terminal Cds1 phosphorylation sites have been substituted to alanine results in bypass of the DNA replication checkpoint. However, these results were acquired by expression of the phosphorylation mutant using a multicopy expression vector in a genetic background where the DNA replication checkpoint is intact. In order to clarify these results we constructed a Cdc25(9A)-GFP native promoter integrant and examined its effect on the replication checkpoint at endogenous expression levels. In this strain the replication checkpoint operates normally, conditional on the presence of the Mik1 kinase. In response to replication arrest the Cdc25(9A)-GFP protein is degraded, suggesting the presence of a backup mechanism to eliminate the phosphatase when it cannot be inhibited through phosphorylation
Histone H3K56 Acetylation, CAF1, and Rtt106 Coordinate Nucleosome Assembly and Stability of Advancing Replication Forks
Chromatin assembly mutants accumulate recombinogenic DNA damage and are sensitive to genotoxic agents. Here we have analyzed why impairment of the H3K56 acetylation-dependent CAF1 and Rtt106 chromatin assembly pathways, which have redundant roles in H3/H4 deposition during DNA replication, leads to genetic instability. We show that the absence of H3K56 acetylation or the simultaneous knock out of CAF1 and Rtt106 increases homologous recombination by affecting the integrity of advancing replication forks, while they have a minor effect on stalled replication fork stability in response to the replication inhibitor hydroxyurea. This defect in replication fork integrity is not due to defective checkpoints. In contrast, H3K56 acetylation protects against replicative DNA damaging agents by DNA repair/tolerance mechanisms that do not require CAF1/Rtt106 and are likely subsequent to the process of replication-coupled nucleosome deposition. We propose that the tight connection between DNA synthesis and histone deposition during DNA replication mediated by H3K56ac/CAF1/Rtt106 provides a mechanism for the stabilization of advancing replication forks and the maintenance of genome integrity, while H3K56 acetylation has an additional, CAF1/Rtt106-independent function in the response to replicative DNA damage
Processing of joint molecule intermediates by structure-selective endonucleases during homologous recombination in eukaryotes
Homologous recombination is required for maintaining genomic integrity by functioning in high-fidelity repair of DNA double-strand breaks and other complex lesions, replication fork support, and meiotic chromosome segregation. Joint DNA molecules are key intermediates in recombination and their differential processing determines whether the genetic outcome is a crossover or non-crossover event. The Holliday model of recombination highlights the resolution of four-way DNA joint molecules, termed Holliday junctions, and the bacterial Holliday junction resolvase RuvC set the paradigm for the mechanism of crossover formation. In eukaryotes, much effort has been invested in identifying the eukaryotic equivalent of bacterial RuvC, leading to the discovery of a number of DNA endonucleases, including Mus81–Mms4/EME1, Slx1–Slx4/BTBD12/MUS312, XPF–ERCC1, and Yen1/GEN1. These nucleases exert different selectivity for various DNA joint molecules, including Holliday junctions. Their mutant phenotypes and distinct species-specific characteristics expose a surprisingly complex system of joint molecule processing. In an attempt to reconcile the biochemical and genetic data, we propose that nicked junctions constitute important in vivo recombination intermediates whose processing determines the efficiency and outcome (crossover/non-crossover) of homologous recombination
Mineralogy of ODP Leg 104 holes
The mineralogical and geochemical study of samples from Sites 642, 643, and 644 enabled us to reconstruct several aspects of the Cenozoic paleoenvironmental evolution (namely volcanism, climate, hydrology) south of the Norwegian Sea and correlate it with evolution trends in the northeast Atlantic. Weathering products of early Paleogene volcanic material at Rockall Plateau, over the Faeroe-Iceland Ridge and the Voring Plateau indicate a hot and moist climate (lateritic environment) existed then. From Eocene to Oligocene, mineralogical assemblages of terrigenous sediments suggest the existence of a warm but somewhat less moist climate at that time than during the early Paleogene. At the beginning of early Miocene, climatic conditions were warm and damp. The large amounts of amorphous silica in Miocene sediment could indicate an important flux of silica from the continent then, or suggest the formation of upwelling. Uppermost lower Miocene and middle to upper Miocene clay assemblages suggest progressive cooling of the climate from warm to temperate at that time. At the end of early Miocene, hydrological exchanges between the North Atlantic and the Norwegian Sea became intense and gave rise to an important change in the mineralogy of deposits. From Pliocene to Pleistocene, the variable mineralogy of deposits reflects alternating glacial/interglacial climatic episodes, a phenomenon observed throughout the North Atlantic
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