Nitric oxide is involved in growth regulation and re-orientation of pollen tubes

Nitric oxide (NO) controls diverse functions in many cells and organs of animals. It is also produced in plants and has a variety of effects, but little is known about their underlying mechanisms. In the present study, we have discovered a role for NO in the regulation of pollen tube growth, a fast tip-growing cellular system. Pollen tubes must be precisely oriented inside the anatomically complex female ovary in order to deliver sperm. We hypothesized that NO could play a role in this guidance and tested this hypothesis by challenging the growth of pollen tubes with an external NO point source. When a critical concentration was sensed, the growth rate was reduced and the growth axis underwent a subsequent sharp reorientation, after which normal growth was attained. This response was abrogated in the presence of the NO scavenger CPTIO and affected by drugs interfering in the cGMP signaling pathway. The sensitivity threshold of the response was significantly augmented by sildenafil citrate (SC), an inhibitor of cGMP-specific phosphodiesterases in animals. NO distribution inside pollen tubes was investigated using DAF2-DA and was shown to occur mostly in peroxisomes. Peroxisomes are normally excluded from the tip of pollen tubes and little if any NO is found in the cytosol of that region. Our data indicate that the rate and orientation of pollen tube growth is regulated by NO levels at the pollen tube tip and suggest that this NO function is mediated by cGMP

Enzymatic heterozygosity and morphological variance in synthetic populations of Drosophila melanogaster

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Endocytic intermediates involved with the intracellular trafficking of a fluorescent cellular prion protein

We have investigated the intracellular traffic of PrPc, a glycosylphosphatidylinositol (GPI)-anchored protein implicated in spongiform encephalopathies. A fluorescent functional green fluorescent protein (GFP)-tagged version of PrPc is found at the cell surface and in intracellular compartments in SN56 cells. Confocal microscopy and organelle-specific markers suggest that the protein is found in both the Golgi and the recycling endosomal compartment. Perturbation of endocytosis with a dynamin I-K44A dominant-negative mutant altered the steady-state distribution of the GFP-PrPc, leading to the accumulation of fluorescence in unfissioned endocytic intermediates. These pre-endocytic intermediates did not seem to accumulate GFP-GPI, a minimum GPI-anchored protein, suggesting that PrPc trafficking does not depend solely on the GPI anchor. We found that internalized GFP-PrPc accumulates in Rab5-positive endosomes and that a Rab5 mutant alters the steady-state distribution of GFP-PrPc but not that of GFP-GPI between the plasma membrane and early endosomes. Therefore, we conclude that PrPc internalizes via a dynamin-dependent endocytic pathway and that the protein is targeted to the recycling endosomal compartment via Rab5-positive early endosomes. These observations indicate that traffic of GFP-PrPc is not determined predominantly by the GPI anchor and that, different from other GPI-anchored proteins, PrPc is delivered to classic endosomes after internalization

The SWR1 Histone Replacement Complex Causes Genetic Instability and Genome-Wide Transcription Misregulation in the Absence of H2A.Z

The SWR1 complex replaces the canonical histone H2A with the variant H2A.Z (Htz1 in yeast) at specific chromatin regions. This dynamic alteration in nucleosome structure provides a molecular mechanism to regulate transcription, gene silencing, chromosome segregation and DNA repair. Here we show that genetic instability, sensitivity to drugs impairing different cellular processes and genome-wide transcriptional misregulation in htz1Δ can be partially or totally suppressed if SWR1 is not formed (swr1Δ), if it forms but cannot bind to chromatin (swc2Δ) or if it binds to chromatin but lacks histone replacement activity (swc5Δ and the ATPase-dead swr1-K727G). These results suggest that in htz1Δ the nucleosome remodelling activity of SWR1 affects chromatin integrity because of an attempt to replace H2A with Htz1 in the absence of the latter. This would impair transcription and, either directly or indirectly, other cellular processes. Specifically, we show that in htz1Δ, the SWR1 complex causes an accumulation of recombinogenic DNA damage by a mechanism dependent on phosphorylation of H2A at Ser129, a modification that occurs in response to DNA damage, suggesting that the SWR1 complex impairs the repair of spontaneous DNA damage in htz1Δ. In addition, SWR1 causes DSBs sensitivity in htz1Δ; consistently, in the absence of Htz1 the SWR1 complex bound near an endonuclease HO-induced DSB at the mating-type (MAT) locus impairs DSB-induced checkpoint activation. Our results support a stepwise mechanism for the replacement of H2A with Htz1 and demonstrate that a tight control of this mechanism is essential to regulate chromatin dynamics but also to prevent the deleterious consequences of an incomplete nucleosome remodelling

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

Brucellosis remains a neglected disease inthe developing world: a call forinterdisciplinary action

Brucellosis places significant burdens on the human healthcare system and limits the economic growth of individuals, communities, and nations where such development is especially important to diminish the prevalence of poverty. The implementation of public policy focused on mitigating the socioeconomic effects of brucellosis in human and animal populations is desperately needed. When developing a plan to mitigate the associated consequences, it is vital to consider both the abstract and quantifiable effects. This requires an interdisciplinary and collaborative, or One Health, approach that consists of public education, the development of an infrastructure for disease surveillance and reporting in both veterinary and medical fields, and campaigns for control in livestock and wildlife species

A New Approach for Adipose Tissue Treatment and Body Contouring Using Radiofrequency-Assisted Liposuction

A new liposuction technology for adipocyte lipolysis and uniform three-dimensional tissue heating and contraction is presented. The technology is based on bipolar radiofrequency energy applied to the subcutaneous adipose tissue and subdermal skin surface. Preliminary clinical results, thermal monitoring, and histologic biopsies of the treated tissue demonstrate rapid preaspiration liquefaction of adipose tissue, coagulation of subcutaneous blood vessels, and uniform sustained heating of tissue