For rapid growth and appropriate pigmentation,Porphyra requires the constant availability of nutrients, especially in summer when temperate waters are generally nutrient depleted.
Cultivation near salmon cages allows the alleviation of this seasonal depletion by using the significant loading of fishf
arms, which is then valued (wastes become fertilisers) and managed (competition for nutrients between desirable algal crops
and problem species associated with severe disturbances). Porphyra,being an extremely efficient nutrient pump, is an excellent candidate for integrated aquaculture for bioremediation and economic
diversification. Frequent harvesting provides for constant removal of significant quantities of nutrients from coastal waters,
and for production of seaweeds of commercial value. The production of P. yezoensis being limited in the Gulf of Maine, an assessment of the potential of seven native north-west Atlantic Porphyra species is presently in progress. To enable the production of conchospores for net seeding, the phenology of these species
and the conditions for their vegetative conchocelis exponential growth, conchosporangium induction, and conchospore maturation
were determined. The development of integrated aquaculture systems is a positive initiative for optimising the efficiency
of aquaculture operations, while maintaining the health of coastal waters.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
A global loss of cytosine methylation in DNA has been implicated in a wide range of diseases. There is growing evidence that modifications in DNA methylation can be brought about by altering the intake of methyl donors such as folate. We examined whether long-term daily supplementation with 0.8 mg of folic acid would increase global DNA methylation compared with placebo in individuals with elevated plasma homocysteine. We also investigated if these effects were modified by MTHFR C677T genotype. Two hundred sixteen participants out of 818 subjects who had participated in a randomized double-blind placebo-controlled trial were selected, pre-stratified on MTHFR C677T genotype and matched on age and smoking status. They were allocated to receive either folic acid (0.8 mg/d; n = 105) or placebo treatment (n = 111) for three years. Peripheral blood leukocyte DNA methylation and serum and erythrocyte folate were assessed. Global DNA methylation was measured using liquid chromatography-tandem mass spectrometry and expressed as a percentage of 5-methylcytosines versus the total number of cytosine. There was no difference in global DNA methylation between those randomized to folic acid and those in the placebo group (difference = 0.008, 95%CI = -0.05,0.07, P = 0.79). There was also no difference between treatment groups when we stratified for MTHFR C677T genotype (CC, n = 76; CT, n = 70; TT, n = 70), baseline erythrocyte folate status or baseline DNA methylation levels. In moderately hyperhomocysteinemic men and women, long-term folic acid supplementation does not increase global DNA methylation in peripheral blood leukocytes.ClinicalTrials.gov NCT00110604. 相似文献
Ultraviolet (UV) radiation-induced DNA lesions can be efficiently repaired by nucleotide excision repair (NER). However, NER is less effective during replication of UV-damaged chromosomes. In contrast, translesion DNA synthesis (TLS) and homologous recombination (HR) are capable of dealing with lesions in replicating DNA. The core HR protein in mammalian cells is the strand exchange protein RAD51, which is aided by numerous proteins, including RAD54. We used RAD54 as a cellular marker for HR to study the response of mammalian embryonic stem (ES) cells to UV irradiation. In contrast to yeast, ES cells lacking RAD54 are not UV sensitive. Here we show that the requirement for mammalian RAD54 is masked by active NER. By genetically inactivating NER and HR through disruption of the Xpa and Rad54 genes, respectively, we demonstrate the contribution of HR to chromosomal integrity upon UV irradiation. We demonstrate using chromosome fiber analysis at the individual replication fork level, that HR activity is important for the restart of DNA replication after induction of DNA damage by UV-light in NER-deficient cells. Furthermore, our data reveal RAD54-dependent and -independent contributions of HR to the cellular sensitivity to UV-light, and they uncover that RAD54 can compensate for the loss of TLS polymerase η with regard to UV-light sensitivity. In conclusion, we show that HR is important for the progression of UV-stalled replication forks in ES cells, and that protection of the fork is an interplay between HR and TLS. 相似文献
TIG3 is a tumor suppressor protein that limits keratinocyte survival during normal differentiation. It is also important in cancer, as TIG3 level is reduced in tumors and in skin cancer cell lines, suggesting that loss of expression may be required for cancer cell survival. An important goal is identifying how TIG3 limits cell survival. In the present study we show that TIG3 expression in epidermal squamous cell carcinoma SCC-13 cells reduces cell proliferation and promotes morphological and biochemical apoptosis. To identify the mechanism that drives these changes, we demonstrate that TIG3 localizes near the centrosome and that pericentrosomal accumulation of TIG3 alters microtubule and microfilament organization and organelle distribution. Organelle accumulation at the centrosome is a hallmark of apoptosis and we demonstrate that TIG3 promotes pericentrosomal organelle accumulation. These changes are associated with reduced cyclin D1, cyclin E and cyclin A, and increased p21 level. In addition, Bax level is increased and Bcl-XL level is reduced, and cleavage of procaspase 3, procaspase 9 and PARP is enhanced. We propose that pericentrosomal localization of TIG3 is a key event that results in microtubule and microfilament redistribution and pericentrosomal organelle clustering and that leads to cancer cell apoptosis. 相似文献
The xylem in plants has mainly been described as a conduit for water and minerals, but emerging evidence also indicates that the xylem contains protein. To study the proteins in xylem sap, we characterized the identity and composition of the maize xylem sap proteome. The composition of the xylem sap proteome in maize revealed proteins related to different phases of xylem differentiation including cell wall metabolism, secondary cell wall synthesis, and programmed cell death. Many proteins were found to be present as multiple isoforms and some of these isoforms are glycosylated. Proteins involved in defense mechanisms were also present in xylem sap and the sap proteins were shown to have antifungal activity in bioassays. 相似文献
We reconsider the deterministic haploid mutation–selection equation with two types. This is an ordinary differential equation that describes the type distribution (forward in time) in a population of infinite size. This paper establishes ancestral (random) structures inherent in this deterministic model. In a first step, we obtain a representation of the deterministic equation’s solution (and, in particular, of its equilibria) in terms of an ancestral process called the killed ancestral selection graph. This representation allows one to understand the bifurcations related to the error threshold phenomenon from a genealogical point of view. Next, we characterise the ancestral type distribution by means of the pruned lookdown ancestral selection graph and study its properties at equilibrium. We also provide an alternative characterisation in terms of a piecewise-deterministic Markov process. Throughout, emphasis is on the underlying dualities as well as on explicit results.
We have examined the transport of the precursor of the 17-kD subunit of the photosynthetic O2-evolving complex (OE17) in intact chloroplasts in the presence of inhibitors that block two protein-translocation pathways in the thylakoid membrane. This precursor uses the transmembrane pH gradient-dependent pathway into the thylakoid lumen, and its transport across the thylakoid membrane is thought to be independent of ATP and the chloroplast SecA homolog, cpSecA. We unexpectedly found that azide, widely considered to be an inhibitor of cpSecA, had a profound effect on the targeting of the photosynthetic OE17 to the thylakoid lumen. By itself, azide caused a significant fraction of mature OE17 to accumulate in the stroma of intact chloroplasts. When added in conjunction with the protonophore nigericin, azide caused the maturation of a fraction of the stromal intermediate form of OE17, and this mature protein was found only in the stroma. Our data suggest that OE17 may use the sec-dependent pathway, especially when the transmembrane pH gradient-dependent pathway is inhibited. Under certain conditions, OE17 may be inserted across the thylakoid membrane far enough to allow removal of the transit peptide, but then may slip back out of the translocation machinery into the stromal compartment. 相似文献
Knowledge of three-dimensional scapular movements is essential to understand post-stroke shoulder pain. The goal of the present work is to determine the feasibility and the within and between session reliability of a movement protocol for three-dimensional scapular movement analysis in stroke patients with mild to moderate impairment, using an optoelectronic measurement system. Scapular kinematics of 10 stroke patients and 10 healthy controls was recorded on two occasions during active anteflexion and abduction from 0° to 60° and from 0° to 120°. All tasks were executed unilaterally and bilaterally. The protocol’s feasibility was first assessed, followed by within and between session reliability of scapular total range of motion (ROM), joint angles at start position and of angular waveforms. Additionally, measurement errors were calculated for all parameters. Results indicated that the protocol was generally feasible for this group of patients and assessors. Within session reliability was very good for all tasks. Between sessions, scapular angles at start position were measured reliably for most tasks, while scapular ROM was more reliable during the 120° tasks. In general, scapular angles showed higher reliability during anteflexion compared to abduction, especially for protraction. Scapular lateral rotations resulted in smallest measurement errors. This study indicates that scapular kinematics can be measured reliably and with precision within one measurement session. In case of multiple test sessions, further methodological optimization is required for this protocol to be suitable for clinical decision-making and evaluation of treatment efficacy. 相似文献