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At least 145 records · Page 8Linked to original sources
PubMed1979

A study of dielectric membrane breakdown in the Fucus egg.

Unfertilized eggs and zygotes of the marine brown alga, Fucus serratus, have been subjected to single external electric field pulses of 1 to 1760 musec duration (tau p) and 50 to 400 V field strength (Upcm-1). During exposure, the difference in electric potential across the plasmalemma (Vm) was recorded intracellularly from single eggs, and the efflux of 86Rb+(K+) from the cytoplasm was measured on egg populations. A given single pulse instantaneously depolarizes the plasmalemma by a few (i.e., 6) millivolts and releases a certain fraction (i.e., 5%) of the cytoplasmic 86Rb+(K+). The dependence of these responses upon Up and tau p is fully consistent with the assumption that the membrane undergoes a localized reversible dielectric breakdown and reseals within less than 3 sec. The data are treated in terms of the electro-mechanical model for a compressible membrane by H.G.L. Coster and U. Zimmermann (1975, J. Membrane Biol. 22:73) and verify this model on a nonvacuolated plant cell. A threshold Vm for membrane breakdown (Vc) of 0.58 and 0.51 V is estimated for the turgorless unfertilized eggs and the turgescent (4.8 bar) zygotes, respectively. Using these values for Vc, and a reasonable value of the membrane's elastic modulus (i.e., Ym approximately 10(6) Nm-2), possible sites of membrane breakdown are discussed in terms of membrane thickness and relative permittivity.

Electric Stimulation↗
PubMed1975

Ultrastructural changes accompanying mitosporogenesis in Ectocarpus parvus.

The plurilocular zoosporangium of Ectocarpus parvus Saunders in initiated as a uniseriate branch from a vegetative cell. Subsequent anticlinal and periclinal divisions of the cells leads to enlargement of the sporangium and the formation of multiple locules. Each locule containes a single biflagellate zoospore. Ultrastructural changes accompanying these events include a reduction in the size of chromatophores, a reduction in the number of dictyosomes and the appearance of plasmalemmasomes in later stages. Enlargement of the mitochondria and a decrease in size of the nucleus occur in the final stages of zoospore formation. Comparison with the vegetative and sporogenous cells of other brown algae are made.

Cell Division↗
PubMed1991

Molecular phylogenetic analysis of actin genic regions from Achlya bisexualis (Oomycota) and Costaria costata (Chromophyta).

Actin genic regions were isolated and characterized from the heterokont-flagellated protists, Achlya bisexualis (Oomycota) and Costaria costata (Chromophyta). Restriction enzyme and cloning experiments suggested that the genes are present in a single copy and sequence determinations revealed the existence of two introns in the C. costata actin genic region. Phylogenetic analyses of actin genic regions using distance matrix and maximum parsimony methods confirmed the close evolutionary relationship of A. bisexualis and C. costata suggested by ribosomal DNA (rDNA) sequence comparisons and reproductive cell ultrastructure. The higher fungi, green plants, and animals were seen as monophyletic groups; however, a precise order of branching for these assemblages could not be determined. Phylogentic frameworks inferred from comparisons of rRNAs were used to assess rates of evolution in actin genic regions of diverse eukaryotes. Actin genic regions had nonuniform rates of nucleotide substitution in different lineages. Comparison of rates of actin and rDNA sequence divergence indicated that actin genic regions evolve 2.0 and 5.3 times faster in higher fungi and flowering plants, respectively, than their rDNA sequences. Conversely, animal actins evolve at approximately one-fifth the rate of their rDNA sequences.

Actins↗
PubMed1996

Gene structure of a chlorophyll a/c-binding protein from a brown alga: presence of an intron and phylogenetic implications.

A Laminaria saccharina genomic library in the phage EMBL 4 was used to isolate and sequence a full-length gene encoding a fucoxanthin-chlorophyll a/c-binding protein. Contrary to diatom homologues, the coding sequence is interrupted by an intron of about 900 bp which is located in the middle of the transit peptide. The deduced amino acid sequence of the mature protein is very similar to those of related proteins from Macrocystis pyrifera (Laminariales) and, to a lesser extent, to those from diatoms and Chrysophyceae. Seven of the eight putative chlorophyll-binding amino acids determined in green plants are also present. Alignments of different sequences related to the light-harvesting proteins (LHC) demonstrate a structural similarity among the three transmembrane helices and suggest a unique ancestral helix preceded by two beta-turns. The beta-turns are conserved in front of the second helices of the chlorophyll a/c proteins more so than in chlorophyll a/b proteins. Phylogenetic trees generated from sequence data indicate that fucoxanthin-chlorophyll-binding proteins diverged prior to the separation of photosystem I and photosystem II LHC genes of green plants. Among the fucoxanthin-containing algae, LHC I or II families could not be distinguished at this time.

Amino Acid Sequence↗
PubMed1996

The use of nicotinates and sulfoquinovosyl monoacylglycerols in the analysis of monounsaturated n-3 fatty acids by mass spectrometry.

Fatty acyl groups (16:1 and 16:0) liberated from purified sulfoquinovosyl diacylglycerols produced by the unicellular marine microalga, Heterosigma carterae (formerly H. akashiwo), were converted to either the corresponding alcohols or methyl esters. Nicotinate derivatives of the alcohols were examined by combined gas chromatography/mass spectrometry, and the methyl esters were examined by nuclear magnetic resonance (NMR) spectroscopy after separation by high-performance liquid chromatography. Three different hexadecenoyl fatty acyl groups were identified, one of which was cis 13-hexadecenoyl (16:1n-3). Both the configuration and the n-3 position of the double bond in the cis 13-hexadecenoyl moiety were unequivocally established by NMR analysis of the corresponding methyl ester. The nicotinate derived from the alcohol of the 16:1n-3 fatty acyl moiety gave a characteristic fragmentation series in the electron impact mass spectrum which, by careful interpretation, was consistent with, but not unambiguous for, the assigned location of the double bond. Tandem mass spectrometry experiments on a sulfoquinovosyl monoacylglycerol containing the cis 13-hexadecenoyl group in the sn-2 position, using negative-ion liquid secondary ion mass spectrometry, also gave a fragmentation pattern which was consistent with the positional assignment of the double bond.

Alcohols↗
PubMed2005

A new measure to study phylogenetic relations in the brown algal order Ectocarpales: the "codon impact parameter".

We analyse forty-seven chloroplast genes of the large subunit of RuBisCO, from the algal order Ectocarpales, sourced from GenBank. Codon-usage weighted by the nucleotide base-bias defines our score called the codon-impact-parameter. This score is used to obtain phylogenetic relations amongst the 47 Ectocarpales. We compare our classification with the ones done earlier.

Base Composition↗
PubMed2005

Improvement of memory by dieckol and phlorofucofuroeckol in ethanol-treated mice: possible involvement of the inhibition of acetylcholinesterase.

Phlorotannins, the polyphonic compounds found in brown Eisenia and Ecklonia algae, have several pharmacologically beneficial effects such as anti-inflammation. In addition, our recent data show that these compounds may improve the cognitive functions of aged humans suggesting the potential ability to enhance memory in several neurodegenerative disorders. To examine the experimental hypothesis that two effective components of Ecklonia cava, dieckol and phlorofucofuroeckol (PFF), have memory-enhancing abilities, both were administered orally to mice before a passive avoidance test. The repeated administration of either dieckol or PFF dose-dependently reduced the inhibition of latency by the administration of ethanol. To investigate the mode of memory-enhancing actions, the levels of major central neurotransmitters in three different regions (striatum, hippocampus, and frontal cortex) of the mouse brain were measured. The levels of some of the neurotransmitters were significantly changed by ethanol. Both dieckol and PFF altered the levels of some neurotransmitters modified by the ethanol treatment. It is noteworthy that both dieckol and PFF increased the level of acetylcholine, and they exerted anticholinesterase activities. Overall, the memory-enhancing abilities of dieckol and PFF may result from, at least in part, the increment of the brain level of acetylcholine by inhibiting acetylcholinesterase.

Acetylcholinesterase↗
PubMed2006

An antioxidative and antiinflammatory agent for potential treatment of osteoarthritis from Ecklonia cava.

Osteoarthritis is thought to be induced by the ageing-related loss of homeostatic balance between degeneration and repair mechanism around cartilage tissue in which inflammatory mediators such as reactive oxygen species, cytokines and prostaglandins are prone to over-production under undesirable physiological conditions. Phlorotannins are unique polyphenolic compounds bearing dibenzo-1,4-dioxin skeleton which are not found in terrestrial plants but found only in some brown algal species such as Ecklonia and Eisenia families. Phlorotannin-rich extracts of Ecklonia cava including LAD103 showed significant antioxidant activities such as DPPH radical scavenging, ferric ion reduction, peroxynitrite scavenging, and inhibition of LDL oxidation, indicating their possible antioxidative interference both in onset and downstream consequences of osteoarthritis. LAD103 also showed significant down regulation of PGE2 generation in LPS-treated RAW 246.7 cells, and significant inhibition of human recombinant interleukin-1alpha-induced proteoglycan degradation, indicating its beneficial involvement in pathophysiological consequences of osteoarthritis, the mechanism of which needs further investigation. Since LAD103 showed strong therapeutic potentials in arthritic treatment through several in vitro experiments, it is highly encouraged to perform further mechanistic and efficacy studies.

Animals↗
PubMed2004

Anti-diabetic activities of fucosterol from Pelvetia siliquosa.

Fucosterol isolated from Pelvetia siliquosa was tested for its anti-diabetic activity in vivo. Fucosterol, when administered orally at 30 mg/kg in streptozotocin-induced diabetic rats, was caused a significant decrease in serum glucose concentrations, and exhibited an inhibition of sorbitol accumulations in the lenses. Fucosterol, when administered orally at 300 mg/kg in epinephrine-induced diabetic rats, was also caused an inhibition of blood glucose level and glycogen degradation. These results demonstrated that fucosterol is a main anti-diabetic principle from the marine algae P. siliquosa.

Animals↗
PubMed2004

Tyrosinase inhibitors isolated from the edible brown alga Ecklonia stolonifera.

Extracts from seventeen seaweeds were determined for tyrosinase inhibitory activity using mushroom tyrosinase with L-tyrosine as a substrate. Only one of them, Ecklonia stolonifera OKAMURA (Laminariaceae) belonging to brown algae, showed high tyrosinase inhibitory activity. Bioassay-guided fractionation of the active ethyl acetate (EtOAc) soluble fraction from the methanolic extract of E. stolonifera, led us to the isolation of phloroglucinol derivatives [phloroglucinol (1), eckstolonol (2), eckol (3), phlorofucofuroeckol A (4), and dieckol (5)]. Compounds 1 approximately 5 were found to inhibit the oxidation of L-tyrosine catalyzed by mushroom tyrosinase with IC50 values of 92.8, 126, 33.2, 177, and 2.16 microg/mL, respectively. It was compared with those of kojic acid and arbutin, well-known tyrosinase inhibitors, with IC50 values of 6.32 and 112 microg/ mL, respectively. The inhibitory kinetics analyzed from Lineweaver-Burk plots, showed compounds 1 and 2 to be competitive inhibitors with Ki of 2.3x10(-4) and 3.1x10(-4) M, and compounds 3 approximately 5 to be noncompetitive inhibitors with Ki of 1.9x10(-5), 1.4x10(-3) and 1.5x10(-5) M, respectively. This work showed that phloroglucinol derivatives, natural compounds found in brown algae, could be involved in the control of pigmentation in plants and other organisms through inhibition of tyrosinase activity using L-tyrosine as a substrate.

Enzyme Inhibitors↗
PubMed2003

Antioxidative properties of brown algae polyphenolics and their perspectives as chemopreventive agents against vascular risk factors.

Several polyphenolic compounds and complex mixtures were isolated from brown algae species. The 1,1-diphenyl-2-picryhydarzyl (DPPH) radical scavenging activity and ferric reducing antioxidant power (FRAP) of these compounds were evaluated to determine their physiological usefulness as antioxidants for vascular protection. The antioxidative protection of low-density lipoprotein (LDL) was also evaluated and compared with that of catechin, because the generation of oxidized LDL is one of the most active and specific risk factors contributing to atherogenesis. Oral administration to rats of a commercially available sample (VNP) containing 30% of these polyphenolic compounds and 70% dietary fiber revealed that the serum reducing capacity measured in terms of FRAP value was significantly elevated 30 min after the treatment, but declined rather quickly thereafter, indicating the good oral absorption of the compounds and their fast binding to the lumenal surface of the blood vessels. An eight-week, human, clinical trial (n=31) of VNP showed significant improvement in erectile function measured by IIEF (international index of erectile function) score. These results collectively demonstrated the usefulness of these polyphenolic compounds as fundamental chemopreventive agents against vascular risk factors originating from oxidative stress.

Animals↗