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At least 451 records · Page 25Linked to original sources
PubMed2001

8-Prenylnaringenin, the phytoestrogen in hops and beer, upregulates the function of the E-cadherin/catenin complex in human mammary carcinoma cells.

The E-cadherin/catenin complex is a powerful invasion suppressor in epithelial cells. It is expressed in the human MCF-7 breast cancer cell line family, but functionally defective in the invasive MCF-7/6 variant. Previous experiments have shown that IGF-I, tamoxifen, retinoic acid and tangeretin are able to upregulate the function of this complex in MCF-7/6 cells. We investigated the effect of 8-prenylnaringenin (8-PN), the phytoestrogen present in hops and beer, on aggregation, growth and invasion in MCF-7/6 cells. 8-PN was found to stimulate E-cadherin-dependent aggregation and growth of MCF-7/6 cells in suspension. These effects could be inhibited by the pure anti-estrogen ICI 182,780. 8-PN did not affect invasion of MCF-7/6 cells in the chick heart assay in vitro. In all these aspects 8-PN mimics the effects of 17beta-estradiol on MCF-7/6 cells.

Beer↗
PubMed2002

Chemotaxonomic features associated with flavonoids of cannabinoid-free cannabis (Cannabis sativa subsp. sativa L.) in relation to hops (Humulus lupulus L.).

The major flavonoids present in the leaves and flowers of the cannabinoid-free cannabis (Cannabis sativa subsp. sativa L.) cultivars Felina and Futura are orientin (1), vitexin (2), luteolin-7-O-beta-D-glucuronide (3), and apigenin-7-O-beta-D-glucuronide (4), while prenylated flavonoids, to which the potent estrogenicity of hops (Humilus lupulus L.) is associated, are absent. The different composition of flavonoids has chemotaxonomic value.

Apigenin↗
PubMed2002

Phospholipids undergo hop diffusion in compartmentalized cell membrane.

The diffusion rate of lipids in the cell membrane is reduced by a factor of 5-100 from that in artificial bilayers. This slowing mechanism has puzzled cell biologists for the last 25 yr. Here we address this issue by studying the movement of unsaturated phospholipids in rat kidney fibroblasts at the single molecule level at the temporal resolution of 25 micros. The cell membrane was found to be compartmentalized: phospholipids are confined within 230-nm-diameter (phi) compartments for 11 ms on average before hopping to adjacent compartments. These 230-nm compartments exist within greater 750-nm-phi compartments where these phospholipids are confined for 0.33 s on average. The diffusion rate within 230-nm compartments is 5.4 microm2/s, which is nearly as fast as that in large unilamellar vesicles, indicating that the diffusion in the cell membrane is reduced not because diffusion per se is slow, but because the cell membrane is compartmentalized with regard to lateral diffusion of phospholipids. Such compartmentalization depends on the actin-based membrane skeleton, but not on the extracellular matrix, extracellular domains of membrane proteins, or cholesterol-enriched rafts. We propose that various transmembrane proteins anchored to the actin-based membrane skeleton meshwork act as rows of pickets that temporarily confine phospholipids.

Actins↗
PubMedDate not supplied

Unifying principles in terrestrial locomotion: do hopping Australian marsupials fit in?

Mammalian terrestrial locomotion has many unifying principles. However, the Macropodoidea are a particularly interesting group that exhibit a number of significant deviations from the principles that seem to apply to other mammals. While the properties of materials that comprise the musculoskeletal system of mammals are similar, evidence suggests that tendon properties in macropodoid marsupials may be size or function dependent, in contrast to the situation in placental mammals. Postural differences related to hopping versus running have a dramatic effect on the scaling of the pelvic limb musculoskeletal system. Ratios of muscle fibre to tendon cross-sectional areas for ankle extensors and digital flexors scale with positive allometry in all mammals, but exponents are significantly higher in macropods. Tendon safety factors decline with increasing body mass in mammals, with eutherians at risk of ankle extensor tendon rupture at a body mass of about 150 kg, whereas kangaroos encounter similar problems at a body mass of approximately 35 kg. Tendon strength appears to limit locomotor performance in these animals. Elastic strain energy storage in tendons is mass dependent in all mammals, but exponents are significantly larger in macropodid. Tibial stresses may scale with positive allometry in kangaroos, which result in lower bone safety factors in macropods compared to eutherian mammals.

Animals↗
PubMed1983

Hop stunt viroid: molecular cloning and nucleotide sequence of the complete cDNA copy.

The complete cDNA of hop stunt viroid (HSV) has been cloned by the method of Okayama and Berg (Mol.Cell.Biol.2,161-170. (1982] and the complete nucleotide sequence has been established. The covalently closed circular single-stranded HSV RNA consists of 297 nucleotides. The secondary structure predicted for HSV contains 67% of its residues base-paired. The native HSV can possess an extended rod-like structure characteristic of viroids previously established. The central region of the native HSV has a similar structure to the conserved region found in all viroids sequenced so far except for avocado sunblotch viroid. The sequence homologous to the 5'-end of U1a RNA is also found in the sequence of HSV but not in the central conserved region.

Base Sequence↗
PubMed1984

Nucleotide sequence of cucumber pale fruit viroid: homology to hop stunt viroid.

Double stranded cDNA of cucumber pale fruit viroid ( CPFV ) has been cloned by the method of Okayama and Berg (Mol.Cell.Biol.2,161-170 (1982] and the complete nucleotide sequence was established. The covalently closed circular molecules of single-stranded CPFV RNA consists of 303 nucleotides. The nucleotide sequence of CPFV was compared with the previously established sequence of hop stunt viroid (HSV), which consists of 297 nucleotides ( Ohno et al. Nucleic Acid Res.11,6185-6197 (1983]. CPFV differs from HSV in the nucleotide sequence at 16 positions which include 8 exchanges, 7 insertions and 1 deletion. Both viroids share about 95% sequence homology. Considering the pathogenic properties of both viroids together, it is concluded that CPFV is a cucumber isolate of HSV.

Base Sequence↗
PubMed1994

LISTA, LISTA-HOP and LISTA-HON: a comprehensive compilation of protein encoding sequences and its associated homology databases from the yeast Saccharomyces.

We continued our effort to make a comprehensive database (LISTA) for the yeast Saccharomyces cerevisiae. In this database each sequence has been attributed a single genetic name. In the case of duplicated sequences a simple method has been applied to distinguish between sequences of one and the same gene from non-allelic sequences of duplicated genes. If necessary, synonyms are given in the case of allelic duplicated sequences. Thus sequences can be found either by the name or by synonyms given in LISTA. Each entry contains the genetic name, the mnemonic from the EMBL data bank, the codon bias, reference of the publication of the sequence, Chromosomal location as far as known, Swissprot and EMBL accession numbers. To obtain more information on the included sequences, each entry has been screened against non-redundant nucleotide and protein data bank collections resulting in LISTA-HON and LISTA-HOP. The LISTA data base can be linked to the associated data sets or to nucleotide and protein banks by the Sequence Retrieval System (SRS).

Base Sequence↗
PubMed1996

LISTA, LISTA-HOP and LISTA-HON: a comprehensive compilation of protein encoding sequences and its associated homology databases from the yeast Saccharomyces.

We continued our effort to make a comprehensive database (LISTA) for the yeast Saccharomyces cerevisiae. As in previous editions the genetic names are consistently associated to each sequence with a known and confirmed ORF. If necessary, synonyms are given in the case of allelic duplicated sequences. Although the first publication of a sequence gives-according to our rules-the genetic name of a gene, in some instances more commonly used names are given to avoid nomenclature problems and the use of ancient designations which are no longer used. In these cases the old designation is given as synonym. Thus sequences can be found either by the name or by synonyms given in LISTA. Each entry contains the genetic name, the mnemonic from the EMBL data bank, the codon bias, reference of the publication of the sequence, Chromosomal location as far as known, SWISSPROT and EMBL accession numbers. New entries will also contain the name from the systematic sequencing efforts. Since the release of LISTA4.1 we update the database continuously. To obtain more information on the included sequences, each entry has been screened against non-redundant nucleotide and protein data bank collections resulting in LISTA-HON and LISTA-HOP. This release includes reports from full Smith and Watermann peptide-level searches against a non-redundant protein sequence database. The LISTA data base can be linked to the associated data sets or to nucleotide and protein banks by the Sequence Retrieval System (SRS). The database is available by FTP and on World Wide Web.

Amino Acid Sequence↗
PubMed1984

Double-stranded cDNAs of hop stunt viroid are infectious.

Restriction fragments composed of only hop stunt viroid (HSV) cDNA were prepared from recombinant clone pHS-P4P, which carries four tandemly repeated HSV cDNAs, and inoculated into cucumber cotyledons. The results showed that double-stranded cDNAs consisting of 1 to 3 units of HSV sequences were infectious. In cucumber plants inoculated with these double-stranded cDNAs, infectious RNA molecules indistinguishable from authentic HSV were propagated.

Base Sequence↗
PubMed2005

Expression of allene oxide cyclase and accumulation of jasmonates during organogenic nodule formation from hop (Humulus lupulus var. Nugget) internodes.

A crucial step in the biosynthesis of jasmonic acid (JA) is the formation of its stereoisomeric precursor, cis-(+)-12-oxophytodienoic acid (OPDA), which is catalyzed by allene oxide cyclase (AOC, EC 5.3.99.6). A cDNA of AOC was isolated from Humulus lupulus var. Nugget. The ORF of 765 bp encodes a 255 amino acid protein, which carries a putative chloroplast targeting sequence. The recombinant protein without its putative chloroplast target sequence showed significant AOC activity. Previously we demonstrated that wounding induces organogenic nodule formation in hop. Here we show that the AOC transcript level increases in response to wounding of internodes, peaking between 2 and 4 h after wounding. In addition, Western blot analysis showed elevated levels of AOC peaking 24 h after internode inoculation. The AOC increase was accompanied by increased JA levels 24 h after wounding, whereas OPDA had already reached its highest level after 12 h. AOC is mostly present in the vascular bundles of inoculated internodes. During prenodule and nodule formation, AOC levels were still high. JA and OPDA levels decreased down to 10 and 118 pmol (g FW)(-1), respectively, during nodule formation, but increased during plantlet regeneration. Double immunolocalization analysis of AOC and Rubisco in connection with lugol staining showed that AOC is present in amyloplasts of prenodular cells and in the chloroplasts of vacuolated nodular cells, whereas meristematic cells accumulated little AOC. These data suggest a role of AOC and jasmonates in organogenic nodule formation and plantlet regeneration from these nodules.

Amino Acid Sequence↗
PubMed2005

Mechanisms of the antiangiogenic activity by the hop flavonoid xanthohumol: NF-kappaB and Akt as targets.

Xanthohumol (XN), the principal flavonoid of the hop plant (Humulus lupulus L.) and a constituent of beer, has been suggested to have potential cancer chemopreventive activities. We have observed that most cancer chemopreventive agents show antiangiogenic properties in vitro and in vivo, a concept we termed "angioprevention." Here we show for the first time that XN can inhibit growth of a vascular tumor in vivo. Histopathology and in vivo angiogenesis assays indicated that tumor angiogenesis inhibition was involved. Further, we show the mechanisms for its inhibition of angiogenesis in vivo and related endothelial cell activities in vitro. XN repressed both the NF-kappaB and Akt pathways in endothelial cells, indicating that components of these pathways are major targets in the molecular mechanism of XN. Moreover, using in vitro analyses, we show that XN interferes with several points in the angiogenic process, including inhibition of endothelial cell invasion and migration, growth, and formation of a network of tubular-like structures. Our results suggest that XN can be added to the expanding list of antiangiogenic chemopreventive drugs whose potential in cancer prevention and therapy should be evaluated.

3T3 Cells↗
PubMed1998

Regulation of pathogenicity in hop stunt viroid-related group II citrus viroids.

Nucleotide sequences were determined for two hop stunt viroid-related Group II citrus viroids characterized as either a cachexia disease non-pathogenic variant (CVd-IIa) or a pathogenic variant (CVd-IIb). Sequence identity between the two variants of 95.6% indicated a conserved genome with the principal region of nucleotide difference clustered in the variable (V) domain. Full-length viroid RT-PCR cDNA products were cloned into plasmid SP72. Viroid cDNA clones as well as derived RNA transcripts were transmissible to citron (Citrus medica L.) and Luffa aegyptiaca Mill. To determine the locus of cachexia pathogenicity as well as symptom expression in Luffa, chimeric viroid cDNA clones were constructed from segments of either the left terminal, pathogenic and conserved (T1-P-C) domains or the conserved, variable and right terminal (C-V-T2) domains of CVd-IIa or CVd-IIb in reciprocal exchanges. Symptoms induced by the various chimeric constructs on the two bioassay hosts reflected the differential response observed with CVd-IIa and -IIb. Constructs with the C-V-T2 domains region from clone-IIa induced severe symptoms on Luffa typical of CVd-IIa, but were non-symptomatic on mandarin as a bioassay host for the cachexia disease. Constructs with the same region (C-V-T2) from the clone-IIb genome induced only mild symptoms on Luffa, but produced a severe reaction on mandarin, as observed for CVd-IIb. Specific site-directed mutations were introduced into the V domain of the CVd-IIa clone to construct viroid cDNA clones with either partial or complete conversions to the CVd-IIb sequence. With the introduction of six site-specific changes into the V domain of the clone-IIa genome, cachexia pathogenicity was acquired as well as a moderation of severe symptoms on Luffa.

Base Sequence↗
PubMed2000

Quantum hopping models for kinetic processes

We propose that a quantum operator, apart from representing quantum dynamics, may also represent a dynamical (steady-state) situation of a classical system. We consider a Hamiltonian that describes hopping of single (spinless, noninteracting) bosons to nearest-neighbor sites in a hypercubic lattice and find exactly the mass distribution (in arbitrary dimension) for the ground state and the first excited state. The density shows a peak at a mass equal to the density. A variant of this Hamiltonian is shown to have an exponential mass distribution (in the ground state) that is identical with an analogous classical model.

Journal Article↗
PubMed2001

Rectification by hopping motion through nonsymmetric potentials: local versus global bias.

The hopping motion of noninteracting classical particles through nonsymmetric potentials is investigated in the case of alternating local bias. Different to the case of alternating global bias, a resonancelike behavior is observed. The system exhibits rectification effects in the regime of small to medium bias, whereas rectification effects are absent in the strong bias regime. Possible generalizations and applications are outlined.

Journal Article↗
PubMed2001

Hopping motion of interacting particles: from time-dependent interaction to directed transport.

The hopping motion of three or more pairwise interacting particles on a linear equipotential chain is investigated. It is shown that a directed transport of the particle array can be obtained by introducing time-dependent interactions such as switching the interaction strength periodically between two values. The direction and mean velocity of the motion are determined by the nature of the imposed time dependence and can, hence, be chosen dynamically. The possibility of transporting a passive cargo and some other applications are discussed.

Journal Article↗
PubMed2002

Multistability, noise, and attractor hopping: the crucial role of chaotic saddles.

We investigate the hopping dynamics between different attractors in a multistable system under the influence of noise. Using symbolic dynamics we find a sudden increase of dynamical entropies, when a system parameter is varied. This effect is explained by a bifurcation involving two chaotic saddles. We also demonstrate that the transient lifetimes on the saddle obey a scaling law in analogy to crisis.

Journal Article↗
PubMed2002

Hopping diffusion of two coupled particles in the random trap model.

We show that the hopping dynamics of two strongly connected particles can be mapped exactly to single particle dynamics. In this way we are able to calculate the exact asymptotic diffusion coefficient of two connected particles on a linear chain in the random trap model. In particular we calculate the diffusion coefficient for exponentially distributed site energies and show that there exists a critical temperature below which a subdiffusive behavior appears. It turns out that this critical temperature is twice higher than the critical temperature in the single particle case [S. Havlin, B. L. Trus, and G. H. Weiss, J. Phys. A: Math. Gen. 19, L817 (1986)].

Journal Article↗
PubMed2005

Resistance distribution in the hopping percolation model.

We study the distribution function P (rho) of the effective resistance rho in two- and three-dimensional random resistor networks of linear size L in the hopping percolation model. In this model each bond has a conductivity taken from an exponential form sigma proportional to exp (-kappar) , where kappa is a measure of disorder and r is a random number, 0< or = r < or =1 . We find that in both the usual strong-disorder regime L/ kappa(nu) >1 (not sensitive to removal of any single bond) and the extreme-disorder regime L/ kappa(nu) <1 (very sensitive to such a removal) the distribution depends only on L/kappa(nu) and can be well approximated by a log-normal function with dispersion b kappa(nu) /L , where b is a coefficient which depends on the type of lattice, and nu is the correlation critical exponent.

Journal Article↗