bluuebunny/crossref_metadata_2025 huggingface dataset:
Microtubules and lithocyst morphogenesis in Pilea cadierei
Authors: Galatis B. , Apostolakos P. , Panteris E.
Published: September 2008

Lithocysts in Pilea cadierei are initiated by differential divisions, the plane of which is predicted by typical preprophase microtubule bands. They soon become polarized and undergo a unique differentiation. The external periclinal wall thickens considerably in the absence of microtubules. In incipient lithocysts, a periclinal band of microtubules lines the external ends of the anticlinal walls. A distinct local thickening, possessing periclinal cellulose microfibrils, underlies the microtubule band. The cystolith stalk originates as a cylindrical wall ingrowth of a limited central region of the external periclinal wall. This grows inwards in the absence of microtubules in a preformed cytoplasmic diaphragm, approaching the internal periclinal wall. Stalk formation as well as the external periclinal wall thickening are not affected by colchicine and isopropyl n(3-chlorophenyl) carbamate. A cystolith body is formed within a cytoplasmic diaphragm in which most of the lithocyst organelles are located; this body is rich in cellulose microfibrils and is formed by the deposition of large amounts of wall material at the free end of the stalk, at right angles to its axis. This morphogenetic shift is preceded by the formation of a system of microtubules that converge in cortical sites close to the stalk. They proliferate and form an axial sheath around the cystolith body. The cellulose microfibrils are aligned in a parallel fashion with microtubules. Microtubule destruction by colchicine results in malformation of both the lithocyst and the cystolith body. Aberrant cystolith bodies are also formed in the presence of isopropyl n(3-chlorophenyl) carbamate, which seems to interfere with microtubule formation. These observations suggest that the lithocyst – cystolith body morphogenesis is controlled by microtubules.
Morphology and development of rumen fungi: Neocallimastix sp., Piromyces communis, and Orpinomyces bovis gen.nov., sp.nov.
Authors: Barr D. J. S. , Kudo H. , Jakober K. D. , Cheng K.-J.
Published: September 2008

Developmental stages and morphological variation are described for three species of fungi from the rumen of a Holstein steer. Neocallimastix sp. is monocentric and has endogenous, rarely exogenous, sporangial development. Piromyces communis is monocentric, rarely polycentric, and has both endogenous sporangium development and exogenous sporangia on sporangiophores. Orpinomyces bovis is described for a polycentric fungus with terminal and intercalary sporangiophore complexes that develop from the rhizomycelium, and polyflagellate zoospores. The advantages and limitations of the light microscope and the enigmatic problem of classification of diverse and polymorphic rumen fungi are discussed.
Two plants with contrasting architectures: growth responses to light gradients
Authors: Maillette Lucie , Keddy Paul A.
Published: September 2008

Securing light energy is a vitally important foraging activity of all plants. This experiment used screens with different combinations of sizes and numbers of perforations to create varying conditions of light intensity and patchiness. We tested the response of two annual wetland plant species, Bidens cernua L. and Eleocharis obtusa (Willd.) Schult., with contrasting morphologies to different combinations of light intensity and patchiness. Low light intensity reduced growth more than increased light patchiness. Erect B. cernua fared better under reduced light intensities than caespitose E. obtusa: when light became limiting, no E. obtusa shoots flowered but B. cernua still produced capitula. This is likely a consequence of the disadvantages of a caespitose life form in partially shaded conditions and may contribute to the different field distributions of these two species and the growth forms they represent.
Effect of long-term flooding on root metabolic response in five freshwater marsh plant species
Authors: McKee Karen L. , Mendelssohn Irving A. , Burdick David M.
Published: September 2008

Five freshwater marsh plant species exhibited different root metabolic responses when flooded to three water depths in field macrocosms. The capacity for alcoholic fermentation (as indicated by alcohol dehydrogenase activity) increased and remained at a relatively high level in the roots of the least flood-tolerant species, Scolochloa festucacea, but was not stimulated significantly or only temporarily in the more tolerant species, Scirpus acutus, Scirpus validus, Typha glauca, and Phragmites australis. During the first month of flooding, alcohol dehydrogenase activity showed a positive relationship with flooding depth and a negative relationship with soil redox potential. Malate accumulated in the roots of S. acutus, S. validus, and to a lesser extent in P. australis in response to flooding; concentrations showed a significant positive relationship with water depth and a significant negative relationship with soil redox potential during the first month of flooding. Differences in root metabolism among the five species were still evident after 1 year of continual flooding. Root specific gravities and air space cross-sectional volumes demonstrated potential species differences in root resistance to oxygen movement and root oxygen volume, respectively. The results suggest that the observed metabolic response reflected differential aeration of the roots resulting from differences in root structure and soil oxygen demand (reducing power).
Experimental removal of a dominant species at two levels of soil fertility
Authors: Gurevitch Jessica , Unnasch Robert S.
Published: September 2008

Fertilization of the soil in herbaceous plant communities has been observed to lead to an increase in productivity but a decline in species richness and diversity. We tested the hypothesis that the decline in diversity is due to increased competition from a dominant species by removing the dominant species, Dactylis glomerata L., from an old field community with and without fertilization. Fertilization without the removal of Dactylis resulted in a steep decline in species numbers and in species diversity. The removal of Dactylis when fertilizer was added prevented the decline in species richness. Removal of this dominant species led to an increase in species diversity, an increase in either the frequency or the abundance of almost half of the common species in the system, and an increase in the combined biomass of uncommon species. The response to the removal of Dactylis was greater at higher than at low soil fertility for most but not all variables. Key words: old-field, fertilization, competition, species diversity, community structure, Dactylis glomerata.
A field study on the respiration rates in the leaves of temperate plants
Authors: Collier Donald E. , Cummins W. Raymond
Published: September 2008

The field respiration rates of leaves, in terms of total dark respiration, cytochrome (cyanide sensitive) pathway respiration, and alternative (salicylhydroxamic acid sensitive) pathway respiration, were measured in 10 temperate species. Five spring understory herbs and five ruderal species were used. All species displayed resistance to cyanide and sensitivity to salicylhydroxamic acid, indicating a capacity and some engagement of the alternative pathway. In comparison with reports on the field respiration rates of leaves in arctic and boreal species, the temperate plants had significantly less O2 uptake along both respiratory pathways. Rates of alternative pathway respiration in this study were comparable with those reported in the leaves of crop plants. In a comparison of respiration rates between the ruderal and understory species, the ruderal species had significantly greater activity along the alternative pathway. The ruderals also had a significantly greater capacity for the alternative pathway. It is proposed that the presence of the alternative pathway somehow allows physiological flexibility in the ruderals, and this in turn aids in their survival in fluctuating environments. Key words: alternative pathway, cyanide resistance, respiration, ruderal, understory.
Disease development in Cucurbita maxima (squash) infected with Fusarium solani f.sp. cucurbitae
Authors: Samac Deborah A. , Leong Sally A.
Published: September 2008

A scanning electron microscopic study was carried out to establish the mode of infection, growth, and sporulation of three strains of Fusarium solani f.sp. cucurbitae in squash hypocotyls. Strains of F. solani f.sp. cucurbitae race 1 cause a cortical stem rot and dry fruit rot of cucurbits, whereas race 2 strains only attack cucurbit fruit. Spores of the race 2 strain (FS75) germinated, and mycelium grew on the surface of the epidermis of hypocotyls but did not appear to penetrate epidermal cells. Both race 1 strains, FS37, which has two linear mitochondrial plasmids, and FS3, a naturally occurring plasmidless strain, germinated and grew similarly in hypocotyl tissue. Penetration into host tissue by hyphae of these two strains was directly through the epidermis. Hyphae grew intercellularly and intracellularly but did not extend far into apparently living cells from lesions of dead tissue. Sporodochia erupted above the soil line in or near lesions. The events in development of disease in squash infected with F. solani f.sp. cucurbitae are quite distinct from those reported in pea infected with F. solani f.sp. pisi and in bean infected with F. solani f.sp. phaseoli.
Average radial growth rate and chlamydospore production of Ceratocystis minor, Ceratocystis minor var. barrasii, and SJB 122 in culture
Authors: Goldhammer David S. , Stephen Frederick M. , Paine Timothy D.
Published: September 2008

Two symbiotic fungi (SJB 122, an unidentified basidiomycete, and Ceratocystis minor (Hedgecock) Hunt variety barrasii Taylor) and one pathogenic phoretic fungus (C. minor (Hedgecock) Hunt variety minor) of the southern pine beetle, Dendroctonus frontalis Zimmermann, were inoculated onto six different concentrations of D. frontalis frass, loblolly pine (Pinus taeda L.) phloem, and uric acid media to observe radial growth rates and chlamydospore production. The average radial growth rate per day of C. minor var. barrasii increased significantly from the control on all three media, but growth was faster at increased concentrations of added phloem compared with the other supplemented media. Significant increases in chlamydospores produced by C. minor var. barrasii from the control occurred only on frass media, with more chlamydospores being produced at higher concentrations. The average radial growth rate per day of SJB 122 fungus increased significantly from the control on only one concentration of phloem and two concentrations of uric acid, but decreased significantly on low concentrations of frass media. SJB 122 chlamydospore production increased with increasing concentration on frass, was not different from the control on phloem, and increased significantly at intermediate concentrations on uric acid. Ceratocystis minor var. minor average radial growth rate per day increased with increasing concentration on both frass and phloem media but on uric acid decreased significantly at higher concentrations, following an initial signficant increase as compared with the controls.
A study of fungal endophytes of needles of balsam fir (Abies balsamea) and red spruce (Picea rubens) in New Brunswick, Canada, using culture and electron microscope techniques
Authors: Johnson John A. , Whitney Norman J.
Published: September 2008

Endophytic fungi were isolated from the interiors of surface-sterilized needles of balsam fir (Abies balsamea) and red spruce (Picea rubens) in New Brunswick, Canada. Four different fungi were isolated frequently. One species, designated X-W, was isolated exlusively from the petiole segment of red spruce needles. There was no difference in the variety of species isolated from fir needles from two sites, but a difference in frequency of species did exist. Micrographs of the interior of balsam fir needles showed hyphae occupying intercellular spaces and adhering to the outer walls of parenchyma cells. No penetration of cells by either fungus was observed.
Experimental taxonomy of Potentilla fruticosa
Authors: Davidson Campbell G. , Lenz Louis M.
Published: September 2008

Potentilla fruticosa is a dwarf north temperate circumpolar species. Numerical and experimental taxonomic approaches were utilized to study the taxonomy of this species. The Gower general coefficient of similarity was calculated for 127 representatives, including wild material from North America, Europe, and Asia, as well as cultivars. Interpretation of cluster analysis suggests that all accessions are variants of a common central theme (over 80% similarity). Hybridization may have clouded any distinct phenetic differences. Eight geographic representatives were selected to study breeding relationships. All were successfully crossed with the exception of a tetraploid plant. Heteroploid matings were noted by a reduced success rate. Backcrosses to existing putative F1 hybrids were successful. On the basis of this study, P. fruticosa should be used as the species name for the shrubby cinquefoil complex.
Flavonoid taxonomic analysis of Vicia species of section Faba
Authors: Perrino P. , Maruca G. , Linsalata V. , Bianco V. V. , Lester R. N. , Lattanzio V.
Published: September 2008

The flavonoids rutin, quercitrin, hyperoside, quercetin-3-arabinoside, kaempferol-3-rutinoside, and robinin were identified in leaves of six Vicia species of section Faba. Flavonoid glycosidic pattern was utilized to draw taxonomical relationships amongst the six species. The four botanical varieties of Vicia faba were found to be distinct from the narbonensis group and Vicia bithynica. Indeed, flavonoid fingerprints using high performance liquid chromatography show that the four botanical varieties of V. faba L. are closely related, whereas the wild species separate into three subgroups.
The developmental history of peatlands at Muskiki and Marguerite lakes, Alberta
Authors: Kubiw Helen , Hickman Michael , Vitt Dale F.
Published: September 2008

The peat stratigraphy of fens at Muskiki Lake (52°50′N, 116°51′W) and Marguerite Lake (54°38′N, 110°43′W) in central Alberta was examined to determine the developmental history of the fens on the basis of radiocarbon dating and bryophyte macrofossil analyses. Peat accumulation at Muskiki Lake peatland began about 9000 years BP via lake filling. Expansion of the peatland by paludification and vegetation changes, including string and flark formation, are secondary occurrences, the latter occurring subsequent to environmental changes, including mid-Holocene thermal events. Peat inception at Marguerite Lake began about 2400 years BP via paludification. This delay, relative to Muskiki Lake peatland, may be related to the mid-Holocene warm period. Fire activity and increased wetness, as well as autogenic successional processes, altered species composition and abundance.
Stream macroalgae of the eastern boreal forest region of North America
Authors: Sheath Robert G. , Hamilton Paul B. , Hambrook Julie A. , Cole Kathleen M.
Published: September 2008

Fifty-one stream segments were sampled in northwestern Newfoundland, central Labrador, and west-central Quebec during June and July 1987. There was a great range in stream size, current velocity, pH, and ion content. The eastern boreal forest was found to be one of the most diverse regions in North America for stream macroalgae, having a flora of 67 species. The major divisions in terms of species numbers were the Chlorophyta (43%), Cyanophyta (21%), Chrysophyta (19%), and Rhodophyta (16%). Mats were the most widespread form (51% of the species), followed by filaments (27%), colonies (13%), tissues (5%), and palmelloid forms (3%). Species number was positively correlated with water temperature and total cover and negatively correlated with pH. The most widespread species was Batrachospermum moniliforme, which occurred in 31% of the stream segments examined. Distribution was patchy, with total cover varying from < 1 to ca. 60% of the stream bottom. Species numbers per segment ranged from 1 to 11. The most closely associated species were Microspora pachyderma, Mougeotia sp., and Batrachospermum keratophytum. The known distribution range of the rare rhodophyte Boldia erythrosiphon was extended north by ca. 1000 km.
Ultrastructure of the early stages of infection of peanut leaves by the rust fungus Puccinia arachidis
Authors: Mims C. W. , Taylor J. , Richardson E. A.
Published: September 2008

Peanut rust disease proved to be an excellent system for ultrastructural study of development of infection structures by the fungus Puccinia arachidis. Fungal structures were clearly visible by light microscopy in fixed and embedded samples and could be located either on leaf surfaces or within the large substomatal chambers of peanut leaves. Samples could easily be oriented for thin sectioning. The infection process was a highly orchestrated process involving precisely timed events and highly specialized structures. Infection pegs developed from appressoria over stomata and entered the leaf by growing into the openings between guard cells. Once past the rim formed by the guard cell walls, the infection peg expanded to form a substomatal vesicle in which a synchronous mitotic division of the four nuclei occurred. A primary infection hypha then developed from the vesicle and grew into the mesophyll of the leaf until its tip or side contacted a host cell. A septum then delimited a binucleate or trinucleate terminal haustorial mother cell from the remainder of the infection hypha. The wall of the haustorial mother cell became closely appressed to that of the host cell. Following differentiation of the haustorial mother cell, a penetration peg arose from it and penetrated the host cell wall. The peg invaginated the host cell plasma membrane as it elongated and then expanded at its tip to form the haustorium body into which most of the contents of the haustorial mother cell moved. Meanwhile, the primary infection hypha formed secondary hyphae that gave rise to additional haustorial mother cells and haustoria. Key words: Puccinia arachidis, peanut rust, infection process, ultrastructure.
Anatomy of Dianthoveus cremnophilus (Cyclanthaceae)
Authors: Wilder George J.
Published: September 2008

Dianthoveus is a monotypic genus of the Cyclanthaceae and in this paper the anatomy of D. cremnophilus is described, including that of the lamina, petiole, peduncle, rhizome and first-order root. The lamina within interridge areas is hypostomatic and the mesophyll between boundary layers exhibits either two main regions according to sizes of intercellular spaces, or three main regions according to wall thickness of ordinary parenchyma cells. Expansion tissue occurs opposite adaxial and abaxial ridges of the lamina and where the median costa and noncostal portions of lamina are joined together. The petiole exhibits three main zones of ground tissue and the median costa has two to three zones. Certain veins of the petiole compose a conspicuous V in cross section. The peduncle has four main zones of ground tissue, including pith. This organ contains simple vascular bundles (commonly, collateral bundles) and bipolar compound vascular bundles. The rhizome has a conspicuous periderm, cortex (including endodermis), and central cylinder. Diverse forms of vascular bundles occur within the central cylinder, e.g., collateral, amphivasal, compound-tetrapolar, and compound-multipolar. In the first-order root the cortex exhibits various regions, including exodermis and endodermis, and the stele contains peripheral and nonperipheral fascicles, each type of fascicle of either xylem or phloem. Styloid sacs and raphide sacs occur in all and some organs studied, respectively, and in the rhizome and interridge areas of the lamina the styloid sacs are randomly oriented and abundant. Mucilage canals occur in the peduncle and petiole. These anatomical data are used to compare Dianthoveus with other cyclanthaceous genera, particularly Evodianthus.
Inclusions in nuclei and plastids of Boraginaceae and their possible taxonomic significance
Authors: Fisher Deborah D. , Thorsch Jennifer , Esau Katherine
Published: September 2008

A survey of 68 species representing 28 genera in the family Boraginaceae was conducted at the ultrastructural level to determine presence of nuclear crystalloids in sieve elements and occurrence of crystalline structures in chloroplasts of phloem parenchyma cells. Nuclear crystalloids were identified in 55 of the species examined, and 25 of the species contained chloroplast crystals. The nuclear crystals were mainly composed of thin rods densely packed in parallel arrangement. Their sizes, shapes, and numbers varied, but they were basically prismatic or possibly cubical. During maturation, the sieve element nuclei disintegrated and the crystalloids were released into the cell lumen where they remained intact. Loosely arranged paracrystalline components associated with the dense nuclear crystalloids were found only in the genus Amsinckia. Crystalline inclusions in the parenchyma chloroplasts were made up of fibers loosely aligned in a herringbone pattern. The lability of the chloroplast crystals to the proteolytic enzyme, protease, was tested on 10 species, and only Onosma stellulatum Waldst. & Kit. chloroplast crystals were routinely digested. The high percentage of nuclear crystalloids found in this family suggests that these inclusions could be valuable as a systematic character. Key words: sieve elements, nuclear inclusions, plastid crystals, Boraginaceae.
Ecological plasticity in Carex lyngbyei: evidence from transplant experiments
Authors: Smythe Susan R. , Hutchinson Ian
Published: September 2008

Four populations of Carex lyngbyei from each of three estuaries with contrasting salinity regimes in northwestern North America (deltas of the Nanaimo, Skagit, and Squamish rivers) were grown in a reciprocal transplant experiment to determine the degree to which morphological differences were genetic or environmentally based. Shoot height, biomass per shoot, and aboveground biomass differences were generally not maintained in the transplant environment, suggesting that genetic control on morphological variation was weak. Transplant site salinity regimes had little effect on shoot density or survival. It is suggested that broadly adapted genotypes, capable of this sort of plastic response, may have a competitive advantage in these fluctuating estuarine environments. Key words: Carex lyngbyei, Pacific Northwest, plasticity, reciprocal transplants.
Organogénèse de la fleur pistillée du Begonia dregei et de l’Hillebrandia sandwicensis (Begoniaceae)
Authors: Charpentier Anne , Brouillet Luc , Barabé Denis
Published: September 2008

The pistillate flower organogenesis of Begonia dregei Otto Dietr. (section Augustia) and Hillebrandia sandwicensis Oliver is described. Vascular anatomy and scanning electron microscopy show that the inferior ovary of B. dregei develops below the perianth, whereas the semi-inferior ovary of H. sandwicensis grows both above and below the insertion level of the perianth. A developmental study of both species showed that placental tissues have a mixed nature: parietal placentae develop from the ovary wall, whereas axile placentae are derived from the floral apex, with a gradual transition zone between the two tissues. Depending on the rate of growth of the two placental regions, the ovary becomes mostly axile or parietal, all intermediates being possible. Our study does not allow us to determine unambiguously which of the two types of placentation is the most primitive. Also, it is impossible to clearly ascertain the evolutionary status of the semi-inferior ovary of H. sandwicensis. However, ontogenetic results allowed us to shed new light on the nature of the ovary wall in Begonia. One may hypothesize that it is an intermediate structure between axial and appendicular organs, difficult to compare directly with a set of fused carpels and perianth parts, as postulated by the classical theory of the flower.
ON KHOVANOV'S COBORDISM THEORY FOR $\mathfrak{su}_3$ KNOT HOMOLOGY
Authors: MORRISON SCOTT , NIEH ARI
Published: September 2008

We reconsider the [Formula: see text] link homology theory defined by Knovanov in [9] and generalized by Mackaay and Vaz in [15]. With some slight modifications, we describe the theory as a map from the planar algebra of tangles to a planar algebra of complexes of "cobordisms with seams" (actually, a "canopolis"), making it local in the sense of Bar-Natan's local [Formula: see text] theory of [2].

We show that this "seamed cobordism canopolis" decategorifies to give precisely what you had both hope for and expect: Kuperberg's [Formula: see text] spider defined in [14]. We conjecture an answer to an even more interesting question about the decategorification of the Karoubi envelope of our cobordism theory.

Finally, we describe how the theory is actually completely computable, and give a detailed calculation of the [Formula: see text] homology of the (2,n) torus knots.
PERMANENCE OF A DISCRETE n-SPECIES LOTKA–VOLTERRA TYPE FOOD-CHAIN SYSTEM WITH FEEDBACK CONTROLS AND TIME DELAYS
Authors: HUANG XUMING , YANG WENSHENG , LI XUEPENG
Published: September 2008

In this paper, a discrete n-species Lotka–Volterra type food-chain system with time delays and feedback controls is proposed. By applying the comparison theorem of difference equation, sufficient conditions are obtained for the permanence of the system.
THE EXISTENCE OF POSITIVE PERIODIC SOLUTIONS OF AN ECO-EPIDEMIC MODEL WITH IMPULSIVE BIRTH
Authors: XUE YAKUI , KANG AIHUA , JIN ZHEN
Published: September 2008

In this paper, we considered an eco-epidemic model with impulsive birth. By using the coincidence degree theorem, a set of easily verifiable sufficient conditions are obtained for the existence of at least one strictly positive periodic solutions.
POSITIVE PERIODIC SOLUTION FOR A GAUSE-TYPE RATIO-DEPENDENT PREDATOR-PREY SYSTEM WITH DIFFUSION AND TIME DELAY
Authors: DING XIAOQUAN , WANG YUANYUAN
Published: September 2008

A two-species Gause-type ratio-dependent predator-prey system with time delay in a two-patch environment is investigated. By using a continuation theorem based on coincidence degree theory, we establish easily verifiable criteria for the existence of periodic solution for the system. As corollaries, some applications are listed. In particular, our results extend and improve some known results.
A FOOD CHAIN SYSTEM WITH HOLLING IV FUNCTIONAL RESPONSES AND IMPULSIVE EFFECT
Authors: XIONG ZUOLIANG , XUE YING , LI SHUNYI
Published: September 2008

In the paper, according to biological and chemical control strategy for pest control, our main purpose is to construct a three trophic level food chain system with Holling IV functional responses and periodic constant impulsive effect concerning integrated pest management (IPM), and investigate the dynamic behaviors of this system. By using the Floquet theory and comparison theorem of impulsive differential equation and analytic method, we prove that there exists a globally asymptotically stable pest-eradication periodic solution when the impulsive period is less than some critical value. Further, condition for permanence of the system is established. Finally, numerical simulation shows that there exists a stable positive periodic solution with a maximum value no larger than a given level.
STABILITY AND HOPF BIFURCATION FOR AN ECO-EPIDEMIOLOGY MODEL WITH HOLLING-III FUNCTIONAL RESPONSE AND DELAYS
Authors: ZOU WEI , XIE JIEHUA , XIONG ZUOLIANG
Published: September 2008

In this paper, a system of retarded functional differential equations is proposed as a predator-prey model with disease in the prey. The invariance of non-negativity, nature of boundary equilibrium and global stability are analyzed. It also shows that positive equilibrium is locally asymptotically stable when time delay τ = τ1 + τ2 is suitable small, while a loss of stability by a Hopf bifurcation can occur around the positive equilibrium as the delays increase.
A DISCRIMINATION MEASURE FOR PHYLOGENETIC TREE CONSTRUCTION
Authors: FENG JIE , WANG TIAN-MING
Published: September 2008

Traditional approaches for phylogenetic analysis require a multiple alignment and therefore are not directly applicable to complete genomes, besides, all of these methods assume some sort of an evolutionary model which may not always be correct. We propose a new sequence distance based on the relative information between the sequences using discrimination measure. By making use of the obtained distance matrix, we construct a phylogenic tree for eutherians using the mitochondrial proteins. The examination of topology belong to 20 species illustrates the utility of our approach.
REPEATED BURST ERROR CORRECTING LINEAR CODES
Authors: Dass B. K. , Verma Rashmi
Published: September 2008

Many kinds of errors in coding theory have been dealt with for which codes have been constructed to combat such errors. Though there is a long history concerning the growth of the subject and many of the codes developed have found applications in numerous areas of practical interest, one of the areas of practical importance in which a parallel growth of the subject took place is that of burst error detecting and correcting codes. The nature of burst errors differ from channel to channel depending upon the behaviour of channels or the kind of errors which occur during the process of data transmission. In very busy communication channels, errors repeat themselves more frequently. In view of this, it is desirable to consider repeated burst errors. The paper presents lower and upper bounds on the number of parity-check digits required for a linear code correcting errors in the form of repeated bursts. An upper bound for a code that detects m-repeated bursts has also been derived. Illustrations of several codes that correct 2-repeated bursts of different lengths have also been given.
HYPERSUBSTITUTIONS OF MANY-SORTED ALGEBRAS
Authors: Denecke Klaus , Lekkoksung Somsak
Published: September 2008

Many-sorted algebras are used in Computer Science for abstract data type specifications. It is widely believed that many-sorted algebras are the appropriate mathematical tools to explain what abstract data types are ([1]). In this paper we want to extend the concept of a hypersubstitution from the one-sorted to the many-sorted case. Hypersubstitutions are used for one-sorted algebras to define hyperidentities and M-solid varieties ([2]). We will prove that extensions of hypersubstitutions for many-sorted algebras are endomorphisms of the many-sorted clone of a given type. As in the one-sorted case we define a binary operation for hypersubstitutions and prove that with respect to this operation all many-sorted hypersubstitutions form a monoid.
WHEN IS A SEMIPERFECT RING RIGHT PF?
Authors: Dung Banh Duc , Thoang Le Duc , van Sanh Nguyen
Published: September 2008

It is well-known that a ring R is right PF if and only if it is semiperfect and right self-injective with essential right socle. In this note, it is shown that a ring R is right PF if and only if u.dim(RR) < ∞ and every colocal, injective right R-module is projective. Consequently, a semiperfect ring R is right PF if and only if the two classes of colocal injective right R-modules and local projective right modules coincide.
THE VARIETY OF RINGS WITH INVOLUTION SATISFYING x7≈ x
Authors: Musunthia Tiwadee
Published: September 2008

We give a complete description of the lattice of varieties of rings with involution satisfying x7≈ x by identity bases. There are 90 such varieties. If we substitute in each ring of such a variety the operations by term operations of the same arity we obtain a so-called class of derived rings. We discuss the case when the class of derived rings belongs to the original variety. In particular, we describe the class of derived rings for the variety of rings generated by the two-element Galois-field.
ZEROS OF ULTRAMETRIC MEROMORPHIC FUNCTIONS f′ fn(f − a)k− α
Authors: Ojeda Jacqueline
Published: September 2008

Let 𝕂 be an algebraically closed field of characteristic zero, complete for an ultrametric absolute value. Similarly to the Hayman problem, here we study meromorphic functions in 𝕂 or in an open disk that are of the form f′ fn(f − a)k− α with α a small function, in order to find sufficient conditions on n, k assuring that they have infinitely many zeros. We first define and characterize a special value for a meromorphic function and check that, if it exists, it is unique. So, such values generalize Picard exceptional values.
ON HYPER AND HYPO ABELIAN-OF-FINITE-RANK GROUPS
Authors: Wehrfritz B. A. F.
Published: September 2008

We prove that a hyper(abelian of finite rank) group, whose images are all hypo (abelian of finite rank), is hypo(central and rank-1 divisible) by hypo(finite abelian).
Reverse changes in cardiac substrate oxidation in dogs recovering from heart failure
Authors: Qanud Khaled , Mamdani Mohammed , Pepe Martino , Khairallah Ramzi J. , Gravel John , Lei Biao , Gupte Sachin A. , Sharov Victor G. , Sabbah Hani N. , Stanley William C. , Recchia Fabio A.
Published: September 2008

When recovering from heart failure (HF), the myocardium displays a marked plasticity and can regain normal gene expression and function; however, recovery of substrate oxidation capacity has not been explored. We tested whether cardiac functional recovery is matched by normalization of energy substrate utilization during post-HF recovery. HF was induced in dogs by pacing the left ventricle (LV) at 210–240 beats/min for 4 wk. Tachycardia was discontinued, and the heart was allowed to recover. An additional group was studied in HF, and healthy dogs served as controls ( n = 8/group). Cardiac free fatty acids (FFAs) and glucose oxidation were measured with [3H]oleate and [14C]glucose. At 10 days of recovery, hemodynamic parameters returned to control values; however, the contractile response to dobutamine remained depressed, LV end-diastolic volume was 28% higher than control, and the heart mass-to-body mass ratio was increased (9.8 ± 0.4 vs. 7.5 ± 0.2 g/kg, P < 0.05). HF increased glucose oxidation (76.8 ± 19.7 nmol·min−1·g−1) and decreased FFA oxidation (20.7 ± 6.4 nmol·min−1·g−1), compared with normal dogs (24.5 ± 6.3 and 51.7 ± 9.6 nmol·min−1·g−1, respectively), and reversed to normal values at 10 days of recovery (25.4 ± 6.0 and 46.6 ± 6.7 nmol·min−1·g−1, respectively). However, similar to HF, the recovered dogs failed to increase glucose and fatty acid uptake in response to pacing stress. The activity of myocardial citrate synthase and aconitase was significantly decreased during recovery compared with that in control dogs (58 and 27% lower, respectively, P < 0.05), indicating a persistent reduction in mitochondrial oxidative capacity. In conclusion, cardiac energy substrate utilization is normalized in the early stage of post-HF recovery at baseline, but not under stress conditions.
Ranolazine combined with enalapril or metoprolol prevents progressive LV dysfunction and remodeling in dogs with moderate heart failure
Authors: Rastogi Sharad , Sharov Victor G. , Mishra Sudhish , Gupta Ramesh C. , Blackburn Brent , Belardinelli Luiz , Stanley William C. , Sabbah Hani N.
Published: September 2008

Acute intravenous infusion of ranolazine (Ran), an anti-ischemic/antiangina drug, was previously shown to improve left ventricular (LV) ejection fraction (EF) without a concomitant increase in myocardial oxygen consumption in dogs with chronic heart failure (HF). This study examined the effects of treatment with Ran alone and in combination with metoprolol (Met) or enalapril (Ena) on LV function and remodeling in dogs with HF. Dogs ( n = 28) with microembolization-induced HF were randomized to 3 mo oral treatment with Ran alone [375 mg twice daily (bid); n = 7], Ran (375 mg bid) in combination with Met tartrate (25 mg bid; n = 7), Ran (375 mg bid) in combination with Ena (10 mg bid; n = 7), or placebo (PL; Ran vehicle bid; n = 7). Ventriculographic measurements of LV end-diastolic volume (EDV) and end-systolic volume (ESV) and LV EF were obtained before treatment and after 3 mo of treatment. In PL-treated dogs, EDV and ESV increased significantly. Ran alone prevented the increase in EDV and ESV seen in the PL group and significantly increased EF, albeit modestly, from 35 ± 1% to 37 ± 2%. When combined with either Ena or Met, Ran prevented the increase in EDV, significantly decreased ESV, and markedly increased EF compared with those of PL. EF increased from 35 ± 1% to 40 ± 1% with Ran + Ena and from 34 ± 1% to 41 ± 1% with Ran + Met. Ran alone or in combination with Ena or Met was also associated with beneficial effects at the cellular level on histomorphometric parameters such as hypertrophy, fibrosis, and capillary density as well as the expression for pathological hypertrophy and Ca2+ cycling genes. In conclusion, Ran prevented progressive LV dysfunction and global and cellular myocardial remodeling, and Ran in combination with Ena or Met improved LV function beyond that observed with Ran alone.
A Key Role for Cyclic AMP-Responsive Element Binding Protein in Hypoxia-Mediated Activation of the Angiogenesis Factor CCN1 (CYR61) in Tumor Cells
Authors: Meyuhas Ronit , Pikarsky Eli , Tavor Einat , Klar Avihu , Abramovitch Rinat , Hochman Jacob , Lago Tal Goshen , Honigman Alik
Published: September 2008

Hypoxia is a prominent feature of solid tumors known to contribute to malignant progression and therapeutic resistance. Cancer cells adapt to hypoxia using various pathways, allowing tumors to thrive in a low oxygen state. Induction of new blood vessel formation via the secretion of proangiogenic factors is one of the main adaptive responses engaged by tumor cells under hypoxic conditions. Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that plays a pivotal role in mediating such responses. In addition, several other transcription factors have also been implicated in hypoxic gene regulation, either independently or in cooperation with HIF-1. In this work, we show that the expression of the angiogenesis-related, immediate early gene CCN1 (formerly known as CYR61), considered to be involved in tumor growth and invasiveness, is enhanced upon hypoxia stress primarily in a protein kinase A and cyclic AMP-responsive element binding protein (CREB) and CRE–dependent manner in various cell lines. The hypoxia-mediated activation of the CCN1 promoter is independent of HIF-1 and HIF-2, as shown by small interfering RNA knockdown. We identify the cis element in the mouse CCN1 promoter responsible for CREB binding to be one of two partial CRE sites present in the promoter. Moreover, we report for the first time that CREB-mediated CCN1 transcription is enhanced in hypoxic regions of tumors in vivo. Identifying and characterizing the molecular mechanisms that govern the response of tumors to hypoxia may be instrumental to identify the tumors that will respond favorably to inhibition of angiogenesis and thus lead to the development of treatments that could complement hypoxia-inducing treatment modalities. (Mol Cancer Res 2008;6(9):1397–409)
The Circadian Gene NPAS2, a Putative Tumor Suppressor, Is Involved in DNA Damage Response
Authors: Hoffman Aaron E. , Zheng Tongzhang , Ba Yue , Zhu Yong
Published: September 2008

Apart from regulating sleep and wakefulness, the circadian system may play an important role in other biological processes, including pathways involved in tumorigenesis. Two genetic association studies recently conducted by our lab have shown that a missense mutation in neuronal PAS domain protein 2 (NPAS2), a core circadian gene and transcriptional regulator, is significantly associated with risk of breast cancer and non–Hodgkin's lymphoma. Our current functional analyses provide the first in vitro evidence further demonstrating that cells with RNA interference–mediated depletion of NPAS2 fail to exhibit the expected cell cycle delay in response to mutagen treatment. DNA repair capacity, as measured by the comet assay, is also impaired. Moreover, a pathway-based PCR expression array of genes important for DNA damage signaling showed that knockdown of NPAS2 significantly represses the expression of several cell cycle and DNA repair genes. Thus, NPAS2 may play a role in tumorigenesis by affecting expression of cancer-related genes and could be considered a novel tumor suppressor. (Mol Cancer Res 2008;6(9):1461–8)
Repression of the Desmocollin 2 Gene Expression in Human Colon Cancer Cells Is Relieved by the Homeodomain Transcription Factors Cdx1 and Cdx2
Authors: Funakoshi Shinsuke , Ezaki Toshihiko , Kong Jianping , Guo Rong Jun , Lynch John P.
Published: September 2008

Desmosomes are intracellular junctions that provide strong cell-cell adhesion in epithelia and cardiac muscle. Their disruption causes several human diseases and contributes to the epithelial-to-mesenchymal transition observed in cancer. Desmocollin 2 (DSC2) is a cadherin superfamily member and a critical component of desmosomes found in intestinal epithelium. However, the mechanism regulating DSC2 gene expression in intestinal cells is not known. Cdx1 and Cdx2 are homeodomain transcription factors that regulate intestine-specific gene expression. Cdx expression in the past has been associated with the induction of desmosomes. We now show that the DSC2 gene is a transcriptional target for Cdx1 and Cdx2. Colon cancer cell lines retaining Cdx2 expression typically express DSC2. Restoration of Cdx expression in Colo 205 cells induced DSC2 mRNA and protein and the formation of desmosomes. The 5′-flanking region of the DSC2 promoter contains two consensus Cdx-binding sites. Electrophoretic mobility shift assays show that Cdx1 and Cdx2 bind these sites in vitro, and chromatin immunoprecipitation confirmed Cdx2 binding in vivo. DSC2 promoter truncations established that these regions are Cdx responsive. The truncations also identify a region of the promoter in which potent transcriptional repressors act. This repressor activity is relieved by Cdx binding. We conclude that the homeodomain transcription factors Cdx1 and Cdx2 regulate DSC2 gene expression in intestinal epithelia by reversing the actions of a transcriptional repressor. The regulation of desmosomal junctions by Cdx contributes to normal intestinal epithelial columnar morphology and likely antagonizes the epithelial-to-mesenchymal transition necessary for the metastasis of colon cancer cells in humans. (Mol Cancer Res 2008;6(9):1478–90)
Sox7 Is an Independent Checkpoint for β-Catenin Function in Prostate and Colon Epithelial Cells
Authors: Guo Lizheng , Zhong Diansheng , Lau Stephen , Liu Xiuju , Dong Xue-Yuan , Sun Xiaodong , Yang Vincent W. , Vertino Paula M. , Moreno Carlos S. , Varma Vijay , Dong Jin-Tang , Zhou Wei
Published: September 2008

The presence of somatic β-catenin mutations in some prostate cancers implies that aberrant WNT signaling is involved in the cancer development. Although β-catenin stability is regulated by a multicomponent destruction complex, mutational alterations of β-catenin or other components of the destruction complexes are rare in prostate tumors. Therefore, β-catenin may be regulated by another protein in the prostate. In fact, recent linkage and somatic deletion analyses in prostate cancers reveal a 1.4-Mb candidate tumor suppressor locus on 8p23.1, which includes the Sox7 gene. Here we show that Sox7 protein expression was indeed down-regulated in 47% (15 of 32) of prostate adenocarcinomas. In addition, Sox7 mRNA was down-regulated in 60% of snap-frozen tumors. This down-regulation was found to be due to tumor-specific promoter hypermethylation, which was present in 48% (10 of 21) of primary prostate tumors and 44% (11 of 25) of prostate cancer cell lines/xenografts. We discovered that Sox7 protein physically interacts with β-catenin and suppresses β-catenin–mediated transcription by depleting active β-catenin. Furthermore, in HCT116 colorectal cancer cell lines with Sox7 inactivation, ectopic Sox7 expression suppressed cell proliferation and inhibited transcription that was activated by an endogenous mutant β-catenin. Although nearly all colorectal cancers contain mutations in β-catenin or adenomatous polyposis coli/axin, epigenetic silencing of Sox7 was still observed. These data suggest that Sox7 is a tumor suppressor that functions as an independent checkpoint for β-catenin transcriptional activity. Inactivation of Sox7 could promote the development of a majority of colorectal tumors and approximately half of prostate tumors. (Mol Cancer Res 2008;6(9):1421–10)
Autoubiquitination of BCA2 RING E3 Ligase Regulates Its Own Stability and Affects Cell Migration
Authors: Amemiya Yutaka , Azmi Peter , Seth Arun
Published: September 2008

Accumulating evidence suggests that ubiquitination plays a role in cancer by changing the function of key cellular proteins. Previously, we isolated BCA2 gene from a library enriched for breast tumor mRNAs. The BCA2 protein is a RING-type E3 ubiquitin ligase and is overexpressed in human breast tumors. In order to deduce the biochemical and biological function of BCA2, we searched for BCA2-binding partners using human breast and fetal brain cDNA libraries and BacterioMatch two-hybrid system. We identified 62 interacting partners, the majority of which were found to encode ubiquitin precursor proteins including ubiquitin C and ubiquitin A-52. Using several deletion and point mutants, we found that the BCA2 zinc finger (BZF) domain at the NH2 terminus specifically binds ubiquitin and ubiquitinated proteins. The autoubiquitination activity of BCA2, RING-H2 mutant, BZF mutant, and various lysine mutants of BCA2 were investigated. Our results indicate that the BCA2 protein is strongly ubiquitinated and no ubiquitination is detected with the BCA2 RING-H2 mutant, indicating that the RING domain is essential for autoubiquitination. Mutation of the K26 and K32 lysines in the BZF domain also abrogated autoubiquitination activity. Interestingly, mutation of the K232 and K260 lysines in and near the RING domain resulted in an increase in autoubiquitination activity. Additionally, in cellular migration assays, BCA2 mutants showed altered cell motility compared with wild-type BCA2. On the basis of these findings, we propose that BCA2 might be an important factor regulating breast cancer cell migration/metastasis. We put forward a novel model for BCA2 E3 ligase–mediated cell regulation. (Mol Cancer Res 2008;6(9):1385–96)
IFN-Induced Protein with Tetratricopeptide Repeats 2 Inhibits Migration Activity and Increases Survival of Oral Squamous Cell Carcinoma
Authors: Lai Kuo-Chu , Chang Kuo-Wei , Liu Chung-Ji , Kao Shou-Yen , Lee Te-Chang
Published: September 2008

The function of the IFN-stimulated gene family protein, IFN-induced protein with tetratricopeptide repeats 2 (IFIT2), is poorly understood. Here, we report that IFIT2 colocalizes with cytokeratin 18 in oral squamous cell carcinoma (OSCC) cells. Treatment of OSCC cells with IFN-β significantly increased the expression of IFIT2 and remarkably inhibited cell migration. To further explore the effect of IFIT2 on cell migration, IFIT2 expression was either silenced with a small interfering RNA or increased by ectopic expression. IFIT2 knockdown in OSCC cells led to a significantly higher level of migration in vitro (P < 0.05) compared with control cells; by contrast, IFIT2 overexpression led to a significantly lower level of migration in vitro (P < 0.05). Immunohistochemically, 71.4% of OSCC tissues had elevated IFIT2 protein levels compared with noncancerous matched tissues. Elevated IFIT2 protein expression was positively associated with tumor differentiation status and inversely associated with nodal stage in OSCC specimens (P < 0.05). Higher IFIT2 protein levels in tumor tissues were also associated with better patient survival (P < 0.01). Our present study shows an inverse correlation between IFIT2 expression and cell migration, suggesting that IFIT2 plays an important role in inhibiting this process and that its expression may be associated with better prognosis in patients with OSCC. (Mol Cancer Res 2008;6(9):1431–9)