bluuebunny/crossref_metadata_2025 huggingface dataset:
Xylitol fermentation by human dental plaque
Authors: Assev Synnøve , Wåler Sonni Mette , Rølla Gunnar
Published: October 2007

The aim of the present study was to examine xylitol metabolism by dental plaque collected immediately after the use of xylitol gum. Plaque was collected from 12 individuals immediately before and after xylitol exposure. The effect on xylitol metabolism by dental plaque of a 3 d discontinuation of the xylitol exposure was also examined. Xylitol metabolism by the plaque suspensions was initiated by adding [14C]xylitol and analyzed by HPLC. The results showed increased xylitol metabolism after 11 wk of chewing xylitol‐containing gum. The ability to metabolize xylitol was rapidly reduced after the discontinuation of the xylitol exposure. It is suggested that an induction of enzymes in one or more of the species of plaque bacteria may have caused this effect. Glucose metabolism, which also was studied in the plaque samples, was decreased after xylitol exposure, but increased again 3 d after cessation of the xylitol exposure. It is suggested that the reduced glycolysis was caused by accumulation of intracellular xylitol‐5‐phosphate in some plaque bacteria during the xylitol exposure.
Cellular events concurrent with porphyromonas gingivalis invasion of oral epithelium in vitro
Authors: Sandros Jens , Madianos Phoebus N. , Papapanou Panos N.
Published: October 2007

The aim of the present study was to elucidate events related to receptor function, signal transmission and cytoskeletal rearrangements concurrent with Porphyromonas gingivalis invasion of oral epithelial cells in vitro. Porphyromonas gingivalis strain FDC 381 and the KB cell line (ATCC CCL 17) were used in a previously described antibiotic protection assay. The involvement of a receptor‐mediated endocytosis pathway in the internalization process was demonstrated after treatment of the epithelial cells with monodansylcadaverine and ouabain. substances that inhibit formation of coated pits, resulting in reduction in the number of invading P. gingivalis. Treatment of the epithelial cells with the protein kinase (PK) inhibitor staurosporine and the tyrosine‐specific PK inhibitor genistein was also found to significantly decrease the number of invading bacteria, suggesting involvement of tyrosine phosphorylation in signal transduction during invasion. This was further supported by the identification of a 43 kD protein acting as a substrate for tyrosine phosphorylation subsequent to the microbial‐host cell interaction. Tyrosine phosphorylation of the 43 kD protein was strongly reduced by treatment with PK inhibitors. The decrease in invasion observed after treatment of epithelial cells with colchicine and nocodazole, inhibitors of microtubuli polymerization, suggested that the bacterial‐receptor interaction and the phosphotyrosine‐dependent intracellular signalling trigger an internalization process involving rearrangements of cytoskeletal microtubuli.
Influence of dose and cessation of kiraiku, cigarettes and alcohol use on the risk of developing oral leukoplakia
Authors: Macigo Francis Githua , Mwaniki David Lemmy , Guthua Symon Wang'ombe
Published: October 2007

Data from a previously‐reported study of oral leukoplakia‐associated risk factors in a Kenyan population were further analyzed to determine the influence of dose and cessation. Specifically, risk analysis was made with respect to kiraiku (a traditional Kenyan type of home‐made, hand‐rolled tobacco product), cigarettes, and commercial beer. The relative risk (RR) of oral leukoplakia among those who smoked 10 cigarettes was 14.7. as compared to 6.7 among those who smoked 10 cigarettes. With regard to duration, the RR increased from 7.4 in those who had smoked for 15 years to 10.8 in those who had smoked for 30 years. Among those who had quit smoking, RR value was significant only in ex‐kiraiku smokers (RR=4.9. 95% confidence interval (Cl)=2.3–20.4) and was dependent on both the duration of smoking and duration since quitting. For commercial beer, the RR was significant in consumers of >10 bottles per drinking day (RR=4.2. 95% Cl=1.0–3.9) and in those whose who drank for 5 days per month (RR=3.8, 95% Cl=1.0–15.1). Duration of beer consumption did not significantly influence the RR of oral leukoplakia. The RR in ex‐beer consumers was not statistically significant. These findings suggest a dose‐dependent association between oral leukoplakia and the use of tobacco and alcohol, in which the number of cigarettes smoked, the quantity of beer consumed, and the frequency of consumption were more important than the duration of use of these products. Furthermore, while oral leukoplakia due to cigarette smoking may regress completely, those due to kiraiku may persist for more than 10 years after cessation of these habits
Prediction of caries in pre‐school children in relation to fluoride exposure
Authors: Twetman Svante , Petersson Lars G.
Published: October 2007

The levels of salivary mutans streptococci and caries experience were used as predictors for caries incidence in 3 groups of pre‐school children from areas with different levels of natural and topical fluoride exposure. Altogether 1022 children, 4‐5 years of age at baseline, were examined according to the WHO‐criteria and followed for 2 years. The low fluoride group (n=374) had a low fluoride level in the piped water and no topical fluoride applications: the F‐varnish group (n=442) had low water fluoride but semiannual topical applications of a fluoride varnish; the optimal fluoride group (n=206) had an optimal level of fluoride in the drinking water and semiannual F‐varnish applications. The number of salivary mutans streptococci was estimated and scored at baseline with the Strip mutans chair‐side method. The sampling procedure was repeated in 337 children of the low fluoride group 3 weeks after baseline. In comparison with the low fluoride group, caries incidence was 30% and 60% lower in the F‐varnish and the optimal fluoride group respectively. The caries predictive ability decreased with increasing fluoride exposure. The sum of sensitivity and specificity decreased from 151% (65%+86%) in the low fluoride group to 131% (40%+91%) in the optimal fluoride group. The positive predictive value was highest (62%) in the low fluoride group. Repeated salivary samplings at baseline did not improve the caries predictive power. The results suggest that the overall fluoride exposure should be taken into account when caries risk assessment strategies for preschool children are developed and implemented.
Antiplaque, antibacterial, and anti‐inflammatory properties of triclosan mouthrinses in combination with zinc citrate or polyvinylmethylether maleic acid (PVM‐MA) copolymer
Authors: Kjaerheim Vibeke , Skaare Anne , Barkvoll Pål , Rölla Gunnar
Published: October 2007

The antibacterial agent triclosan has demonstrated antiplaque and antigingivitis activity in several clinical studies. Retention of antiplaque agents is of significance for their clinical effect. Triclosan has a relatively rapid clearance from the oral cavity, and attempts have been made to increase its oral retention. In the present clinical antiplaque study, it was found that 0.5% copolymer poly‐vinyl‐methylether maleic acid (PVM‐MA) or 0.5% zinc citrate, which are both added to commercial products, inhibited plaque formation to a similar degree when used in combination with 0.3% triclosan, 1.5% sodium lauryl sulfate (SLS) and diluted propylene glycol (PG) in water (1:8). Plaque inhibition was significantly improved compared to a placebo solution. It was shown that these results could not be explained by an increase in antibacterial activity or by a change in the critical micellar concentration. The effect of the same solutions on SLS‐induced inflammation on skin was also tested. It was seen that the triclosan/zinc citrate solution and the control (triclosan/ethanol) decreased the inflammatory response, whereas the solutions containing triclosan in either propylene glycol (PG) or copolymer/PG did not exhibit any anti‐inflammatory capacity.
Caries and plaque inhibition in rats by five topically applied dentifrices
Authors: Guggenheim Bernhard , Lutz Felix , Schmid Rudolf
Published: October 2007

The effectiveness of 5 different brands of dentifrices on caries and plaque were tested in rats in 2 experiments, 10 litters of rats each were infected with Streptococcus sobrinus OMZ‐176 and Actinomyces viscosus Nyl. The rats were offered the diet 2000a containing either 40% of sucrose (study I) or 10% of sucrose (study II). The following products were tested topically: (1) H2O, (negative control): (2) chlorhexidine diacetate. (positive control); (3) Parodontax NF; (4) Meridol; (5) Colgate Total; (6) Mentadent C: (7) Dent Xpress. Comparisons with the water control in study I showed that plaque extent was decreased by chlorhexidine diacetate. Dent Xpress and by Mentadent C only. All fluoride‐containing dentifrices tested reduced caries. In study II, comparisons with the water control showed that plaque extent was reduced by chlorhexidine diacetate, Parodontax, Meridol, Dent Xpress and by Mentadent C. All dentifrices reduced caries, however, the incidence was low. These 2 studies confirm that fluorides incorporated in dentifrices decrease dental caries in the rat. Differences in the effectiveness of caries inhibition between the 5 dentifrices could not be explained either by the form of fluoride utilized or by the antimicrobials added. Rather, the performance of a given dentifrice depended upon the concerted action of the particular ingredients. It appears that the effect of antiplaque agents should be evaluated in the rat model using a diet containing sucrose at a low level.
Review on fluoride, with special emphasis on calcium fluoride mechanisms in caries prevention
Authors: ten Cate J. M.
Published: October 2007

Low concentrations of fluoride have a beneficial effect on enamel and dentin de‐ and remineralization. After fluoride treatments, such as topical applications, rinses or dentifrices, salivary fluoride concentrations decrease exponentially in a biphasic manner to very low concentrations within a few hours. For treatments to be effective over periods longer than the brushing and the following salivary clearance, fluoride needs to be deposited and slowly released. Calcium fluoride (or like) deposits act in such a way. owing to a surface covering of phosphate and/or proteins, which makes the CaF2 Jess soluble under in vivo conditions than in a pure form in inorganic solutions. Moreover, due to the phosphate groups on the surface of the calcium fluoride globules, fluoride is assumed to be released with decreasing pH when the phosphate groups are protonated in the dental plaque.
Dentinal and pulpal uptake of mercury from lined and unlined amalgam restorations in minipigs
Authors: Hörsted‐Bindslev Preben , Danscher Gorm , Hansen Jens Carl
Published: October 2007

The aim of the present investigation was to examine dentin and pulp in amalgam‐restored teeth in minipigs with respect to presence of mercury, and to evaluate whether lining of restored cavities with a resin‐modified glass, ionomer cement had any effect on the penetration of mercury. Class I and V cavities were cut in 49 posterior and canine teeth of 4 minipigs. 35 cavities were restored with amalgam and 14 with composite material. 26 of the amalgam cavities were lined with a resin‐modified glass ionomer cement. Following observation periods of 17‐28 months, the pigs were killed and the jaws sectioned. After decalcification, the teeth were processed for light or electron microscopy examinations. Mercury was visualized by autometallography. Silver‐enhanced mercury was found m all teeth with amalgam, whereas teeth with composites were devoid of mercury. Mercury could be traced in the odontoblast processes, in the body of odontoblasts, and on rare occasions in the nerve tissue of the pulp from lined and from unlined amalgam restorations. The present study thus demonstrates transport of mercury through dentinal tubules to the pulp, and that lining of cavities with a resin‐modified glass ionomer cement does not prevent penetration of mercury.
How different curing methods affect mechanical properties of composites for inlays when tested in dry and wet conditions
Authors: Kildal Kjersti Karine , Ruyter Ivar Eystein
Published: October 2007

The purpose of this investigation was to evaluate the differences in the mechanical properties of 3 composite materials in relationship to the intraoral and extraoral curing techniques of direct and indirect (inlay) restorations, and how the mechanical properties are affected by water sorption. Creep characteristics in compression as well as the stress‐strain relationship at a constant loading rate both in compression and flexure, were determined. A secondary aim was to investigate the Influence of filler content and monomer composition on the mechanical properties. The results are presented as creep curves and as values for elastic moduli, ultimate strength, and ultimate strain. The materials were cured with 2 curing methods. Method A was light curing with a handheld curing unit, and method B was curing in light curing ovens. Water sorption increased the creep values for all types of specimens. Curing in light ovens (method B) gave significantly lower creep values at high stresses than curing with a handheld curing unit (method A). Water sorption decreased the modulus and ultimate strength values for specimens cured with method A. The ultimate strength values also differed for dry and wet specimens cured with method B. There were no general differences in compressive and flexural stress‐strain properties between specimens cured according to the methods A and B.
Cartilage matrix macromolecules in lavage fluid of temporomandibular joints before and 6 months after diskectomy
Authors: Flygare Lennart , Wendel Mikael , Saxne Tore , Ericson Sune , Eriksson Lars , Petersson Arne , Rohlin Madeleine
Published: October 2007

The purpose was to investigate if antigenic fragments of aggrecan and cartilage oligomeric matrix protein (COMP) are detectable by enzyme‐linked immunosorbent assay in lavage fluids from the temporomandibular joint (TMJ) and to examine if the relative content of these cartilage markers changes during development of osteoarthrosis (OA) after diskectomy. Lavage fluid was obtained at surgery and 6 months postoperatively in 13 patients. Computed tomography or magnetic resonance imaging was without evidence of hard‐tissue changes prior to surgery in all patients. In 9 of the patients, sufficient material for analysis was obtained at both examinations. Aggrecan and COMP were detectable in all but 2 fluids, in which the COMP levels were below detection limit. The aggrecan/COMP ratio increased in all 9 patients during the 6‐month period, indicating increased release of aggrecan relative to COMP fragments. The changed aggrecan, COMP ratio possibly reflects increased cartilage turnover during development of OA. Changes compatible with OA were present on computed tomography in all cases at the 6‐month follow‐up. This study shows that the lavage procedure is feasible for obtaining synovial fluid from the TMJ for immunochemical analyses of tissue‐derived macromolecules.
Rifampin Inhibits Prostaglandin E2Production and Arachidonic Acid Release in Human Alveolar Epithelial Cells
Authors: Yuhas Yael , Azoulay-Alfaguter Inbar , Berent Eva , Ashkenazi Shai
Published: October 2007

Rifampin, a potent antimicrobial agent, is a major drug in the treatment of tuberculosis. There is evidence that rifampin also serves as an immunomodulator. Based on findings that arachidonic acid and its metabolites are involved in the pathogeneses ofMycobacterium tuberculosisinfections, we investigated whether rifampin affects prostaglandin E2(PGE2) production in human alveolar epithelial cells stimulated with interleukin-1β. Rifampin caused a dose-dependent inhibition of PGE2production. At doses of 100, 50, and 25 μg/ml, it inhibited PGE2production by 75%, 59%, and 45%, respectively (P< 0.001). Regarding the mechanism involved, rifampin caused a time- and dose-dependent inhibition of arachidonic acid release from the alveolar cells. At doses of 100, 50, 25, and 10 μg/ml, it significantly inhibited the release of arachidonic acid by 93%, 64%, 58%, and 35%, respectively (P< 0.001). Rifampin did not affect the phosphorylation of cytosolic phospholipase A2or the expression of cyclooxygenase-2. The inhibition of PGE2, and presumably other arachidonic acid products, probably contributes to the efficacy of rifampin in the treatment of tuberculosis and may explain some of its adverse effects.
Phosphoinositide-3-Kinase-Dependent, MyD88-Independent Induction of CC-Type Chemokines Characterizes the Macrophage Response toToxoplasma gondiiStrains with High Virulence
Authors: Lee Chiang W. , Sukhumavasi Woraporn , Denkers Eric Y.
Published: October 2007

Chemokines play an important role in inflammation and infection due to their ability to recruit cells of innate and adaptive immunity. Here we examined mouse macrophage chemokine responses during intracellular infections with high- and low-virulenceToxoplasma gondiistrains. The high-virulence type I strain RH induced a large panel of CC-type chemokines, whereas responses elicited by strains PTG (type II) and M7741 (type III) were much weaker. Strikingly, theT. gondii-induced chemokine response occurred independently of signaling through the Toll-like receptor adaptor MyD88. Instead, production of chemokines during infection was heavily dependent upon phosphoinositide-3-kinase signaling pathways. Because infection with type I strains such as RH results in an uncontrolled proinflammatory cytokine response, we hypothesize that this virulence phenotype is a consequence of early strong induction of chemokines by type I, but not type II or III,Toxoplasmastrains.
Hybrid Cell Vaccination ResolvesLeishmania donovaniInfection by Eliciting a Strong CD8+Cytotoxic T-Lymphocyte Response with Concomitant Suppression of Interleukin-10 (IL-10) but Not IL-4 or IL-13
Authors: Basu Rajatava , Bhaumik Suniti , Haldar Arun Kumar , Naskar Kshudiram , De Tripti , Dana Syamal Kumar , Walden Peter , Roy Syamal
Published: October 2007

There is an acute dearth of therapeutic interventions against visceral leishmaniasis that is required to restore an established defective cell-mediated immune response. Hence, formulation of effective immunotherapy requires the use of dominant antigen(s) targeted to elicit a specific antiparasitic cellular immune response. We implemented hybrid cell vaccination therapy inLeishmania donovani-infected BALB/c mice by electrofusing dominantLeishmaniaantigen kinetoplastid membrane protein 11 (KMP-11)-transfected bone marrow-derived macrophages from BALB/c mice with allogeneic bone marrow-derived dendritic cells from C57BL/6 mice. Hybrid cell vaccine (HCV) cleared the splenic and hepatic parasite burden, eliciting KMP-11-specific major histocompatibility complex class I-restricted CD8+cytotoxic T-lymphocyte (CTL) responses. Moreover, splenic lymphocytes of HCV-treated mice not only showed the enhancement of gamma interferon but also marked an elevated expression of the Th2 cytokines interleukin-4 (IL-4) and IL-13 at both transcriptional and translational levels. On the other hand, IL-10 production from splenic T cells was markedly suppressed as a result of HCV therapy. CD8+T-cell depletion completely abrogated HCV-mediated immunity and the anti-KMP-11 CTL response. Interestingly, CD8+T-cell depletion completely abrogated HCV-induced immunity, resulting in a marked increase of IL-10 but not of IL-4 and IL-13. The present study reports the first implementation of HCV immunotherapy in an infectious disease model, establishing strong antigen-specific CTL generation as a correlate of HCV-mediated antileishmanial immunity that is reversed by in vivo CD8+T-cell depletion of HCV-treated mice. Our findings might be extended to drug-nonresponsive visceral leishmaniasis patients, as well as against multiple infectious diseases with pathogen-specific immunodominant antigens.
Immunoepidemiology ofWuchereria bancroftiInfection: Parasite Transmission Intensity, Filaria-Specific Antibodies, and Host Immunity in Two East African Communities
Authors: Jaoko Walter G. , Michael Edwin , Meyrowitsch Dan W. , Estambale Benson B. A. , Malecela Mwele N. , Simonsen Paul E.
Published: October 2007

We compared the age profiles of infection and specific antibody intensities in two communities with different transmission levels in East Africa to examine the contribution of humoral responses to human immunity to the vector-borne helminthWuchereria bancrofti. The worm intensities were higher and exhibited a nonlinear age pattern in a high-transmission community, Masaika, in contrast to the low but linearly increasing age infection profile observed for a low-transmission community, Kingwede. The mean levels of specific immunoglobulin G1 (IgG1), IgG2, IgG4, and IgE were also higher in Masaika, but intriguingly, the IgG3 response was higher in Kingwede. The age-antibody patterns differed in the two communities but in a manner apparently contrary to a role in acquired immunity when the data were assessed using simple correlation methods. By contrast, multivariate analyses showed that the antibody response to infection may be classified into three types and that two of these types, a IgG3-type response and a response measuring a trade-off in host production of IgG4 and IgG3 versus production of IgG1, IgG2, and IgE, had a negative effect onWuchereriacirculating antigen levels in a manner that supported a role for these responses in the generation of acquired immunity to infection. Mathematical modeling supported the conclusions drawn from empirical data analyses that variations in both transmission and worm intensity can explain community differences in the age profiles and impacts of these antibody response types. This study showed that parasite-specific antibody responses may be associated with the generation of acquired immunity to human filarial infection but in a form which is dependent on worm transmission intensity and interactions between immune components.
The zoospore of Schizochytrium aggregatum
Authors: Kazama Frederick
Published: October 2007

The zoospore ultrastructure of the marine protist Schizochytrium aggregatum was examined in detail. The zoospores of S. aggregatum differed considerably from the zoospores of the presumably closely related marine protist Thraustochytrium. The flagella of S. aggregatum emerged from an erumpent area and followed along shallow grooves on the spore body. The mastigonemes of the anterior flagellum are localized along one-third the circumference of the flagellar shaft. There is a concertina-like structure just distal to the kinetosome terminal plate and osmiophilic granules are present within the kinetosome lumen. Microtubular bundles are associated with the kinetosomes and form a "backbone root" system. Serial reconstructions show that each zoospore contains a single tubular mitochondrion. Closely associated with the mitochondrion is a single microbody which in turn is appressed to the nuclear membrane. The ultrastructural data suggest that Schizochytrium aggregatum can be accommodated among the Fungi.
Patterns of variation in the yeast florae of exudates in an oak community
Authors: Bowles Jane M. , Lachance Marc-André
Published: October 2007

Yeasts associated with exudates of 16 red oak trees (Quercus rubra) were sampled repeatedly over a 2-year period. The 210 yeasts isolated were assigned to 28 species whose frequencies were characteristic of each habitat. Significant variation among the habitats was detected in the species diversity, composition, nutritional breadth, and physiological specificity of their yeasts. Some exudates were recognized as "typical" sap fluxes by their physical characteristics and their similar yeast florae. Others differed to various degrees in their yeast species composition, or in the physiological structure of their yeast communities. Among the factors linked to the observed variation were features of the adjacent vegetation, colonization by ants, or growth in open parts of the study area.
Imbibitional chilling injury in cultivars of soybeans differing in temperature sensitivity to pod formation and maturation periods
Authors: Orr Winson , Roche A. I. De La , Singh J. , Voldeng H.
Published: October 2007

The occurrence and extent of chilling injury during imbibition of seeds from five cultivars and four lines of soybeans (Glycine max (L.) Merr) were tested. Seeds were imbibed and incubated at 2 °C for up to 72 h on moist filter papers and their ability to germinate when returned to 25 °C was recorded. Early-maturing varieties with the ability to form pods and seeds at lower temperatures were most susceptible to irreversible injury during imbibitional chilling. Rate of water uptake during low-temperature imbibition was measured, and seeds which were most susceptible to imbibitional chilling also had the highest rate of water uptake. In controlled-environment studies, seeds from the same cultivars that were set at different temperatures showed corresponding differences in susceptibility to imbibitional chilling injury. These results suggest that environmental temperatures during seed set or pod formation can play a role in chilling tolerance during seed imbibition.
Shoot development in Betula papyrifera. II. Comparison of vegetative and reproductive short-shoot growth
Authors: Caesar J. Cartey , Macdonald Alastair D.
Published: October 2007

Short shoots of Betula papyrifera Marsh, may be vegetative or reproductive. The latter bear a female inflorescence. Early flushing and rapid growth of short-shoot buds depend on the age and position of the short shoot. Axillary short-shoot buds flush later than 2- to 4-year-old short-shoot terminal buds, which in turn flush later than 5- to 10-year-old shoots. Mean relative growth rate (RGR) of 5- to 10-year-old short-shoot buds is greater than that of younger short-shoot buds. It is suggested that older short-shoot buds are relatively autonomous and that the flushing long shoot exhibits an inhibitory influence on the proximal axillary buds and possibly on young short-shoot terminal buds. Reproductive short shoots differ from vegetative short shoots in that they have lower leaf area ratios and leaf RGR, higher specific leaf area, smaller leaf areas, and fewer side nerve pairs and they grow more in length than in width. These findings are related to reproductive cost. The developing inflorescences act as preferred "sinks" for resource allocation.
Vegetation ordination of subalpine meadows using adaptive strategies
Authors: Moral Roger Del
Published: October 2007

The vegetation of subalpine meadows was investigated by several multivariate analytical methods. Detrended correspondence analysis (DCA) revealed overall patterns of vegetation response to environmental gradients and identified many indicator species. Binary discriminant analysis confirmed these interpretations and identified indicator species with more clarity than did DCA. A plant strategy ordination was developed from a morphological index of competitiveness and from a relative growth rate index. Results converge to these conclusions: (i) the strategy ordination was consistent with habitat types and DCA; (ii) the degree of species niche differentiation within a community varied with productivity and disturbance; (iii) morphological and physiological niche differentiation is least in productive sedge meadows and greatest in mesic grasslands where production and disturbance are moderate. The adaptation spectra of species in a community provide useful insights about site conditions, history, and response to manipulations.
The cells of Nephromyces: developmental stages of a single life cycle
Authors: Saffo Mary Beth , Nelson Rebecca
Published: October 2007

Nephromyces Giard is a diverse collection of funguslike microbial cells, endosymbiotic in the ductless renal sac of molgulid ascidian tunicates (phylum Chordata). Though Giard considered Nephromyces a Chytridiomycete, the taxonomic affinities of these peculiar cells remain uncertain. In Molgula manhattensis DeKay, at least seven Nephromyces cell types can be distinguished. Despite their diverse appearance, these cell types are not separate taxa, but instead are separate life-history stages of a single organism. Developmental roles for these life-history stages are discussed, as are the possible taxonomic relations of Nephromyces. A new Nephromyces cell, a motile but nonflagellated infective stage, is described. The experiments reported here confirm earlier suggestions that the molgulid renal sac is not merely the site of an occasional or random microbial infection. Instead, this organ is the locus of an exclusive, presumably coevolved, association between two taxa: Nephromyces and the tunicate family Molgulidae.
Evidence for the production of similar toxins by Pseudomonas syringae pv. glycinea and Pseudomonas syringae pv. phaseolicola
Authors: Gnanamanickam S. S. , Starratt A. N. , Ward E. W. B.
Published: October 2007

Systemic chlorotic mottling of trifoliate leaves of soybean cultivars developed following inoculation of unifoliate leaves with strains of Pseudomonas syringae pv. glycinea. This symptom could not be reproduced by application of coronatine, a toxin previously isolated from this bacterium, but resembled systemic symptoms that were produced on bean (Phaseolus vulgaris) by inoculation with P. syringae pv. phaseolicola or by application of toxic principles derived from this pathovar. Attempts to isolate a second toxin from pv. glycinea culture fluids using methods employed for the isolation of phaseolotoxin from pv. phaseolicola were not successful. Evidence was obtained for the presence of inhibitory material that interfered with assays for toxin with Escherichia coli K12 as the test organism. Partial separation of the toxin from the inhibitor and other substances was achieved by high-performance liquid chromatography of culture fluids and further purification was effected by ion exchange, partition, and thin-layer chromatography. Biological activity of the pv. glycinea toxin preparation was similar to a toxin prepared from pv. phaseolicola. Both toxins produced similar systemic symptoms on soybean leaves, inhibited E. coli (reversed by arginine, citrulline, and certain tripeptides), inhibited ornithine carbamoyl transferase, and caused the accumulation of ornithine in soybean leaves, as has been reported for phaseolotoxin. There were small differences between the pv. glycinea and pv. phaseolicola toxins in chromatographic behaviour. It is concluded that, in addition to coronatine, pv. glycinea produces a second toxin that is similar to that produced by pv. phaseolicola.
Graine et procaulôme d'Orobanche crenata Forsk: étude histocytologique et cytochimique
Authors: Aber M. , Sallé G.
Published: October 2007

A study of Orobanche crenata Forsk. seeds and their germination was carried out using scanning and transmission electron microscopy. The minute seeds possess a brownish testa, representing vestiges of the cell wall of a superficial layer. The embryo is slightly differentiated with small cells in the micropylar zone and vacuolated ones in the chalazal region. In response to a host root stimulus, germination of the seeds occurs, giving rise to a very delicate organ, the "procaulôme," whose tip is composed of approximately 10 meristematic cells. These cells are rich in dictyosomes emitting numerous vesicles whose polysaccharide contents react strongly to PATAg. The other part of the "procaulôme" is entirely parenchymatous and has no conducting elements. Both the nature and function of this organ formed during germination are discussed on the basis of the new histological and ultrastructural data. The terms root, radicule, and germ tubelike organ should be replaced by "procaulôme," which is more appropriate for describing its special character.
Inhibition of Phytophthora cactorum by a bacterial antagonist
Authors: Utkhede R. S. , Gaunce A. P.
Published: October 2007

Bacterial iolate B8 inhibited the growth of six isolates of Phytophthora cactorum on cornmeal agar. Under greenhouse conditions, B8 reduced infections by three isolates of P. cactorum in sterile field soil. Growth of P. cactorum on cornmeal agar was completely inhibited with 40% autoclaved B8 extract. The growth was significantly reduced by low pH alone (pH 4.5 or less) but even when the pH of B8 extract was raised to 6, P. cactorum growth was completely inhibited. Cornmeal agar buffered with 15 mM citrate, pH 5, was suitable for assaying extracts for antagonism to P. cactorum. Acetic acid and other fatty acids (possible metabolites of B8) were also inhibitory, with degree of antibiosis increasing with the size of the fatty acid molecule. The antibiotic produced by B8 was characterized as neutral (not absorbed by ion exchange resins) and of low molecular weight.
The effect of colonization by Verticillium dahliae on the root tips of Russet Burbank potatoes
Authors: Perry James W. , Evert Ray F.
Published: October 2007

The structure and development of tissues in potato (Solanum tuberosum L.) root tips colonized by Verticillium dahliae Kleb. were contrasted with those of uninoculated root tips. Within 2 days of inoculation hyphae had penetrated the root cap without eliciting any wall appositions in the root cap cells. Callose-like deposits were found along the walls of protodermal cells bordering the colonized cap cells. Overall, colonized root tips had lost their meristematic appearance owing to increased vacuolation in the cells. In contrast to the normal longitudinal course of primary vascular differentiation, in infected root tips the protoxylem matured in advance of the protophloem. Fifteen days after inoculation the root tips had lapsed into maturity. The endodermis and exodermis extended completely around what was once the apical meristem. Although the xylem had differentiated to within several cell layers of the colonized apex, xylem infection had not occurred in this region. Sieve elements in colonized root tips failed to develop sieve-plate pores.
Meristem characteristics of genetically modified pea (Pisum sativum) leaf primordia
Authors: Meicenheimer R. D. , Muehlbauer F. J. , Hindman J. L. , Gritton E. T.
Published: October 2007

Meristem characteristics of normal, afila (af), acacia (tl), reduced stipule (st), and combinations of these leaf phenotypes were investigated in pea (Pisum sativum L.). The multiple tendrils of the afila leaf are formed from numerous secondary branches on the leaflet primordia. Adaxial and marginal meristems are absent in afila leaflets. The tendril-like morphology of the terminal and secondary branches of the afila leaflets is derived from a radial marginal meristem, which is characteristic of normal tendril development. The small terminal leaflet lamina on tendrils of the acacia leaf is produced by adaxial and marginal meristems which become apparent in the distal portion of the tendril late in leaf ontogeny. The reduced stipules of the reduced stipule leaf result from early loss of abaxial and adaxial stipule marginal meristems. Combinations of the af, tl, and st genes apparently have no modifying influences on their mutual expression with one exception; the aftlst mature reduced stipule is significantly wider than stipules in st, afst, and tlst phenotypes. The greater final width of triple recessive stipules is attributed to the persistence of the adaxial stipular marginal meristem in this phenotype.
Haustorial development of Peronospora tabacina infecting Nicotiana tabacum
Authors: Trigiano R. N. , Dyke C. G. Van , Spurr Jr. H. W.
Published: October 2007

The development of haustoria in tobacco by the blue-mold fungus Peronospora tabacina was examined using light, scanning, and transmission electron microscopy. Electron-lucent, callose-like appositions were observed between the host plasmalemma and the host mesophyll cell wall prior to haustorial penetration. An electron-opaque penetration matrix was present between the apposition and the host cell wall. The intercellular hyphal wall consisted of two layers which differed in staining quality. The haustorial wall was also two layered, but was primarily composed of and continuous with the inner wall layer of the intercellular hypha. Haustoria were either finger-like or branched and were encased with callose-like material. Most encasements were thickened at the proximal regions of haustoria but were thinner along the distal portions. Vesicles were present in host cytoplasm and were occasionally attached to the invaginated host plasmalemma. These vesicles might contribute to the deposition of the encasement material. The encasement stained positively for callose using aniline blue; calcofluor and toluidine blue O tests for cellulose were inconclusive, and lignin was not detected using toluidine blue O or phloroglucinol–HCl.
Thermal acclimation and in vitro stabilization of malate dehydrogenase from Machaeranthera gracilis
Authors: Moore Brandon d. , Szarek Stan R.
Published: October 2007

Thermal acclimation of NAD+-malate dehydrogenase (MDH) was examined in leaves of two chromosomal races of Machaeranthera gracilis, an annual composite. Plants of both the parental foothills race and the derived desert race, produced a more thermostable enzyme when grown at 35:25 °C than when grown at 25:15 °C. Increased enzyme thermostability during acclimation may potentially be augmented by thermal protection of malate dehydrogenase (MDH) by cellular metabolites, including most significantly the coenzyme nicotinamide adenine dinucleotide (reduced from) (NADH). The Arrhenius activation energy for MDH from plants of both races did not show adjustments induced by growth at higher temperatures. Growth at 35:25 °C, resulted in MDH with a relatively more constant coenzyme binding affinity (assayed from 25 to 24 °C), as determined from substrate dissociation constants. Substrate Michaelis constants for MDH were largely independent of plant growth temperatures. Responses by MDH during acclimation by both races of M. gracilis are unique to those reported from other less thermotolerant plants, but do not explicitly account for habitat preferences between the two genetic races.
Ultrastructure of the zoospore of Blastocladia ramosa (Blastocladiales)
Authors: Lingle Wilma L. , Barstow William E.
Published: October 2007

Species of Blastocladia, unlike other members of the order Blastocladiales, have an obligately fermentative metabolism. The ultrastructure of the zoospores of Blastocladia ramosa is described and compared with that of zoospores of aerobic members of the Blastocladiales. Zoospores of Blastocladia ramosa are structurally similar to other blastocladialean zoospores in that they have (i) a nuclear cap composed of aggregated ribosomes delimited by an envelope of endoplasmic reticulum; (ii) a posteriorly located nucleus; (iii) nine sets of microtubules that surround the nucleus and nuclear cap; and (iv) a striated rootlet associated with the kinetosome. Zoospores of Blastocladia ramosa differ by having mitochondria with unusual fine structure and by lacking microbodies and microbody – lipid globule complexes. As shown by enzymatic digestion and staining, glycogen appears to be the primary storage material in the zoospore. Structures which resemble water expulsion vacuoles are present. The morphological differences between zoospores of Blastocladia ramosa and other zoospores of the Blastocladiales appear to be related to physiological differences.
Bayoud disease of date palm: ultrastructure of root infection through pneumatodes
Authors: Belarbi-Halli Rosa , Mangenot François
Published: October 2007

Young axenically grown plants of date palm, Phoenix dactylifera cv. Deglet-nour, were inoculated with Fusarium oxysporum Schl. f. sp. albedinis (Killian et Maire) Gordon, using conidia applied either on the pneumatode-free main root or on the pneumatodes of rootlets. After incubation for 15 days, infection was successful only in the latter case. The fungus grew inside the aerenchyma and clung tightly to the cell walls, the wartlike outgrowths, and the matrix present in the intercellular spaces. These structures were more or less altered in the presence of the hyphae. The fungus proceeded both intercellularly and intracellularly through the cortex. A dense hyphal sheet was observed facing the suberized endodermis, but the fungus somehow made its way into the stele. Penetrations of thick-walled cells commonly occurred through pits. Root colonization was slower toward the root apices than toward the base. After 15 days, the fungus was present at least 8 cm above the inoculation point at the base of the root.
Tilletia indica: cytology and teliospore formation in vitro and in immature kernels
Authors: Fuentes-Dávila Guillermo , Durán Rubén
Published: October 2007

In teliospores of Tilletia indica Mitra meiosis occurred at germination, followed by a series of mitoses in teliospores, promycelia, or both, resulting in promycelia with numerous haploid nuclei. Primary sporidia initially were single, monokaryotic cells. After abstriction cell division occurred, but each cell stayed monokaryotic. Mycelia isolated from incipiently infected wheat caryopses formed teliospores on potato sucrose agar after 2–3 weeks and continued to do so for about 2 years. Nuclear stages of the fungus in culture and host tissue were demonstrated with haematoxylin, HCl–Giemsa, and (or) the Feulgen nucleal reaction. During formation of teliospores in vitro, conjugately associated nuclei of sporogenous mycelia migrated to probasidial initials which formed at right angles to the parent hypha. The dikaryotic probasidia usually were subtended by Y-shaped septa. Karyogamy was not seen, but circumstantial evidence suggested that it occurred during very early stages of probasidial development because even immature teliospores were monokaryotic. The process of teliospore formation and the concomitant changes in nuclear condition were easily observed in cultures, but in vivo the gelatinoid nature of the mycelium in the host tissue made this much more difficult. Moreover, some stages of teliospore formation observed in vitro were not seen in soral sections and presumably did not form in son on the host.
Long-term effects on cowpea plant growth of a short-term cowpea aphid infestation
Authors: Hawkins C. D. B. , Whitecross M. I. , Aston M. J.
Published: October 2007

Two-week-old cowpea seedlings (Vigna unguiculata (L.) Walp.) were infested with cowpea aphids (Aphis craccivora Koch (Homoptera: Aphididae)) for 5, 10, 15, and 20 days at which time the aphids were removed with a systemic insecticide. The seedlings were then allowed to grow for another 3 months. By day 10, plant dry weights, mean relative growth rates [Formula: see text], and mean unit leaf rates (Ē) were all significantly reduced in the infested plants, and these relationships still held at day 20. Apparent decreases in photosynthesis and (or) increases in respiration were the primary causes of these reductions. There were no significant differences between control and experimental treatments for [Formula: see text] calculated from day 0, and total number of seeds and seed pods produced at the end of the study. Control plants had significantly more mature seed pods and seeds, while formerly infested plants had significantly more mature and unripe seeds per pod, more unripe seed pods and seeds produced, and greater values for [Formula: see text] from the time of aphid removal until the end of the experiment. This latter increase in [Formula: see text] indicates a form of compensatory growth. It is proposed that the compensatory growth of previously infested plants and ultimate similarity in seed production, as compared with control plants, may have resulted from aphid-induced changes via nonhormonal compounds acting as phytohormone regulators. The different durations of aphid infestation used had no detectable effect on long-term growth.
Inoculation of citrus with root fragments containing chlamydospores of the mycorrhizal fungus Glomus intraradices
Authors: Graham J. H. , Fardelmann D.
Published: October 2007

The vesicular–arbuscular mycorrhizal fungus, Glomus intraradices, was found sporulating in citrus roots in an orchard soil. Dead root fragments of citrus accounted for a high proportion of the propagules in soil as measured by the most probable number technique. Sudan grass root fragments from pot cultures containing 7 and 94 chlamydospores of G. intraradices per milligram dry root had 11 and 184 (most probable number) propagules per milligram dry root, respectively. Inoculum densities of 20–40 mg of root fragments per 100 cm3 of potting media resulted in 100% inoculation success of Carrizo citrange grown from seed. A decrease in root fragment density to as low as 2.5 mg per 100 cm3 of medium reduced inoculation success and root colonization, but did not reduce growth and nutrient uptake by inoculated seedlings. The growth of vesicular–arbuscular mycorrhizal plants in a soilless medium amended with relatively insoluble rock phosphate was less than that of nonmycorrhizal plants fertilized with soluble phosphorus; copper uptake, however, was significantly increased by vesicular–arbuscular mycorrhizae. Root fragments stored up to 1 year under moist conditions did not lose colonization potential, whereas drying reduced colonization potential to near zero after 9 months.
Totipotence du péricycle des organes souterrains et aériens de Rorippa sylvestris. I. Rhizogenèse et caulogenèse à partir de racines sur plante intacte ou de fragments de racines cultivés in vitro
Authors: Projetti Maurie-Laure , Chriqui Dominique
Published: October 2007

Old and tuberized roots of Rorippa sylvestris (Brassicaceae) can form adventitious buds. Moreover, in vitro culture on Murashige and Skoog medium supplemented with sucrose can induce bud regeneration from nontuberized young root explants. An unusual stimulation of both lateral rhizogenesis and caulogenesis is obtained in the presence of auxin (indoleacetic acid), with optimal responses at 5 mg∙L−1. Kinetin inhibits rhizogenesis but strongly enhances caulogenesis, with optimal responses between 1 and 5 mg∙L−1. In all conditions (natural and experimental), lateral roots and buds arise from the pericycle layer or pericycle-derived tissues (outer layer of a several-layered pericycle, phellogen, and pericycle-derived callus). Thus, the pericycle of R. sylvestris roots, as well as the pericycle-derived cells, exhibits an original double potential for rhizogenesis and caulogenesis, especially in the close vicinity of the xylem poles. As the early steps of root and bud regeneration are similar, the possibility that the two kinds of meristems are undetermined and perhaps interchangeable is considered.
Electrophoretic evidence of relationships among Quercus (oaks) of eastern North America
Authors: Guttman Sheldon I. , Weigt Lee A.
Published: October 2007

An evaluation of electrophoretic analysis as a potential tool for elucidating systematic relationships of Quercus utilized 478 trees representing 10 species from subgenus Erythrobalanus and 8 from subgenus Quercus. Leaf tissue was used to resolve 18 putative genetic loci representing 12 enzyme systems in each taxon. Subgeneric differentiation was apparent with intrasubgeneric genetic differentiation (mean modified Rogers' distance (D): Erythrobalanus 0.27; Quercus 0.44) being less than between subgenera (D = 0.68). Relationships among species within subgenera derived from electrophoretic data often compared well with published affinities. However, several discrepancies existed that might reflect disparities in rates of morphological, ecological, and allozymic divergence, or hybridization within subgenera, or both. Electrophoretic analysis of oak leaf tissue has the potential to yield valuable data for elucidating relationships among Quercus.