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PubMed2001

Modeling capacity of ENDOflash files in simulated root canals.

With the development of rotary nickel-titanium files and their applications in Endodontics, the concepts of root canal preparation have changed. The objective of this research is to evaluate the transportation of simulated root canals caused by stainless steel ENDOflash rotary files compared to nickel-titanium ProFile files (.04, .06 and Orifice Shapers). Twenty-four simulated root canals with a 30 degrees curvature were randomly divided into 2 groups and prepared with ENDOflash or ProFile files according to manufacturers' instructions. Comparison between the simulated root canals before and after instrumentation showed significant differences (p < 0.001) between the groups, with greater transportation observed with ENDOflash files. One case of deformation was observed with a ProFile instrument (#20/.04) and there were no fractures.

Dental Alloys↗
PubMed2006

Growth rings in the roots of temperate forbs are robust annual markers.

There is increasing interest in the analysis of annual growth rings in the secondary root xylem of perennial forbs (herb-chronology). Therefore, we need to verify whether these growth rings are always formed annually. To investigate the formation of root rings we performed common garden experiments at two distinct sites in Switzerland. We grew nine unrelated forb species from seed and subjected them to competition and clipping treatments. Anatomical developments in the roots of the individuals were tracked during five growing seasons. Across all species and treatments at least 94 % of the expected growth rings associated with full growing seasons were identifiable and the development of the anatomical patterns was consistently seasonal. While the distinctness of annual rings varied somewhat between species and sites, the treatments had no effect on the presence of annual rings. In no case were false rings developed. The results of this study demonstrate that the growth rings in the roots of northern temperate forbs represent robust annual growth increments and, hence, can reliably be used in herb-chronological studies of age- and growth-related questions in plant ecology.

Ecosystem↗
PubMed2006

The developmental and organ specific expression of sucrose cleaving enzymes in sugar beet suggests a transition between apoplasmic and symplasmic phloem unloading in the tap roots.

Sucrose utilisation in sink tissues depend on its cleavage and is mediated by two different classes of enzymes, invertase and sucrose synthase, which determine the mechanism of phloem unloading. Cloning of two extracellular (BIN35 and BIN46) and one vacuolar invertase (BIN44) provided the basis for a detailed molecular analysis of the relative contribution of the sucrose cleaving enzymes to the sink metabolism of sugar beets (Beta vulgaris) during development. The determination of the steady state levels of mRNAs has been complemented by the analysis of the corresponding enzyme activities. The present study demonstrates an inverse regulation of extracellular invertase and sucrose synthase during tap root development indicating a transition between functional unloading pathways. Extracellular cleavage by invertase is the dominating mechanism to supply hexoses via an apoplasmic pathway at early stages of storage root development. Only at later stages sucrose synthase takes over the function of the key sink enzyme to contribute to the sink strength of the tap root via symplasmic phloem unloading. Whereas mRNAs for both extracellular invertase BIN35 and sucrose synthase were shown to be induced by mechanical wounding of mature leaves of adult plants, only sucrose synthase mRNA was metabolically induced by glucose in this source organ supporting the metabolic flexibility of this species.

Beta vulgaris↗
PubMed1995

Expression of CD15 in a subset of dorsal root ganglion cells during the chick embryonic development.

We have investigated the distribution of CD15 immunoreactivity (IR) in chick sensory neurons during the embryonic development. IR first appeared around embryonic day 6 (E6) preferentially in the lateroventral part of the dorsal root ganglion (drg). Here it was located in the cytoplasm of the ganglion cells. Starting at E11, CD15 positive cells have been detected also in the dorsomedial part of the drug. Towards the end of embryonic development, these immunoreactive (ir) cells were evenly distributed within the drg. Around E 16 nerve fibres could also be found, expressing the CD15 epitope. These fibres run both in centripetal and centrifugal direction, and could be followed throughout peripheral nerves. IR was confined to peripheral nerves of the skin, where after its subepidermal arborisation fine nerve terminals entered the basal stratum of the epidermis or the dermal bulbous part of feathers. Until hatching no staining in visceral structures was detected. Our results suggest that CD15 is restricted to a subset of drg neurons innervating somatosensory targets. A role for the CD15 epitope for myelination is discussed.

Animals↗
PubMedDate not supplied

Role of neuron-target interactions in the development of a subpopulation of avian sensory neurons.

Subpopulations of sensory neurons appear in embryonic dorsal root ganglia during development. In this paper, we examine what role neuron-target interactions play in this process. Previous work has shown that alterations in the environment of developing sensory neurons regulate the proportion of neurons that express a cell surface antigen identified by the monoclonal antibody SN1 (Marusich et al.: Dev. Biol. 118: 505-510, 1986). We now report that neuron-target interactions may also act to stabilize the phenotype of sensory neurons. Thus, older SN1- neurons, which would normally remain SN1- if left undisturbed in vivo, can express SN1 immunoreactivity in vitro when they are deprived of contact with their normal peripheral targets. We also demonstrate that naive sensory neurons, i.e., those that have never made contact with peripheral targets, can be identified and maintained in culture. At least some of these naive neurons (all of which are initially SN1-) can express SN1 immunoreactivity in vitro, in the absence of contact with normal peripheral targets. We conclude that subpopulations of sensory neurons may arise from naive neurons in the absence of neuron-target interactions but that subsequent neuron-target interactions may act to stabilize or modulate subpopulation-specific phenotypes.

Animals↗
PubMed2004

Development of the Casparian strip in primary roots of maize under salt stress.

The Casparian strip in the endodermis of vascular plant roots appears to play an important role in preventing the influx of salts into the stele through the apoplast under salt stress. The effects of salinity on the development and morphology of the Casparian strip in primary roots of maize ( Zea mays L.) were studied. Compared to the controls, the strip matured closer to the root tip with increase in the ambient concentration of NaCl. During growth in 200 mM NaCl, the number and the length of the endodermal cells in the region between the root tip and the lowest position of the endodermal strip decreased, as did the apparent rate of production of cells in single files of endodermal cells (the rate of cell formation being equal to the rate at which cells are lost from the meristem). The estimated time required for an individual cell to complete the formation of the strip after generation of the cell in the presence of 200 mM NaCl was not very different from that required in controls. Thus, salinity did not substantially affect the actual process of formation of the strip in individual cells. The radial width of the Casparian strip, a morphological parameter that should be related to the effectiveness of the strip as a barrier, increased in the presence of 200 mM NaCl. The mean width of the lignified region was 0.92 microm in distilled water and 1.33 microm in 200 mM NaCl at the lowest position of the strip. The mean width of the strip relative to that of the radial wall at this position was significantly greater after growth in the presence of 200 mM NaCl than in the controls, namely, 20.5% in distilled water and 33.9% in 200 mM NaCl. These observations suggest that the function of the strip is enhanced under salt stress.

Plant Roots↗
PubMed2000

Transgenic hairy roots. recent trends and applications.

Agrobacterium rhizogenes causes hairy root disease in plants. The neoplastic roots produced by A. rhizogenes infection is characterized by high growth rate and genetic stability. These genetically transformed root cultures can produce higher levels of secondary metabolites or amounts comparable to that of intact plants. Hairy root cultures offer promise for production of valuable secondary metabolites in many plants. The main constraint for commercial exploitation of hairy root cultures is their scaling up, as there is a need for developing a specially designed bioreactor that permits the growth of interconnected tissues unevenly distributed throughout the vessel. Rheological characteristics of heterogeneous system should also be taken into consideration during mass scale culturing of hairy roots. Development of bioreactor models for hairy root cultures is still a recent phenomenon. It is also necessary to develop computer-aided models for different parameters such as oxygen consumption and excretion of product to the medium. Further, transformed roots are able to regenerate genetically stable plants as transgenics or clones. This property of rapid growth and high plantlet regeneration frequency allows clonal propagation of elite plants. In addition, the altered phenotype of hairy root regenerants (hairy root syndrome) is useful in plant breeding programs with plants of ornamental interest. In vitro transformation and regeneration from hairy roots facilitates application of biotechnology to tree species. The ability to manipulate trees at a cellular and molecular level shows great potential for clonal propagation and genetic improvement. Transgenic root system offers tremendous potential for introducing additional genes along with the Ri T-DNA genes for alteration of metabolic pathways and production of useful metabolites or compounds of interest. This article discusses various applications and perspectives of hairy root cultures and the recent progress achieved with respect to transformation of plants using A. rhizogenes.

Journal Article↗
PubMed1992

Alteration of thiol pools in roots and shoots of maize seedlings exposed to cadmium : adaptation and developmental cost.

Roots of intact 5-day-old maize (Zea mays L.) seedlings were exposed to 3 micromolar Cd during a 7-day period. Cysteine, gamma-glutamylcysteine, glutathione (GSH), and Cd-induced acid-soluble thiols (ASTs), including phytochelatins, were quantified in roots and shoots. Adaptation to Cd and its cost to seedling development were evaluated by measuring Cd content, tissue fresh weight, and rate of root elongation. Roots contained 60 to 67% of the Cd in the seedlings between 4 and 7 days of exposure. Exposure to Cd decreased the fresh weight gain in roots from day 4 onward without affecting the shoots. Between days 1.5 and 3.5 of Cd treatment, roots elongated more slowly than controls; however, their growth rate recovered thereafter and exceeded that of controls. Exposure to Cd did not appreciably affect the concentration of cysteine in the seedlings. However, the initial low concentration of gamma-glutamylcysteine increased (after a lag of 6 hours in roots and 2 days in shoots), reaching a plateau by day 6 at 28.5 nanomoles per gram of fresh weight in roots and by day 5 at 19.1 nanomoles per gram of fresh weight in shoots. During the first 9 hours of Cd exposure, the concentration of GSH in roots decreased dramatically (at 31.6 nanomoles per gram of fresh weight per hour) and thereafter decreased more slowly than in controls. The depletion of GSH in the roots (366 nanomoles per gram of fresh weight) matched the synthesis of ASTs (349 nanomoles per gram of fresh weight) during the first 48 hours. The concentration of ASTs in roots increased steadily thereafter to reach 662.2 nanomoles per gram of fresh weight by 6 days of Cd exposure. In shoots, Cd had little influence on the concentration of GSH, but ASTs still accumulated to 173.3 nanomoles per gram fresh weight after 5 days. The molar ratio of thiols in ASTs to Cd increased to a maximum of 10.24 in roots after 4 hours and of 4.25 in shoots after 2 days of Cd exposure. After 4 days, the ratio reached a plateau of approximately 2 in roots and between 2 and 3 in shoots, as if a steady state of Cd chelation had been achieved in both organs. The plateau coincided with recovered root elongation or an adaptation to Cd. The reduced fresh weight gain of the roots during this time, however, indicated that the synthesis of Cd-induced thiols was at a cost to root development.

Journal Article↗
PubMed1986

Cytodifferentiation of polar plant cells: use of anti-microtubular agents during the differentiation of statocytes from cress roots (Lepidium sativum L.).

The development of the structural polarity of statocytes from cress roots (Lepidium sativum L.) was studied in a time- and stage-dependent manner. outgrowing radicles had statocytes with abundant lipid droplets, sparsely developed endoplasmic reticulum (ER) and nuclei located at the proximal cell poles. During differentiation, coincidentally the lipid droplets disappeared while rough ER increased in length. The ER was translocated into the distal cell pole to establish a complex of stacked ER. Microtubules occurred first at the distal cell edges. As a second step, ER was produced in the vicinity of the nucleus and was also translocated distally. By application of the antimicrotubular agents heavy water (90%), colchicine (10(-4) mol l-1) and triethyl lead chloride (20 micromoles l-1), the involvement of microtubules in these events was studied. Triethyl lead chloride led to a complete cessation of differentiation; root-cap cells remained at a stage without polar arrangement of the ER. Colchicine affected the development of structural polarity slightly, as shown by a higher density of cortical ER cisternae. Heavy water inhibited the translocation of ER almost completely and yielded ER located also in the cell center. All anti-microtubular agents inhibited cell division and the differentiation of the distal cell layer of the dermatocalyptrogen into statocytes. It is hypothesized that microtubules serve as anchoring sites for microfilaments, which actually mediate the translocation of the ER. Hence, an intact system of microtubules and microfilaments is necessary for the expression of structural polarity.

Brassicaceae↗
PubMed2000

Coronary artery narrowing after aortic root reconstruction with resorcin-formalin glue.

Severe stenosis of right and left main coronary artery ostia developed after aortic root reconstruction with gelatin-resorcin-formol glue for correction of acute type A aortic dissection. Surgical treatment of this condition required grafting of the right and left anterior descending arteries with bilateral mammary arteries on the beating heart.

Adult↗
PubMed2001

Cell biological changes of outer cortical root cells in early determinate nodulation.

In the symbiosis of leguminous plants and Rhizobium bacteria, nodule primordia develop in the root cortex. This can be either in the inner cortex (indeterminate-type of nodulation) or outer cortex (determinate-type of nodulation), depending upon the host plant. We studied and compared early nodulation stages in common bean (Phaseolus vulgaris) and Lotus japonicus, both known as determinate-type nodulation plants. Special attention was paid to the occurrence of cytoplasmic bridges, the influence of rhizobial Nod factors (lipochitin oligosaccharides [LCOs]) on this phenomenon, and sensitivity of the nodulation process to ethylene. Our results show that i) both plant species form initially broad, matrix-rich infection threads; ii) cytoplasmic bridges occur in L. japonicus but not in bean; iii) formation of these bridges is induced by rhizobial LCOs; iv) formation of primordia starts in L. japonicus in the middle root cortex and in bean in the outer root cortex; and v) in the presence of the ethylene-biosynthesis inhibitor aminoethoxyvinylglycine (AVG), nodulation of L. japonicus is stimulated when the roots are grown in the light, which is consistent with the role of cytoplasmic bridges during nodulation of L. japonicus.

Ethylenes↗
PubMed2006

Interactive factors leading to dying-off Carex tato in Momoge wetland polluted by crude oil, Western Jilin, China.

Momoge wetland is an internationally important wetland not only because it is a habitat for many rare bird species but also because it is an internationally important stopover for some rare global migratory bird species. However the petroleum exploitation in wetland has brought about many environmental problems. One of the most severe problems is crude oil pollution, which has caused the dying-off Carex tato and imposes great threat on survival of rare birds. This work studied the factors that caused the dying off of Carex tato. The results showed that death of Carex tato was the result narcosis toxicity of alcohols, intermediate biodegradation products of crude oil, on the root tissue, and the fragmentization of cuticle of leaves by light components of crude oil volatized from soil surface. However, the mechanism involved was much more complex and three interactive factors including crude oil pollution of soil, long-term drought and poor permeability of soil were responsible for the dying-off of Carex tato grassland. The distribution of crude oil in soil profile was characterized with high concentrations at top silty layer and the layer below root zone and low or no crude oil at root zone layer. This distribution was relative to root system characteristics and rhizospheric biodegradation. In root zone, substantive oxygen could be transported to root zone through dense root system and well developed aerenchyma. The crude oil in root zone was easily biodegraded by aerobic rhizosphere microbes. However, some toxic intermediate products, such as some alcohols, was sealed in root zone due to poor permeability of the top soil layer and the deeper soil layer and they had lethal effects on root tissue. Above ground, low molecular components of crude oil in top soil layer was easily volatized into atmosphere during long-term drought. Some of the volatized components were adsorbed onto leaves. SEM analysis showed that these components destroyed the leaves by fragmentization of cuticle of leave. This study also shows that although wetland has natural attenuation of pollutants, natural attenuation of pollutants by natural wetland should not be overemphasized. This attenuation function may lose under some conditions such as long-term drought and poor soil texture.

Carex Plant↗
PubMed1998

Air pressures developed beyond the apex from drying root canals with pressurized air.

Air introduced into tissues during invasive procedures can be harmful. Endodontic treatment is not frequently associated with this phenomenon, but serious results can occur if air forced into tissues impinges on critical anatomical structures and/or carries infection into deeper areas. Extracted teeth were connected to a pressure gauge during and after canal instrumentation and pressures measured. Also, a fresh porcine jaw was instrumented in the presence of a radiopaque tracer during air drying. Significant pressures were detected beyond the apex of the roots, especially with root apical diameters of file sizes larger than 20.

Air Pressure↗
PubMed2004

Flavonoid distribution during the development of leaves, flowers, stems, and roots of Rosmarinus officinalis. postulation of a biosynthetic pathway.

The distribution of seven flavonoids, eriocitrin, luteolin 3'-O-beta-d-glucuronide, hesperidin, diosmin, isoscutellarein 7-O-glucoside, hispidulin 7-O-glucoside, and genkwanin, has been studied in Rosmarinus officinalis leaves, flowers, stems, and roots during plant growth. The maximum level reached by luteolin 3'-O-beta-d-glucuronide in leaves during June-August suggests the existence of a delay between the activation of the enzymes involved in the flavanone and flavone biosynthesis. The presence of hesperidin and diosmin in the vascular system is significant, and hesperidin shows even higher levels than the phenolic diterpenes and rosmarinic acid. The distribution of flavonoids observed in R. officinalis suggests a functional and structural relationship between phytoregulators and flavonoids, where flavonoids would be "protectors" of the activity of phytoregulators. A hypothesis for the general pathway of biosynthesis of these compounds in plants of the family Labiatae is proposed.

Chromatography, High Pressure Liquid↗