[Root canal therapy--understanding and evaluating the conditions of periapical diseases].
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Exudates and Transudates↗
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Pathogenicity of experimental caryosporosis.
Pathogenicity of the coccidia C. bigenetica and C. simplex was studied in experimentally inoculated pigs, goat kids (untreated and immunosuppressed) and severe combined immunodeficient (SCID) mice. The major pathological changes of caryosporosis were similar in all inoculated animals. In pigs and goat kids, caryosporosis was self-limiting, with clinical responses that included focal swelling and erythema of the muzzle, snout, jaws, cheeks, eyelids, bases of the ears, backs of the necks, scrotum, external genitalia of females, legs and footpads. Histopathological changes were characterized by involvement of the cutaneous mononuclear phagocyte system with an inflammatory exudate containing numerous macrophages, especially around the root sheaths, sensory nervous corpuscles of the hair follicles and surrounding dermal free nerve endings. The tactile hair follicles in the muzzle, snout and upper jaw were most severely changed. In SCID mice, inoculation with C. bigenetica or C. simplex caused a severe, fatal, systemic disease characterized by dissemination of numerous caryosporan developmental stages into the host mononuclear phagocyte system. This study presents evidence that both caryosporan species tested caused similar clinical signs and lesions of dermal coccidiosis in the mammalian secondary hosts.
Animals↗
Soil nematodes mediate positive interactions between legume plants and rhizobium bacteria.
Symbiosis between legume species and rhizobia results in the sequestration of atmospheric nitrogen into ammonium, and the early mechanisms involved in this symbiosis have become a model for plant-microbe interactions and thus highly amenable for agricultural applications. The working model for this interaction states that the symbiosis is the outcome of a chemical/molecular dialogue initiated by flavonoids produced by the roots of legumes and released into the soil as exudates, which specifically induce the synthesis of nodulation factors in rhizobia that initiate the nodulation process. Here, we argue that other organisms, such as the soil nematode Caenorhabditis elegans, also mediate the interaction between roots and rhizobia in a positive way, leading to nodulation. We report that C. elegans transfers the rhizobium species Sinorhizobium meliloti to the roots of the legume Medicago truncatula in response to plant-released volatiles that attract the nematode. These findings reveal a biologically-relevant and largely unknown interaction in the rhizosphere that is multitrophic and may control the initiation of the symbiosis.
Animals↗
Concurrent Synthesis and Release of nod-Gene-Inducing Flavonoids from Alfalfa Roots.
Flavonoid signals from alfalfa (Medicago sativa L.) induce transcription of nodulation (nod) genes in Rhizobium meliloti. Alfalfa roots release three major nod-gene inducers: 4',7-dihydroxyflavanone, 4',7-dihydroxyflavone, and 4,4'-dihydroxy-2'-methoxychalcone. The objective of the present study was to define temporal relationships between synthesis and exudation for those flavonoids. Requirements for concurrent flavonoid biosynthesis were assessed by treating roots of intact alfalfa seedlings with [U-(14)C]-l-phenylalanine in the presence or absence of the phenylalanine ammonia-lyase inhibitor l-2-aminoxy-3-phenylpropionic acid (AOPP). In the absence of AOPP, each of the three flavonoids in exudates contained (14)C. In the presence of AOPP, (14)C labeling and release of all the exuded nod-gene inducers were reduced significantly. AOPP inhibited labeling and release of the strongest nod-gene inducer, methoxychalcone, by more than 90%. Experiments with excised cotyledons, hypocotyls, and roots incubated in solution showed that the flavonoids could be synthesized in and released from each organ. However, the ratio of the three flavonoids in exudates from intact plants was most similar to the ratio recently synthesized and released from excised roots. A portion of recently synthesized flavonoid aglycones was found conjugated, presumably as glycosides, in root extracts and may have been involved in the release process. Data from root extracts showed that formononetin, an isoflavonoid which does not induce nod genes, was present in conjugated and aglycone forms but was not released by normal intact roots. In contrast, roots stressed with CuCl(2) did release the aglycone formononetin. Thus, the release process responsible for exudation of nod-gene inducers appears to be specific rather than a general phenomenon such as a sloughing off of cells during root growth. The synthesis and specific concurrent release of flavonoid nod-gene inducers in this study is consistent with the physiological requirement for nodule formation of the 3-day-old seedlings used.
Journal Article↗
Apoplastic binding of aluminum is involved in silicon-induced amelioration of aluminum toxicity in maize.
The alleviating effect of silicon (Si) supply on aluminum (Al) toxicity was suggested to be based on ex or in planta mechanisms. In our experiments with the Al-sensitive maize (Zea mays) cultivar Lixis, Si treatment but not Si pretreatment ameliorated Al-induced root injury as revealed by less root-growth inhibition and callose formation. Si treatment did not affect monomeric Al concentrations in the nutrient solution, suggesting an in planta effect of Si on Al resistance. A fractionated analysis of Si and Al in the 1-cm root apices revealed that more than 85% of the root-tip Al was bound in the cell wall. Al contents in the apoplastic sap, the symplastic sap, and the cell wall did not differ between -Si and +Si plants. Si did not affect the Al-induced exudation of organic acid anions and phenols from the root apices. However, Al treatment greatly enhanced Si accumulation in the cell wall fraction, reducing the mobility of apoplastic Al. From our data we conclude that Si treatment leads to the formation of hydroxyaluminumsilicates in the apoplast of the root apex, thus detoxifying Al.
Aluminum↗
Associations of specific bacteria with some endodontic signs and symptoms.
Although a wide range of bacterial species has been isolated from infected dental root canals it remains necessary to determine whether any particular group of such bacteria is associated with specific endodontic symptoms and clinical signs. In this study 30 root canals were examined microbiologically; of these, 14 were associated with pain, 20 with tenderness to percussion, 23 presented with wet root canals, seven with swelling, five with purulent exudate and four with a sinus. Clinical and microbiological correlation was observed particularly with regard to pain where anaerobes were isolated from 93% of painful canals and only from 53% of painfree canals. The former yielded means of 2.5 anaerobic species and 1.6 facultative species per canal, compared with 1.5 and 2.4 in painfree canals. Prevotella spp. were isolated from 64.2% of painful canals and 12.5% of painless canals (P < 0.01) similarly, peptostreptococci were isolated from 71.4% of painful and 31.3% of painless canals (P < 0.05). It was concluded that a significant association exists between pain and the presence of Prevotella and Peptostreptococcus spp. in dental root canals.
Bacteria, Anaerobic↗
Endodontic retreatment: a rational approach to non-surgical root canal therapy of immature teeth.
The specificity of retreating immature teeth involves generally a broadly wide open apex and/or an inverted root canal conicity (apical opening wider than the root canal orifice), a periapical pathology leading often to a continuous canal exudation and thin and fragile dentinal walls. Nonsurgical endodontic retreatment of immature teeth consists at first in removing coronal and root canal iatrogenic obstructions in order to regain total canal patency. Apexification is then the treatment of choice, preceding a final gutta-percha obturation. The present article outlines a step-by-step rational approach to the root canal retreatment of immature teeth, pertaining to their biomechanical and pathological specificity.
Calcium Hydroxide↗
Production of root hair deformation factors by Rhizobium meliloti nodulation genes in Escherichia coli: HsnD (NodH) is involved in the plant host-specific modification of the NodABC factor.
The role of the hsnD (nodH) gene in the determination of the host-specific nodulation ability of Rhizobium meliloti was studied by expressing the common nodulation genes (nodABC) with or without the hsnD gene in Escherichia coli and testing for biological activity on various leguminous plants. In this way, four categories of plants were established. Upon infection with E. coli carrying the nodABC construct, root hair deformation (Had) was detected on clovers while the hsnD gene was additionally needed for the elicitation of the same response on alfalfa and sweet clover. A weak root hair deformation was seen on siratro by inoculation with E. coli harbouring the nodABC genes and was highly increased when hsnD was also introduced. Cowpea and Desmodium did not respond to any of the E. coli strains constructed. Exudates or cytosolic fractions of the respective E. coli derivatives elicited the same root hair deformation as the intact bacteria. These data indicate that not only the nodABC gene products but also the hsnD product are involved in the synthesis of Had factors. Subclones expressing only the nodA, nodB, or nodC genes or the same genes in pairs (nodAB, nodBC, nodAC) did not provide a compound with activity comparable to the NodABC factor, suggesting that all three genes are required for the production of the Had factor which is active on clover. Coinoculation of alfalfa plants with two strains of E. coli, one carrying the nodABC genes and the other expressing only hsnD, or combining exudates or cytosolic fractions from these strains did not result in root hair deformation on alfalfa. These data indicate that the HsnD protein itself or its product is not an additional alfalfa-specific extracellular signal but more likely is enzymatically involved in the modification of the basic compound determined by the nodABC genes.
DNA, Bacterial↗
Histologic reactions to root canal fillings.
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Animals↗
The response of the phosphate uptake system and the organic acid exudation system to phosphate starvation in Sesbania rostrata.
It is well known that the P(i) uptake system via the high-affinity P(i) transporter and the organic acid exudation system via PEPC are enhanced in the roots of P(i)-starved plants. In this paper, we compared the expression of these two systems in Sesbania rostrata, a leguminous plant, on whose roots and stems it forms nodules. When S. rostrata plants were transferred to a 0 microM P(i) nutrient solution, the expression of both the high-affinity P(i) transporter and PEPC was enhanced within 2 d. The enhancement of the expression of the high-affinity P(i) transporter genes and the PEPC gene coordinated with the increases in the P(i) uptake rate and the PEPC activity, respectively. This suggests that the expression of the high-affinity P(i) transporters and PEPC is regulated in part at the transcript level. Furthermore, we examined which of the environmental or the endogenous P(i) level regulates the expression of these two systems. The P(i) content in the 6-day-old plants decreased to a lower level than that in the 15-day-old plants when grown in a 30 microM P(i) solution. At that time, the expression of the high-affinity P(i) transporters and PEPC was enhanced only in the 6-day-old plants. Moreover, the P(i) content in plants forming many nodules on their stems decreased. The expression of the high-affinity P(i) transporters and PEPC was then enhanced in the nodulated plants. These facts suggest that the expression of these two systems may be regulated by the P(i) content in the plants, not by the P(i) concentration in the soil.
Fabaceae↗
Radicular lesions in tuberculous meningitis. A clinicopathological study.
In the present work, the involvement of cranial and spinal nerve roots in tuberculous meningitis was studied. Cranial nerves of 11 cases and the spinal roots of three patients were examined by means of serial sections of the base of the brain, brainstem and spinal cord. Although entrapment of the nerves by the tenacious inflammatory exudate was prominent, vasculitis lesions of the cranial nerves and spinal roots were also frequently observed. The latter could be an additional cause of nerve palsies in tuberculous meningitis.
Adult↗
Scanning microscopic evaluation of canal débridement as compared to present methods.
Ninety-one samples of root canal contents were obtained from thirty-one teeth. The paper point samples were evaluated for exudate, subjected to bacteriologic analysis, and/or examined with the scanning electron microscope. A comparison was made between the presence or absence of exudate, positive and negative cultures, and the presence or absence of contaminants as examined under the SEM. All three methods of evaluation showed some degree of correlationmscanning electron microscopy appears to be a more sensitive test for canal status.
Adolescent↗
[The clinical evaluation of tinidazole-iodoform-phenocamphor paste as an intra-canal sterilization medication for acute periapical periodontitis].
OBJECTIVE: To compare the clinical effect of tinidazole-iodoform-phenocamphor paste on acute periapical periodontitis with of formocresol. METHODS: 80 permanent teeth of acute periapical periodontitis were selected and divided randomly into tinidazole-iodoform-phenocamphor paste group (T group) and formocresol group (C group). The periapical signs and symptoms were recorded. Radiographs were taken and periapical radiolucent areas were calculated. After root canal preparation,the tinidazole-iodoform-phenocamphor paste was used as an intra-canal dressing medication for 7 days in T group and the formocresol paper point was used in C group. During the course of root canal treatment,the standard paper-point sampling method was used to collect and quantify the periapical exudates and the clinical findings were assessed with clinical periapical index(CPI). All statistical analyses were finished with Sigmastat software. RESULTS: At the first visit, there was no significant difference between two groups of CPI indexes and exudates volumes (P>0.05). The stepwise regression results suggested that exudates volumes had a significant correlation to periapical percussion(P=0.0031). There was a close relationship between radiolucent areas and periapical percussion or swelling degree (P=0.1148, P<0.0001). After the root canal sterilization, there was a statistically significant decrease in exudates volumes and CPI indexes (P<0.01), but the difference of exudates volumes and CPI indexes between two groups was not statistically significant (P>0.05). CONCLUSION: It indicated that tinidazole-iodoform-phenocamphor paste had the same effect on controlling acute periapical periodontitis as that of formocresol.
Clinical Trial↗
Cellular and organ level localization of maltose in maltose-excess Arabidopsis mutants.
Maltose is the predominant form of carbon exported from the chloroplast at night. Plants that lack either the chloroplast maltose transporter or disproportionating enzyme 2 (DPE2, EC 2.4.1.25) have excess maltose in leaves. We confirmed that DPE2 is not associated with the chloroplast in Arabidopsis thaliana. Using non-aqueous fractionation methods, we found that essentially all the maltose in mex1-1 leaves is located inside chloroplasts but only 40% of maltose in dpe2-1 leaves is located inside chloroplasts. We found that maltose exists in a significant amount in the exudates collected from maltose-accumulating dpe2-1 Arabidopsis petioles. However, the amount of maltose in the exudates from mex1-1 petioles was not significantly different from that in wild-type phloem exudates. We found twice as much maltose in the roots of dpe2-1 plants relative to wild type but the maltose level in the roots of mex1-1 plants was not higher than wild type. We conclude that maltose accumulated in the cytosol of leaves can be carried from the shoots to the roots and that maltose accumulated in the chloroplast of mex1-1 leaves is not mobilized. By measuring the transcript levels and enzymatic activities, we show that maltose-metabolizing enzymes are active in wild-type roots. The amount of maltose moved from the shoots to the roots increased in dpe2-1 plants. The roots of dpe2-1 plants must have the capacity to metabolize the excess maltose.
Arabidopsis↗
Iron deficiency differently affects metabolic responses in soybean roots.
Iron deficiency responses were investigated in roots of soybean, a Strategy I plant species. Soybean responds to iron deficiency by decreasing growth, both at the root and shoot level. Chlorotic symptoms in younger leaves were evident after a few days of iron deficiency, with chlorophyll content being dramatically decreased. Moreover, several important differences were found as compared with other species belonging to the same Strategy I. The main differences are (i) a lower capacity to acidify the hydroponic culture medium, that was also reflected by a lower H(+)-ATPase activity as determined in a plasma membrane-enriched fraction isolated from the roots; (ii) a drastically reduced activity of the phosphoenolpyruvate carboxylase enzyme; (iii) a decrease in both cytosolic and vacuolar pHs; (iv) an increase in the vacuolar phosphate concentration, and (v) an increased exudation of organic carbon, particularly citrate, phenolics, and amino acids. Apparently, in soybean roots, some of the responses to iron deficiency, such as the acidification of the rhizosphere and other related processes, do not occur or occur only at a lower degree. These results suggest that the biochemical mechanisms induced by this nutritional disorder are differently regulated in this plant. A possible role of inorganic phosphate in the balance of intracellular pHs is also discussed.
Gene Expression Regulation, Plant↗
[Exudation and accumulation of citric acid in common bean in response to Al toxicity stress].
Significant differences in the exudation and accumulation of citric acid in common bean genotypes were observed in response to Al toxicity stress by hydroponic cultural experiments. Secreted citric acid increased with increasing external concentrations of Al3+ which ranged from 0 to 50 mumol.L-1, while ranged from 50 to 80 mumol.L-1, secreted citric acid decreased with increasing external concentrations of Al3+. Among different genotypic common beans, citric acid secreted in G19842 was the largest, while Al uptake per unit dry weight in G19842 was the least. No difference in the accumulation of citric acid in leaves was found among different genotypic common beans, while the size of the content of citric acid in roots was G19842 > AFR > ZPV > G5273. The amount of citric acid exuded was smaller induced by phosphorus deficiency than that induced by Al toxicity stress. Exposure to 50 mumol.L-1 LaCl3 could not induce the exudation of citric acid, and it implied that the exudation and accumulation of citric acid in common bean was an important physiological response of resistance to Al toxicity stress.
Aluminum↗
Cadmium distribution and chemical fate in soybean plants.
The distribution and chemical behavior of Cd(2+) in tissues and its chemical form in xylem water of soybean plants (cv. Williams) were investigated. Following root absorption, Cd is strongly retained by roots, with only 2% of the accumulated Cd being transported to leaves; as much as 8% was transported to seeds during seed filling. In vivo xylem exudates contained two anionic Cd complexes in addition to inorganic forms of Cd. Once accumulated in root and leaf tissues, Cd rapidly equilibrated between the insoluble, soluble, and organelle fractions. Of the solubles, which contain 50% of the Cd, >50% was associated with components of >10,000 molecular weight, and <8% was associated with <500 molecular weight components. Cadmium accumulated in soybean seeds was primarily associated with cotyledons. Fractionation of seeds showed the soy proteinate and soy whey to contain 32 and 50% of the accumulated Cd, respectively.
Journal Article↗
Aluminum activates a citrate-permeable anion channel in the aluminum-sensitive zone of the maize root apex. A comparison between an aluminum- sensitive and an aluminum-resistant cultivar.
In search for the cellular and molecular basis for differences in aluminum (Al) resistance between maize (Zea mays) cultivars we applied the patch-clamp technique to protoplasts isolated from the apical root cortex of two maize cultivars differing in Al resistance. Measurements were performed on protoplasts from two apical root zones: The 1- to 2-mm zone (DTZ), described as most Al-sensitive, and the main elongation zone (3-5 mm), the site of Al-induced inhibition of cell elongation. Al stimulated citrate and malate efflux from intact root apices, revealing cultivar differences. In the elongation zone, anion channels were not observed in the absence and presence of Al. Preincubation of intact roots with 90 microM Al for 1 h induced a citrate- and malate-permeable, large conductance anion channel in 80% of the DTZ protoplasts from the resistant cultivar, but only 30% from the sensitive cultivar. When Al was applied to the protoplasts in the whole-cell configuration, anion currents were elicited within 10 min in the resistant cultivar only. La3+ was not able to replace or counteract with Al3+ in the activation of this channel. In the presence of the anion-channel blockers, niflumic acid and 4, 4'-dinitrostilbene-2, 2'disulfonic acid, anion currents as well as exudation rates were strongly inhibited. Application of cycloheximide did not affect the Al response, suggesting that the channel is activated through post-translational modifications. We propose that the Al-activated large anion channel described here contributes to enhanced genotypical Al resistance by facilitating the exudation of organic acid anions from the DTZ of the maize root apex.
Aluminum↗