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Results for “Root physiology”

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At least 73 records · Page 4Linked to original sources

PubMed1990

[Changes of vibration frequency due to root resorption of deciduous tooth].

The purpose of this study was to investigate the changes of vibration frequency of a deciduous tooth due to physiological root resorption. The author developed an analysis system for tooth vibration by applying an impact-hammer to the tooth. Peak frequency (Hz) of the tooth stimulated by the impact-hammer was observed by the analysis system. The following results were obtained: 1) Peak frequency of the tooth vibration shifted to a lower range according to the root resorption both in vitro (simulation model) and in vivo (15 children) and a high positive correlation was found between the peak frequency and the crown-root length ratio (r = 0.840). 2) A cause of the frequency shift to the lower range was not related to the tooth weight but to the change of tooth gravity due to the root resorption. 3) It was considered that the vibration analysis system could be useful on measuring tooth mobility in vivo and in clinic as well.

Child↗

PubMed2000

Role of hormones in the induction of iron deficiency responses in Arabidopsis roots.

In "strategy I" plants, several alterations in root physiology and morphology are induced by Fe deficiency, although the mechanisms by which low Fe levels are translated into reactions aimed at alleviating Fe shortage are largely unknown. To prove whether changes in hormone concentration or sensitivity are involved in the adaptation to suboptimal Fe availability, we tested 45 mutants of Arabidopsis defective in hormone metabolism and/or root hair formation for their ability to increase Fe(III) chelate reductase activity and to initiate the formation and enlargement of root hairs. Activity staining for ferric chelate reductase revealed that all mutants were responsive to Fe deficiency, suggesting that hormones are not necessary for the induction. Treatment of wild-type plants with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid caused the development of root hairs in locations normally occupied by non-hair cells, but did not stimulate ferric reductase activity. Ectopic root hairs were also formed in -Fe roots, suggesting a role for ethylene in the morphological responses to Fe deficiency. Ultrastructural analysis of rhizodermal cells indicated that neither Fe deficiency nor 1-aminocyclopropane-1-carboxylic acid treatment caused transfer-cell-like alterations in Arabidopsis roots. Our data indicate that the morphological and physiological components of the Fe stress syndrome are regulated separately.

Arabidopsis↗

PubMed1990

[The study of root resorption of human deciduous teeth. I. Histological observation by light microscope].

Sixty-four human non-carious deciduous teeth were used to observe the root resorption of deciduous teeth by means of light microscope. The extent of root resorption was classified into 6 grades: Res. O, Res. i, Res. 1/4, Res. 1/2, Res. 3/4, Res. Co. In the physiological root resorption of deciduous tooth, there are numerous, large multinucleated odontoclasts and mononuclear fibroblasts or macrophages residing at the Howship's lacunae. The odontoclasts resorbed hard dental tissues, including cementum, dentin. A characteristic of active or "resorbing" odontoclasts, but not in free or inactive odontoclasts is cytoplasmic projections, or brush borders, which were found near the underlying hard dental tissues. The deciduous root resorption was found to be most advanced in the apical areas. Because of the different eruption path of the permanent successors, the position of deciduous root resorption varied. Generally, the lingual surface was resorbed more extensively than the labial surface in the deciduous anterior teeth; the resorption of the furcal area and interradicular cementum surface of the roots were more advanced in the deciduous molars. Predentin can be resorbed by odontoclasts, too. However, it seems more resistant to resorption than dentin. Resorption lacunae could be observed in the root canal and pulp chamber. This means that the internal root resorption probably occur simultaneously. Periodontal fiber attachment was observed in some Howship's lacunae of the root surface. Inflammatory changes occurred in the pulp of deciduous teeth during the shedding process, especially when the deciduous root was resorbed more than one half way. The appearance of the repairing cellular cementum and periodontal fiber attachment was clearly observed in some deciduous roots.

Child↗

PubMed2003

Physiological mechanism of plant roots exposed to cadmium.

Physiological experiments on plant roots exposed to cadmium were conducted on carrot and radish using a liquid culture and a pot experiment with a series of cadmium applications. Activities of four enzymes (catalase, peroxidase, polyphenol oxidase, superoxide dismutase), and concentrations of free proline and malonaldehyde in the roots of both plants were investigated. Results showed that the germination rate and growth of roots of both plants were inhibited at the concentration of 20 mg Cd/l, and the inhibition was increased with the increasing concentrations of cadmium, both in the liquid culture and in the pot experiment; activities of the four enzymes declined similarly in both species. The concentration of proline in roots reached the maximum when the application of cadmium was at the level of 20 mg/l in the liquid culture (or 20 mg/kg in soil), and then it declined slowly with the increasing concentration of cadmium. However, the reverse trend was observed for the concentration of malonaldehyde. All of bio-indicators measured here was quite sensitive to the addition of cadmium.

Biomass↗

PubMed2004

Spatial distribution of lead in the roots of human primary teeth.

Lead remains one of the most hazardous metals in our environment. The concentrations of lead in coronal dentine and enamel have previously been reported but limited information is available regarding lead levels in radicular dentine and cementum. This study reports the distribution of lead in 26 roots of 16 human maxillary primary teeth from seven individuals. In addition, calcium and phosphorous concentrations were also measured to detect any variations in the degree of mineralization in different regions of the roots. The mean lead concentration in these roots was 1.67 +/- 1.43 microg/g, which is comparable to other studies. In all cases there were higher lead concentrations in the apices of non-resorbed roots of primary maxillary teeth relative to middle and cervical regions. The findings reported here are of potential significance during the process of physiological root resorption whence periapical tissue may be exposed to higher levels of lead.

Calcium↗

PubMedDate not supplied

Conservative treatment of severely luxated maxillary primary central incisors: case report.

The treatment and follow-up evaluation of two orally luxated maxillary primary central incisors in a three-year-old girl is described. The injured teeth were displaced into a cross-bite with their mandibular opposing teeth. They were repositioned shortly after the injury and splinted with composite resin for two weeks. Oral hygiene instructions and antibiotic therapy were prescribed. Two weeks after the injury a necrotic pulp was removed and the root canals filled with a resorbable paste. Thirty months after the injury, the teeth and the surrounding tissues were clinically and radiographically asymptomatic and physiologic root resorption could be noted. The permanent successors erupted soon after natural exfoliation of the injured primary teeth. Only mild hypocalcified defects were observed on the permanent incisors.

Acute Disease↗

PubMed2000

Ultrastructural study of the root dentine surface resuming resorption on human deciduous teeth.

Resorption of deciduous teeth is not continuous, but alternates with periods of repair or rest. Dentine surfaces in periods of rest or repair resume resorption by odontoclasts during physiological root resorption of the deciduous teeth. However, no observations of such dentine surfaces have been shown. The characteristic feature of the dentine surfaces resuming resorption remains unknown. Tartrate-resistant acid phosphatase activity (TRAP) was detected on human deciduous teeth. The root resorbing surfaces on these teeth were photographed with a whole-mount light microscope, and the photographed areas were serially sectioned into 0.5 micron semithin sections. Preodontoclasts and odontoclasts were three-dimensionally reconstructed. On root resorbing surfaces, areas with small scattered TRAP-positive cells were observed among areas with many TRAP-positive resorbing odontoclasts and TRAP-negative areas. The sections showed that areas with small scattered TRAP-positive cells have features similar to those of TRAP-negative areas, but there were three kinds of characteristic TRAP-positive cells: preodontoclasts, odontoclasts forming small lacunae, and preodontoclasts, and odontoclasts with cytoplasmic processes extending to the dentine surface, which is covered with cells. These results suggest that the areas with small scattered TRAP-positive cells could be at the stage of resuming resorption, and show that the presence of preodontoclasts and odontoclasts with cytoplasmic processes extending to the covered dentine surface is a characteristic feature of the dentine surface at this stage.

Acid Phosphatase↗

PubMedDate not supplied

Valve-sparing aortic root replacement.

Aortic root replacement with sparing of the aortic valve in selected patients with isolated sinus of Valsalva or sinotubular aneurysm and a normal valve provides the advantages of an anticoagulation-free milieu and a more physiological root hemodynamic. The clinical efficacy and durability have been documented. This report describes a simple and reproducible technique of aortic root remodeling that uses a prosthetic conduit as originally pioneered by Magdi Yacoub and later by Tirone David.

Aortic Aneurysm↗

PubMed2003

Distribution of the epithelial rests of Malassez and their relationship to blood vessels of the periodontal ligament during rat tooth development.

BACKGROUND: There is some evidence that the epithelial cell rests of Malassez partition the root surface from the periodontal ligament blood vessels, and may protect the root from resorption. OBJECTIVE: The aim of the present study was to determine the distributions of the epithelial rests of Malassez (ERM) and blood vessels in the periodontal ligament (PDL) of the developing rat first molar before, during and after emergence. METHODS: Four Sprague-Dawley rats were sacrificed at two days, one week, two weeks, three weeks, four weeks and six weeks of age. After processing, the maxillae were embedded in paraffin, and sectioned longitudinally and transversely. The sections were stained with a double immuno-histochemical technique which utilised a keratin antibody AE1-AE3 (1:2,000) and an endothelial antibody Factor VIII (1:10,000) to enable simultaneous labelling of ERM and blood vessels. ERM and blood vessel counts were obtained from the mesio-buccal roots of three week, four week and six week-old rats, whilst qualitative observations were made for the earlier developmental stages. RESULTS: ERM cells and cell clusters were found in the tooth third of the PDL width at the three, four and six week stages. Cells and cell clusters increased in number with age, especially in the upper third of the mesio-buccal root. The largest numbers of cells and clusters were found on the distal surfaces of the roots in all age groups. Cells and clusters in all root surfaces increased from three to four weeks, but decreased from four to six weeks. The greatest number of blood vessels was found in the bone-side third of the PDL. The distal surface had the highest proportion of blood vessels, and the palatal surface the least proportion. The number of blood vessels in all surface quadrants did not vary much from three to four weeks of age, but increased from four to six weeks of age, possibly as a reaction to tooth emergence and occlusal function. Physiological root resorption was only observed after tooth emergence, and appeared to be related to loss of continuity of the ERM network and the incursion of blood vessels. CONCLUSIONS: Orthodontic root resorption can be regarded as an exaggerated response to loss of PDL homeostatic control, possibly mediated by the epithelial rests of Malassez.

Age Factors↗

PubMed2002

The role of long-distance signalling in plant responses to nitrate and other nutrients.

The phenotypic plasticity that plants display in response to changes in their nutrient supply requires the operation of both short- and long-range signalling pathways. Long-distance signals arising in the root can provide the shoot with an early warning of fluctuations in external nutrient concentrations, while signals in the reverse direction are needed to ensure that root physiology and development are integrated with the nutritional demands of the shoot. In this review, the focus is on recent advances in the understanding of these long-distance signalling pathways with an emphasis on nitrate nutrition, and a personal view of the key issues for future research is put forward.

Carbohydrate Metabolism↗

PubMed1995

Anion channels as central mechanisms for signal transduction in guard cells and putative functions in roots for plant-soil interactions.

In higher plants anion channels have recently been suggested to play key roles in controlling cellular functions, including turgor- and osmoregulation, stomatal movements, anion transport, signal transduction and possibly also signal propagation. In guard cells and roots, physiological functions of anion channels have been proposed which will be discussed here. In initial investigations it was proposed that anion channels in the plasma membrane of guard cells provide a prominent control mechanism for stomatal closing. The proposed model suggests that anion channel activation and the resulting anion efflux from guard cells cause membrane depolarization, thereby driving K+ efflux through outward-rectifying K+ channels required for stomatal closing. This article provides a brief review of new and recent insights into the molecular properties and cell biological functions of anion channels in guard cells. Furthermore, recently implicated putative functions of anion channels in roots during salt stress, xylem loading and Al3+ tolerance are addressed.

Anions↗

PubMed2006

Plasma membrane anion channels in higher plants and their putative functions in roots.

Recent years have seen considerable progress in identifying anion channel activities in higher plant cells. This review outlines the functional properties of plasma membrane anion channels in plant cells and discusses their likely roles in root function. Plant anion channels can be grouped according to their voltage dependence and kinetics: (1) depolarization-activated anion channels which mediate either anion efflux (R and S types) or anion influx (outwardly rectifying type); (2) hyperpolarization-activated anion channels which mediate anion efflux, and (3) anion channels activated by light or membrane stretch. These types of anion channel are apparent in root cells where they may function in anion homeostasis, membrane stabilization, osmoregulation, boron tolerance and regulation of passive salt loading into the xylem vessels. In addition, roots possess anion channels exhibiting unique properties which are consistent with them having specialized functions in root physiology. Most notable are the organic anion selective channels, which are regulated by extracellular Al3+ or the phosphate status of the plant. Finally, although the molecular identities of plant anion channels remain elusive, the diverse electrophysiological properties of plant anion channels suggest that large and diverse multigene families probably encode these channels.

Anions↗

PubMed1998

Dentin bridge formation following direct pulp capping in dog's.

The effectiveness of two different calcium hydroxide pastes; "Calvital and "Dycal", for the direct pulp capping in dog's permanent teeth with incompletely formed roots were evaluated in this study. Forty-eight vital permanent premolar teeth with incompletely formed apices were obtained from 6 dog's (6 months of age). Exposure sites on contralateral pairs of teeth were capped with either "Calvital" or "Dycal". Then intravenous injections of tetracycline were administered to the dogs at various intervals. Animals were sacrificed at 56 days. The teeth were fixed, undecalcified ground sectioned, observed by microradiography, and evaluated by ultraviolet light. In cases treated with "Calvital", a fluorescent line resulting from tetracycline administration 7 days after experimental procedures was seen in the newly formed dentin bridge. In cases treated with "Dycal", a fluorescent line resulting from tetracycline administration 14 days after experimental procedures was seen in the newly formed dentin bridge. Continued physiological root formation was observed well in all teeth. This experiment may explain why some "Dycal" failures occur in the earlier postoperative periods; serves as a stimulus potential for a hardening reaction.

Animals↗

PubMed2006

Transgenic rice plants ectopically expressing AtBAK1 are semi-dwarfed and hypersensitive to 24-epibrassinolide.

Brassinosteroids (BRs) are endogenous plant hormones essential for plant growth and development. Brassinosteroid insensitive1 (BRI1)-assocaiated receptor kinase (BAK1) is one of the key components in the BR signal transduction pathway due to its direct association with the BR receptor, BRI1. Although BRI1 and its orthologs have been identified from both dicotyledonous and monocotyledonous plants, less is known about BAK1 and its orthologs in higher plants other than Arabidopsis. This article provides the first piece of evidence that AtBAK1 can greatly affect growth and development of rice plants when ectopically expressed, suggesting that rice may share similar BR perception mechanism via BRI1/BAK1 complex. Interestingly, transgenic rice plants displayed semi-dwarfism and shortened primary roots. Physiological analysis and cell morphology assay demonstrated that the observed phenotypes in transgenic plants were presumably caused by hypersensitivity to endogenous levels of BRs, different from BR insensitive and deficient rice mutants. Consistently, several known BR inducible genes were also upregulated in transgenic rice plants, further suggesting that BAK1 was able to affect BR signaling in rice. On the other hand, the transgenic plants generated by overproducing AtBAK1 may potentially have agricultural applications because the dwarfed phenotype is generally resistant to lodging, while the fertility remains unaffected.

Agriculture↗

PubMed2004

Evaluation of native valve-sparing aortic root reconstruction with direct imaging--reimplantation or remodeling?

BACKGROUND: Aortic root reimplantation and remodeling have been used to preserve the native aortic valve. However, direct observation of valve motions with these techniques has not been performed. METHODS: Mongrel dogs were studied. The beating heart model was created using modified Tyrode's solution. Normal aortic valves and aortic valves preserved with the remodeling or reimplantation procedure were observed with an endoscope, and behavior was recorded on a high-speed video (200 frames/s). The aortic valve orifice area was measured at 11 data points per beat. A predictable maximum valve orifice area was defined as an area encircled by the three commissures. A ratio of each aortic valve orifice area to the predictable maximum valve orifice area was calculated. The control group, the reimplantation group, and the remodeling group were compared. RESULTS: The preserved aortic valve with reimplantation showed bending and asymmetric motion. The ratio of aortic valve orifice area and predictable maximum valve orifice area in the reimplantation group was significantly smaller compared with the control and remodeling groups. CONCLUSIONS: The opening and closing behavior of the aortic valve preserved with the reimplantation procedure was impaired. It was speculated that the remodeling procedure may preserve more physiologic root function compared with the reimplantation procedure.

Animals↗

PubMed2003

Differentiation and functions of osteoclasts and odontoclasts in mineralized tissue resorption.

The differentiation and functions of osteoclasts (OC) are regulated by osteoblast-derived factors such as receptor activator of NFKB ligand (RANKL) that stimulates OC formation, and a novel secreted member of the TNF receptor superfamily, osteoprotegerin (OPG), that negatively regulates osteoclastogenesis. In examination of the preosteoclast (pOC) culture, pOCs formed without any additives expressed tartrate-resistant acid phosphatase (TRAP), but showed little resorptive activity. pOC treated with RANKL became TRAP-positive OC, which expressed intense vacuolar-type H(+)-ATPase and exhibited prominent resorptive activity. Such effects of RANKL on pOC were completely inhibited by addition of OPG. OPG inhibited ruffled border formation in mature OC and reduced their resorptive activity, and also induced apoptosis of some OC. Although OPG administration significantly reduced trabecular bone loss in the femurs of ovariectomized (OVX) mice, the number of TRAP-positive OC in OPG-administered OVX mice was not significantly decreased. Rather, OPG administration caused the disappearance of ruffled borders and decreased H(+)-ATPase expression in most OC. OPG deficiency causes severe osteoporosis. We also examined RANKL localization and OC induction in periodontal ligament (PDL) during experimental movement of incisors in OPG-deficient mice. Compared to wild-type OPG (+/+) littermates, after force application, TRAP-positive OC were markedly increased in the PDL and alveolar bone was severely destroyed in OPG-deficient mice. In both wild-type and OPG-deficient mice, RANKL expression in osteoblasts and fibroblasts became stronger by force application. These in vitro and in vivo studies suggest that RANKL and OPG are important regulators of not only the terminal differentiation of OC but also their resorptive function. To determine resorptive functions of OC, we further examined the effects of specific inhibitors of H(+)-ATPase, bafilomycin A1, and lysosomal cysteine proteinases (cathepsins), E-64, on the ultrastructure, expression of these enzymes and resorptive functions of cultured OC. In bafilomycin A1-treated cultures, OC lacked ruffled borders, and H(+)-ATPase expression and resorptive activity were significantly diminished. E-64 treatment did not affect the ultrastructure and the expression of enzyme molecules in OC, but significantly reduced resorption lacuna formation, by inhibition of cathepsin activity. Lastly, we examined the expression of H(+)-ATPase, cathepsin K, and matrix metalloproteinase-9 in odontoclasts (OdC) during physiological root resorption in human deciduous teeth, and found that there were no differences in the expression of these molecules between OC and OdC. RANKL was also detected in stromal cells located on resorbing dentine surfaces. This suggests that there is a common mechanism in cellular resorption of mineralized tissues such as bone and teeth.

Acid Phosphatase↗

PubMed2002

Localization of cathepsin K in bovine odontoclasts during deciduous tooth resorption.

Cathepsin K is a cysteine proteinase, which is abundantly and selectively expressed in osteoclasts. It is believed to play an important role in the proteolysis of bone resorption by osteoclasts. The objectives of this study were to investigate the association of cathepsin K in the physiological root resorption of deciduous teeth and to identify the cathepsin K-producing cells in deciduous root resorption. RT-PCR and Northern blot analysis of the total RNAs extracted from bovine active and resting root-resorbing tissues, which lie between the root of deciduous tooth and its permanent successor, were performed. The active root-resorbing tissue, which has a high population of odontoclasts on its surface that is attached to resorbing root surface, showed an extremely high expression of cathepsin K in comparison with the resting root-resorbing tissue. By in situ hybridization, cathepsin K mRNA was highly and selectively expressed in multinucleated odontoclasts that aligned along the surface of the tissue and apposed to the resorbing root surface of the deciduous tooth. Western blot analysis of the active root-resorbing tissue was used to characterize the anti-cathepsin K antibody. A band of 27 kDa, corresponding with the predicted size for mature cathepsin K, was demonstrated. Immunohistochemistry confirmed the specific localization of cathepsin K protein to the odontoclasts. These results demonstrate that odontoclasts in the deciduous root resorption express cathepsin K mRNA and protein that may participate in the proteolysis of root resorption of the deciduous tooth.

Animals↗

PubMed2006

Expression of MT1-MMP during deciduous tooth resorption in odontoclasts.

Membrane type 1-matrix metalloproteinase (MT1-MMP) is a membrane-bound matrix metalloproteinase capable of mediating pericellular proteolysis of extracellular matrix components. In osteoclasts, the localization of MT1-MMP has been reported at the tips of specialized membrane protrusions (podosomes and lamellipodia) so that osteoclasts might use MT1-MMP to perform focal proteolysis and move through the extracellular matrix to the bone surface. The objectives of this study were to investigate an association of MT1-MMP in physiological root resorption of the deciduous tooth by reverse transcriptase-polymerase chain reaction (RT-PCR) and Northern blot analysis, and to identify MT1-MMP-producing cell during deciduous tooth resorption by in situ hybridization and immunohistochemistry. RT-PCR and Northern blot analysis revealed the exclusively high expression of MT1-MMP mRNA in bovine root-resorbing tissue, which lies between the root of the deciduous tooth and its permanent successor. Expression of MT1-MMP mRNA was seen in odontoclasts aligning in the surface layer of the root-resorbing tissue at sites of root resorption. Furthermore, immmunohistochemistry also confirmed the localization of MT1-MMP protein to the odontoclasts. The present identification of MT1-MMP in odontoclasts during deciduous tooth resorption might be relevant to the migration activity that these cells have to gain access to the root surface.

Animals↗