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PubMed1991

Organ-specific invertase deficiency in the primary root of an inbred maize line.

An organ-specific invertase deficiency affecting only the primary root system is described in the Oh 43 inbred maize (Zea mays). Invertases (acid and neutral/soluble and insoluble) were assayed in various tissues of hybrid (NK 508) and inbred (Oh 43, W 22) maize lines to determine the basis for an early report that Oh 43 root tips were unable to grow on sucrose agar (27). Substantial acid invertase activity (7.3 to 16.1 micromoles of glucose per milligram of protein per hour) was evident in extracts of all tissues tested except the primary root system of Oh 43. This deficiency was also evident in lateral roots arising from the primary root. In contrast, morphologically identical lateral roots from the adventitious root system had normal invertase levels. These results suggest that ontogenetic origin of root tissues is an important determinant of invertase expression in maize. Adventitious roots (including the seminals) arise above the scutellar node and are, therefore, of shoot origin. The Oh 43 deficiency also demonstrated that invertase activity was not essential for maize root growth. Sucrose synthase was active in extracts from all root apices and theoretically provided the only available avenue for sucrose degradation in primary root tips of Oh 43. The deficiency described here will provide a useful avenue of investigation into the expression and significance of root invertase.

Journal Article↗
PubMed2004

Differences in structure of adventitious roots in Salix clones with contrasting characteristics of cadmium accumulation and sensitivity.

Various clones of Salix spp. have contrasting characteristics of accumulation, translocation to shoots and of sensitivity to cadmium (Cd). The aim was to investigate the structure of adventitious roots and find out if differences between groups of clones in root anatomy accounted for differences in relation to Cd. Stem cuttings of eight clones of Salix spp. with different combinations of high or low Cd accumulation, translocation of Cd to shoots and sensitivity to Cd, were cultivated for 3 weeks in hydroponics containing 100 micro M Ca(NO(3))(2). No Cd was added in this experiment. Equal-sized roots were selected for hand-sectioning and fluorescence staining to detect the beginning of Casparian band formation and suberin lamellae deposition in endodermis. In addition, root apices were fixed, embedded, sectioned longitudinally and transversally, and stained. The image analysis system LUCIA was used for quantitative evaluation of tissue differences. The structure of adventitious root apices showed an intermediate-open type of root apical meristem and the clones differed in organization of root apices. Clones with low accumulation of Cd and high Cd tolerance had smaller meristematic zones and more extensive vacuolation of cells in the root apices than clones characterized by high accumulation of, and high sensitivity to, Cd. The apoplastic barriers, exo- and endodermis, were developed relatively close to the apex. In both layers the first ontogenetic stage, the Casparian band development, was followed by the second stage, the suberin lamellae deposition. This process started in the endodermis, preferentially against phloem poles, which is a common phenomenon also in other plant species. However, preferential development of exodermis in the sectors against phloem poles was observed in this study for the first time in plants. Development of endodermal Casparian bands in clones characterized by high accumulation of Cd occurred more distant from the root tip than in clones with low accumulation. Furthermore, the suberin lamellae were more distant from the root tip in clones with high translocation of Cd compared with those with low translocation. This indicates that apoplastic movement of Cd into the stele and the upward translocation may vary due to the endodermal anatomy. The proportion of root apoplastic barriers, exodermis and endodermis as well as epidermis to other root tissues was significantly increased in clones with higher tolerance to Cd ions, indicating the importance of these tissues in protection of the root against toxic effects of Cd.

Journal Article↗
PubMed1996

The excitatory and inhibitory modulation of primary afferent fibre-evoked responses of ventral roots in the neonatal rat spinal cord exerted by nitric oxide.

1. We investigated the role of nitric oxide (NO) in modulating spinal synaptic responses evoked by electrical and noxious sensory stimuli in the neonatal rat spinal cord in vitro. 2. Potentials were recorded extracellularly from a ventral root (L3-L5) of the isolated spinal cord preparation or spinal cord-saphenous nerve-skin preparation of 0- to 2-day-old rats. Spinal reflexes were elicited by electrical stimulation of the ipsilateral dorsal root or by noxious skin stimulation. 3. In the spinal cord preparation, single shock stimulation of a dorsal root at C-fibre strength induced mono-synaptic reflex followed by a slow depolarizing response lasting about 30 s (slow ventral root potential; slow VRP) in the ipsilateral ventral root of the same segment. Bath-application of NO gas-containing medium (10(-4)- 10(-2) dilution of saturated medium) and NO donors, 1-hydroxy-2-oxo-3-(N-ethyl-2-aminoethyl)-3-ethyl-1-triazene (NOC12, 3-300 microM), S-nitroso-N-acetyl-D,L-penicillamine (SNAP, 3-300 microM) and S-nitroso-L-glutathione (GSNO, 3-300 microM), produced an inhibition of the slow VRP and a depolarization of ventral roots. Another NO donor, 3-morpholinosydononimine (SIN-1, 30-300 microM), also depressed the slow VRP but did not depolarize ventral roots. These agents did not affect the mono-synaptic reflex. 4. In the spinal cord-saphenous nerve-skin preparation, application of capsaicin (0.1-0.2 microM) to skin evoked a slow depolarizing response of the L3 ventral root. This slow VRP was depressed by NOC12 (10-300 microM) and SIN-1 (100-300 microM). When the concentration of NOC12 was increased to 1 mM, spontaneous synaptic activities were augmented and the depressant effect of NOC12 on the slow VRP became less pronounced. 5. A NO-scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide( carboxy- PTIO, 100-300 microM) prevented the depressant effect on the dorsal root-evoked slow VRP and ventral root depolarizing effects of NO donors. Carboxy-PTIO increased spontaneous synaptic activities and markedly potentiated the slow VRP. A NO synthase (NOS) inhibitor, N omega-nitro-L-arginine methyl ester (L-NAME, 0.03-1 microM), but not D-NAME (0.03-1 microM), also markedly potentiated the slow VRP and this effect was reversed by L-arginine (300 microM). 6. 8-Bromo-cyclic guanosine 3': 5'-monophosphate (8-Br-cyclic GMP, 100-300 microM) produced both an inhibition of the slow VRP and a depolarization of ventral roots. A cyclic GMP-dependent protein kinase inhibitor, KT5823 (0.3 microM), partly inhibited the depressant effects of NO donors and 8-Br-cyclic GMP on the dorsal root-evoked slow VRP. In contrast, KT5823 did not inhibit the depolarizing effects of NO donors. 7. Perfusion of the spinal cord with medium containing tetrodotoxin (0.3 microM) and/or low Ca2+ (0.1 mM)-high Mg2+ (10 mM) markedly potentiated the depolarizing effect of NO donors. The SNAP-evoked depolarization in the tetrodotoxin-containing low Ca(2+)-high Mg2+ medium was significantly inhibited by excitatory amino acid receptor antagonists D-(-)-2-amino-5-phosphonovaleric acid (30 microM) and 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM). 8. The present study suggests that inhibitory and excitatory mechanisms meditated by the NO-cyclic GMP cascade are involved in the primary afferent fibre-evoked nociceptive transmission in the neonatal rat spinal cord. The inhibitory mechanism, but not the excitatory mechanism, appears to be partly mediated by cyclic GMP-dependent protein kinase. It is also suggested that Ca(2+)-independent release of excitatory amino acid neurotransmitters contributes to the depolarizing response to NO of ventral roots.

Animals↗
PubMedDate not supplied

Medtronic Freestyle aortic root bioprosthesis: Implant techniques.

BACKGROUND: The Medtronic Freestyle aortic root bioprosthesis is a complete porcine aortic root to allow implantation (1) as a subcoronary valve replacement by removing graft sinus aorta, (2) as a cylinder with the sinotubular junction intact within the aorta (root inclusion), or (3) as a complete aortic root replacement. The choice among the three implant techniques depends on surgeon preference or upon the pathology encountered. The advantages and differences among the three implant techniques are examined. METHODS: The Medtronic Freestyle bioprosthesis was implanted in 1163 patients in a Food and Drug administration (FDA) clinical trial between August 1992 and October 1997. There were 21 centers in the international trial using a single data repository. Clinical data was collected prior to and at operation, at 3 to 6 months and annually. The data were compiled and statistical analysis performed at the data center. RESULTS: Patients having subcoronary valve implants were older (80% > 65 years) and aortic occlusion time was about 20 minutes less than the other methods. Patients having aortic root replacement presented with more aortic valve insufficiency (20%). Pathology of the aortic root and ascending aorta requiring repair was 26%, and larger (27 mm) valves were used in 40% of patients. Risk of operation was lowest (5.0%) with subcoronary valve implants and highest (11.7%) with root replacement technique. Thromboembolism was higher, early and late, with root inclusion (3.0, 3.9%/patient per year) and root replacement (3.2, 3.0%/patient per year) than for subcoronary implants (1.8, 1.6%/patient per year). There were more patients taking warfarin at the 4-year point with root inclusion (20%) or root replacement techniques (24%) than among patients having subcoronary implants (14%). Explants of the valve occurred in 2% of patients, none of whom had aortic root replacement. CONCLUSIONS: The Medtronic Freestyle bioprosthesis is an effective and versatile device for replacement of the aortic valve. It offers implant techniques that can treat the aortic root pathology encountered at surgery and allows the operation to proceed according to surgeon preference.

Aged↗
PubMed1982

Alteration of the Trifoliin A-Binding Capsule of Rhizobium trifolii 0403 by Enzymes Released from Clover Roots.

The effect of white clover root exudate on capsules of Rhizobium trifolii 0403 was examined. The clover lectin trifoliin A was detected in root exudate of two clover varieties by indirect immunofluorescence with antibody against this lectin purified from clover seed. Trifoliin A bound uniformly to encapsulated, heat-fixed cells during 1 h of incubation with root exudate. After 4 to 8 h of incubation, trifoliin A was only bound to one pole of the cells. Transmission electron microscopy showed that the capsule itself was altered. The disorganization of the acidic polymers of the capsule began in the equatorial center of the rod-shaped cell and then progressed toward the poles at unequal rates. Trifoliin A could no longer be detected on heat-fixed cells after 12 h of incubation with root exudate. However, trifoliin A was detected in situ on one pole of cells grown for 4 days in the clover root environment of Fahraeus slide cultures. Inhibition studies with the hapten 2-deoxy-d-glucose showed that trifoliin A in root exudate had a higher affinity for one of the cell poles. Immunoelectrophoresis was used to monitor the alteration of the extracellular polysaccharides from R. trifolii 0403 by concentrated root exudate. These polysaccharides were converted into products which eventually lost their ability to immunoprecipitate with homologous antibody. This progressive loss of antigenic reactivity proceeded more rapidly with root exudate from seedlings grown under nitrogen-free conditions than with root exudate from plants grown with 15 mM KNO(3). The root exudate, depleted of trifoliin A by immunoaffinity chromatography, was still able to alter the capsule of R. trifolii 0403. Reconstitution experiments showed that the substance(s) in root exudate which induced this alteration of the capsule was of a high molecular weight, heat labile, trypsin sensitive, and antigenically unrelated to trifoliin A. A variety of glycosidase activities were also detected in the fraction depleted of trifoliin A. These results suggest that enzymes in clover root exudate alter the trifoliin A-binding capsule in a way which would favor polar attachment of R. trifolii to clover root hairs.

Journal Article↗
PubMed1993

Cellular organisation of the Arabidopsis thaliana root.

The anatomy of the developing root of Arabidopsis is described using conventional histological techniques, scanning and transmission electron microscopy. The root meristem is derived from cells of the hypophysis and adjacent cells of the embryo proper. The postembryonic organization of the root is apparent in the mature embryo and is maintained in the growing primary root after germination. Cell number and location is relatively invariant in the primary root, with 8 cortical and endodermal cell files but more variable numbers of pericycle and epidermal cells. The organisation of cells in lateral roots is similar to that of the primary root but with more variability in the numbers of cell files in each layer. [3H]thymidine labeling of actively growing roots indicates that a quiescent centre of four central cells (derived from the hypophysis) is located between the root cap columella and the stele. This plate of four cells is surrounded by three groups of cells in, proximal, distal and lateral positions. The labeling patterns of these cells suggest that they are the initials for the files of cells that comprise the root. They give rise to four sets of cell files: the stele, the cortex and endodermis, the epidermis and lateral root-cap and the columella. A model of meristem activity is proposed based on these data. This description of Arabidopsis root structure underpins future work on the developmental genetics of root morphogenesis.

Arabidopsis↗
PubMed1980

Flagellar roots, mating structure and gametic fusion in the green alga Ulva lactuca (Ulvales).

The slightly anisogamous gametes of Ulva lactuca exhibit a cruciate flagellar root system consisting of 4 microtubular roots (4-2-4-2 system) and an elaborate system of fibrous roots associated with the 2-stranded microtubular roots. Two fibres (32-nm striation periodicity; system I fibres) closely underlie each of the 2-stranded roots, while different fibres (150-nm striation periodicity; system II fibres) run parallel to the root microtubules, and are 150-200 nm more internally located. Female gametes have 4 system II fibres, 3 of which are combined into a compound fibre associated with one microtubular root, while the fourth fibre is associated with the opposite root. In male gametes only 2 system II fibres are present, each underlying one of the two 2-stranded roots. A special region of the plasmalemma of both gamete types about 0.5 mum away from the basal bodies and located between 2 adjacent microtubular roots is structurally specialized and acts as a mating structure in gametic fusion. The region is oval-shaped and up to I.I mum long with a maximum diameter of 0.7 mum. A continuous electron-dense boundary layer underlies the plasmalemma at the edges of the mating structure. In both gamete types the mating structure consists of a fuzzy layer of material underlying the plasmalemma and special granules (60 nm diameter) are associated with this layer on its cytoplasmic side. In addition diffuse material overlies the mating structure, especially in male gametes. The mating structure is connected to 3 different kinds of flagellar roots: the boundary layer is linked to a 2-stranded microtubular root and its associated system I fibre; the fuzzy layer of the mating structure is connected with a system II fibre; and in female gametes this is the compound system II fibre. The ultrastructural changes which occur after mixing the 2 gamete types have been followed. Mating structure activation involves contraction of system II fibres (change of striation periodicity to 100 nm), detachment of special granules from the fuzzy layer of the mating structure and their replacement by electron-transparent vesicles at the prospective cell fusion site. Furthermore, release of electron-dense contents from Golgi-derived vesicles in the anterior part of both gamete types precedes cell fusion. Cell fusion is exclusively initiated in a region delimited by the 2 mating structures. After partial dissolution the 2 plasma membranes unite within the mating structure regions. The ultrastructure of gametic fusion in Ulva lactuca is compared to that of other green algae and the significance of flagellar roots in the mating process of green algae is discussed.

Chlorophyta↗
PubMed2001

Cellular events at the onset of physiological root resorption in rabbit deciduous teeth.

For elucidation of how physiological root resorption of deciduous teeth is initiated, the cellular events that occur surrounding the root of rabbit deciduous teeth before and at the onset of physiological root resorption were observed by means of light and electron microscopy. In addition, the cytodifferentiation of odontoclasts during the initial phase of this root resorption was evaluated by histochemical staining of tartrate-resistant acid phosphatase (TRAP) activity as a marker odontoclasts and their precursors. The present investigation was focused on the physiological root resorption of the deciduous lower second molar of rabbits from Day 0-5 postnatally. At birth, the deciduous molar had not erupted yet, and no TRAP-positive cell could be found surrounding the tissue adjacent to the root of the deciduous tooth. TRAP-positive mononuclear cells were initially detected in the coronal portion of the dental follicle of the permanent tooth at Day 1 postnatally. Ultrastructurally, these mononuclear cells had moderate numbers of mitochondria and short-strand rough endoplasmic reticulum, as well as scattered free ribosomes throughout their cytoplasm. TRAP-positive mononuclear cells then appeared in the cementoblast layer immediately adjacent to the surface of the deciduous roots. These mononuclear cells projected cytoplasmic extensions between the cementoblasts and made contact with the cementum. At that time, cell-cell contact was frequently observed between these mononuclear cells and cementoblasts. During 3-5 days postnatally, the number of TRAP-positive multinucleate odontoclasts on the root surface gradually increased. They had well-developed ruffled borders and made typical resorption lacunae on the root surface of the deciduous tooth. During this early postnatal period, neither inflammatory cells nor necrotic tissue could be observed surrounding the deciduous root. This study demonstrates that the dental follicle of the permanent tooth as well as the connective tissue adjacent to the deciduous root might play important role in site- and time-specific recruitment, development, and activation of odontoclasts before and at the onset of physiological root resorption.

Acid Phosphatase↗
PubMed2026

The circadian clock proteins PRR modulate root hair development via the RHD6/RSL module in Arabidopsis.

Root hairs, derived from trichoblasts, are critical for plant growth and environmental adaptation. Although environmental cues are known to influence root hair development, how endogenous timing systems such as the circadian clock integrate into the core transcriptional network governing root hair formation remains unclear. Here, we show that the circadian clock-associated protein PSEUDO-RESPONSE REGULATOR5 (PRR5) physically interacts with ROOT HAIR DEFECTIVE6 (RHD6) and RHD6 LIKE1 (RSL1), two basic helix-loop-helix transcription factors essential for root hair initiation. Genetic analyses suggest that PRR proteins contribute to root hair development under long-day conditions in Arabidopsis thaliana. Simultaneous disruption of PRR5, PRR7, and PRR9 results in defective root hairs, whereas PRR5 overexpression markedly increases root hair density and length. Transcriptomic and RT-qPCR analyses reveal that PRRs enhance the expression of RHD6, RSL1, and multiple downstream root hair-responsive genes, while modulating their temporal expression patterns. Furthermore, PRR5-mediated root hair promotion requires RHD6/RSL1, and PRR proteins enhance RHD6-dependent activation of the RSL4 promoter. PRRs also contribute to root hair development under phosphate-deficient and salt-stress conditions. Together, these findings establish a molecular framework in which PRR proteins regulate the RHD6/RSL network to coordinate root hair development and environmental responses.

Arabidopsis↗
PubMed2005

An investigation of microleakage from root-end fillings in ultrasonic retrograde cavities with or without finishing: a quantitative analysis.

OBJECTIVE: The aim of this study was to make a quantitative assessment of the sealing ability of Super-EBA, IRM, and Pro Root MTA root-end fillings subjected to 3 different finishing techniques. STUDY DESIGN: Eighty-one ultrasonically prepared root-end cavities in human canines were separated randomly into 3 test groups of 27 roots each. The cavities were filled with Super-EBA, IRM, or Pro Root MTA and finished by ball burnishing. Sequentially, 18 roots from each group received a final smoothing with either a 30-fluted tungsten carbide finishing bur or a Zekrya carbide 28-mm bur. Samples were prepared and immersed in 2% methylene blue dye neutral solution for 12 hours. Roots were ground into a powder and prepared for analysis in an absorbency spectrophotometer. RESULTS: The results revealed that Pro Root MTA displayed significantly less mean dye microleakage ( P < .05) than Super-EBA and IRM root-end fillings. The Super-EBA root-end fillings, although presenting a greater mean dye microleakage, did not differ significantly from IRM ( P > .05). The finishing technique did not significantly ( P > .05) affect the incidence of microleakage among the materials tested. CONCLUSIONS: The favorable results obtained with MTA in leakage studies may be related to its good marginal adaptation. Spectrophotometric analysis may provide valuable information about the sealing capacity of root-end fillings. None of the procedures tested were able to avoid leakage, a finding that stresses the importance of the eradication of irritants within the root canal system.

Aluminum Compounds↗
PubMed2003

The promotive effect of latrunculin B on maize root gravitropism is concentration dependent.

The cytoskeleton has been proposed to be a key player in the gravitropic response of higher plants. A major approach to determine the role of the cytoskeleton in gravitropism has been to use inhibitors to disrupt the cytoskeleton and then to observe the effect that such disruption has on organ bending. Several investigators have reported that actin or microtubule inhibitors do not prevent root gravitropism, leading to the conclusion that the cytoskeleton is not involved in this process. However, there are recent reports showing that disruption of the actin cytoskeleton with the actin inhibitor, latrunculin B, promotes the gravitropic response of both roots and shoots. In roots, curvature is sustained during prolonged periods of clinorotation despite short periods of gravistimulation. These results indicate that an early gravity-induced signal continues to persist despite withdrawal of the constant gravity stimulus. To investigate further the mechanisms underlying the promotive effect of actin disruption on root gravitropism, we treated maize roots with varying concentrations of latrunculin B in order to determine the lowest concentration of latrunculin B that has an effect on root bending. After a 10-minute gravistimulus, treated roots were axially rotated on a one rpm clinostat and curvature was measured after 15 hours. Our results show that 100 nM latrunculin B induced the strongest promotive effect on the curvature of maize roots grown on a clinostat. Moreover, continuously gravistimulated roots treated with 100 nM latrunculin B exhibited stronger curvature responses while decapped roots treated with this concentration of latrunculin B did not bend during continuous gravistimulation. The stronger promotive effect of low concentrations of latrunculin B on the curvature of both clinorotated and continuously gravistimulated roots suggests that disruption of the finer, more dynamic component of the actin cytoskeleton could be the cause of the enhanced tropic responses of roots to gravity.

Actins↗
PubMed1998

Ultrasonic root end cavity preparation assessed by an in situ impression technique.

PROBLEM: In vitro studies have demonstrated microfractures in resected roots after root end cavity preparation with ultrasonic tips. Such microfractures are of concern; however, they may be artifacts. OBJECTIVES: To assess the incidence of microfractures after ultrasonic root end cavity preparation in situ. STUDY DESIGN: Fifty-two roots in two cadavers were endodontically treated, the soft tissues excised, and the root ends exposed and resected. The resected root surfaces were replicated with polyvinylsiloxane impressions. Root end cavities were prepared with ultrasonic tips, then impressed a second time. The roots were retrieved; 25 were processed for direct SEM examination as were both the impressions of each root. The specimens were examined by stereomicroscope and scanning electron microscope. RESULTS: In the impressions, the resected and prepared surfaces appeared irregular, but none demonstrated microfractures. In contrast, 15 retrieved roots showed microfractures. CONCLUSIONS: Ultrasonic root end cavity preparation in situ did not cause root microfractures, and the impression technique could be clinically usable with minor modifications.

Artifacts↗
PubMed2003

Touch modulates gravity sensing to regulate the growth of primary roots of Arabidopsis thaliana.

Plants must sense and respond to diverse stimuli to optimize the architecture of their root system for water and nutrient scavenging and anchorage. We have therefore analyzed how information from two of these stimuli, touch and gravity, are integrated to direct root growth. In Arabidopsis thaliana, touch stimulation provided by a glass barrier placed across the direction of growth caused the root to form a step-like growth habit with bends forming in the central and later the distal elongation zones. This response led to the main root axis growing parallel to, but not touching the obstacle, whilst the root cap maintained contact with the barrier. Removal of the graviperceptive columella cells of the root cap using laser ablation reduced the bending response of the distal elongation zone. Similarly, although the roots of the gravisensing impaired pgm1-1 mutant grew along the barrier at the same average angle as wild-type, this angle became more variable with time. These observations imply a constant gravitropic re-setting of the root tip response to touch stimulation from the barrier. In wild-type plants, transient touch stimulation of root cap cells, but not other regions of the root, inhibited both subsequent gravitropic growth and amyloplast sedimentation in the columella. Taken together, these results suggest that the cells of the root cap sense touch stimuli and their subsequent signaling acts on the columella cells to modulate their graviresponse. This interaction of touch and gravity signaling would then direct root growth to avoid obstacles in the soil while generally maintaining downward growth.

Arabidopsis↗
PubMed2001

Deciduous canine and permanent lateral incisor differential root resorption.

When a permanent maxillary canine erupts apical to the permanent lateral incisor and the deciduous canine, resorption typically takes place only on the deciduous canine root. An understanding of this differential resorption could provide insight into the reasons for excessive iatrogenic root resorption during orthodontic tooth movement. The purpose of the present study was to examine the response of roots of permanent lateral incisors and deciduous canines to simulated resorption, and to acid and enzyme attack, reflecting the physiologic environment of an erupting permanent canine. Groups of maxillary permanent lateral incisor and deciduous canine roots were exposed to 5 combinations of Ten Cate demineralizing solution, Ten Cate demineralizing solution with EDTA, and a Type I collagenase solution. Sections of the roots were examined under a polarized light microscope. Analysis of variation of the resulting root lesions demonstrated that the lesion depths for deciduous canines were greater than those for permanent lateral incisors when averaged across 4 of the conditions (F(1,24) = 7.49, P =.0115). On average, deciduous canine roots demonstrated lesions 10% deeper than did permanent lateral incisor roots. We concluded that when deciduous canine and permanent lateral incisor roots are subjected to acid and enzyme attack, reflecting the physiologic environment of an erupting permanent canine, significantly deeper demineralized lesions are seen in the deciduous roots compared with the permanent roots. This finding may partially explain the differential root resorption during permanent tooth eruption.

Acids↗
PubMed1999

Histological and histochemical quantification of root resorption incident to the application of intrusive force to rat molars.

This study was conducted to investigate the nature of root resorption resulting from intrusive forces applied to the rat lower molars, by means of histological and histochemical techniques with tartrate resistant acid phosphatase (TRAP). Thirty-eight 13-week-old Wistar strain male rats were used. Intrusive force was created by a fixed appliance which was adjusted to exert an initial force of 50 g for the duration of 1, 2, and 3 weeks. The degree of root resorption and distribution of TRAP positive cells were evaluated. On the root surface, the TRAP positive scores were low in the apical regions. Significant differences in the scores were found in the inter-radicular region of the roots between the experimental and control groups for the 2- and 3-week groups. More active resorption of bone occurred during the experimental period, as denoted by greater TRAP positive scores on the bone than on the root surface. Root resorption scores in the apical root region were larger in the 2- and 3-week groups than in the 1-week group. Significant differences in the root resorption scores were also found between the 1- and 3-week groups in the inter-radicular region, indicating that intrusive force application of a longer duration may lead to a higher frequency of root resorption. It is shown that, irrespective of the level of TRAP positive cells and root resorption scores, the degree of root resorption activity is higher in the apical root region than in the inter-radicular area. These results indicate that cellular cementum may be resorbed more easily because of its richer organic components and low mineralized structure.

Acid Phosphatase↗
PubMed1985

A morphometric analysis of the redistribution of organelles in columella cells in primary roots of normal seedlings and agravitropic mutants of Hordeum vulgare.

The redistribution of organelles in columella cells of horizontally-oriented roots of Hordeum vulgare was quantified in order to determine what structural changes in graviperceptive (i.e., columella) cells are associated with the onset of the root gravicurvature. The sedimentation of amyloplasts is the only major change in cellular structure that correlates positively with the onset of root gravicurvature, which begins within 15 min after re-orientation. There is no consistent contact between sedimented amyloplasts and any other organelles. Nuclei are restricted to the proximal ends of columella cells in vertically-oriented roots, and remain there throughout gravicurvature after roots are oriented horizontally. Root gravicurvature does not involve significant changes in (1) the volume of columella cells, (2) the relative or absolute volumes of organelles in columella cells, or (3) the distribution of endoplasmic reticulum (ER). The size, number and sedimentation rates of amyloplasts in columella cells of non-graviresponsive roots of mutant seedlings are not significantly different from those of graviresponsive roots of normal seedlings. Similarly, there is no significant difference in (1) cellular volume, (2) distribution or surface area of ER, (3) patterns or rates of organelle redistribution in horizontally-oriented roots, (4) relative or absolute volumes of organelles in columella cells of graviresponsive and non-graviresponsive roots. These results suggest that the lack of graviresponsiveness by roots of mutant seedlings is probably not due to either (1) structural differences in columella cells, or (2) differences in patterns or rates of organelle redistribution as compared to that characteristic of graviresponsive roots. Thus, the basis of non-graviresponsiveness in this mutant is probably different from other agravitropic mutants so far studied.

Endoplasmic Reticulum↗
PubMed2004

Investigation of the effect of the coronal restoration quality on the composition of the root canal microflora in teeth with apical periodontitis by means of T-RFLP analysis.

AIM: To investigate the effect of the radiographic and clinical quality of coronal restorations on the composition of the root canal flora of teeth with necrotic pulps and teeth with root fillings associated with apical periodontitis. METHODOLOGY: Twenty-eight necrotic pulps and 35 root filled canals with signs of apical periodontitis were studied. Both the coronal filling (presence of radiographically or clinically deficient margins and/or secondary caries) and the root filling (homogeneity and length) were scored. Bacterial root canal samples were taken with sterile paper points under rubber dam and using measures to prevent contamination. A DNA-based nonculture bacterial identification technique was used, namely terminal restriction fragment length polymorphism (T-RFLP) analysis. RESULTS: Twelve samples were negative for bacterial DNA. A total of 33 different terminal restriction fragments (TRFs) were detected. The Fusobacterium nucleatum/Streptococcus mitis group was the most frequently encountered TRF. The mean number of TRFs per necrotic pulp was 6.2 and 5.8 for the groups with acceptable and unacceptable coronal restorations, respectively. This difference was not significant. In the root filled group, these values (respectively, 5.2 and 8.6) were statistically significantly different (P < 0.05). The following parameters in root filled teeth had no significant influence on the mean numbers of TRFs detected: the length and homogeneity of the root filling and the type of tooth (anterior-premolar-molar). CONCLUSION: T-RFLP allowed the rapid assessment of bacterial biodiversity in root canal samples. The technique revealed the presence of bacteria that have rarely been described in the root canals of teeth with apical periodontitis. Biodiversity in the root filled group was high, as compared with culture-dependent studies where monoinfections were more frequently reported. Only in root filled teeth did defective coronal restorations have a statistically significant influence on the mean numbers of detected TRFs per sample.

Adult↗
PubMed2006

An ex vivo evaluation of a new root canal irrigation technique with intracanal aspiration.

AIM: To evaluate the effectiveness of a new root canal irrigation technique with intracanal aspiration in removing the smear layer and to assess irrigant extrusion ex vivo. METHODOLOGY: Thirty-five instrumented canals of extracted human canine teeth that had been resected apically by removing 3 mm of the root tip were divided into one control and four experimental groups of seven teeth each. The roots were fixed in a plastic case and surrounded with normal saline agar coloured with 1% acid red. No irrigation was performed in the control teeth. Each root canal in the experimental groups was irrigated with 9 mL of 14% ethylenediaminetetraacetic acid for 3 min, and then with 6 mL of 6% sodium hypochlorite (NaOCl) for 2 min. In the intracanal aspiration technique, the irrigant was delivered from the tip of an injection needle placed 12 mm from the apical root-end and an aspiration needle that was connected to a Root ZX apex locator placed 2 and 3 mm short of the apical root-end in groups 1 and 2, respectively. In the conventional method, the tip of an injection needle used for delivery of the irrigant and as an active electrode was placed 2 and 3 mm short of the apical root-end in groups 3 and 4, respectively, the tip of the aspiration needle was placed 12 mm from the apical root-end in these groups. The readings of the Root ZX during irrigation were recorded. The cleanliness of the canal was evaluated by scoring smear layer from scanning electron microscopy (SEM) images of the canal. Extrusion of NaOCl was detected by measuring the discoloured area of the agar around the apical root-end. The data obtained were statistically analysed by one-way anova, the Kruskal-Wallis test and Friedman's test. RESULTS: In the SEM study, the canals in groups 1-3 were significantly cleaner than those in the control and group 4 (P < 0.05). The mean Root ZX readings in groups 1-3 were approximately "0.5". The discoloured area in group 3 was significantly larger than the other groups (P < 0.05). CONCLUSIONS: Irrigation using the intracanal aspiration technique allowed more effective removal of the smear layer than that performed by the conventional method in an apically resected canine tooth. The intracanal aspiration technique produced limited extrusion of the irrigant beyond the apical foramen.

Apicoectomy↗