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PubMed2003

Nylon filter arrays reveal differential gene expression in proteoid roots of white lupin in response to phosphorus deficiency.

White lupin (Lupinus albus) adapts to phosphorus deficiency (-P) by the development of short, densely clustered lateral roots called proteoid (or cluster) roots. In an effort to better understand the molecular events mediating these adaptive responses, we have isolated and sequenced 2,102 expressed sequence tags (ESTs) from cDNA libraries prepared with RNA isolated at different stages of proteoid root development. Determination of overlapping regions revealed 322 contigs (redundant copy transcripts) and 1,126 singletons (single-copy transcripts) that compile to a total of 1,448 unique genes (unigenes). Nylon filter arrays with these 2,102 ESTs from proteoid roots were performed to evaluate global aspects of gene expression in response to -P stress. ESTs differentially expressed in P-deficient proteoid roots compared with +P and -P normal roots include genes involved in carbon metabolism, secondary metabolism, P scavenging and remobilization, plant hormone metabolism, and signal transduction.

Algorithms↗

PubMed1991

Postnatal development of small and large dorsal root ganglion neurons in the cat. A study on cervical levels (C5-C6) and on phrenic afferents.

During feline postnatal development, the size of phrenic afferent neurons labelled by horseradish peroxidase was evaluated in comparison to that of the bulk of counterstained neurons located in the same cervical dorsal root ganglia (DRG) (C5-C6). From age 1 week to maturity, small and large cell components were individualized from experimental size distributions using a mathematical approach. The analysis of data in adult indicated a close correspondence between small cells and unmyelinated afferents and between large cells and myelinated afferents, respectively. From age 1 week to adulthood, mean increases in cell diameter ranged between 10 microns (small cells from phrenic afferents) and 29.5 microns (large counterstained cells). In each population, the ratio of small/large cells remained constant during growth. In contrast to data in adults, at 1 week, large phrenic neurons were bigger than the counterstained ones. At 19 weeks, the cat DRG cells had not yet reached their adult size.

Animals↗

PubMed1979

A comparison of glutamate synthase obtained from maize endosperms and roots.

Glutamate synthase (EC 2.6.1.53) has been examined in developing endosperms and roots of maize. KCl is required for maximum activity in each tissue. The effect with KCl is seen with buffer strength of 25 to 100 millimolar in the assay. The optimum concentration for the enzyme from endosperm is 20 millimolar and for the enzyme from root tissue the saturating concentration is about 20 millimolar. In root material the enzyme is labile but activity can be restored if KCl is added to the assay. Divalent cations such as Mg(2+) or Mn(2+) also activate the enzyme to some extent.In each case NADH or NADPH can serve as reductant. The reaction is insensitive to alpha-aminooxyacetate, but is inhibited by glutamate, the glutamate analogs methionine sulfoximine and methionine sulfone, and by the glutamine analogs azaserine and albizziin.

Journal Article↗

PubMed1992

An mRNA that specifically accumulates in maize roots delineates a novel subset of developing cortical cells.

A near full-length cDNA clone (pZRP3) corresponding to an mRNA that accumulates specifically in roots of maize was isolated. The ZRP3 mRNA is ca. 600 nucleotides in length. The amino acid sequence of the predicted polypeptide is rich in leucine (16%), proline (11%), and cysteine (8.5%). The zrp3 gene appears to be expressed exclusively in roots, whereas other ZRP3-related genes are expressed in additional organs of the maize plant. In situ hybridization shows that ZRP3 mRNA accumulation is largely confined to the cells of the cortical ground meristem. Furthermore, accumulation of this mRNA occurs within a distinct subset of cortical cells, the inner three to four cell layers.

Amino Acid Sequence↗

PubMed1995

Nod factors produced by Rhizobium leguminosarum biovar viciae induce ethylene-related changes in root cortical cells of Vicia sativa ssp. nigra.

Vicia sativa ssp. nigra plants develop the "Thick short root" (Tsr) phenotype when both (i) the roots are inoculated with the root nodule inducing bacterium Rhizobium leguminosarum biovar viciae, and (ii) the plants, including the roots, are grown in the light. Tsr roots have a reduced length, are locally twice as thick as normal roots and have an increased number of root hairs. Development of the Tsr phenotype is correlated with the presence of nod (nodulation) genes in the rhizobia. Nod factors (lipochitin oligosaccharides), products of these nod genes, can induce the Tsr phenotype in the absence of rhizobia. The Tsr phenotype can be mimicked by addition of the ethylene-releasing compound ethephon. Using several microscopical techniques, we compared roots showing the Tsr phenotype (Tsr roots) with normal roots and roots grown in the presence of the ethylene inhibitor aminoethoxyvinylglycine (AVG). The thickening of Tsr roots appeared to be caused by a swelling of the cortical cells, which corresponded with (i) a reorientation of the interphase cortical microtubules from a transverse to a longitudinal direction, (ii) general cell wall modifications, (iii) frequent absence of middle lamellae, and (iv) local maceration. The same changes could be induced by ethephon and were inhibited by AVG. This strongly suggests that the Tsr phenotype is caused by excessive ethylene production. The ethylene-related changes mentioned above are also seen during infection thread formation, but only very locally. Apparently, Vicia roots when grown in the light overrespond to Nod factors leading to overproduction of ethylene and to a non-local "ripening" process. These phenomena inhibit nodulation of the main root by preventing formation of pre-infected threads and by reducing formation of root nodule primordia. Local controlled production of ethylene, as induced by Nod factors, may, however, be an essential element of the nodulation process.

Cell Wall↗

PubMed1996

Modulated expression of plasminogen activator system components in cultured cells from dissociated mouse dorsal root ganglia.

The development and regeneration of the peripheral nervous system (PNS) is highly dependent on the migration of Schwann cells and the extension of axons toward their distant targets. Plasminogen activators (PAs) are associated with the surface of several cell types of neural origin where they are believed to mediate localized degradation of extracellular matrix, thus facilitating cell motility. In this study, we characterize the expression of tissue-type (tPA) and urokinase (uPA) PAs, as well as the urokinase cell surface receptor (uPAR) during differentiation of cultured cells from mouse dorsal root ganglia. During the first day in culture, the mRNA levels of all three components increase from 75- to 163-fold, as shown using a quantitative PCR method. By 72 hr, the mRNA levels decrease and approach basal levels. This transient increase is in direct correlation with the differentiation of neurons and Schwann cells and the formation of a neuritic network in these regenerating cultures. Densitometric analysis of gel zymographs demonstrates that the elevation in mRNA levels is accompanied by similar increases in the activity levels of tPA and uPA. Interestingly, in situ hybridization studies of the cultures show that tPA mRNA is restricted to small sensory neurons, whereas uPA mRNA is localized predominantly in large sensory neurons. uPAR mRNA is expressed by both neuronal subpopulations and, to a lesser extent, by Schwann cells and fibroblasts. Taken together, these results further support a role for the PA system in facilitating axon extension and cell migration during development and regeneration of the PNS.

Animals↗

PubMed2000

Tornado1 and tornado2 are required for the specification of radial and circumferential pattern in the Arabidopsis root.

The cell layers of the Arabidopsis primary root are arranged in a simple radial pattern. The outermost layer is the lateral root cap and lies outside the epidermis that surrounds the ground tissue. The files of epidermal and lateral root cap cells converge on a ring of initials (lateral root cap/epidermis initial) from which the epidermal and lateral root cap tissues of the seedling are derived, once root growth is initiated after germination. Each initial gives rise to a clone of epidermal cells and a clone of lateral root cap cells. These initial divisions in the epidermal/lateral root cap initial are defective in tornado1 (trn1) and trn2 plants indicating a requirement for TRN1 and TRN2 for initial cell function. Furthermore, lateral root cap cells develop in the epidermal position in trn1 and trn2 roots indicating that TRN1 and TRN2 are required for the maintenance of the radial pattern of cell specification in the root. The death of these ectopic lateral root cap cells in the elongation zone (where lateral root cap cells normally die) results in the development of gaps in the epidermis. These observations indicate that TRN1 and TRN2 are required to maintain the distinction between the lateral root cap and epidermis and suggest that lateral root cap fate is the default state. It also suggests that TRN1 and TRN2 repress lateral root cap fate in cells in the epidermal location. Furthermore, the position-dependent pattern of root hair and non-root hair cell differentiation in the epidermis is defective in trn1 and trn2 mutants. Together these results indicate that TRN1 and TRN2 are required for the maintenance of both the radial pattern of tissue differentiation in the root and for the subsequent circumferential pattern within the epidermis.

Arabidopsis↗

PubMed1986

Numbers of rat dorsal root axons and ganglion cells during postnatal development.

The present study demonstrates that T4 and S2 rat dorsal root axons decrease significantly from birth to adulthood with almost all of the decrease occurring in the first two weeks of life. Dorsal root ganglion cell numbers do not change during this time period. This is thus an example of postnatal axon elimination not associated with death of the cells that give rise to the axons. Presumably this regressive process is important in the formation of the normal adult nervous system. In addition, these findings raise the possibility that certain types of neonatal denervation may increase adult axon numbers by stopping a regressive process, the loss of axons, rather than initiating a progressive process, the formation of new axons.

Animals↗

PubMed1998

[The effects of fluoride and dexamethasone on the phenotypic development of osteoblast grown on the demineralized dental root surface]

OBJECTIVE: To investigate the effects of the phenotypic development of osteoblast growing on the periodontitis affected root surface in the condition with fluoride and dexamethasone.METHODS:Cell culture technique in vitro had been used to study the growth condition of MC3T3-E1 osteoblast line on the surf ace of cementum treated with various methods.RESULTS:The present study showed that osteoblast treated with fluoride and dexamethasone had a better cellular growth behavior.CONCLUSION: The results demonstrated that demineralization procedure by citric acid might promote the osteoblasts attachment and growth on root surface; and dexamethasone and low dose fluoride were of benefit to maintain the phenotype of osteoblast as well as promote the maturation of bone-like matrix and increase the mineralization formation.

Journal Article↗

PubMed1998

[Injuries to the permanent teeth. Periodontal lesions].

Tooth luxations are relatively common. In case of concussion or subluxation the tooth is not displaced. The treatment will consist of relief of the tooth. Most frequent complications are pulp necrosis and obliteration of pulpal tissues. In case of extrusive luxation pulpal tissues and the periodontal ligament are injured. When tooth mobility is increased flexible splinting should be considered. Endodontic treatment is necessary after extrusive luxation of a tooth with completed root formation. Teeth with open apex often show pulpal obliteration after extensive luxation. Lateral luxation is more complex than extrusive luxation since the alveolar bone is also damaged. Repositioning and splinting of the tooth are necessary. When the apical foramen in closed, endodontic treatment will be necessary. Teeth with incomplete root formation will develop pulp obliteration. Following lateral luxation, external root resorption and loss of marginal bone are not infrequent. Intrusive luxation is the type of trauma with most unfavorable prognosis. All intruded teeth will become necrotic and external root resorption and marginal bone loss are frequent. There is no consensus regarding the therapeutic approach. Orthodontic extrusion or surgical mobilisation are possible options. In case of avulsion, both the pulpal tissues and the periodontal ligament are disrupted. Preservation of the vitality of the periodontal ligament covering the root will determine the prognosis of the reimplanted tooth. Therefore the tooth will be repositioned as soon as possible. When this is not possible, milk or a specific solution are most appropriate for tooth conservation. When the reimplanted tooth has complete root formation, devitalization will be performed one week after after repositioning. In case of a tooth with open apex revascularisation can be awaited. Healing of the periodontal ligament will determine prognosis. When a normal ligament is obtained during healing or when surface resorption is obtained, the tooth can be preserved for a long period. When progressive replacement resorption (ankylosis) develops, most teeth can remain in position for about 10 years. When inflammatory resorption develops, the tooth will be lost within a short time.

Dental Pulp Calcification↗

PubMed1970

Time course of exudation from excised corn root segments of different stages of development.

Xylem exudates were collected at hourly intervals from short segments which had been excised from two portions of the primary root of corn (Zea mays L.) seedlings and partially immersed in experimental salt solution containing (86)Rb. All segments showed variation in rates of output of both volume and ions for several hours, after which a steady state was attained which persisted for many hours. Apical segments produced little or no exudate for several hours and did not reach a steady state until 18 or more hours after excision. Basal segments produced exudate containing detectable quantities of isotope within an hour and they reached a steady state about 12 hours after excision. During their respective steady states, apical segments produced three times the volume per hour and translocated eight times as much Rb per hour as did basal segments.These differences in the time course of exudation and the large differences in output are interpreted as indicating that two independent systems of ion transport operate simultaneously in intact roots. If this interpretation is correct, then it would appear that one of these systems has a greater potential capacity for ion transport than the other.

Journal Article↗

PubMed2000

In vivo colocalization of xyloglucan endotransglycosylase activity and its donor substrate in the elongation zone of Arabidopsis roots.

We have developed a method for the colocalization of xyloglucan endotransglycosylase (XET) activity and the donor substrates to which it has access in situ and in vivo. Sulforhodamine conjugates of xyloglucan oligosaccharides (XGO-SRs), infiltrated into the tissue, act as acceptor substrate for the enzyme; endogenous xyloglucan acts as donor substrate. Incorporation of the XGO-SRs into polymeric products in the cell wall yields an orange fluorescence indicative of the simultaneous colocalization, in the same compartment, of active XET and donor xyloglucan chains. The method is specific for XET, as shown by competition experiments with nonfluorescent acceptor oligosaccharides, by negligible reaction with cello-oligosaccharide-SR conjugates that are not XET acceptor substrates, by heat lability, and by pH optimum. Thin-layer chromatographic analysis of remaining unincorporated XGO-SRs showed that these substrates are not extensively hydrolyzed during the assays. A characteristic distribution pattern was found in Arabidopsis and tobacco roots: in both species, fluorescence was most prominent in the cell elongation zone of the root. Proposed roles of XET that include cell wall loosening and integration of newly synthesized xyloglucans could thus be supported.

Arabidopsis↗

PubMed2003

Autogenous free tooth transplantation with a two-stage operation technique.

If tooth transplantation is to succeed, it is crucial to preserve the vitality of the cells on the root surface of the tooth transplant. Insufficient postoperative nutrition to the cells on the root surface of the tooth transplant was thought to contribute to their devitalization of these cells. Impaired nutrition may be a result of poor contact between the recipient bed and the root surface of the transplanted tooth, and development of an interposed blood clot. To improve postoperative nutrition to the root surface cells, teeth were transplanted to the recipient beds in which the tissues were regenerated during a 14 day period, i.e., using the two-stage transplantation technique. In a clinical study of this technique, a total of 95 autogenous teeth with fully developed roots were transplanted in 84 patients, and examined both clinically and radiographically for up to 13 years after the transplantation. In a dog model, a comparative experimental study was made between teeth transplanted to beds left to heal for 5 days and teeth transplanted to beds prepared immediately before the transplantation. The clinical study showed a low prevalence of tooth graft loss and root resorption even when infection of the root canal occurred. Periodontal attachment loss of less than 3 mm was found in 97% of 6 defined surfaces around the transplanted teeth. Transplanted teeth which were later extracted were often hypermobile, and signalled pain when provoked with heavy loading. Excessive extraction trauma, fixation failure, and excessive plaque accumulation after transplantation were all shown to be detrimental to tooth transplant. Transplanted teeth were used as abutments for fixed partial dentures and provided the necessary dental support for crowns and bridges even in patients with atrophic alveolar bone. The experimental histological study showed no differences between test and control teeth in terms of the prevalence of root resorption, which was suspected to be caused by traumatic injuries to the roots during extraction and non-rigid fixation of the transplanted teeth.

Age Factors↗

PubMed2003

Root canal disinfection: a review of concepts and recent developments.

This paper reviews current concepts of root canal infection and the consequences for endodontic treatment strategies and practices. In particular, root canal disinfection by chemical and mechanical means is discussed, as are the possibilities and limitations of proposed methods to reduce the time necessary to obtain a disinfected canal.

Bacterial Infections↗

PubMed2006

Dynamics of Aerenchyma distribution in the cortex of sulfate-deprived adventitious roots of maize.

BACKGROUND AND AIMS: Aerenchyma formation in maize adventitious roots is induced in nutrient solution by the deprivation of sulfate (S) under well-oxygenated conditions. The aim of this research was to examine the extent of aerenchyma formation in the cortex of sulfate-deprived adventitious roots along the root axis, in correlation with the presence of reactive oxygen species (ROS), calcium levels and pH of cortex cells and root lignification. METHODS: The morphometry of the second whorl of adventitious (W2) roots, subject to S-deprivation conditions throughout development, was recorded in terms of root length and lateral root length and distribution. W2 roots divided into sectors according to the mean length of lateral roots, and cross-sections of each were examined for aerenchyma. In-situ detection of alterations in ROS presence, calcium levels and pH were performed by means of fluorescence microscopy using H(2)DCF-DA, fluo-3AM and BCECF, respectively. Lignification was detected using the Wiesner test. KEY RESULTS: S-deprivation reduced shoot growth and enhanced root proliferation. Aerenchyma was found in the cortex of 77 % of the root length, particularly in the region of emerging or developing lateral roots. The basal and apical sectors had no aerenchyma and no aerenchyma connection was found with the shoot. S-deprivation resulted in alterations of ROS, calcium levels and pH in aerenchymatous sectors compared with the basal non-aerenchymatous region. Lignified epidermal layers were located at the basal and the proximal sectors. S-deprivation resulted in shorter lateral roots in the upper sectors and in a limited extension of the lignified layers towards the next lateral root carrying sector. CONCLUSIONS: Lateral root proliferation is accompanied by spatially localized induced cell death in the cortex of developing young maize adventitious roots during S-deprivation.

Calcium↗

PubMed1995

The development of cell pattern in the root epidermis.

The root epidermis of most angiosperms is composed of a patterned array of hair and non-hair cells. Hair cells may develop randomly in any location in the epidermis (type 1), from specialized cells that form as result of an asymmetric cell division in a mother cell (type 2) or cells may be arranged in files of one cell type or the other (type 3). The development of the epidermis in Arabidopsis has been examined in detail and corresponds to type 3 epidermal development. A combination of physiological and genetic observations indicates that ethylene is a positive regulator of root hair differentiation. Differential exposure of epidermal cells to ethylene as a result of the cellular geometry of the root may account for the wild-type epidermal pattern.

Arabidopsis↗

PubMed2002

Genetic diversity of root-knot nematodes from Brazil and development of SCAR markers specific for the coffee-damaging species.

RAPD markers were used to characterize the genetic diversity and relationships of root-knot nematodes (RKN) (Meloidogyne spp.) in Brazil. A high level of infraspecific polymorphism was detected in Meloidogyne arenaria, Meloidogyne exigua, and Meloidogyne hapla compared with the other species tested. Phylogenetic analyses showed that M. hapla and M. exigua are more closely related to one another than they are to the other species, and illustrated the early divergence of these meiotically reproducing species from the mitotic ones. To develop a PCR-based assay to specifically identify RKN associated with coffee, three RAPD markers were further transformed into sequence-characterized amplified region (SCAR) markers specific for M. exigua, Meloigogyne incognita and Meloidogyne paranaensis, respectively. After PCR using the SCAR primers, the initial polymorphism was retained as the presence or absence of amplification. Moreover, multiplex PCR using the three pairs of SCAR primers in a single reaction enabled the unambiguous identification of each species, even in mixtures. Therefore, it is concluded that the method developed here has potential for application in routine diagnostic procedures.

Animals↗

PubMed2000

Employing a transgenic animal model to obtain cementoblasts in vitro.

BACKGROUND: Proper formation of cementum, a mineralized tissue lining the tooth root surface, is required for development of a functional periodontal ligament. Further, the presence of healthy cementum is considered to be an important criterion for predictable restoration of periodontal tissues lost as a consequence of disease. Despite the significance of cementum to general oral health, the mechanisms controlling development and regeneration of this tissue are not well understood and research has been hampered by the lack of adequate in vitro experimental models. METHODS: In an effort to establish cementoblast cell populations, without the trappings of a heterogeneous population containing periodontal ligament (PDL) cells, cells were obtained from the root surface of first mandibular molars of OC-TAg transgenic mice. These mice contain the SV40 large T-antigen (TAg) under control of the osteocalcin (OC) promoter. Therefore, only cells that express OC also express TAg and are immortalized in vitro. Based on results of prior in situ studies, OC is expressed by cementoblasts during root development, but not by cells within the PDL. Consequently, when populations are isolated from developing molars using collagenase/trypsin digestion, only cementoblasts, not PDL cells, are immortalized and thus, will survive in culture. RESULTS: The resulting immortalized cementoblast population (OC/CM) expressed bone sialoprotein (BSP), osteopontin (OPN), and OC, markers selective to cells lining the root surface. These cells also expressed type I and XII collagen and type I PTH/PTHrP receptor (PTH1R). In addition to expression of genes associated with cementoblasts, OC/CM cells promoted mineral nodule formation and exhibited a PTHrP mediated cAMP response. CONCLUSIONS: This approach for establishing cementoblasts in vitro provides a model to study cementogenesis as required to enhance our knowledge of the mechanisms controlling development, maintenance, and regeneration of periodontal tissues.

Animals↗