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PubMed1988

Oral condition in children treated with bone marrow transplantation.

Oral health was studied in 49 children below 12 years of age treated with bone marrow transplantation (BMT). Dental treatment prior to BMT was required in 41% of the children. Ulceration of the mucous membranes in the mouth was observed in 37% of the patients during treatment. Those given methotrexate as prophylaxis against graft-versus-host disease (GVHD) exhibited oral ulcerations more frequently (p less than 0.05) than those given cyclosporin. One year after BMT all patients with a clinical chronic GVHD exhibited changes in the oral mucosa. During the first year after BMT 31% of the children developed carious lesions. Children treated with 10 Gy total body irradiation (TBI) had a significantly (p less than 0.05) reduced salivary secretion rate. Dental development was severely affected in children treated with TBI. These disturbances consisted of arrested root development, enamel hypoplasias and microdontia.

Bone Marrow Transplantation↗
PubMed1981

Endodontic treatment during root formation.

Various forms of endodontic treatment may be used in an attempt to maintain pulpal vitality during the period of root formation. In teeth with advanced caries but with no clinical evidence of pulpitis, indirect pulp capping with the retention of a small amount of softened dentine in the base of the cavity is preferable to further excavation and direct capping of a resulting exposure. Direct capping of pulpal exposures in traumatized incisors is confined to teeth in which the tissue loss is limited and the exposure is small and recent. Where there is more serious contamination of the pulp, whether by trauma or by caries, pulpotomy is indicated. In each of these three forms of treatment, calcium hydroxide is the dressing of choice. In incompletely formed teeth with necrotic pulps, the anatomy of the root canal poses problems which may not be entirely evident radiographically because of differential root development in the buccolingual and mesiodistal planes, whilst surgical treatment may result in excessive root shortening, besides being unacceptable to many patients. Treatment of these teeth is directed towards stimulating calcific closure of the apical foramen, preparatory to the insertion of a conventional root filling. Important factors in this form of treatment are the removal of necrotic tissue from the root canal, the preservation of vital tissue in the apical part of the root, and the use of a suitable agent as a root canal dressing. Calcium hydroxide is the agent of choice for this purpose.

Calcium Hydroxide↗
PubMed1992

Initial formation of cellular intrinsic fiber cementum in developing human teeth. A light- and electron-microscopic study.

The present study describes the formative process of the initiation of cellular intrinsic fiber cementum (CIFC) in still growing human teeth. From 29 premolars and molars with incomplete roots developed to 60-90% of their final length, 8 premolars (with roots formed to three quarters of their final length) were selected for electron-microscopic investigation. All teeth were clinically intact and prefixed in Karnovsky's fixative immediately after extraction. Most of them were decalcified in ethylene diaminetetraacetic acid (EDTA), and the apical part of the roots was divided axially into mesial and distal portions that were subdivided in about 5 slices each. Following osmication and embedding in Epon, these blocks were cut for light- and electron-microscopic examination. In addition, 5 teeth with incomplete roots were freed from organic material and processed for scanning electron microscopy. It was found that CIFC-initiation commenced very close to the advancing root edge and resulted in a rapid cementum thickening. Thereafter, appositional growth continued on the already established cementum surface. Large, basophilic and rough endoplasmic reticulum-rich cementoblasts, some of which became cementocytes, were responsible for both fast and slow CIFC-formation. The CIFC-matrix was free of Sharpey's fibers and composed of more or less organized intrinsic collagen fibrils, in part fibril bundles, that ran roughly parallel to the root surface. Initially, the cementum fibrils intermingled with those of the dentinal collagen fibrils, which were not yet mineralized. This boundary subsequently underwent calcification. The development of collagen fibril bundles and their extracellular arrangement were associated with cytoplasmic processes probably involved in fibril formation and fibril assembly. Many cementoblasts contained intracytoplasmic, membrane-bounded collagen fibrils, which probably were related to fibril formation rather than degradation.

Adolescent↗
PubMed1996

Temperature-sensitive mutations that arrest Arabidopsis shoot development.

To identify genes involved in meristem function we have designed a screen for temperature-sensitive mutations that cause a conditional arrest of early shoot development in Arabidopsis. We describe the characterization of three mutations, arrested development (add) 1, 2 and 3. At the restrictive temperature the add1 and add2 mutations disrupt apical meristem function as assayed by leaf initiation. Furthermore, add1 and add2 plants exhibit defects in leaf morphogenesis following upshift from permissive to restrictive temperature. This result suggests that proximity to a functional meristem is required for the completion of normal leaf morphogenesis. The add3 mutation does not have a dramatic effect on the production of leaves by the apical meristem; however, add3 prevents the expansion of leaf blades at high temperature. Thus, in this mutant the temperature-dependent arrest of epicotyl development is due to a failure of normal leaf development rather than new leaf initiation. While all add mutants have a reduced rate of root growth in comparison to wild-type plants, the mutants do not display a temperature-dependent arrest of root development. All add mutants display some developmental defects at low temperature, suggesting that these mutations affect genes involved in inherently temperature-sensitive developmental processes.

Arabidopsis↗
PubMed2001

Endogenous hormone levels in explants and in embryogenic and non-embryogenic cultures of carrot.

Carrot (Daucus carota L. F1 hybrid Starca) excised hypocotyls were cultured on Murashige and Skoog medium with and without 2,4-dichlorophenoxy acetic acid (2,4-D) to determine the effect of this plant growth regulator on their further development and their endogenous hormone levels. Culture in the absence of 2,4-D stimulated root development at one end of the hypocotyl segments and increased the endogenous levels of free indole-3-acetic acid (IAA), zeatin/zeatin riboside and N6(Delta2-isopentenyl) adenine/N6(Delta2-isopentenyl) adenosine, as determined by radio-immunoassay. On the other hand, the presence of 2,4-D in the culture medium promoted callus induction and proliferation, together with abscisic acid (ABA) accumulation, in the hypocotyl segments during the first weeks of culture. When the callus segments generated in the hypocotyl sections cultured in the presence of 2,4-D were cultivated further, the development of two callus types was observed, one composed of preglobular and globular embryos and the other translucent, watery and lacking any sign of organisation. The embryos of the first type germinated when callus segments were transferred to regeneration conditions, while no change was observed when the second type was induced to regenerate. Higher levels of free IAA and ABA were obtained in the embryogenic calli when compared to the non-embryogenic, while no differences were observed among callus types in the other hormones evaluated. The possible role of the different plant hormones during induction of somatic embryogenesis is discussed.

Journal Article↗
PubMed1999

Adventitious root growth and cell-cycle induction in deepwater rice

Deepwater rice (Oryza sativa) is adapted to survive conditions of severe flooding over extended periods of time. During such periods adventitious roots develop to provide water, nutrients, and anchorage. In the present study the growth of adventitious roots was induced by treatment with ethylene but not auxin, cytokinin, or gibberellin. Root elongation was enhanced between 8 and 10 h after submergence. The population of cells in the S phase and expression of the S-phase-specific histone H3 gene increased within 4 to 6 h. Within 6 to 8 h the G2-phase population increased. Cell-cycle activation was accompanied by sequential induction of a cdc2-activating kinase homolog, R2, of two cdc2 genes, cdc2Os-1 and cdc2Os-2, and of three cyclin genes, cycA1;3, cycB2;1, and cycB2;2, but only induction of the R2 gene expression preceded the induction of the S phase, possibly contributing to cell-cycle regulation in the G1 phase. Both cdc2 genes were expressed at slightly higher levels during DNA replication. Transcripts of the A-type cyclin accumulated during the S and G2 phases, and transcripts of the B-type cyclins accumulated during the G2 phase. Cyclin expression was induced at all nodes with a similar time course, suggesting that ethylene acts systemically and that root primordia respond to ethylene at an early developmental stage.

Journal Article↗
PubMed1991

Regulation of phytochrome message abundance in root caps of maize.

In many cultivars of maize (Zea mays L.) red light affects root development via the photomorphogenetic pigment phytochrome. The site of perception for the light is the root cap. In the maize cultivar Merit, we investigated phytochrome-mediated events in the cap. We established that the message encoded by the phyA1 gene was most abundant in dark-grown tissue and was asymmetrically distributed in the root cap, with greatest expression in the cells which make up the central columella core of the cap. Phytochrome message was negatively autoregulated in a specific region within the root cap. This autoregulation was sensitive to very-low-fluence red light, and thus was characterized as a phytochrome-mediated, very-low-fluence event. The kinetics of message reaccumulation in the dark were also examined and compared to the kinetics of the light requirement for root gravitropism in this cultivar. Similarly, the degree of autoregulation present in two other maize cultivars with different light requirements for gravitropic sensitivity was investigated. It appears that the Merit cultivar expresses a condition of hypersensitivity to phytochrome-mediated light regulation in root tissues. We conclude that phytochrome regulates many activities within the cap, but the degree to which these activities share common phytochrome-mediated steps is not known.

Darkness↗
PubMed2000

Treatment of teeth with open apices using mineral trioxide aggregate.

Injuries to the dentition may ultimately result in the interruption of root development. If the pulp remains vital following trauma, this state should be maintained and root-end closure should be induced by apexogenesis. When the pulp is necrotic, the placement of an apical barrier can be utilized as an alternative to establish an environment that facilitates the closure of the apical opening. This article demonstrates the use of mineral trioxide aggregate as an apical barrier material for root-end closure in the permanent teeth of three patients.

Aluminum Compounds↗
PubMed2001

[Radiographic study of the development of the permanent teeth].

OBJECTIVE: To study the development of permanent teeth by radiographic methods. METHODS: The permanent teeth development of children ranging from 4-17 years was evaluated from 1709 panoramic radiographs by the Nolla's method. Each tooth was graded from 0 to 10 stage. The average developmental stage for girls and boys were calculated. RESULTS: The average developmental stage and development curves for girls and boys were obtained respectively. For the completion of crown and root development, girls are more advanced than boys by an average of 0.3 and 0.6 years. CONCLUSIONS: Girls are ahead of boys for the development of the permanent teeth. The norms of the maturation of permanent teeth can be used to evaluated the development of the individual teeth.

Adolescent↗
PubMed2000

Characterizing the interaction between fire ants (Hymenoptera: Formicidae) and developing soybean plants.

This research characterizes the interaction between the fire ants Solenopsis invicta Buren and developing soybean plants. Phagostimulant studies showed that fire ant foraging on soybean seeds increased once the seeds imbibed water. During seedling development over a 5-d germination period, fire ant foraging shifted from the stem/cotyledons to the roots, despite continual increases in fresh weights for each region, and the fact that stem/cotyledon tissue contained the majority of food reserves. Carbohydrate analysis showed that although 2-d-old seedlings had higher concentrations of phagostimulant carbohydrates, especially sucrose, than tissues of mature plants, all tissues analyzed had enough of these sugars to induce a phagostimulant response. Fire ant association with seeds/seedlings germinated in soil resulted in reduced seedling vigor, as determined by a doubling of seedling emergence time, a threefold increase in malformed seedlings, and visible damage to cotyledons. Seeds germinated and grown to mature plants in association with fire ants, allocated 43% more assimilate into pods, but produced 28% less root dry matter, 11% less total dry matter, and there was an 81% reduction in the number of root nodules compared with control plants. We propose that reduced root development and inhibitions of nodule formation would be major yield limiting factors under field conditions. This work demonstrates that fire ant damage to soybeans is not limited to seedling establishment and that more research should be directed at the subterranean activities of the fire ant.

Animals↗
PubMed1997

Cellular differentiation regulated by gibberellin in the Arabidopsis thaliana pickle mutant.

The plant growth regulator gibberellin (GA) has a profound effect on shoot development and promotes developmental transitions such as flowering. Little is known about any analogous effect GA might have on root development. In a screen for mutants, Arabidopsis plants carrying a mutation designated pickle (pkl) were isolated in which the primary root meristem retained characteristics of embryonic tissue. Expression of this aberrant differentiation state was suppressed by GA. Root tissue from plants carrying the pkl mutation spontaneously regenerated new embryos and plants.

Arabidopsis↗
PubMed1996

The Early Entry of Al into Cells of Intact Soybean Roots (A Comparison of Three Developmental Root Regions Using Secondary Ion Mass Spectrometry Imaging).

Al localization was compared in three developmental regions of primary root of an Al-sensitive soybean (Glycine max) genotype using secondary ion mass spectrometry. In cryosections obtained after a 4-h exposure to 38 [mu]M [Al3+], Al had penetrated across the root and into the stele in all three regions. Although the greatest localized Al concentration was consistently at the root periphery, the majority of the Al in each region had accumulated in cortical cells. It was apparent that the secondary ion mass spectrometry 27Al+ mass signal was spread throughout the intracellular area and was not particularly intense in the cell wall. Inclusion of some cell wall in determinations of the Al levels across the root radius necessitated that these serve as minimal estimates for intracellular Al. Total accumulation of intracellular Al for each region was 60, 73, and 210 nmol g-1 fresh weight after 4 h, increasing with root development. Early metabolic responses to external Al, including those that have been reported deep inside the root and in mature regions, might result directly from intracellular Al. These responses might include ion transport events at the endodermis of mature roots or events associated with lateral root emergence, as well as events within the root tip.

Journal Article↗
PubMed1992

Ehlers Danlos syndrome type I with novel dental features.

The clinical, radiographic and histologic findings are described in two cases of Ehlers Danlos Syndrome Type I with novel dental features. Defective dentinogenesis principally affecting the mandibular incisors result in aplasia or hypoplasia of root development predisposing to localized periodontal disease. A striking radiographic appearance with a bulbous enlargement of the roots together with pulp stones is seen in other teeth. 'Giant channels' and vascular inclusions resembling 'intermediate cementum' are prominent within this area. No evidence of Type III procollagen or collagen was detected with indirect immunofluorescence. It is suggested that an inherited collagen abnormality in a component common to dentin, skin, ligament and tendon probably explains both EDS I and the dentin dysplasia.

Adult↗
PubMedDate not supplied

Dental dysplasia in rats and mice.

Malformations of the maxillary incisors, diagnosed as dental dysplasia, were observed as a spontaneous background lesion in 3% (females) to 9% (males) of CD-1 mice and 14.5% (females) to 10.5% (males) of CD (Sprague-Dawley) rats in a chronic inhalation study. Lesions were reported grossly as overgrown, maloccluded, or malformed incisors. Microscopic findings included tooth pulp and periodontal abscesses, fractured and necrotic teeth, periodontal cysts, malformations of the incisor roots, and expansile masses, including odontomas, of the incisor roots. Development of lesions followed a pattern of tooth pulp necrosis and/or traumatic disruption of the epithelial root sheath at the base of the tooth. Feeding a powdered ration, which reduced the normal wearing of the incisors, and repeated clipping of overgrown incisors were believed to contribute to the incidence of disease.

Animals↗
PubMed1995

The treatment of traumatized permanent anterior teeth: case report & literature review. Part I--Management of intruded incisors.

A case is reported in which an intruded incisor was initially treated by an endodontic dressing with calcium hydroxide and then extruded using a removable orthodontic appliance. A follow-up examination seven years after completion of endodontic therapy and bleaching showed a favourable response. A review of the relevant literature indicates that intrusion occurs in five to twelve per cent of luxation cases. In this type of injury maximum damage occurs to the pulp and all supporting structures because the tooth is driven into the alveolar process. Complications which have been reported include: pulp necrosis, apical radiolucencies, partial or total pulp calcification, root resorption (surface, inflammatory or replacement), marginal periodontal bone breakdown, and arrested or disturbed root development. The prognosis for pulp survival after intrusion is much more favourable for teeth with incomplete root formation than for teeth with complete root formation. Treatment options available to bring an intruded tooth into alignment are: to await spontaneous re-eruption which may occur if root formation is incomplete, uncovering of the intruded crown, orthodontic extrusion which is allied with gentle luxation if the tooth does not move, and immediate surgical repositioning.

Adult↗
PubMed1992

Growth of acellular extrinsic fiber cementum (AEFC) and density of inserting fibers in human premolars of adolescents.

The present study describes for the first time the changes of both AEFC thickness and the numerical density of collagen fibers inserting into AEFC at specified levels and sites of human premolars at different stages of development. The investigation was based on 45 premolars (25 maxillary, 20 mandibular; 25 first and 20 second), extracted from adolescents and young adults. All teeth were free of disease and presented with roots developed from 30-100% of their final length. They were prefixed in Karnovsky's fixative, decalcified in EDTA and subdivided into about 14 slices each, cut from mesial and distal root surfaces, vertical to and along the root axis. The slices were postfixed in OsO4, embedded in Epon and cut for light-microscopic study. AEFC thickness (4086 measurements) and the density of the collagenous fiber fringe (454 counts) inserting in AEFC were measured at 1, 3, 5 and 7 mm apical to the cementoenamel junction. The data obtained showed: AEFC thickness increased with age and varied between 0 and 57.5 microns. Between 9 and 17 years, cervical AEFC thickness increased in maxillary first premolars from an average of 5 to 30 microns, and in mandibular second premolars from 6 to 20 microns, i.e., AEFC grew at approximately the same rate as later in life. Depending on the differences in tooth development, AEFC on maxillary first premolars became thicker than that on mandibular second premolars. Due to the corono-apically decreasing gradient of AEFC development, its increase in mid-root regions lagged behind that in cervical regions of all teeth in people younger than about 14 yr.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

[Autotransplantation of teeth].

This article gives a review of autotransplantation of teeth. From being a method of rather poor prognosis, autotransplantation has developed to be a safe treatment procedure. Scientific criteria for selecting patients, donor teeth, surgical procedures and postoperative care has contributed to this. The surgical procedure and the endodontic treatment are discussed. The degree of root development is of importance. Complications may be extern root resorption and ankylosis because of damage to the periodontium.

Humans↗
PubMed1985

Polar transport of 45Ca2+ across the elongation zone of gravistimulated roots.

The movement of calcium across the elongation zone of gravistimulated primary roots of maize (Zea mays L.) was measured using 45Ca2+. Radioactive calcium was applied to one side of the elongation zone about 4 mm back from the root tip and the distribution of radioactivity across the root in the region of application was determined using scintillation spectrometry. The movement of 45Ca2+ across the elongation zone was non-polar in vertically oriented roots. In gravistimulated roots the movement of label was polarized with about twice as much label moving from top to bottom as from bottom to top. A variety of treatments which interfere with gravitropism was found to eliminate the polar movement of 45Ca2+ across the elongation zone. In maize cultivars which require light for gravitropic competency, dark grown roots exhibited neither gravitropism nor polar movement of 45Ca2+ across the elongation zone. Upon illumination the roots developed but gravitropic competency and gravity-induced polar movement of 45Ca2+ across the elongation zone. Similarly, roots of light-grown seedlings lost both gravitropic competency and 45Ca2+ transport polarity upon transfer to the dark. The results indicate a close correlation between calcium movement and gravitropism in primary roots in maize.

Biological Transport↗