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PubMed1988

Disturbances in dental development after total body irradiation in bone marrow transplant recipients.

The dental status of 16 children who had been treated with bone marrow transplantation (BMT) for serious bone marrow diseases was followed for up to 6 years. Several types of disturbances in dental development were observed in children who had been conditioned with total body irradiation (TBI) at 10 Gy before BMT. Thus, impaired root development that caused short V-shaped roots was found in all patients, a complete failure of root development and premature apical closure were found in five patients, enamel hypoplasia was observed in four patients, and microdontia was observed in three patients conditioned with TBI. Patients younger than 6 years of age at BMT exhibited the most severe and extensive dental aberrations. The TBI at 10 Gy appeared to be the major cause of the disturbances found.

Abnormalities, Radiation-Induced↗
PubMed2000

Cortical development in roots of the aquatic plant Pontederia cordata (Pontederiaceae).

Adventitious roots of marsh-grown Pontederia cordata were examined to determine cortical development and structure. The innermost layer of the ground meristem forms the endodermis and aerenchymatous cortex. The outermost layer of the early ground meristem undergoes a precise pattern of oblique and periclinal cell divisions to produce a single or double layer of prohypodermis with an anchor cell for each radial file of aerenchyma cells. At maturity, endodermal cell walls are modified only by narrow Casparian bands. The central regions of the ground meristem become proaerenchyma and exhibit asymmetric cell division and expansion. They produce an aerenchymatous zone with barrel-shaped large cells and irregularly shaped small cells traversing the aerenchyma horizontally along radii; some crystalliferous cells with raphides are present in the aerenchyma. The walls of the hypodermis are modified early by polyphenols. The outermost layer of the hypodermis later matures into an exodermis with Casparian bands that are impermeable to berberine, an apoplastic tracer dye. The nonexodermal layer(s) of the hypodermis has suberin-modified walls. Radial files of aerenchyma are usually connected by narrow protuberances near their midpoints, the aerenchyma lacunae having been produced by expansion of cells along walls lining intercellular spaces. We are terming this type of aerenchyma development, which is neither schizogenous nor lysigenous, "differential expansion."

Journal Article↗
PubMed1990

Oral complications of cancer therapies. Chronic dental complications.

Radiation therapy (RT) and chemotherapy have increased long-term survival with certain cancers. The use of dental investigation and treatment of chronic or delayed oral complications is developing. Altered dental root development, enamel opacities, hypocalcifications, periodontal problems, and a higher caries rate are seen in children treated with chemotherapy. The psychosocial implications of long-term survival on routine dental care are important. Prevention and treatment of long-term oral complications of radiation therapy are changing. Osteoradionecrosis remains complicated and devastating. Strategies that avoid post-RT extractions include caries prevention, oral hygiene measures, meticulous restorative dentistry, overdentures, and improved posts for endodontically treated teeth. Guidelines for post-RT extractions vary greatly. Pediatric patients who receive head and neck irradiation may have total arrest of tooth and jaw development within the portal. The dentist must be able to diagnose and treat the variety of alterations already identified and should engage in scholarly research to answer the questions that remain.

Antineoplastic Agents↗
PubMed2026

Penicillium melinii promotes root growth through subtle host reprogramming across model and crop species.

Root development is highly responsive to microbial interactions, yet the mechanisms by which beneficial fungi promote root growth remain incompletely understood. Here, we identified Penicillium melinii 'isolate 2' through a screen of endophytic fungi isolated from Arabidopsis and characterized it as a promoter of root development in both Arabidopsis and crop species. We combined phenotyping in vitro, rhizotron, greenhouse and field assays with reporter and mutant analyses, transcriptomics, phytohormone profiling and sequencing and annotation of the fungal genome to investigate the basis of this interaction. P. melinii consistently stimulated root growth and modified root architecture across experimental systems and host species. These effects were associated with subtle but reproducible host transcriptional reprogramming, supporting a model in which the fungus fine-tunes endogenous developmental programmes rather than broadly perturbing stress or growth pathways. Genetic and reporter analyses further suggested that this interaction modulates root branching through localized developmental reprogramming. Genomic analysis provided a framework for understanding the fungal traits associated with this beneficial interaction. The conservation of the response across model and crop species supports the relevance of P. melinii as both a useful experimental system to study beneficial plant-fungus interactions and a promising candidate for improving root traits and crop performance.

Penicillium melinii↗
PubMed2000

Molecular Mechanisms in Root Nodule Development.

Under nitrogen-limiting conditions, bacteria from the family Rhizobiaceae establish a symbiosis with leguminous plants to form nitrogen-fixing root nodules. These organs require a coordinated control of the spatiotemporal expression of plant and bacterial genes during morphogenesis. Both plant and bacterial signals are involved in this regulation in the plant host. Plant genes induced during nodule development, the so-called nodulin genes, have been extensively characterized. Products of several of these genes show homologies to known regulators of signal transduction pathways in other plant or animal systems. Initial functional analysis of the molecular mechanisms implicated in nodulation have been undertaken using model legumes. Insertion mutagenesis and transgenic technologies to modify nodulin gene expression, as well as pharmacologic approaches, have been used to analyze molecular mechanisms involved in morphologic responses induced by the bacterial symbiont in the plant. G protein-mediated transduction mechanisms have been implicated, and the nin transcription factor appears to be required for early steps in nodule development. ENOD40, a gene coding for an RNA that contains only short ORFs, seems to be closely tied to nodule primordium formation. In addition, a vascular-associated Krüppel-like transcription factor and small Rab type G-proteins affect bacteroid differentiation and the function of the nitrogen-fixing zone. These initial results presage a wealth of information that will be obtained from the application of genomic approaches to legumes.

Journal Article↗
PubMed1990

Toxicity of root canal sealers on rat bone cells in primary culture.

The cytotoxic effects on cultured rat bone cells of newly-developed root canal sealers and commercially available sealers were compared. Various root canal sealers were applied to cultured bone cells obtained from rat calvaria by the enzyme digestion method. Measurement of [3H]-thymidine incorporation, alkaline phosphatase activity, and calcium release were performed after 24 and 48 h. No significant difference was found in cellular DNA synthesis and alkaline phosphatase activity between cells exposed to New B-1, New B-5 and controls after exposure for 24 and 48 h. Cells in contact with Tubliseal, Diaket and AH-26 demonstrated a significant difference from controls in DNA synthesis and alkaline phosphatase activity. Calcium release at 24 h was significantly different in the cells treated with New B-1 and New B-5 than in controls. No appreciable difference was found, however, between New B-6, Sealapex and controls. At 48 h, cells treated with New B-1, New B-5 and New B-6 showed differed significantly difference from controls, but the cells exposed to Sealapex did not. The newly-developed root canal sealers had lower toxicity in vitro than five types of commercially available root canal sealers.

Alkaline Phosphatase↗
PubMedDate not supplied

The relationship between nodulin gene expression and the Rhizobium nod genes in Vicia sativa root nodule development.

The role of the Rhizobium nod genes in the induction of nodulin gene expression was examined by analyzing nodules formed on vetch roots by bacterial strains containing only the nod region. Introduction of an 11-kb cloned nod region of the R. leguminosarum sym plasmid pRL1JI into sym plasmid-cured rhizobia conferred on the recipient strains the ability to induce nodules in which all nodulin genes were expressed. This proves that from the sym plasmid only the nod region is involved in the induction of nodulin gene expression. A transconjugant of Agrobacterium carrying the same nod region induces nodules in which only early nodulin gene expression is detected. Thus, the nod region is essential for the induction of early nodulin gene expression. In this case, nodule cytology may indicate that a defense response of the plant interferes with the induction of late nodulin gene expression. Indirect evidence is presented that indeed the Rhizobium nod genes are also in some way involved in the induction of the expression of late noduling genes. The combination between histological data and pattern of nodulin gene expression furthermore reveals a correlation between nodule structure and nodulin gene expression. This correlation may aid in speculations about the functions of nodulins.

Blotting, Western↗
PubMed1981

Remodelling processes following transplantation of dental germs in dogs.

Dental germs with different amounts of root development were transplanted from the left side to the right side, and vice versa, in young beagle dogs. The unerupted premolars had been taken out by osteotomy. After transplantation, the dental germs were covered with mucosa. The observation period lasted 7 postoperative weeks. Histological examination of the remodelling processes of the bone and tooth-tissue was carried out by polychromatic sequential labelling. All the transplanted dental germs remained vital, and the eruption continued to the normal occlusion level. From this, it follows that eruption of teeth does not depend on root development alone. In some cases, root length growth stopped immediately as a result of transplantation. Either a stumpy apex was formed, or resorption took place. In other cases root growth continued. There was a bend in the root at the point of transplantation, and the subsequently formed root section was shorter and thinner than in normal teeth.

Animals↗
PubMed1998

Localized changes in apoplastic and cytoplasmic pH are associated with root hair development in Arabidopsis thaliana.

Morphogenesis in plants is characterized by highly regulated cell enlargement. However, the mechanisms controlling and localizing regions of growth remain essentially unknown. Root hair formation involves the induction of a localized cell expansion in the lateral wall of a root epidermal cell. This expanded region then enters a second phase of localized growth called tip growth. Root hair formation therefore provides a model in which to study the cellular events involved in regulating localized growth in plants. Confocal ratio imaging of the pH of the cell wall revealed an acidification at the root hair initiation site. This acidification was present from the first morphological indications of localized growth, but not before, and was maintained to the point where the process of root hair initiation ceased and tip growth began. Preventing the wall acidification with pH buffers arrested the initiation process but growth resumed when the wall was returned to an acidic pH. Cytoplasmic pH was found to be elevated from approximately 7.3 to 7. 7 at the initiation site, and this elevation coincided with the acidification of the wall. Preventing the localized increase in cytoplasmic pH with 10 mM butyrate however did not inhibit either the wall acidification or the initiation process. In contrast, there was no detectable gradient in pH associated with the apex of tip growing root hairs, but both elevated apoplastic pH and butyrate treatment irreversibly inhibited the tip growth process. Thus the processes of tip growth and initiation of root hairs show differences in their pH requirements. These results highlight the role of localized control of apoplastic pH in the control of cell architecture and morphogenesis in plants.

Arabidopsis↗
PubMed1989

Prognosis of root-fractured permanent incisors--prediction of healing modalities.

A population of 85 patients, comprising 95 root-fractured permanent incisors followed up to 11 years, was studied prospectively for the type of fracture healing that occurred (i.e. union of the fragments by interposition of hard tissue (HT) or connective tissue (CT), or nonunion characterized by interposition of granulation tissue between the fragments (GT)). Initial treatment was provided according to established treatment guidelines by the attending oral surgeon at the emergency room. Follow-up examination and treatment were provided by 2 of the authors. It appeared that GT could be diagnosed after approximately 3 weeks, while HT or CT could be diagnosed approximately 6 weeks after trauma. Many factors considered one at a time were found to have a significant or nearly significant effect on the type of fracture healing that occurred. However, a multivariate regression analysis revealed that the following factors were significantly related to fracture healing by HT: a large diameter of the apical foramen and severity of luxation of the coronal fragment (concussion/subluxation greater than lateral luxation greater than extrusion); fracture healing by CT: the presence of restorations in the injured teeth at the time of injury and the presence of marginal periodontal disease; and fracture nonhealing by GT: type of fixation (i.e. orthodontic band fixation versus acid etch or no fixation), antibiotic therapy, a constricted apical foramen, increased loosening of the coronal fragment, and stage of root development (GT never occurred in teeth with open apices). It was previously demonstrated following luxation injuries that type of luxation, stage of root development and type of fixation (orthodontic bands versus acid etch or no fixation) determined the prognosis of pulp survival. It therefore appears that the general factors that are able to predict the type of healing seen after root fracture are the same as those after luxation injuries, supporting the hypothesis that root fractures are another form of luxation injury, this time of only the coronal fragment.

Humans↗
PubMed1978

Proliferative and degenerative events in the early development of chick dorsal root ganglia. I. Normal development.

Development of the chick dorsal root ganglia was examined in 4.5- to 9.5-day embryos. Tritiated thymidine (3H-TdR) and autoradiography was used to analyze proliferative activity and the Feulgen procedure to analyze degenerative activity in ganglia 12-17. Proliferative activity was found to be elevated through 4.5 days of incubation when as many as 14% of the ganglionic cells become labelled following a one-hour exposure to 3H-TdR. By 6.5 to 7.5 days proliferative activity decreases to 2-4% in the lateroventral (LV) regions and to approximately 1% in the mediodorsal (MD) regions of the ganglia. However, there appears to be increased proliferative activity by the end of the experimental period at 9.5 days. Birthdate studies demonstrate that large-scale neuronal production occurs between 4.5 and 6.5 days in the LV regions and between 4.5 and 7.5 days in the MD regions. After those times ganglionic proliferative activity must be largely nonneuronal in nature. This nonneuronal proliferation is greater in LV than in MD regions and in brachial than in nonbrachial ganglia. Degenerative activiy was found to be absent from the ganglia until after 4.5 days of incubation. It then increases rapidly, and by 5.5 days 5% of the LV cells in nonbrachial ganglia are degenerating. Degenerative activity then declines but is still present at 9.5 days. In contrast to results of an earlier study (Hamburger and Levi-Montalcini, '49), degenerative activity was also found in the LV region of brachial ganglia and the MD regions of brachial and nonbrachial ganglia. The pattern of LV degenerative activity in brachial ganglia is similar to that in nonbrachial ganglia, but the level of activity is lower. In the MD regions degenerative activity increases throughout the experimental period, and by 9.5 days as many as 4% of the MD cells are degenerating.

Age Factors↗
PubMed1976

Radiographic and clinical manifestations of the impacted mandibular third molar.

Observations were made on 200 impacted mandibular third molars that were removed from 200 unselected patients under local anesthesia. Sixty percent of the teeth were found to be in apparent relationship with the inferior dental canal: 19 % in true relationship and 41 % in superimposition. The vertical impacted molars were mainly found to be in true relationship with the inferior dental canal. On comparison of the clinical postoperative diagnosis with the radiographic preoperative findings an error of only 0.8 % was shown. Most of the molars showed fully developed roots in the third decade of life. Most of the teeth in this series were vertically impacted having mostly fully developed roots. There was a significant correlation between the patients suffering from pain, trismus, and swelling. Swelling and trismus were the mostly affected postoperative sequelae.

Adolescent↗
PubMed1988

Autogenous free tooth transplantation in man by a 2-stage operation technique. A longitudinal intra-individual radiographic assessment.

Insufficient nutrition to the root surface of autotransplanted mature human teeth after transplantation could be an explanation for the high rates of complications such as root resorption and loss of the tooth transplant. Insufficient nutrition is suggested as being due to the distance between the recipient site tissue and the root surface, and the presence of a blood-clot between the tissues. Improved nutrition could be achieved by transplanting into contact with the vascularised connective tissue of a healing wound. To test this hypothesis, a series of human teeth with fully developed roots were autotransplanted to recipient sites prepared and left to heal for 14 days before transplantation. This study is a follow-up of 57 transplants with a minimum observation time of 1 year. Periodic radiographic examinations of the teeth were performed up to 5 years after transplantation. The results presented, showed a lower incidence of root resorption and extractions than previously reported for teeth with fully developed roots.

Adolescent↗
PubMed1998

Paracrine production of nerve growth factor during rat dorsal root ganglion development.

Nerve growth factor is a target derived growth factor. In the peripheral nervous system, it is produced by tissues innervated by the sympathetic nervous system and small sensory neurons. In the present study, we tested the hypothesis that an alternate source of nerve growth factor must be available to support dorsal root ganglion neurons before they make connection with the target. Using reverse transcriptase polymerase chain reaction (RT-PCR), we detected nerve growth factor mRNA at embryonic day 12 to 17, but not in adult dorsal root ganglia. In situ hybridization studies revealed positive staining in satellite/supportive cells juxtaposed to dorsal root ganglion neurons. Our study suggests that nerve growth factor from supporting cells may have a paracrine function during development of primary sensory neurons.

Animals↗
PubMed1997

Specific localization of the respiratory alternative oxidase in meristematic and xylematic tissues from developing soybean roots and hypocotyls.

We used tissue printing and specific immunostaining to examine the localization of the alternative oxidase (AOX) protein in correlation with measurements of AOX capacity. Selected root and hypocotyl regions were analyzed during the first 14 d of growth. It is shown that AOX protein is localized in the apical meristem and in developing xylem. The temporal pattern of expression is coincident with the evolution of AOX capacity. Data suggest that AOX expression is linked to xylem differentiation. Since heat is a major product of the alternative pathway, we speculate that thermogenesis is implicated in morphogenesis.

Gene Expression Regulation, Developmental↗
PubMed2000

Carbon metabolism in developing soybean root nodules: the role of carbonic anhydrase.

A full-length cDNA clone encoding carbonic anhydrase (CA) was isolated from a soybean nodule cDNA library. In situ hybridization and immunolocalization were performed in order to assess the location of CA transcripts and protein in developing soybean nodules. CA transcripts and protein were present at high levels in all cell types of young nodules, whereas in mature nodules they were absent from the central tissue and were concentrated in cortical cells. The results suggested that, in the earlier stages of nodule development, CA might facilitate the recycling of CO2 while at later stages it may facilitate the diffusion of CO2 out of the nodule system. In parallel, sucrose metabolism was investigated by examination of the temporal and spatial transcript accumulation of sucrose synthase (SS) and phosphoenolpyruvate carboxylase (PEPC) genes, with in situ hybridization. In young nodules, high levels of SS gene transcripts were found in the central tissue as well as in the parenchymateous cells and the vascular bundles, while in mature nodules the levels of SS gene transcripts were much lower, with the majority of the transcripts located in the parenchyma and the pericycle cells of the vascular bundles. High levels of expression of PEPC gene transcripts were found in mature nodules, in almost all cell types, while in young nodules lower levels of transcripts were detected, with the majority of them located in parenchymateous cells as well as in the vascular bundles. These data suggest that breakdown of sucrose may take place in different sites during nodule development.

Amino Acid Sequence↗
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↗