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PubMed1987

The CNS-PNS transitional zone of rat cervical dorsal roots during development and at maturity. A morphological and morphometric study.

Each seventh cervical dorsal nerve root is attached to the spinal cord surface by four to eight rootlets. A tapering outgrowth of central nervous tissue, the central tissue projection, extends distally into the proximal part of each rootlet in the immediate postnatal period. The central ends of the most proximal peripheral internodes surround this projection. Thus a length of rootlet contains both CNS and PNS tissue. This is termed the transitional zone. Material was processed by standard preparative techniques for electron microscopy. Serial semithin and ultrathin sections were made over the entire extent of several transitional zones at ages ranging from 2 to 300 days postnatum. Central tissue projections were reconstructed in three dimensions and analysed morphometrically. The morphology of the central tissue projection varies during development. At first, it forms an irregular projection into the anterior portion of the rootlet. It than elongates and takes the form of a dorsoventrally flattened, distally tapering wedge. By 20 days postnatum it has attained its definitive form. This consists of three segments: a proximal wedge-shaped portion, similar to that described above; continuous with this is a distally tapering, dorsoventrally flattened, cone-shaped segment which generally branches into two or more slender projections of central tissue. The latter comprise the third segment. The projection comes to form a substantial proportion of the anterior, proximal and distal surfaces of the dorsal rootlet from an early stage. The mean length of the central tissue projection increases progressively over all intervals studied, except that between 12 and 30 days postnatum, when a reduction in length is associated with reorganisation of the morphology of the projection. Projection length varies considerably between rootlets and is relatively weakly correlated with rootlet cross sectional area. There is a great deal of overlap between the distributions of projection lengths at all stages between 20 and 300 days.

Age Factors↗
PubMed1999

The HD-Zip gene ATHB6 in Arabidopsis is expressed in developing leaves, roots and carpels and up-regulated by water deficit conditions.

Homeodomain-leucine zipper (HD-Zip) proteins are transcription factors as yet found only in plants. We have characterized one HD-Zip gene, ATHB6, from Arabidopsis thaliana. ATHB6 was expressed constitutively in seedlings, but significantly up-regulated in seedlings subjected to water deficit, osmotic stress or exogenous treatment with abscisic acid (ABA), an induction being detectable within 30 min. The ATHB6 induction was impaired in the two ABA-insensitive mutants, abi1 and abi2, but unaffected in the abi3 mutation. The induction was ABA-dependent, since no increase in ATHB6 transcript was detected in the ABA-deficient mutant aba-3 subjected to drought treatment. These results suggest that ATHB6 may act downstream to both ABI1 and ABI2 in a signal transduction pathway mediating a drought stress response. A translational fusion of the ATHB6 promoter with the reporter gene GUS (ATHB6::GUS) in transgenic A. thaliana plants showed high-level expression in leaf primordia. Expression in developing cotyledons, leaves, roots and carpels was restricted to regions of cell division and/or differentiation. The expression in the cotyledons was detectable in the epidermis and high in the stomatal cells. In mature cotyledons and leaves the marker gene was expressed only in the vascular tissue. These expression data suggest ATHB6 to have a function related to cell division and/or differentiation in developing organs.

Abscisic Acid↗
PubMed1992

Differential distribution of two microtubule-associated proteins, MAP2 and MAP5, during chick dorsal root ganglion development in situ and in culture.

Microtubule-associated proteins (MAPs) are essential components necessary for the early growth process of axons and dendrites, and for the structural organization within cells. Both MAP2 and MAP5 are involved in these events, MAP2 occupying a role predominantly in dendrites, and MAP5 being involved in both axonal and dendritic growth. In the chick dorsal root ganglia, pseudo-unipolar sensory neurons have a T-shaped axon and are devoid of any dendrites. Therefore, they offer an ideal model to study the differential expression of MAPs during DRG development, specifically during axonal growth. In this study we have analyzed the expression and localization of MAP2 and MAP5 isoforms during chick dorsal root ganglia development in vivo, and in cell culture. In DRG, both MAPs appeared as early as E5. MAP2 consists of the 3 isoforms MAP2a, b and c. On blots, no MAP2a could be found at any stage. MAP2b increased between E6 and E10 and thereafter diminished slowly in concentration, while MAP2c was found between stages E6 and E10 in DRG. By immunocytochemistry, MAP2 isoforms were mainly located in the neuronal perikarya and in the proximal portion of axons, but could not be localized to distal axonal segments, nor in sciatic nerve at any developmental stage. On blots, MAP5 was present in two isoforms, MAP5a and MAP5b. The concentration of MAP5a was highest at E6 and then decreased to a low level at E18. In contrast, MAP5b increased between E6 and E10, and rapidly decreased after E14. Only MAP5a was present in sciatic nerve up to E14. Immunocytochemistry revealed that MAP5 was localized mainly in axons, although neuronal perikarya exhibited a faint immunostaining. Strong staining of axons was observed between E10 and E14, at a time coincidental to a period of intense axonal outgrowth. After E14 immunolabeling of MAP5 decreased abruptly. In DRG culture, MAP2 was found exclusively in the neuronal perikarya and the most proximal neurite segment. In contrast, MAP5 was detected in the neuronal cell bodies and all along their neurites. In conclusion, MAP2 seems involved in the early establishment of the cytoarchitecture of cell bodies and the proximal axon segment of somatosensory neurons, while MAP5 is clearly related to axonal growth.

Animals↗
PubMed1996

Developmentally regulated neurite outgrowth response from dorsal root ganglion neurons to heparin-binding growth-associated molecule (HB-GAM) and the expression of HB-GAM in the targets of the developing dorsal root ganglion neurites.

Heparin-binding growth-associated molecule (HB-GAM) is a highly conserved cell surface- and extracellular matrix-associated protein that enhances neurite outgrowth in brain neurons in vitro. To study the possible response of peripheral neurons, we cultured chicken dorsal root ganglion neurons from different developmental stages from embryonic day 4.5 (E4.5; St 25) to E9 (St 35) on recombinant HB-GAM. We discovered that the neurite outgrowth response to HB-GAM is maximal at E5.5-6.5 (St 28-30). In order to correlate this in vitro phenomenon with in vivo phenomena, immunohistochemical staining and in situ hybridization were performed on cryosections. The protein expression of HB-GAM peaked at E6 (St 29) and was most extensive on the dorsal spinal cord and dorsal roots. Using Dil labelling, we confirmed that at the time when sensory afferents travel longitudinally in the bundle of His of the spinal cord, HB-GAM protein expression there is at its peak. Though HB-GAM is a secreted protein, at the RNA level the timing of HB-GAM appearance and existence in the spinal cord and sensory ganglia is in accordance with its protein expression. Our results demonstrate that peripheral neurons are responsive to substrate-bound HB-GAM in a developmentally regulated manner, and that the expression of both HB-GAM mRNA and protein in vivo is spatially and temporally matched to this in vitro phenomenon. HB-GAM is therefore a putative cue for the growth of sensory afferents to and within the dorsal spinal cord.

Animals↗
PubMed1998

Ethylene-mediated phenotypic plasticity in root nodule development on Sesbania rostrata.

Leguminous plants in symbiosis with rhizobia form either indeterminate nodules with a persistent meristem or determinate nodules with a transient meristematic region. Sesbania rostrata was thought to possess determinate stem and root nodules. However, the nature of nodule development is hybrid, and the early stages resemble those of indeterminate nodules. Here we show that, depending on the environmental conditions, mature root nodules can be of the indeterminate type. In situ hybridizations with molecular markers for plant cell division, as well as the patterns of bacterial nod and nif gene expression, confirmed the indeterminate nature of 30-day-old functional root nodules. Experimental data provide evidence that the switch in nodule type is mediated by the plant hormone ethylene.

Journal Article↗
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↗
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↗
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↗