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PubMed1996

Methods of reducing observer variation in age estimation from panoramic radiographs.

OBJECTIVE: To compare inter- and intra-observer variation in age estimation using subjective and objective methods. METHODS: Fifty-six panoramic radiographs of patients aged 13 to 25 years were assessed subjectively twice by four observers for the stage of root development of the lower third molars on a seven-point scale. Two of the observers were calibrated before the first evaluation, and the other two before the second. The same observers also digitized predefined reference points in a subsample of the third molars ten times by means of a computer-based digitizer system. Observer variation in classifying different root stages and in digitizing coordinates and measuring root lengths were studied. RESULTS: Significant systematic differences existed between two of the observers in the subjective assessment. One non-pre-calibrated observer changed her pattern most. Scattergrams from the digitizer measurements showed a good precision within and between observers with no significant differences in calculating root lengths. When, however, the teeth were analysed separately, some significant differences were found. CONCLUSIONS: The overall observer agreement was best using the objective method on several teeth. With only one tooth there were some significant differences. Subjective evaluation was improved by prior calibration.

Adolescent↗
PubMed1993

Histological reconstruction of dental development and age at death of a juvenile Paranthropus robustus specimen, SK 63, from Swartkrans, South Africa.

There has been disagreement about whether the earliest hominids grew in a similar manner to great apes or modern humans. This has important biological implications, since it may have been inappropriate to apply modern human developmental standards to early hominids. The aim of the present study was to combine data from replicas of tooth surfaces, computed tomographic (CT) scans, and radiographs with data from a histological section of the canine crown, in order to provide a complete description of tooth crown and tooth root development in a single early hominid specimen (SK 63). Although partially destructive in nature, we have been able to determine the most reliable data yet for aspects of dental development in an important juvenile early hominid specimen. Appositional enamel formation time in the permanent right canine was estimated at between 305 and 418 days, imbricational enamel formation time at 819 days, and total crown formation time at between 3.18 and 3.48 years. The most likely age at death was estimated at around 4 years with a range of ages calculated between 3.18 and 4.23 years based on differences in timing of initial mineralization of the canine and differences in appositional enamel formation times. Crown formation times of the lower central and lateral incisors were estimated between 2.35-2.68 years and 2.57-2.91 years, respectively. Crown formation time of the first permanent molar was estimated at 2.4 years. Wear facets on the first permanent molars indicate that gingival emergence had occurred sometime prior to death, between 3 and 4 years of age. Estimates of root extension rates in the first permanent molars and in the permanent incisors are fast, and either within or above ranges of rates estimated for modern great apes. While we recognize that data for one individual may not be representative of data for a whole population of early hominids, the data for age at death, for age of M1 emergence, and for root extension rates presented here accord with those known for modern great apes and fall beyond the known ranges for modern humans.

Age Determination by Teeth↗
PubMed1995

Cellular and molecular events in a newly organizing lateral root meristem.

Spontaneous or auxin-induced lateral root formation in radish and Arabidopis provides an efficient system in which to examine molecular and cellular events associated with the initiation of a new meristem. Subtracted cDNA libraries made at different times in lateral root initiation were used as a source of genes that are expressed differentially during this developmental process, and expression studies on a small gene family of ribosomal protein genes were conducted. From analysis of cell division patterns in pericycle cells the number of founder cells for lateral roots was established. By the use of in vitro growth assays lateral root formation was determined to be a two-stage process. First a primordium is formed, and subsequently a subset of primordial cells begins to function as the lateral root apical meristem. This mode of root development has implications for pattern formation in newly organizing organs.

Arabidopsis↗
PubMed1997

Characterization of the common bean uricase II and its expression in organs other than nodules.

Uricase II is a purine metabolic enzyme highly induced in root nodules during the symbiosis established between legumes and bacteria of the genera Rhizobium and Bradyrhizobium. Here we describe the characterization of bean (Phaseolus vulgaris) nodule uricase II cDNA and show that uricase II is encoded by a single gene in the bean genome. This gene is also expressed in cotyledons, roots, and hypocotyls during bean seedling establishment, and an anti-uricase antibody recognizes the protein in different seedling organs. Uricase II has also been found in Leucaena leucocephala seedlings, suggesting that it participates during seedling establishment in legumes that do not transport ureides. A 50-kD polypeptide that is detected by the anti-uricase antibody is found in cotyledons during seedling development. This higher-molecular-mass form is also detected in developing roots and hypocotyls but not in nodules. In situ hybridization experiments in root seedlings showed uricase II transcripts in the metaxylem parenchyma cells and phloem fibers of the vascular system.

Amino Acid Sequence↗
PubMed1993

Transient expression of beta-NADPH diaphorase in developing rat dorsal root ganglia neurons.

We report here that during early fetal rat development, most, if not all, dorsal root ganglion (DRG) cells were stained by the beta-NADPH diaphorase histochemical reaction, indicating that they expressed nitric oxide synthase. During late fetal development, most DRG cells lost their diaphorase activity, but a small subset (located in all DRGs, but primarily in mid-thoracic DRGs) remained diaphorase-positive in adult animals. The transient expression of this enzyme suggests that nitric oxide may play a role during development that differs from its function in mature cells.

Amino Acid Oxidoreductases↗
PubMed2003

Ethylene modulates root-wave responses in Arabidopsis.

When stimulated to bend downward by being held at 45 degrees off vertical but unable to penetrate into agar-based media, Arabidopsis roots develop waving and looping growth patterns. Here, we demonstrate that ethylene modulates these responses. We determined that agar-containing plates sealed with low-porosity film generate abiotic ethylene concentrations of 0.1 to 0.3 microL L(-1), whereas in plates wrapped with porous tape, ethylene remains at trace levels. We demonstrate that exogenous ethylene at concentrations as low as a few nanoliters per liter modulates root waving, root growth direction, and looping but through partly different mechanisms. Nutrients and Suc modify the effects of ethylene on root waving. Thus, ethylene had little effect on temporal wave frequency when nutrients were omitted but reduced it significantly on nutrient-supplemented agar. Suc masked the ethylene response. Ethylene consistently suppressed the normal tendency for roots of Landsberg erecta to skew to the right as they grow against hard-agar surfaces and also generated righthanded petiole twisting. Furthermore, ethylene suppressed root looping, a gravity-dependent growth response that was enhanced by high nutrient and Suc availability. Our work demonstrates that cell file twisting is not essential for root waving or skewing to occur. Differential flank growth accounted for both the extreme root waving on zero-nutrient plates and for root skewing. Root twisting was nutrient-dependent and was thus strongly associated with the looping response. The possible role of auxin transport in these responses and the involvement of circadian rhythms are discussed.

Arabidopsis↗
PubMedDate not supplied

[Nonsurgical endodontic treatment of an invaginated canine].

We present a case of a maxillary canine with a dens invaginatus treated successfully. The patient had pain, swelling and a sinus tract coming from the inmature apex of the canine. The canals were enlarged and cleaned and the main canal was filled with Calcium Hydroxide to allow the root development. Seven months later, the patient was asymptomatic and the tooth was obturated with guttapercha. One year later it was confirm the success in the treatment.

Adolescent↗
PubMed1976

Root fractures in permanent anterior teeth with incomplete root formation.

A follow-up study was made of seven teeth with incomplete root formation observed in a group of 66 permanent teeth with root fracture. Three fractures were overlooked on the initial radiographs, two other teeth were suspected of being fractured, and an accurate diagnosis was made in two cases only. All teeth exhibited markedly increased mobility at the initial examination, and slight dislocation of the coronal fragment was found in two teeth. Following reduction (two teeth) and fixation (all teeth), the observation period ranged from 1 1/2 to 19 years. Retained pulp vitality, repair in the fracture area and, most important, approximately normal root development with closure of the apical foramen were observed in all teeth. Even the occurrence of re-fracture in two semmingly repaired teeth did not jeopardize the long-term result.

Child↗
PubMed2003

External apical root resorption in Class II malocclusion: a retrospective review of 1- versus 2-phase treatment.

External apical root resorption (EARR) is an imperfectly understood problem of orthodontic treatment. The records of 138 children with Class II malocclusion (overjet > 7 mm) participating in a randomized clinical trial of early orthodontic treatment were reviewed. The patients were treated in either 1 phase with fixed appliances only (n = 49) or 2 phases with headgear (n = 49) or bionator (n = 40) followed by fixed appliances. The 3 groups were similar in age, sex, and malocclusion severity at enrollment. The records examined included anamnestic data, clinical examination records, panoramic radiographs before and after fixed appliance therapy, and posttreatment periapical radiographs. All radiographs were reviewed and scored independently by 2 examiners for maxillary incisor root development, morphology, and EARR. Of the 532 incisors scored, 11% of central and 14% of lateral incisors demonstrated moderate to severe (>2 mm) EARR. The proportion of incisors with moderate to severe EARR was slightly greater in the 1-phase treatment group. There was no difference in the incidence of EARR between teeth that had had trauma and those that had not, and there was only a slight increase in frequency of root resorption in teeth with unusual root morphology. Significant associations exist among EARR, the magnitude of overjet reduction, and the time spent wearing fixed appliances. However, not all incisors in a child respond in the same way, so other variables must play a role in determining the root response to orthodontic forces.

Child↗
PubMed1998

The PASTICCINO genes of Arabidopsis thaliana are involved in the control of cell division and differentiation.

The control of cell division by growth regulators is critical to proper plant development. The isolation of single-gene mutants altered in the response to plant hormones should permit the identification of essential genes controlling the growth and development of plants. We have isolated mutants pasticcino belonging to 3 complementation groups (pas1, pas2, pas3) in the progeny of independent ethyl methane sulfonate and T-DNA mutagenized Arabidopsis thaliana plants. The screen was performed in the presence or absence of cytokinin. The mutants isolated were those that showed a significant hypertrophy of their apical parts when grown on cytokinin-containing medium. The pas mutants have altered embryo, leaf and root development. They display uncoordinated cell divisions which are enhanced by cytokinin. Physiological and biochemical analyses show that cytokinins are probably involved in pas phenotypes. The PAS genes have been mapped respectively to chromosomes 3, 5 and 1 and represent new plant genes involved in the control of cell division and plant development.

Adenine↗
PubMed1995

Experimental root surface caries in hamsters the development of the disease after inoculations of two types of cariogenic bacteria.

The aim of this study was to investigate the development of root surface caries in hamsters fed a high-sucrose diet over a 24-week period after inoculations of two types of cariogenic bacteria. Twenty-one day old male golden hamsters (n = 103) were divided into 5 groups. Four groups were given diet 2000, and one group was given a stock diet CE-2, Of the groups given diet 2000, three groups were infected with Actinomyces viscosus ATCC 15987 and Streptococcus mutans NTCC 10449 separately (AV and SM groups) or in combination (AVSM group), and one group remained uninfected. A grid method was used to evaluate the plaque accumulation, alveolar bone loss, and root surface caries. After 12 weeks, root surface caries developed mainly on the first mandibular molars in the three infected groups. At 24 weeks, the prevalence of root surface caries was highest in the AV group, but root caries scores were not significantly different among the three infected groups. In the groups SM and AVSM, the molar crowns were extensively destroyed by caries, while in the AV group the crowns were almost intact. It was concluded that challenge with Actinomyces viscosus may be appropriate to study root surface caries in hamsters.

Actinomyces viscosus↗
PubMed1988

1987 Kreshover lecture. Gene regulation in the development of oral tissues.

The regulatory processes associated with tooth formation are being investigated by the identification of when, where, and how cell adhesion molecules (CAMs), substrate adhesion molecules (SAMs), dentin phosphoprotein, enamel gene products, and intermediate cementum products are expressed during sequential developmental stages of morphogenesis, cytodifferentiation, dentin, enamel and cementum extracellular matrix (ECM) formation, and biomineralization. Instructive and permissive signaling is required for both morphogenesis and cytodifferentiation based upon in vitro organotypic culture studies in serumless, chemically-defined medium. Intrinsic developmental instructions, independent of exogenous growth factors, mediate tooth morphogenesis from the initiation of the dental lamina through crown and initial root development. Recent progress using recombinant DNA methods has advanced descriptions of several dental structural genes. The complete nucleic acid sequence for mouse amelogenin has been defined. This sequence is located on the mouse X chromosome and on the human X and Y chromosomes. This discussion summarizes recent results using experimental embryology, recombinant DNA technology, and immunocytology in the context of instructive epithelial-mesenchymal interactions associated with epithelial differentiation into ameloblasts, ectomesenchyme differentiation into odontoblasts, and dentin and enamel ECM biomineralization. The tooth organ provides opportunities at several levels of biological organization to investigate cellular, molecular, and developmental processes.

Animals↗
PubMed2003

Ectopic expression of atRSZ33 reveals its function in splicing and causes pleiotropic changes in development.

Splicing provides an additional level in the regulation of gene expression and contributes to proteome diversity. Herein, we report the functional characterization of a recently described plant-specific protein, atRSZ33, which has characteristic features of a serine/arginine-rich protein and the ability to interact with other splicing factors, implying that this protein might be involved in constitutive and/or alternative splicing. Overexpression of atRSZ33 leads to alteration of splicing patterns of atSRp30 and atSRp34/SR1, indicating that atRSZ33 is indeed a splicing factor. Moreover, atRSZ33 is a regulator of its own expression, as splicing of its pre-mRNA is changed in transgenic plants. Investigations by promoter-beta-glucuronidase (GUS) fusion and in situ hybridization revealed that atRSZ33 is expressed during embryogenesis and early stages of seedling formation, as well as in flower and root development. Ectopic expression of atRSZ33 caused pleiotropic changes in plant development resulting in increased cell expansion and changed polarization of cell elongation and division. In addition, changes in activity of an auxin-responsive promoter suggest that auxin signaling is disturbed in these transgenic plants.

Agrobacterium tumefaciens↗
PubMed2002

Functional significance of the alternative transcript processing of the Arabidopsis floral promoter FCA.

The Arabidopsis gene FCA encodes an RNA binding protein that functions to promote the floral transition. The FCA transcript is alternatively processed to yield four transcripts, the most abundant of which is polyadenylated within intron 3. We have analyzed the role of the alternative processing on the floral transition. The introduction of FCA intronless transgenes resulted in increased FCA protein levels and accelerated flowering, but no role in flowering was found for products of the shorter transcripts. The consequences of the alternative processing on the FCA expression pattern were determined using a series of translational FCA-beta-glucuronidase fusions. The inclusion of FCA genomic sequence containing the alternatively processed intron 3 restricted the expression of the transgene predominantly to shoot and root apices and young flower buds. Expression of this fusion also was delayed developmentally. Therefore, the alternative processing of the FCA transcript limits, both spatially and temporally, the amount of functional FCA protein. Expression in roots prompted an analysis of root development, which indicated that FCA functions more generally than in the control of the floral transition.

Alternative Splicing↗
PubMedDate not supplied

Disturbances in the oral cavity in pediatric long-term survivors after different forms of antineoplastic therapy.

Oral health and disturbances in dental development were studied in long-term survivors after antineoplastic therapy. Fifty-seven children treated with combination chemotherapy and 19 children treated with total body irradiation (TBI) prior to bone marrow transplantation (BMT) were examined. The variables studied were dental caries, salivary flow, salivary microbial counts, enamel disturbances, and disturbances in dental development. The results showed no increased caries experience in children treated with BMT or chemotherapy compared with controls. Children treated with BMT had a significantly lower salivary secretion rate of 0.7 +/- 0.4 ml/min, compared with 1.1 +/- 0.5 in the chemotherapy group, and 1.3 +/- 0.6 in the control group (P < 0.05). The clinical examination showed equal numbers of teeth affected by disturbances in enamel mineralization in the BMT and chemotherapy groups. A mean 15.9 +/- 8.2 teeth were affected by disturbances in root development in the BMT group compared with 1.2 +/- 1.6 in the chemotherapy group (P < 0.001). The results show that children who are long-term survivors of pediatric malignant diseases exhibit a wide range of disturbances in the oral cavity. In this study the most severe disturbances are found in children treated with total body irradiation prior to BMT.

Antineoplastic Agents↗
PubMed1987

Redistribution of Schwann cells in developing feline L7 ventral spinal roots.

The length and distribution of Schwann cells along fibres in the ventral root L7 of the developing cat have been studied electron microscopically in serial sections. The average Schwann cell length at the beginning of myelin formation - the 'initial internodal length' - was 118 micron (110 micron in alpha-axons and 124 micron in gamma-axons). The number of Schwann cells found in a fully developed root segment was already present at the beginning of the myelination. It showed no systematic age-dependent variation from the beginning of myelination to adulthood. The Schwann cells associated with alpha-axons increased their length 12.6 times during this period, while the root elongated 5.6 times. About 50% of the Schwann cells had to be eliminated in order to make the elongation of the remaining Schwann cells possible. Corresponding calculations from the mean length of Schwann cells associated with gamma-axons, showed that about 50% too few Schwann cells were associated with the gamma-axons during the period of initial myelination of the alpha-axons. At birth, when the myelination of gamma-axons had just begun, both the large surplus along alpha-axons and the deficit along gamma-axons had disappeared. We suggest that Schwann cells are eliminated from the alpha-axons and re-utilized along the gamma-axons. During this process of cellular redistribution, affected cells constitute so-called aberrant Schwann cells.

Age Factors↗
PubMed1990

A radiographic four-year follow-up study of asymptomatic mandibular third molars in young adults.

Fifty-five asymptomatic mandibular third molars (M3) in 34 dental students (mean age 20.6 years at the start of the study) were followed radiographically for 4 years. Based on clinical evaluation the 55 teeth included 20 almost erupted, 13 partly erupted and 22 non-erupted M3. The following were assessed on the radiographs: root development, level of eruption, sagittal angulation, resorption, pericoronitis/bony pockets/paradental cysts and widening of the periodontal space/dentigerous cysts. The state of 21 teeth (38 per cent) was radiographically changed at the end of the observation period. The most remarkable finding was that 15 teeth changed their sagittal angulation, all in a distal direction; five mesioangular to vertical, five vertical to distoangular, five mesioangular to distoangular. Radiographically, 13 M3 moved to a more advanced level of eruption. No real pathological osseous lesions and no root resorption were observed at initial or follow-up examinations. It is concluded that there are frequent essentially unpredictable changes in the position of M3 after the age of 19 years which may influence decisions on their removal or preservation.

Adult↗
PubMed1982

Canine eruption into grafted bone in maxillary alveolar cleft defects.

Forty-six patients with clefts of the alveolus who had received alveolar bone grafts (secondary osteoplasties) at ages 7-14 years, were studied. A total of 64 affected canines from 18 bilateral and 28 unilateral alveolar cleft patients was available. Follow up orthopantomographs were examined to determine the state of root development and spontaneous canine movement through the grafted site. The postoperative observation period ranged from 2-8 years (mean 4.3 +/- 1.5). All test canines erupted through the graft. Spontaneous eruption occurred for 27% of test canines, 17% required surgical uncovering (either bony or soft tissue), and 56% required surgical uncovering and orthodontic assistance to accomplish eruption. All patients required orthodontic treatment to accomplish arch alignment. The prognosis for canine eruption through a graft site is most favorable if the graft is performed at 1/4-1/2 canine root formation and when the patient is aged 9-12 years. The post graft observation period is very important and requires complete cooperation between the orthodontist and the surgeon.

Adolescent↗