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PubMed1983

Cell clusters on rat ventral roots: postnatal development.

The cell clusters found on the most proximal parts of rat ventral spinal nerve rootlets during prenatal development, persist into the postnatal period. Clusters become smaller as cells leave them to invest axon segments. By 2 weeks after birth, clusters have largely disappeared. Fine processes stemming from clusters interweave at first to envelop axons in a complex matrix. This matrix disappears soon after birth. Axons then become enveloped by cells in clusters in the manner of premyelin Schwann cells. Many of these premyelin cells leave the parent cluster but continue to envelop the unmyelinated axon segment as they do so. Meanwhile, myelination of axons immediately distal to the proximal rootlet segment proceeds at the same rate as in the ventral root generally. Thus, the proximodistal maturation gradient comes to be reversed in relation to many axons in the ventral root, the most proximal peripheral internode being unmyelinated, while more distal internodes are myelinated. This reversal gradually lessens in some cases as the short internodes produce myelin sheaths. It is possible that these short internodes become progressively more heavily myelinated and elongate in subsequent development. All axons in the most proximal part of the ventral rootlet do not necessarily become enveloped by short premyelin Schwann cells, however. When some are released from envelopment by the matrix, the myelinating Schwann cells at more distal root levels extend proximally along each of them, up to the level of the surface of the spinal cord. Some clusters in the early postnatal period contain cells resembling astrocytes.

Animals↗

PubMed2026

Identification and functional analysis of MeJA-responsive bHLH family genes in Taraxacum kok-saghyz.

Taraxacum kok-saghyz (T. kok-saghyz) is considered a highly promising alternative source of natural rubber (NR), as its roots synthesize high-molecular-weight NR comparable to that produced by Hevea brasiliensis. The basic helix-loop-helix (bHLH) family of transcription factors (TFs) plays crucial roles in plant organogenesis, hormonal signal transduction, and the regulation of secondary metabolism. This study aimed to systematically identify TkbHLH family members and to elucidate their potential functions in responding to methyl jasmonate (MeJA) and regulating root development. Based on the T. kok-saghyz genome, 172 TkbHLH members were identified and phylogenetically classified into 16 subfamilies. Among these, 37 genes were selected due to their significant induction by MeJA. Sequence analysis confirmed all encoded proteins contain the conserved bHLH domain. Subcellular localization verified nuclear localization of five core TkbHLH proteins. Interactions were shown by yeast two-hybrid and bimolecular fluorescence complementation, revealing these proteins form homodimers and heterodimers. Notably, a specific interaction was detected between TkbHLH162 and TkHMGS1, a key enzyme in the mevalonate (MVA) pathway, suggesting a potential molecular link between JA signaling and the rubber biosynthesis precursor pathway. Functional characterization via overexpression assays showed that selected TkbHLH genes significantly either promoted or inhibited root elongation. In summary, this study presents the first systematic characterization of the bHLH TF family in T. kok-saghyz, elucidating its involvement in JA signal response, protein interaction networks, and root development regulation. These findings provide a crucial foundation for further investigation into the molecular mechanisms by which TkbHLH TFs influence root morphogenesis and NR biosynthesis in T. kok-saghyz.

Taraxacum kok-saghyz (T. kok-saghyz)↗

PubMed1993

Neurotrophin receptor genes are expressed in distinct patterns in developing dorsal root ganglia.

All members of the neurotrophin family of neuronal growth factors promote survival and neurite outgrowth of dorsal root ganglion (DRG) neurons in vitro. The trk family of protooncogenes encodes receptors that are now thought to mediate the biological effects of neurotrophins. In order to learn more about the dependence of DRG neurons on neurotrophins in vivo, we have studied mRNA expression of members of the trk family in developing DRGs in embryonic and postnatal rats. We show here that neurotrophin receptors are expressed in thoracic and lumbar DRGs by embryonic day 13 (E13), which is only 24-48 hr after neurogenesis begins in these ganglia. Distinct patterns of expression of trkA, trkB, and trkC are readily apparent by E15. At this age, 40% of thoracic DRG neurons express trkA. In contrast, trkB and trkC are expressed by only 6% and 8%, respectively, of thoracic DRG neurons. These percentages change little between E15 and postnatal day 1. Although absolute numbers of DRG neurons expressing neurotrophin receptors are greater in lumbar than in thoracic ganglia, the ratios of DRG neurons expressing different members of the trk family are similar in the two regions. The different trks are expressed by distinct populations of DRG neurons from E15 onward. trkA is expressed predominantly by small neurons with darkly staining cytoplasm. trkB and trkC are expressed by large, lightly staining neurons. Size-frequency histograms show that trkA is expressed by neurons of variable sizes, but particularly by neurons at the smallest end of the spectrum. In contrast, trkC is expressed predominantly by large DRG neurons, including those with the largest soma areas. trkB is expressed by DRG neurons of intermediate size. Our results show that a majority of DRG neurons express mRNA for at least one member of the trk protooncogene family. Furthermore, trk expression occurs in a time frame consistent with the idea that trks mediate responses of DRG neurons to neurotrophins that are synthesized in both the periphery and spinal cord at early developmental stages. Finally, different populations of DRG neurons express different trks. We hypothesize that DRG neurons subserving different functions express different trks, and that trk expression of a particular class of DRG neurons determines its neurotrophin dependence during development.

Aging↗

PubMed1996

1,25-Dihydroxyvitamin D(3) receptors in developing dorsal root ganglia of fetal rats.

We observed immunostaining for the 1,25-dihydroxyvitamin D(3) receptor (VDR) and calbindin-D(28k) in neurons, but not glial cells, of fetal rat dorsal root ganglia (DRG) from days 13 through 21 of gestation. Dispersed cultures of DRG collected from rat fetuses at gestational day 15 also contained epitopes for VDR and calbindin-D(28k) in neurons, but not in glial cells. 1,25-Dihydroxyvitamin D(3), through VDR, may perform significant functions in the development of neuronal cells.

Animals↗

PubMed1988

Longitudinal study of electrometric sensitivity of young permanent incisors.

Electrometric sensitivity of permanent maxillary central incisors was studied longitudinally in 34 children at 6-month intervals over 2 1/2 yr (mean age of the children at the beginning of the study: 94.6 months). Root development stages were determined from radiographs obtained at the beginning of the study, after 1 yr, and after 2 1/2 yr. An increase in sensitivity was found over the study period, but large variations were found from child to child and even within the same child. Especially at the first examinations a few children showed very low sensitivity. Statistical analysis showed that examination number, root development and side of the mouth (right or left central incisor) all were statistically significantly related to sensitivity. Statistically significant differences were also found between the individuals.

Child↗

PubMed1983

Cell clusters on fetal rat ventral roots: prenatal development.

Clusters of cells are a prominent feature on the most proximal part of rat ventral rootlets between 15 and 21 days of fetal life and they increase to a maximum size at 17 days post conception. By means of extensive sheath-like processes the component cells of the clusters encapsulate one another in a very complex manner. Cells also give rise to processes which extend into the underlying axon bundles in the most proximal part of the ventral root and there form a highly complex matrix of interwoven fine cytoplasmic processes which separate individual axons from one another from a very early stage. With maturation, the clusters become smaller and the complex matrix disappears. Cells separate off from the clusters and enter the underlying ventral rootlets where they differentiate into Schwann cells and come to envelop the axons in the manner characteristic of the latter. However, the proximal part of the rootlet remains at a much less advanced state of maturation than more distal parts up to the end of fetal life. It is possible that cell clusters are in part produced by overgrowth of CNS tissue around the axon bundles in the ventral rootlets. This strips the cells distally and causes them to become piled up as collars around the most proximal part of the ventral rootlet.

Animals↗

PubMed2026

Dual Roles of RAD23b and RAD4 on the Desiccation Tolerance of Germinated Seeds.

Desiccation tolerance (DT) is a survival trait enabling orthodox seeds to withstand extremely low water content. While some protective factors are characterised, it remains mechanistically obscure. Here, based on PEG-induced DT re-establishment in germinated Brassica napus L. seeds, we investigated the dual functions of nucleotide excision repair (NER) components RAD23b and RAD4 in DNA repair and transcriptional regulation of root development. PEG pre-treatment alleviated dehydration-induced DNA damage and activated NER genes, suggesting the involvement of NER in seed DT. Unexpectedly, Arabidopsis atrad23b mutant and BnRAD23b/BnRAD4 over-expressing seeds all exhibited significantly decreased DT after dry back, which evoked a hypothesis that BnRAD23b-BnRAD4 functions beyond NER. Normally, BnRAD4 interacted with BnRAD23b and repressed the expression of root development genes NAC103, EMB1444, RRA1 by directly binding to STRE elements within their promoters. Dehydration stress alleviated this repression, drove transcriptional reprogramming and might redirect the complex to execute DNA repair. Genetic analyses revealed that germinated seeds of atnac103, atemb1444, and atrra1 single mutants all exhibited reduced DT, and double mutants under atrad23b background almost abolished DT. This study suggests that RAD23b and RAD4 may regulate DT re-establishment of germinated seeds through balancing genome integrity and radicle development, with implications for DT study broadly.

Brassica napus L.↗

PubMed2002

Surgical repositioning of an impacted dilacerated incisor in mixed dentition.

BACKGROUND: Treatment options for a dilacerated incisor are either extraction or surgery and orthodontic traction. Because patients with such incisors usually are young, and because of the root angulation of the impacted incisor, treatment usually is lengthy and complicated. Surgical repositioning provides another option for treatment of this unique problem. CASE DESCRIPTION: The author presents the case of a 9-year-old girl with an impacted dilacerated maxillary central incisor to demonstrate the timing, technique and results of the surgical repositioning treatment approach. The advantages of this approach include immediate esthetic improvement, use of a single and simplified surgical procedure, simple and short orthodontic therapy, a normal gingival margin and the possibility of the developing root's adapting to the new position. CLINICAL IMPLICATIONS: Surgical repositioning is a simplified treatment for dilacerated incisors. It is especially valuable in cases of difficult-to-treat impaction. Timing of surgical repositioning depends on the incisor's root development and the space available for the transplant.

Child↗

PubMed1988

Glutamate synthase in Medicago sativa L. Occurrence and properties of FD-dependent enzyme in plant cell fraction during root nodule development.

In the plant cell fraction of Medicago sativa (L. cv Europe) nodules, glutamate synthase is active with reduced Fd, MV, NADH and NADPH as an electron donor. Up to 25 to 30 days after inoculation, the activities of Fd-dependent glutamate synthase (EC 1.4.1.7), the most active form of the enzyme, NADH-dependent (EC 1.4.1.14) and NADPH-dependent (EC 1.4.1.13) glutamate synthases increase about 2-fold followed by a relatively constant level per gram fresh weight of nodules. The activities of glutamate synthases with different electron carriers increase constantly about 30-fold after 46 days of inoculation by total fresh weight of nodules per plant. These nodule glutamate synthase activities with Fd, NADH or NADPH represent 30% relative to those of root glutamate synthases per plant with the respective electron donor. Fd-glutamate synthase in nodule plant fraction is a protein molecule immunochemically distinct from pyridine nucleotide-glutamate synthases. MV-linked enzyme activity is associated with Fd-glutamate synthase. The Fd-glutamate synthase has a subunit molecular mass of 68.2 kDa, and it exhibits a high affinity for spinach Fd as an electron carrier. The increase in Fd-glutamate synthase activity during nodule development is accompanied by a rise in the enzyme protein content. The total activity of different forms of glutamate synthase in vitro ensures a higher level than the rate of ammonia production during N2 fixation in bacteroids of Medicago sativa nodules.

Blotting, Western↗

PubMed1997

Sequential functioning of Sym-13 and Sym-31, two genes affecting symbiosome development in root nodules of pea (Pisum sativum L.).

Two Fix- mutants of pea (Pisum sativum L.) which are unable to fix molecular nitrogen, E135f (sym-13) and Sprint-2Fix- (sym-31), were crossed to create the doubly homozygous recessive line, named RBT (sym-13, sym-31). The ultrastructural organization of nodules of the RBT line was compared with that of each of the two parental mutant lines and with the original wild-type genotypes of the cultivars Sparkle and Sprint-2. It was shown that the RBT line is similar to the mutant line Sprint-2Fix- in having abnormal symbiosome composition and bacteroids with relatively undifferentiated morphology. Because the phenotypic manifestation of the sym-31 mutant allele suppresses the phenotypic manifestation of the sym-13 mutant allele, it is concluded that the function of the gene Sym-31 (which is mutated in the Sprint-2Fix- line) is necessary at an earlier stage of symbiosome development than the gene Sym-13 (which is mutant in the E135f line).

Genes, Plant↗

PubMed1978

[Induction of jaw bone formation by tooth autotransplantation].

A case-report of segmental underdevelopment of the alveolar process in the upper jaw of an eleven-year old girl is presented. At the site where the alveolar ridge was underdeveloped, two impacted malformed incisors were found. The malformed teeth had almost normal crowns, but the root-development had terminated 1-2 mm beyond the cementoenamel junction. The patient was treated by removal of the two malformed impacted teeth, followed by autotransplantation of the developing second premolar with the intention of inducing bone formation. The result was promising. After 3 years the alveolar process had developed to almost normal vertical hight. Some considerations are made regarding the possible origin of the bone induction factors in tooth buds. The fact that this patient demonstrated an underdevelopment of the alveolar process in spite of the formation of almost normal crowns, is taken as evidence that the bone stimulating principle in tooth buds are not to be found in the enamel organ proper, but must be related to Hertwig's epithelial sheath, root development and tooth eruption.

Alveolar Process↗

PubMed2026

Genome-Wide Analysis of Triticum aestivum Root Meristem Growth Factor (RGF) Gene Family Highlights TaRGF5 as a Putative Component of Root-Associated Signaling.

Wheat (Triticum aestivum), a key global crop, faces rising drought stress that limits root growth and water uptake. Root meristem growth factors (RGFs) are small peptides that regulate root stem cell maintenance, meristem activity, and lateral root formation in model plants, yet the RGF gene family remains unexplored in wheat. Here, we performed a comprehensive genome-wide analysis of the TaRGF gene family, identifying 15 genes distributed across the A, B, and D subgenomes and classified into five homeologous groups (TaRGF1-TaRGF5), predominantly located on chromosomes 2 and 6. All TaRGFs contained a characteristic RGF motif, with dibasic cleavage sites and Asp-Tyr motifs indicating conserved maturation mechanisms. Based on the phylogenetic analysis, the TaRGF5 homeologs showed the highest similarity to Arabidopsis thaliana RGF5. Tested RNA-seq data revealed predominantly root-enriched expression for all TaRGF genes, with TaRGF5 exhibiting the most root-preferential and downregulation under drought stress. Quantitative real-time PCR (qRT-PCR) confirmed that drought stress suppressed the expression of TaRGF5A, TaRGF5B, and TaRGF5D in roots of wheat cultivar Sids-13 across all time points, unlike the higher accumulation seen in controls. Promoter analysis predicted a unique BES1 transcription factor binding site exclusively in TaRGF5B, linking brassinosteroid signaling to peptide-mediated root regulation. Structural modeling and molecular docking predicted an interaction between wheat TaRGF5 homeologs and root growth factor-insensitive receptor kinase (TaRGI3), characterized by conserved sulfotyrosine-mediated binding and favorable interaction energetics. Based on this characterization of the wheat RGF gene family, particularly the potential role of TaRGF5 in root development and drought-adaptation signaling, we propose targeting this gene for functional analysis to improve wheat resilience under water-limited conditions.

Triticum↗

PubMedDate not supplied

Effects of CO2 laser irradiation on tooth-root cementum.

With the aging of the American population and the endemic problem of gingival recession, patients will inevitably suffer from greater exposure of root surfaces and therefore will be more likely to develop root caries. The treatment of root caries is often frustrating. Traditional biomaterials used for the restoration of enamel caries have been less than satisfactory when margins of a cavity are adjacent to cementum. Although topical fluoride gels, toothpastes, and rinses have been used to prevent or to inhibit the development of root caries, there is a problem of access to the proximal surfaces. Consequently, the development of better methods to facilitate the prevention of root caries has become an important issue in dentistry.

Dental Cementum↗

PubMed1988

Improvement of dental development in osteopetrotic mice by maternal vitamin D3 sulfate administration.

Utilizing the microphthalamic mouse, (mi/mi) as a model of osteopetrosis, vitamin D3 (cholecalciferol) was administered prenatally and postnatally to study its effects on tooth development and subsequent eruption. It has previously been reported that vitamin D3 crosses the placental barrier and is absorbed into mammary gland milk. Fifteen heterozygotes (+/mi) were used as breeders. There were three study groups: A) 5.0 ng/gm cholecalciferol sulfate; B) 2.5 ng/gm cholecalciferol sulfate; and C) no therapy. Intraperitoneal injections were administered three times per week, beginning when pregnancy was evident, and continuing for 4 additional weeks during lactation. Approximately half of the 59 offspring were sacrificed at age 1 day and the other half at 4 weeks. The former group was studied for crown development, and the latter group was studied for root development and eruption. When the osteopetrotic offspring of group A were compared with osteopetrotic offspring of group C, crown development and tooth eruption were substantially more advanced. Parameters examined were maturity of the ameloblasts and odontoblasts, dentin and enamel formation, root sheath development, status of eruption, and degree of apex closure. It was concluded that cholecalciferol sulfate significantly improves tooth development and subsequent eruption in the osteopetrotic mouse. A genetic disease has had its phenotype modified by vitamin therapy during gestation.

Animals↗

PubMed1976

Inhibition of linolenic Acid synthesis and modification of chilling resistance in cotton seedlings.

The temperature at which cotton seeds (Gossypium hirsutum L.) germinated influenced the fatty acid composition of the polar lipids of developing root tips. Seeds were germinated at 15, 20, 25, and 30 C. As the temperature decreased the linolemic acid content of the polar lipid fraction increased. Sandoz 9785[4-chloro-5-(dimethylamino)-2-phenyl-3(2H)-pyridazinone] reduced the low temperature-induced increase in linolenic acid content of the polar lipids and reduced seedling ability to withstand 8 C chilling. The results are consistent with the conclusion that chilling resistance in cotton seedlings is related to the level of linolenic acid in the polar lipids in the developing root tips.

Journal Article↗

PubMed1982

A comparative evaluation of the level of concanavalin a binding by enriched plasma membrane fractions from developing soybean roots.

The Concanavalin A (Con A) binding capacity of plasma membranes isolated from meristematic and mature regions of four-day-old soybean (Glycine max L. Merr. cv. Wells) roots was compared. Con A binding was studied using a radiochemical assay with tritiated ((3)H)-Con A and by an electron microscope technique using Con A-ferritin (Con A-F). In both cases, plasma membranes isolated from meristematic tissue bound significantly more Con A than did corresponding membranes from mature tissue. The relative difference in reactivity, as determined by the two procedures, was approximately 49% ((3)H-Con A) and 46% (Con A-F). In contrast, K(m) values, determined from (3)H-Con A binding curves, were approximately the same, indicating that receptor sites on plasma membranes from both sources were qualitatively similar.Since Con A specifically interacts with saccharide-containing portions of membrane glycoproteins and/or glycolipids, the data suggests that there is a decrease in the concentration of those components in plasma membranes during development or that there are qualitative changes in the structure of their oligosaccharide side chains.

Journal Article↗

PubMed1987

Development of the spinal nerves in the lamprey: III. Spinal ganglia and dorsal roots in 26-day (13 mm) larvae.

Serial sections of the trunk and tail of 26-day (13 mm) larval lampreys were examined by light and electron microscopy. Trunk region: Spinal ganglia and ventral nerves are seen alternately along the spinal cord and the notochord in the trunk. Spinal ganglia are located medially in intermyotome spaces with intersegmental blood vessels and send "dorsal nerves" ventrally along the vessels. "Ventral nerves" are seen on the midmedial surface of each myotome. Fibers containing dense-cored vesicles occur in the dorsal root but not in the ventral root. Caudal region: In the caudal one-third of the tail the ventral nerves are formed earlier than spinal ganglia and dorsal nerves. The most caudal (primitive) ventral nerve (root) develops at the 12th myotome from the caudal end of the series of myotomes, the caudalmost ganglion being formed between the 15th and the 14th myotome in a 13-mm larval lamprey. The intimate association of dorsolateral outflow (DLO) fibers (Nakao and Ishizawa: J. Comp. Neurol. 256:356-368, '87b) with neural crest cells (DO cells of Nakao and Ishizawa; ibid.) strongly suggested that these fibers play an important role as the substrate for guiding the cells to form compact cell masses as primitive spinal ganglia. Two types of cell groups are progressively distinguished in primitive spinal ganglia during development. One of them has a light round nucleus with a prominent nucleolus and a large amount of the perinuclear cytoplasm that contains abundant free ribosomes, rough endoplasmic reticulum (ER), numerous Golgi apparatuses, and dense bodies. Cells of the other type are characterized by a dense, flattened nucleus with a small amount of perinuclear cytoplasm that extends as a thin cytoplasmic sheet to surround cells of the other type as a whole, the basal lamina surrounding the whole cell mass. The former type is interpreted as neural cells and the latter satellite cells of the ganglion. Central processes of ganglionic neural cells are assumed to enter the spinal cord along DLO fibers by using them as a substrate to establish the dorsal root. Intersegmental blood vessels develop later than spinal ganglia and peripheral processes extend along the vessels.

Animals↗

PubMed1987

In vivo effect of brain-derived neurotrophic factor on the survival of developing dorsal root ganglion cells.

Implantation of silastic membranes between neural tube and somites at somitic levels 20-24 in 30-somite-stage chick embryos results in separation of early migrated neural crest cells of the dorsal root ganglion (DRG) anlage from the neural tube and their death within a few hours [Kalcheim and Le Douarin, (1986) Dev. Biol., 116, 451-460]. The in vivo effects of brain-derived neutrotrophic factor (BNDF) on survival of HNK-1 immunoreactive DRG cells separated from the tube were examined by implantation of laminin-treated silastic membranes (controls) or BDNF/laminin-treated membranes. In the presence of BDNF/laminin-treated membranes, 20/25 grafted embryos fixed 10 h after implantation, contained many rescued cells on the operated side. In contrast, only a few rescued cells on the operated side. In contrast, only a few rescued cells were observed in sections on the operated in 2/11 embryos implanted with laminin-treated silastic membranes, and no rescued cells at all could be detected in embryos implanted with NGF/laminin-treated (seven embryos) or untreated silastic membranes (12 embryos). The data presented support the hypothesis that early survival and differentiation of neural crest-derived sensory cells depend on central nervous system-derived factor(s). Moreover, this is the first evidence for the in vivo activity of BDNF on survival of developing DRG cells.

Animals↗