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PubMed1997

Effect of calcium hydroxide dressing on seal of permanent root filling.

Low apical leakage along root fillings following an application of calcium hydroxide was reported in a few methylene blue dye penetration studies. It has been found recently that methylene blue is decolored by calcium hydroxide, indicating that the short penetration of methylene blue may not be due to a tight seal only. Of the 80 roots of human maxillary central incisors used in this study, 40 roots (group 1) received calcium hydroxide root canal dressing whereas another 40 roots (group 2) did not. All the roots were then obturated with gutta-percha and Tubli-Seal sealer. Leakage along 20 filled roots in each group was measured using a modified fluid transport model at 48 h, 2, 4, 8 and 16 weeks after obturation; whereas leakage of another 20 filled roots in each group was measured using dye penetration with 1% methylene blue. Using the fluid transport model, no significant difference was found between the two groups at any time interval (P = 0.4847, 0.3875, 0.9490, 0.4786, 0.9148 respectively after 48 h, 2, 4, 8 and 16 weeks); using the methylene blue penetration method, leakage in group 1 (with root canal dressing) was significantly less than that in group 2 (without root canal dressing) (P = 0.0374). The contradiction in results from the different models indicated that problems existed with the models.

Calcium Hydroxide↗
PubMed1996

Five-year incidence rates and intraoral distribution of root caries among community-dwelling older adults.

The 5-year incidence and intraoral distribution of decayed and filled root surfaces were evaluated in 379 black and 323 white residents of North Carolina aged 65 and older. During the period of study, approximately 39% of blacks developed at least one root DFS compared with 52% for whites (Wald X(2) test, p = 0.062). When the results were calculated using the net root DFS increment, blacks did not have significantly higher rates than whites over the 5-year study period (0.52 surfaces/person versus 0.42 surfaces/person, Survey Regression, n = 363, p = 0.708). However, for blacks, the 5-year incidence density rate of root DFS was 0.26 per 60 surface-months at risk, and for whites the rate was 0.19 new root DFS per 60 surface-months (incidence density ratio = 1.33, 95% CI = 1.01-1.76, p = 0.047). Intraoral distribution patterns for root caries incidence revealed that the approximal surfaces of the anterior teeth were involved most frequently, particularly in the mandible and maxilla in whites, followed in decreasing order by the buccal surfaces of the lower anteriors and the mesial surfaces of the upper anteriors in blacks. Although root caries incidence rates were obviously low, there were significant differences in the occurrence of caries between blacks and whites. The pattern of occurrence was similar for both races with root surface disease being concentrated in the approximal surfaces of the anterior teeth in a small proportion of affected individuals, with whites presenting more filled root increments than blacks. These findings suggest a need for more caries treatment in blacks and increased monitoring of this population since they are at a higher risk for root caries.

Black or African American↗
PubMed1996

Inhibitory effect of the topical administration of a bisphosphonate (risedronate) on root resorption incident to orthodontic tooth movement in rats.

Root resorption associated with tooth movement is an unsolved problem in orthodontics. If such root resorption could be prevented, it would be an important contribution toward reducing risk factors in orthodontic treatment. The purpose of this study was to examine the effects of the topical administration of a bisphosphonate, risedronate, which is known to be a potent blocker of bone resorption, on root resorption during tooth movement and on the repair of the resorbed root surface after tooth movement in rats. In the first experiment, both the right and left upper first molars were moved buccally with a standardized expansion spring under administration of risedronate. After day 7, extensive root resorption had occurred on the control side, and the area of root resorption reached a maximum on day 14. The topical administration of risedronate caused a significant and dose-dependent inhibition of root resorption after the orthodontic force was applied. In the second experiment, the right and left upper molars were first moved buccally for 3 weeks. Risedronate treatment began on the day the spring was removed. After the force was withdrawn, the resorbed root surfaces on both the control and risedronate-treated sides were gradually restored by apposition of repair cementum (cementoid). The topical administration of risedronate did not appear to inhibit the repair process of root resorption. These results suggest that the topical administration of risedronate may be useful in preventing root resorption of teeth during orthodontic treatment.

Administration, Topical↗
PubMed1992

Root surface characteristics associated with subgingival placement of monolithic tetracycline-impregnated fibers.

The purpose of this investigation was to inspect and characterize the subgingival root surface after a 10-day exposure in vivo to 25% tetracycline hydrochloride by weight in an ethylene vinyl acetate copolymer fiber matrix with and without root planing therapy. The root surfaces were examined by fluorescent-light microscopy (FLM), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Thirty-two teeth were selected for study, 4 from each of 8 patients. The teeth of each patient were randomly assigned to one of four treatment groups: non-treated control (C), scaling and root planing only (RP), tetracycline-impregnated fiber only (F), and scaling and root planing with tetracycline-impregnated fiber application (RP/F). SEM revealed a visible reduction in the subgingival microbial flora in both the F and RP/F treatment groups in comparison with the C group specimens. Many of the residual bacteria observed in F and RP/F specimens appeared non-viable, exhibiting obvious loss of membrane integrity. In contrast, the RP specimens exhibited randomly distributed areas of residual subgingival plaque and calculus with newly developing plaque fronts; the plaque fronts undoubtedly having formed during the 10 days post-therapy. All RP/F specimens exhibited an incomplete removal of adsorbed root surface pellicle and demineralization of the subsequently exposed root surface. EDS analysis of large crystals adhering to root surfaces of F and RP/F specimens revealed high chloride peaks, suggesting the presence of residual tetracycline. FLM examination of F and RP/F treated specimens showed a superficial penetration of tetracycline into the root surface of about 10 microns. Areas of demineralized root showed slight tetracycline penetration into exposed dentinal tubules.

Adsorption↗
PubMed1989

[Fundamental study of a local drug delivery system by means of intracanal medication. Influence of iontophoresis on the periphery of the root surface].

The purpose of this study was to evaluate a new system of drug delivery to periodontal pocket by means of intracanal dressing and additional iontophoresis in vitro. Forty extracted human teeth with a single root were used. After the root canal was prepared endodontically, the periphery root apex was painted with the Silux system (3 M Co.) to close the apical foramen. Each tooth was planted into an agar block. Three drugs (zinc iodide-iodine, penicillin G. potassium, minocycline HCl) were used (Table 1), and 50 microliters of each drug was injected into an individual root canal. Then a cathodic current (3 mA x 40 min) was applied using an automatic current volte regulater (PAV-200, Jooko Co.) with a platinum wire electrode inserted in the root canal (Fig. 1). The degree of drugs diffusion in the agar around teeth was estimated by individual color reactions zinc iodide-iodin test for starch, penicillin G. potassium test for phosphomolybdic acid, minocycline HCl test for ferric chloride). And also, the effects of root planing and etching by Quick Jet (Yosida Co.) on the root surface were evaluated in the same way. The results were as follow: 1. The degree of diffusion by intracanal electrical medication was greater in the cervical third area than the middle and apical third. 2. Several small areas stained by the iodo-starch color reaction were observed around the cervical root surface where greater diffusion was observed. 3. Many dentinal tubules were observed on a limited root surface where root planing and Quick Jet, were employed caused greater diffusion. 4. The results suggest the new delivery system for management of the microorganisms by intracanal medication and additional iontophoresis.

Humans↗
PubMed2003

Perception mechanism of gravity stimuli in hypergravity-induced growth inhibition of azuki bean roots.

We reported that elongation growth of plant shoots and roots is suppressed by hypergravity, with the rate decreasing in proportion to logarithm of the magnitude of gravity. In hypergravity-induced growth inhibition of shoots, graviperception is supposed to be independent of that in gravitropism and to involve mechanoreceptors. However, the graviperception mechanism in the hypergravity-induced growth inhibition of roots is not known. In the present study, we compared the mechanism in the hypergravity-induced growth inhibition of roots with that in gravitropism. The removal of root cap did not influence hypergravity-induced growth inhibition of roots, although the gravitropic curvature was completely inhibited. Hypergravity had no effects on growth of azuki bean roots in the presence of lanthanum or gadolinium, which are blockers of mechanoreceptors. On the contrary, lanthanum or gadolinium at the same concentration did not influence gravitropism of roots. These results suggest that the graviperception mechanism in the hypergravity-induced growth inhibition of roots is independent of that in gravitropism. Hypergravity-induced growth inhibition of azuki bean roots was observed irrespective of the direction of stimuli, which disappeared in the presence of lanthanum or gadolinium. Thus, in the hypergravity-induced growth inhibition, roots may perceive the gravity signal by mechanoreceptors on the plasma membrane independently of the direction of stimuli, and may utilize it to regulate their growth rate.

Fabaceae↗
PubMed2006

[A study on the accuracy of electronic root canal length measurement and its influential factors].

PURPOSE: To study the accuracy of JUSTY-II electronic apex locator and the influential factors on the accuracy of root canal working length measurement. METHODS: 148 teeth, including 71 teeth with pulpitis, 46 with necrotic pulp and 31 with apical periodontitis, were divided into two groups in random. The accuracy of electronic root canal working length measurement group was compared with that of the manual measurement group by Chi(2) test. The influence of clinical types, root canal in dry or moisture conditions and root canal preparation on the accuracy of root canal working length measurement was analyzed. RESULTS: The accuracy of electronic apex locator was 87.84%, while it was 43.24% in manual measurement, the difference was significant (P<0.01). The accuracy in the group of apical periodontitis was significantly lower than that of the other groups (P<0.05). Root canal in dry or moisture conditions had no effect on the accuracy of root canal length measurement, but root canal preparation could decrease the accuracy of measurement (P<0.05). CONCLUSION: Electronic apex locator is an accurate and convenient device in measurement of root canal working length. Apical periodontitis and root canal preparation can decrease the accuracy of measurement.

Bicuspid↗
PubMed1999

Obturation of root canals with different sealers using non-instrumentation technology.

AIM: To evaluate and compare the sealing quality of hand- or vacuum-obturated root canals after hand preparation or hydrodynamic cleansing of root canals, respectively. METHODOLOGY: After assessing root curvature, 96 single-rooted deep-frozen teeth were divided into eight comparable groups. The root canals of four groups were instrumented with the balanced force technique. The remaining uninstrumented teeth were connected to a reduced-pressure device (NIT) and the root-canal system perfused with 2.5% NaOCl under alternating pressure fields. This dissolved the pulpal tissues and removed debris from the root-canal system. The canals of the hand-instrumented groups were obturated using the cold lateral condensation method with guttapercha and one of four different sealers (AH26, AH Plus, Apexit and Pulp Canal Sealer EWT). The teeth treated with the alternating pressure device (NIT) were obturated by a vacuum obturation method (NIT) with the same four sealers. The quality of the coronal seal was assessed using a dye penetration method. In order to minimize errors the roots were perfused with water before exposure to the dye, under vacuum. The teeth were then rendered transparent and the depth of penetration of the dye between the wall of the canal and the obturating material was measured with a stereomicroscope. RESULTS: The canals cleaned and filled by NIT showed statistically significantly less dye penetration than those obturated by lateral condensation (P < 0.05). Within the NIT group, Pulp Canal Sealer EWT exhibited significantly more dye penetration than Apexit. Amongst the control lateral condensation groups no significant differences were found between the various sealers. CONCLUSIONS: The present investigation demonstrated the validity of the NIT obturation method in combination with commonly used root-canal sealers.

Bismuth↗
PubMed2001

In vitro infrared thermographic assessment of root surface temperatures generated by the thermafil plus system.

The purpose of this in vitro study was to investigate root surface temperatures generated by the Thermafil Plus system using infrared thermography. A total of 60 extracted human maxillary central incisors and maxillary first molars were biomechanically instrumented using ProFile 0.04 Taper Series 29 rotary instruments. The root canals were obturated using the Thermafil Plus system. An infrared thermography camera was used to measure the external root surface temperatures during and after the completion of obturation. The mean temperature rise of the external root surface from the ambient temperature was 4.26 degrees C for the mesial buccal roots, 4.58 degrees C for the distobuccal roots, 4.76 degrees C for the palatal roots, and 4.87 degrees C for the anterior roots. These temperatures were well below the critical level of 10 degrees C needed to cause damage to the attachment apparatus. From this in vitro experiment, no evidence was discovered which would indicate that the Thermafil Plus obturation system would result in damage to the periodontal ligament and the surrounding attachment apparatus as a consequence of temperature rise on the external root surface.

Body Temperature↗
PubMed2005

Quantification of oxygen release by bulrush (Scirpus validus) roots in a constructed treatment wetland.

Amount of oxygen released by bulrush (Scirpus validus) roots has been quantified based on the radial oxygen loss (ROL) exhibited by the roots, the number and the length of active lateral roots, and the field plant density. It was found that wetland bulrush contains two types of active lateral roots (showing ROL), viz., laterals of brown and white main roots. The two laterals have distinct oxygen release characteristics. Based on the dissolved oxygen (DO) microprofiles of brown and white laterals, the ROLs were found to be approximately 61 ng O2 cm(-2) root surface min(-1) and approximately 68 ng O2 cm(-2) root surface min(-1), respectively, at bulk 5-day biochemical oxygen demand (BOD5) of 76 mg L(-1). The respective average active root lengths of the brown and the white laterals were approximately 40 and approximately 1676 microm. Based on field and laboratory measurements, the average amount of oxygen released by bulrush was found to be 2.30 mg O2 m(-2) wetland surface d(-1); of this approximately 71% is from the white roots. The results of this study indicate that plants do not release enough oxygen to meet the total oxygen demand of bulk wastewater, and therefore, constructed wetlands should be designed as an anaerobic or an aerobic-anaerobic hybrid system rather than as an aerobic system. However, the results of this study should be viewed in the background of possible errors (including a reactor design flaw), which might have made the measured oxygen release significantly lower than what plant roots actually release. Further studies are needed to quantify wetland plant oxygen release based on micro-scale measurements.

Cyperaceae↗
PubMed2002

Morphologic study of the connections between the accessory nerve and the posterior root of the first cervical nerve.

The purpose of this study was to evaluate the anastomotic relationships between the accessory nerve and the posterior root of the first cervical nerve and to determine the course of the posterior root nerve fibers after anastomosis. The relationships between these two nerves were studied in 100 sides of the spinal cord and then classified into four types. In the most common type of anastomosis (38% of cases), either a branch from the posterior C1 root was seen to course cranially and join the accessory nerve, or the posterior root and accessory nerve fused as they coursed orthogonal to one other. In the second most common type (36% of cases), the accessory nerve anastomosed with a posterior C1 root that had no direct connection with the spinal cord; the nerve fibers of the posterior root were observed in stained samples to course caudally along the accessory nerve and join the posterior C2 root. In the least common type (6% of cases), no connection was observed between the accessory nerve and the posterior C1 root. In the next least common type (20% of cases), the posterior C1 root was absent and a connecting branch was sometimes observed between the accessory nerve and the anterior C1 root.

Accessory Nerve↗
PubMed1994

Substance P-, calcitonin gene-related peptide, growth-associated protein-43, and neurotrophin receptor-like immunoreactivity associated with unmyelinated axons in feline ventral roots and pia mater.

The spinal pia mater receives a rich innervation of small sensory axons via the ventral roots. Other sensory axons enter the ventral roots but end blindly or turn abruptly in hairpin loop-like formations and continue in a distal direction. In the present study, the content of substance P (SP)-, calcitonin gene-related peptide (CGRP)-, growth-associated protein (GAP-43)-, and low-affinity neurotrophin receptor protein (p75NGFr)-like immunoreactivity (-LI) associated with these different types of sensory axons was assessed with light and electron microscopic immunohistochemical techniques. In addition, the binding of antibodies against synthetic peptides representing unique sequences of residues in the products of the trk and trkB protooncogenes was analyzed. These genes encode membrane spanning proteins, which have been shown to constitute specific high affinity binding sites for several members of the nerve growth factor family of neurotrophic factors. The results of the present study imply that the ventral root afferents comprise several different types of sensory axons, which all contain SP-, CGRP-, GAP-43-, and p75NGFr-like immunoreactivities. In addition, at least some of the presumed sensory fiber bundles in ventral roots and the pia mater were immunoreactive for the trkB gene product. Moreover, leptomeningeal cells and nonneuronal cells of the ventral roots were shown to bind antibodies to both the trk and trkB gene products. The ventral root afferents seem to share their immunohistochemical pattern with pain-transducing axons at some other locations, such as the tooth pulp. The contents of SP- and CGRP-LI in sensory axons that reach the central nervous system (CNS) through the ventral root indicate that ventral root afferents may be involved in sensory mechanisms, such as the ventral root pain reaction, as well as in the control of the pial blood vessels. The demonstration of GAP-43 and neurotrophin receptor-immunoreactivities associated with unmyelinated fibers in ventral roots and the pia mater is discussed in relation to previous reports on postnatal plasticity in these axonal populations.

Animals↗
PubMed2004

Assessing the use of delta(13)C natural abundance in separation of root and microbial respiration in a Danish beech (Fagus sylvatica L.) forest.

Our understanding of forest biosphere-atmosphere interactions is fundamental for predicting forest ecosystem responses to climatic changes. Currently, however, our knowledge is incomplete partly due to inability to separate the major components of soil CO(2) effluxes, viz. root respiration, microbial decomposition of soil organic matter and microbial decomposition of litter material. In this study we examined whether the delta(13)C characteristics of solid organic matter and respired CO(2) from different soil-C components and root respiration in a Danish beech forest were useful to provide information on the root respiration contribution to total CO(2) effluxes. The delta(13)C isotopic analyses of CO(2) were performed using a FinniganMAT Delta(PLUS) isotope-ratio mass spectrometer coupled in continuous flow mode to a trace gas preparation-concentration unit (PreCon). Gas samples in 2-mL crimp seal vials were analysed in a fully automatic mode with an experimental standard error +/-0.11 per thousand. We observed that the CO(2) derived from root-free mineral soil horizons (A, B(W)) was more enriched in (13)C (delta(13)C range -21.6 to -21.2 per thousand ) compared with CO(2) derived from root-free humus layers (delta(13)C range -23.6 to -23.4 per thousand ). The CO(2) evolved from root respiration in isolated young beech plants revealed a value intermediate between those for the soil humus and mineral horizons, delta(13)C(root) = -22.2 per thousand, but was associated with great variability (SE +/- 1.0 per thousand ) due to plant-specific differences. delta(13)C of CO(2) from in situ below-ground respiration averaged -22.8 per thousand, intermediate between the values for the humus layer and root respiration, but variability was great (SE +/- 0.4 per thousand ) due to pronounced spatial patterns. Overall, we were unable to statistically separate the CO(2) of root respiration vs. soil organic matter decomposition based solely on delta(13)C signatures, yet the trend in the data suggests that root respiration contributed approximately 43% to total respiration. The vertical gradient in delta(13)C, however, might be a useful tool in partitioning respiration in different soil layers. The experiment also showed an unexpected (13)C-enrichment of CO(2) (>3.5 per thousand ) compared with the total-C signatures in the individual soil-C components. This may suggest that analyses of bulk samples are not representative for the C-pools actively undergoing decomposition.

Biomass↗
PubMed2000

Influence of insect larvae and seedling roots on the host-finding ability of Steinernema feltiae (Nematoda: Steinernematidae).

The ability of nematode foragers to locate appropriate insect hosts is essential to their performance as successful biological control agents. We investigated the host-finding ability and chemotaxis of Steinernema feltiae in the presence of cues from Galleria mellonella larvae and tomato and radish seedling roots, given individually and in combination, over 120 min. In agar arena tests, infective juveniles of S. feltiae responded positively to unsterilized and sterilized larvae and tomato seedling roots and negatively to unsterilized radish seedling roots. This negative response changed following surface sterilization of these seeds. The response of the infective juveniles to a combination of larva and seedling roots depended on the nature of the individual cues and their proximity to each other. For example, the response of the nematodes to a combination of cues from a sterilized larva and an unsterilized tomato seedling root placed adjacent to each other was intermediate to the separate responses to cues from a sterilized larva and an unsterilized tomato seedling root given individually. However, the response of the nematodes to a combination of adjacent cues from a sterilized larva and an unsterilized radish seedling root was not significantly different from that to cues from an unsterilized radish seedling root given individually. When the cues from the larva and seedling roots were separated by a distance, the response of the nematodes favored the larva. However, this positive effect was lessened when the larva was surface sterilized as compared with the response to the unsterilized larva. The altered responses of the infective juveniles to target cues following surface sterilization suggest that cues from the larval cuticle and seedling roots, such as those associated with their surface microflora, may significantly influence their host-finding ability. The use of entomopathogenic nematodes as biological control agents under field applications can be improved by careful consideration of the application protocols and by the recognition that chemical alterations of the soil rhizosphere may influence their host-finding ability.

Animals↗
PubMed1994

Identification of a maize root transcript expressed in the primary response to nitrate: characterization of a cDNA with homology to ferredoxin-NADP+ oxidoreductase.

To more fully understand the biochemical and molecular events which occur in plants exposed to nitrate, cDNAs whose accumulation was enhanced in nitrate- and cycloheximide-treated maize (Zea mays L. W64A x W182E) roots were isolated. The 340 bp Zmrprn1 (for Zea mays root primary response to nitrate) cDNA also hybridized with a probe enriched for nitrate-induced sequences, and was characterized further. Sequence analysis of a near full-length cDNA (Zmrprn1A) showed strong homology (> 90% amino acid identity) with a root ferredoxin-NADP+ oxidoreductase (FNR) of rice, and 45-50% amino acid identify with leaf FNR genes. When expressed in Escherichia coli, the Zmrprn1A cDNA produced a protein with NADPH: ferricyanide reductase activity, consistent with the enzymatic properties of an FNR. The Zmrprn1 cDNA hybridized with a 1.4 kb transcript which was expressed in the maize root primary response to nitrate. That is, mRNA levels in roots increased rapidly and transiently in response to external nitrate, and low levels of nitrate (10 microM) induced transcript accumulation. The accumulation of the Zmrprn1 transcript was not prevented by cycloheximide, indicating that the cellular factor(s) required for expression were constitutively present in maize roots. The Zmrprn1 mRNA accumulated specifically in response to nitrate, since neither K+ nor NH4+ treatment of roots caused transcript accumulation. Maize leaves had about 5% of the transcript level found in roots, indicating a strong preference for expression of Zmrprn1 in roots. Analysis of maize genomic DNA indicated the presence of only a single gene or very small gene family for the Zmrprn1. Together, the data indicate that Zmrprn1A encodes a nitrate regulated maize root FNR.

Amino Acid Sequence↗
PubMed1996

Gravitropism of the primary root of maize: a complex pattern of differential cellular growth in the cortex independent of the microtubular cytoskeleton.

The spatio-temporal sequence of cellular growth within the post-mitotic inner and outer cortical tissue of the apex of the primary root of maize (Zea mays L.) was investigated during its orthogravitropic response. In the early phase (0-30 min) of the graviresponse there was a strong inhibition of cell lengthening in the outer cortex at the lower side of the root, whereas lengthening was only slightly impaired in the outer cortex at the upper side. Initially, inhibition of differential cell lengthening was less pronounced in the inner cortex indicating that tissue tensions which, in these circumstances, inevitably develop at the outer-inner cortex interface, might help to drive the onset of the root bending. At later stages of the graviresponse (60 min), when a root curvature had already developed, cells of the inner cortex then exhibited a prominent cell length differential between upper and lower sides, whereas the outer cortex cells had re-established similar lengths. Again, tissue tensions associated with the different patterns of cellular behaviour in the inner and outer cortex tissues, could be of relevance in terminating the root bending. The perception of gravity and the complex tissue-specific growth responses both proceeded normally in roots which were rendered devoid of microtubules by colchicine and oryzalin treatments. The lack of involvement of microtubules in the graviresponse was supported by several other lines of evidence. For instance, although taxol stabilized the cortical microtubules and prevented their re-orientation in post-mitotic cortical cells located at the lower side of gravistimulated roots, root bending developed normally. In contrast, when gravistimulated roots were physically prevented from bending, re-oriented arrays of cortical microtubules were seen in all post-mitotic cortical cells, irrespective of their position within the root.

Cell Size↗
PubMed1987

Gravitropic bending of cress roots without contact between amyloplasts and complexes of endoplasmic reticulum.

The polar arrangement of cell organelles in Lepidium root statocytes is persistently converted to a physical stratification during lateral centrifugation (the centrifugal force acts perpendicular to the root long axis) or by apically directed centrifugation combined with cytochalasin-treatment. Lateral centrifugation (10 min, 60 min at 10g or 50g) causes displacement of amyloplasts to the centrifugal anticlinal cell wall and shifting of the endoplasmic reticulum (ER) complex to the centripetal distal cell edge. After 60 min of lateral centrifugation at 10g or 50g all roots show a clear gravitropic curvature. The average angle of curvature is about 40 degrees and corresponds to that of roots stimulated gravitropically in the horizontal position at 1 g in spite of the fact that the gravistimulus is 10- or 50-fold higher. Apically directed centrifugation combined with cytochalasin B (25 micrograms ml-1) or cytochalasin D (2.5 micrograms ml-1) incubation yields statocytes with the amyloplasts sedimented close to the centrifugal periclinal cell wall and ER cisternae accumulated at the proximal cell pole. Gravitropic stimulation for 30 min in the horizontal position at 1 g and additional 3 h rotation on a clinostat result in gravicurvature of cytochalasin B-treated centrifuged (1 h at 50 g) roots, but because of retarded root growth the angle of curvature is lower than in control roots. Cytochalasin D-treatment during centrifugation (20 min at 50 g) does not affect either root growth or gravicurvature during 3 h horizontal exposure to 1-g relative to untreated roots. As lateral centrifugation enables only short-term contact between the amyloplasts and the distal ER complex at the onset of centrifugation and apically directed centrifugation combined with cytochalasin-treatment even exclude any contact the integrity of the distal cell pole need not necessarily be a prerequisite for graviperception in Lepidium root statocytes.

Brassicaceae↗
PubMed1991

Fibre composition of the ventral roots L7 and S1 in the owl monkey (Aotus trivirgatus).

The ventral roots L7 and S1 of the owl monkey Aotus trivirgatus, were examined by electron microscopy. On average, these roots contain 2950 and 1837 myelinated axons respectively. In both roots the myelinated axons have bimodal size distributions, but the S1 root contains more small myelinated axons. Both roots contain a substantial proportion of unmyelinated axon profiles (UAP). In the L7 root the proportion of UAP decreases as the spinal cord is approached, from 19% distally to 5% in the juxtamedullary rootlets. Unmyelinated and very small myelinated CNS-type axons have not been observed in the L7 transitional region. The average S1 root contains some 40% unmyelinated axons at all examined proximo-distal levels. Unmyelinated/very small myelinated axons are easily found on the CNS side of the S1 transitional region, in direct relation to motoraxon bundles. Bundles of unmyelinated and small myelinated axons occur in the ventral pia mater of both segments. The unmyelinated axons in the L7 root of the owl monkey appear to be arranged like those in the feline L7 ventral root, possibly representing afferents. It is likely that most unmyelinated and small myelinated axons in the ventral root S1 are autonomic efferents.

Animals↗