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PubMed2004

Differences in responses of plant hairy roots to chemical toxicity compared between primary and ramified roots.

As a bioassay system for the assessment of the chronic toxicity of chemicals, successive culturing of pak-bung hairy roots was conducted with serial passaging of the primary and lateral root tips. Based on the elongation rates of these root tips, the dose-response profiles were examined while exposing the roots to 2,4-dichlorophenoxyacetic acid (2,4-D) and 1-methyl-3-nitro-1-nitrosoguanidine (MNNG) at concentrations of 0.01-3.0 micromol/dm3, and the values of the median effective concentration, EC50, were determined under the conditions examined. Irrespective of the test chemicals, the EC50 values of both the primary and lateral roots gradually decreased with increasing exposure period ranging from 7 to 35 days. A marked difference in the EC50 values was observed between the primary and lateral roots exposed to 2,4-D; the EC50 value of the lateral roots following exposure for 35 days was 0.036 micromol/dm3, which was one-eighth that of the primary roots for the same exposure period. Moreover, it was found that this phenotypic difference in the root responses was consistently reflected in the distinct patterns of DNA fingerprints of the primary and lateral roots analyzed by the random amplified polymorphic DNA method.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2005

[Effect of partial dorsal root rhizotomy on expression of GDNF and FGF-2 in spared dorsal root ganglia].

OBJECTIVE: To explore the temporal change on the expression of GDNF and FGF-2 in spared dorsal root ganglia after partial dorsal root rhizotomy. METHODS: Fifteen cats were divided into the normal group, and the partial dorsal root rhizotomy groups. The partial dorsal root rhizotomy groups were sacrificed on day 7 or 14 and the L6 dorsal root ganglia were taken out from each animal and were made into frozen sections 20 microm in thickness respectively. The sections were stained under the same condition using specific GDNF (1 : 500) and FGF-2 (1 : 500) antibody by ABC method. The GDNF and FGF-2 positive large-sized, and medium-small-sized neurons in DRG were counted in each group. All data were analyzed by q test. RESULTS: GDNF immunoreactivity was observed in both large-sized and medium-small-sized DRG neurons. The number of total positive neurons decreased 7 days after partial dorsal root rhizotomy, and was still small after 14 days. Interestingly, the tendency in the number of positive medium-small-sized DRG neurons was just the same as that of total positive neurons while the positive large sized neurons displayed no difference between the 7th day group and the 14th day group, though the number also decreased after operation. FGF-2 immunoreactivity was noted in both large sized and medium-small-sized DRG neurons. After partial dorsal root rhizotomy, the number of total positive neurons decreased on the 7th day and came back to normal level on the 14th day. The number of positive medium-small sized neurons also showed declination followed by escalation, just the same as that of total positive neurons while the number of positive large-sized neurons exhibited no difference between the normal group and the rhizotomy groups. CONCLUSION: Partial dorsal root rhizotomy can lead to continuously declination of total GDNF immunoreactive neurons in spared ganglia, till the 14th day. FGF-2 expression showed declination on the 7th day, but returned to normal level on the 14th day after partial dorsal root rhizotomy. These findings indicate that the expression change of GDNF and FGF-2 after partial dorsal root rhizotomy correlates with the plasticity of spinal cord.

Animals↗

PubMed2004

Morphology of root canal cross-sections of resected roots of first and second lower molars.

Precise preparation of the root canal ostium with a view to hermetical closing with retrograde root filling is an important prognostic factor determining the success of the procedure of tooth resection. Root canals interconnected with a narrow isthmus may cause problems both in endodontic treatment and in retrograde filling. The aim of this work is the research of the transverse cross-section of root canals of first and second lower molars on the resection model. The research encompasses 100 randomly selected molar teeth: 50 first and 50 second lower molars. The tooth root apexes were cut 3 mm below the apex and examined under an electron microscope, special attention being paid to the shape of root canal cross-sections. In the group of first molar teeth, in 20% the presence of an isthmus between canals in the proximal roots was observed; in the group of second molar teeth an isthmus between the canals of proximal roots occurred in 18% of the cases. It seems that the relatively high percentage (20%-18%) of the occurrence of an isthmus, 3 mm below the root apex, between two elongated transverse cross-section proximal root canals of first and second molars should encourage particular caution in the retrograde filling of the above-mentioned canals during the procedure of resection.

Dental Pulp Cavity↗

PubMed2005

[Decomposition of Triploid populus tomentosa fine root and Lolium multiflorum grass root in a composite ecosystem and their nutrient dynamics].

This paper studied the root decomposition and its nutrient dynamics of Triploid populus tomentosa and Lolium multiflorum in a plantation converted from farmland at Tianquan County of Sichuan Province. The results showed that the weight loss rate of fine root and grass root showed an exponential relationship with time, with an annual loss of 76.17%, 69.80%, 73.44% and 79.53% for fine roots of 0 approximately 1, 1 approximately 2 and 0 approximately 2 mm in diameter and grass root, respectively. During the decomposition of fine roots, their N and Ca contents increased, while P, K and Mg contents were in adverse. The nutrient contents of grass root during its decomposition had an irregular variation. The remaining percentage of fine root P, K and Mg had the same trend as root weight loss during its decomposition, while that of N and Ca had a slight decrease. For grass root, its N, P, K, Ca and Mg contents declined rapidly at the initial stage of decomposition, and then decreased slowly with irregular deposition rate.

Ecosystem↗

PubMed2004

Acute aortic dissection versus aortic root aneurysm: comparison of indications for valve sparing aortic root reconstruction.

OBJECTIVES: To prove whether different indications for valve sparing aortic root reconstruction may have an impact on the outcome and longevity of the repair. METHODS: From July 1993 to March 2003, the reimplantation technique for valve sparing aortic root reconstruction was applied to 232 patients. In 44 patients, indication for operation was acute aortic dissection type A (AADA). These patients were compared with 44 randomised patients operated for aortic root aneurysm (root) by matched pair analysis with respect to age, gender, time point of operation and presence of Marfan's syndrome. Peri- and post-operative courses with focus on survival and valvular stability were analysed. RESULTS: Pre-operative grade of aortic insufficiency was 2.4+/-1 in root vs. 1.5+/-1.7 in AADA (P = 0.004) Mean CPB-time (214+/-60 vs. 171+/-42 min;P < 0.001), aortic cross clamp time (158+/-40 vs. 129+/-39 min; P = 0.001) and stay on ICU (5.2+/-9 vs. 1.7+/-1 days; P = 0.034) were longer for AADA, while hospitalisation was comparable (14+/-10 vs. 14+/-7 days; P = 0.88). Five patients (11.4%) from AADA died peri-operatively compared to no patient from root (P = 0.055). None of the early deaths were valve-related. Re-thoracotomy rate was 6.8% for both groups. Mean follow-up was 19+/-21 months for AADA vs. 28+/-21 months for root (P = 0.038) Survival at 3 years was 88+/-5% for AADA and 100% for root (P = 0.028). Freedom from valvular reoperation was 97+/-2.7% for root and 97+/-3% for AADA at 3 years (P = 0.44). At last investigation, mean grade of aortic insufficiency for AADA was 0.2+/-0.3 compared to 0.3+/-0.3 for root (P = 0.34) CONCLUSIONS: Regardless of the underlying indication, the aortic valve preserving reimplantation technique can be performed with favourable functional results.

Acute Disease↗

PubMed1995

The axr4 auxin-resistant mutants of Arabidopsis thaliana define a gene important for root gravitropism and lateral root initiation.

To understand the molecular mechanism of auxin action, mutants of Arabidopsis thaliana with altered responses to auxin have been identified and characterized. Here the isolation of two auxin-resistant mutants that define a new locus involved in auxin response, named AXR4, is reported. The axr4 mutations are recessive and map near the ch1 mutation on chromosome 1. Mutant plants are specifically resistant to auxin and defective in root gravitropism. Double mutants between axr4 and the recessive auxin-resistant mutants axr1-3 and aux1-7 were characterized to ascertain possible genetic interactions between the mutations. The roots of the axr4 axr1-3 double mutant plants are less sensitive to auxin, respond more slowly to gravity, and form fewer lateral roots than either parental single mutant. These results suggest that the two mutations have additive or even synergistic effects. The AXR1 and AXR4 gene products may therefore act in separate pathways of auxin response or perhaps perform partially redundant functions in a single pathway. The axr4 aux1-7 double mutant has the same sensitivity to auxin as the aux1-7 mutant but forms far fewer lateral roots than either parental single mutant. The aux1-7 mutation thus appears to be epistatic to axr4 with respect to auxin-resistant root elongation, whereas in lateral root formation, the effects of the two mutations are additive. The complexity of the genetic interactions indicated by these results may reflect differences in the mechanism of auxin action during root elongation and the formation of lateral roots. The AXR4 gene product, along with those of the AXR1 and AUX1 genes, is important for normal auxin sensitivity, gravitropic response in roots and lateral root formation.

Arabidopsis↗

PubMed1978

Quantitative Assessment of Ultrastructural Changes in Primary Roots of Corn (Zea mays L.) after Geotropic Stimulation: I. Root Cap.

The root cap is the site of gravity perception. In the study of caps of primary roots of corn (Zea mays L.), we compared the ultrastructure of geotropically responding roots that had received a 661 nm (red) irradiation (60 second) with nonresponding dark control roots kept in the dark, at comparable times following geotropic stimulation for a total of 150 minutes. The outstanding differences in the light-exposed root caps at the ultrastructural level were: (a) significantly more Golgi apparatus (dictyosomes) were found in the top than in the bottom of red-exposed cells; a random distribution is seen in the dark control cells; (b) the nucleus preferred the top in a greater number of the red-exposed cells; (c) the pattern of mitochondria localization was identical in both treatments, a greater preference for the top; however, the number of mitochondria was reduced in the bottom of red-treated cap cells as compared to the control cells. A lowering in number in the bottom of the red-treated cells was noted also in the dictyosomes; and (d) in a small percentage of cells that showed a preferential distribution of endoplasmic reticulum (ER), more red-exposed cells than controls, during the period 30 to 135 minutes after stimulation, had less ER in the top; however, a majority of the cells in both treatments showed no preferred position for ER distribution. Commonalities in ultra-structural behavior also existed between the red- and dark-treated root cap cells: (a) sedimentation of amyloplasts, with no difference in total number between treatments; and (b) a close association between amyloplasts and ER in both groups.Polarization of organelles occurred in both the geotropically responding and nonresponding roots. The differences in dictyosome and nuclear localization, and dictyosome and mitochondrial number could be correlated with the tropic response in the red-exposed roots and no response in the dark roots, which in turn could be related to the reported hormonal events in the geotropism of roots.

Journal Article↗

PubMed2003

Impact of preoperative aortic root diameter on long-term aortic valve function after valve sparing aortic root reimplantation.

BACKGROUND: Valve sparing aortic root reimplantation technique in patients with aortic root aneurysm have shown excellent mid-term results. In conjunction with the diameter of the aortic root the mechanical leaflet stress increase, which might have an impact on long-term aortic valve function after valve sparing aortic root reimplantation. METHODS AND RESULTS: From July 1993 to October 2001, 168 patients with aortic root aneurysm underwent valve sparing aortic root reimplantation. Patients with type A aortic dissection were excluded. Thus, 123 patients were analyzed. We identified 47 patients with an preoperative aortic root diameter exceeding 60 mm (group A), 58 patients with an diameter between 50 and 60 mm (group B), and 18 patients with a diameter less than 50 mm (group C). The groups were compared regarding mortality, long-term survival, freedom from reoperation, freedom from severe and moderate aortic valve insufficiency (AI), and postoperative morbidity. Mean follow-up (group A 43+/-26 months, group B 40+/-25 months, group C 23+/-19 months; group C versus group A, P=0.005; group C versus group B, P=0.011) was shorter in group C. Perioperative mortality (group A 2.2%, group B 1.9%, group C 5.2%; P=ns) was comparable between the groups with each one patient. The 3-year survival for group A was 98+/-2%, for group B 96+/-3%, and for group C 100+/-0% (P=ns). Freedom from reoperation for group A was 98+/-2%, for group B 96+/-3%, and for group C 88+/-8% (P=ns). Four patients developed severe or moderate AI, thus freedom from severe and moderate AI for group A was 100+/-0%, for group B 88+/-8%, and for group C 94+/-5% (P=ns). During follow-up no thromboembolic or bleeding events were noticed. CONCLUSIONS: Our data show that the preoperative diameter of the aortic root has no impact on the longevity of the repair. Thus, the reimplantation technique can be recommended for all patients presenting with an aortic root aneurysm and normal leaflets regardless of the aortic root diameter.

Adult↗

PubMed1998

Polymicrobial coronal leakage of super EBA root-end fillings following two methods of root-end preparation.

The aim of this study was to compose in vitro coronal leakage of a super EBA root-end filling material after two root-end cavity preparation techniques. A mixed anaerobic microbial marker was used. Forty-five extracted human teeth with straight, single root canals were prepared chemo-mechanically to a size 40 master apical file. The teeth were divided into experimental groups (35 teeth) and control groups (10 teeth). Forty teeth (35 experimental teeth and five negative control teeth) were obturated by lateral condensation of cold gutta-percha with Tubliseal EWT sealer. The remaining five teeth were not obturated and served as positive controls. These teeth were stored for 6 months in artificial saliva. The apical 3-4 mm of each root was resected perpendicular to the long axis of the root and a root-end cavity prepared to a depth of 3 mm using either a size 008 rosehead burr or an ultrasonic retroprep tip. Freshly mixed EBA cement was placed into the root-end cavity. The entire root surface of each tooth, except the cutting surface of the apical end, was sealed with nail varnish. The coronal part of each root canal was sealed with the cut end of a tube and placed in a bottle containing sterile Brain Heart Infusion Broth (BHIB). A marker consisting of Anaerobic streptococci and Fusobacterium nucleatum in BHIB was placed in each coronal chamber at 7-day intervals and daily observations were made for bacterial growth in the apical chamber for 60 days. All positive control teeth exhibited bacterial leakage within 48 h, whilst the apical chamber of negative control teeth remained uncontaminated throughout the test period. Fifty-nine percent (n = 10) of the specimens prepared with a burr showed leakage after 90 days, whilst only 22% (n = 4) of the ultrasonically prepared group showed leakage after the same time. The group prepared with ultrasonic tips showed statistically significant less specimens with leakage (P < 0.05) than the group prepared with burrs.

Dental Leakage↗

PubMed2003

Investigation of the marginal adaptation of root-end filling materials in root-end cavities prepared with ultrasonic tips.

AIM: To compare the surface topography of root apices following ultrasonic root-end preparation, and again after root-end fillings submitted to three different finishing techniques. METHODOLOGY: Eighty-one root-end cavities prepared ultrasonically in human canines, were divided at random into three test groups of 27 each. The cavities were filled with Super-EBA, IRM, or ProRoot-MTA and finished by ball burnishing. Eighteen roots from each group received a final finish with either a 30-fluted tungsten carbide finishing bur, or a Zekrya carbide 28 mm bur after storage in water at 37 degrees C for 24 h. The root-end surface topographies were reproduced by means of polyvinylsiloxane impressions and epoxy resin replicas. Scanning electron micrography (SEM) images of each replica were taken prior to and after root-end filling. An image analysis system was used to compare the alteration of the marginal chipping areas and to calculate the gaps located in the dentine/root-end filling interface. RESULTS: When a bur was used to finish the set materials, a significant (P < 0.05) area of marginal chipping was eliminated. The finishing technique did not significantly (P > 0.05) affect the incidence of gaps in groups root-end filled with MTA or IRM. Super-EBA and IRM retrofillings finished with a ball burnisher or a Zekrya bur displayed a significantly (P < 0.05) larger calculated gap area than roots filled with MTA. CONCLUSION: Under this in vitro study, the marginal adaptation of MTA was good with or without finishing procedures. Applying a finishing bur over the condensed and set IRM and Super-EBA created better marginal adaptation.

Aluminum Compounds↗

PubMed2002

Aluminium toxicity in rye (Secale cereale): root growth and dynamics of cytoplasmic Ca2+ in intact root tips.

Aluminium (Al) toxicity in rye (Secale cereale L.), an Al-resistant crop, was examined by measuring root elongation and cytoplasmic free activity of calcium ([Ca2+]cyt) in intact root apical cells. Measurement of [Ca2+]cyt, was achieved by loading a Ca2+-sensitive fluorescent probe. Fluo-3/AM ester, into root apical cells followed by detection of intracellular fluorescence using a confocal laser scanning microscope. After 20 min of exposure to 50 microM Al (pH 4-2) a slight increase in [Ca2+]cyt of root apical cells was observed, while the response of [Ca2+]cyt to 100 microM Al (pH 4.2) was faster and larger ([Ca2+]cyt increased by 46% in 10 min). Increases in [Ca2+]cyt were correlated with inhibition of root growth, generally measurable after 2 h. Addition of 400 microM malic acid (pH 4.2) largely ameliorated the effect of 100 microM Al on [Ca2+]cyt in root apical cells and protected root growth from Al toxicity. These results suggest that an increase in [Ca2+]cyt in root apical cells in rye is an early effect of Al toxicity and is followed by the secondary effect on root elongation.

Aluminum↗

PubMed2004

An evaluation of microbial leakage in roots filled with a thermoplastic synthetic polymer-based root canal filling material (Resilon).

The purpose of this study was to compare bacterial leakage using Streptococcus mutans and Enterococcus faecalis through gutta-percha and a thermoplastic synthetic polymer-based root filling (Resilon) using two filling techniques during a 30-day period. Teeth were decoronated, roots prepared to a length of 16 mm, and instrumented to ISO sizes 40 to 50. A total of 156 roots were randomly divided into 8 groups of 15 roots (groups 1-8) and 3 control groups (12 roots each). Roots were filled using lateral and vertical condensation techniques with gutta-percha and AH 26 sealer (groups 1 and 2) or with gutta-percha and Epiphany sealer (groups 3 and 4). Groups 5 and 6 were filled with Resilon and Epiphany sealer using the lateral or vertical condensation techniques. A split chamber microbial leakage model was used in which S. mutans placed in the upper chamber could reach the lower chamber only through the filled canal. Groups 7 and 8 were identical to groups 5 and 6 respectively; however, E. faecalis was used to test the leakage. Positive controls were filled with Resilon (12 roots) and gutta-percha (12 roots) without sealer and tested with bacteria, whereas negative controls (12 roots) were sealed with wax to test the seal between chambers. All but one positive control leaked within 24 h, whereas none of the negative controls leaked. Resilon showed minimal leakage (group 8: one leakage; groups 5-7: each with two leakages), which was significantly less than gutta-percha, in which approximately 80% of specimens with either technique or sealer leaked. Kruskal-Wallis test showed statistical significance when all groups were compared (p < 0.05). Mann-Whitney U test compared the respective groups and found Resilon groups superior to gutta-percha groups (p < 0.05).

Bismuth↗

PubMed1994

Ultrasonic root-end preparation, Part 2. Microleakage of EBA root-end fillings.

The effect of three methods of root-end preparation, following apical resection, on the apical seal of root-end fillings, was studied in vitro. Root canals of 116 single-rooted teeth with mature apices were prepared chemomechanically and obturated with gutta-percha and sealer. The root ends were resected with a diamond bur under water coolant and were prepared as follows: group I a size 010 round bur was used to prepare an apical cavity 2-3 mm down the long axis of the root; group II treatment as per group 1 followed by a 60-s rinse with a solution of 10:3 (10% citric acid: 3% Fe2Cl3); and group III an ultrasonic retrotip was used to prepare a 2-3 mm deep apical cavity. The root end was restored with an EBA cement. Apical leakage was determined using India ink after 7 days and 7 months. The teeth were demineralized, rendered transparent and linear dye penetration was recorded. Results showed that there was no significant difference in leakage between the groups at each time interval (P > 0.05) but there was increased leakage after 7 months (P < 0.01). Cracking of the root surface was seen most often with the ultrasonically prepared roots (P < 0.001).

Chi-Square Distribution↗

PubMed1996

Therapeutic delivery of calcitonin to inhibit external inflammatory root resorption. II. Influence of calcitonin binding to root mineral.

Experimentally-induced external inflammatory tooth-root resorption can be inhibited by therapeutic doses of calcitonin. Such doses can be delivered by an intrinsically slow diffusion pathway, from a reservoir in endodontically-debrided root canals, via the dentinal tubules. While the kinetics of this journey have been followed in an earlier report, the binding characteristics of calcitonin to the tooth mineral, which will be responsible, in part, for these kinetics, have not been reported before. The current study examines the binding potential of calcitonin to root mineral and addresses the potential role of non-specific binding proteins. A modified Scatchard plot indicated that a simple non-reactive type of ligand binding exists between calcitonin and root mineral, represented by a small number of identical binding sites. This interaction is both strong and reversible. Furthermore, it appears to be time-dependent with more time being required for the residual ligands to interact with the diminishing numbers of free calcitonin-binding sites. While preloaded [125I]-calcitonin could be incompletely (75-91%) displaced from dental-root material by non-radioactive calcitonin, its release was slow over 23 h. Calcitonin was four times as effective as bovine-serum albumin in competing for common "calcitonin binding sites" on macerated dental-root material. Thus, even in the presence of extraneous protein, calcitonin will bind tightly but reversibly to tooth-root material, making it a good candidate for therapeutically protracted delivery to external root surfaces from root canals.

Adolescent↗

PubMed1991

Root substance removal by scaling and root planing.

The amount of root substance removed by scaling and root planing is largely unknown. The present study evaluated in vitro the root substance loss caused by a defined number of working strokes at known forces. Forty extracted teeth with loss of connective tissue attachment into the middle third of the roots were washed and embedded in plaster, leaving one entire corono-apical tooth aspect exposed. The teeth were reproducibly repositioned in a bench-vise, where a profilometer repeatedly measured root surface levels at the same location. In a standard area of the roots a total of 40 working strokes were applied. Low forces were used in 30 teeth and high forces in 10 teeth. The forces were recorded using a piezo-electric receiver built into the upper shank of the curet. Root substance loss was measured after 5, 10, 20, and 40 working strokes. The results showed that the mean low force used per working stroke across all 40 strokes was 3.04 Newtons for the low forces, and 8.48 Newtons for the high forces. Mean cumulative loss of root substance across 40 strokes was 148.7 microns at low forces, and 343.3 microns at high forces. The mean force per stroke increased slightly across the 40 strokes, while substance removal per stroke decreased. Substance removal per stroke during strokes 1 to 5 was 6.8 microns using low forces and 20.6 microns using high forces. During strokes 21 to 40 mean removal per stroke was 2.3 microns at low forces, and 5.6 microns at high forces. These results suggest that high forces remove more root substance, and loss per stroke becomes less with increasing numbers of strokes.

Dental Scaling↗

PubMed1991

Periodontal repair in dogs: effect of root surface treatment with stannous fluoride or citric acid on root resorption.

This study evaluated healing, with emphasis on root resorption, following root surface treatment with 1% aqueous stannous fluoride (SnF2), saturated citric acid (CA), or saline control (C) in conjunction with periodontal flap surgery. Supraalveolar periodontal defects were surgically created and immediately treated in the mandibular premolars in 6 beagle dogs. The defect height approximated 5 to 6 mm from the reduced alveolar bone to the cemento-enamel junction. Root treatments were rotated between experimental teeth within jaw quadrants and duplicated in left and right quadrants in the dogs. Flaps were raised to cover most of the crowns of the teeth and sutured. The dogs were sacrificed 12 weeks after surgery and tissue blocks with teeth and adjacent structures were processed for histometric analysis. SnF2-treated teeth healed with significantly longer junctional epithelium, less connective tissue repair to the root surface, and less bone regeneration than CA and C-treated teeth. New cementum formation was limited in all treatment groups. Root resorption was observed in almost all teeth exhibiting connective tissue repair, however to a lesser amount and not as frequent in SnF2 treated teeth due to limited connective tissue repair. No differences were found in amount and frequency of root resorption in CA and C-treated teeth. An inhibitory effect on root resorption of SnF2 could not be disclosed in this experiment, however, it may be concluded that CA treatment of the root surface in conjunction with reconstructive periodontal flap surgery does not seem to enhance root resorption.

Alveolar Process↗

PubMed1996

Morphometric data of canine sacral nerve roots with reference to electrical sacral root stimulation.

Experiments to investigate restoration of lower urinary tract control by electrical stimulation of the sacral nerve roots are mostly performed on dogs, yet little morphometric data (such as canine root and fiber diameter distributions) are available. The aim of this study was to acquire morphometric data of the intradural canine sacral dorsal and ventral roots (S1-S3). Cross-sections of sacral roots of two beagle dogs were analyzed using a light microscope and image processing software. The cross-sectional area of each root was measured. The diameters of the fibers and the axons in the cross-sections of the S2 and S3 roots were measured and used to construct nerve fiber diameter frequency distribution histograms. The results show a unimodal diameter distribution for the dorsal roots and a bimodal distribution for the ventral roots. In addition the average ratio g of the axon diameter to fiber diameter was calculated for each root.

Animals↗

PubMed2002

Wavelike distributions of infections by an introduced and naturally occurring root pathogen along wheat roots.

Previously, we showed that copiotrophic and oligotrophic bacteria fluctuate as moving waves along roots. These waves probably originate as a result of growth and death cycles at any location where a moving nutrient source passed. In this study, we placed sclerotia of Rhizoctonia solani AG8 along growing roots of wheat and showed that the proportions of root sections from which R. solani was isolated fluctuated with distance from the root tip. Similarly, proportions of root sections from which naturally occurring Pythium spp. were isolated fluctuated with distance from the root tip. Fourier analysis showed that these fluctuations constituted significant waves. Cross-correlation analyses demonstrated that there were negative correlations between R. solani infections and colony forming units of copiotrophic bacteria at the time of inoculation at the same locations on the root (lag = 0 cm), indicating that infection by R. solani could have been inhibited by these bacteria. There was a positive correlation between Pythium infections and copiotrophic bacteria at a lag of 6 cm along the roots. It therefore appears that Pythium infection took place shortly after the initial peak in copiotrophic bacteria following the passage of the root tip.

Colony Count, Microbial↗