First Report of Root Rot on Atractylodes macrocephala (Largehead Atractylodes Rhizome) Caused by Ceratobasidium sp. in China

Atractylodes macrocephala is a perennial herbaceous plant (family Asteraceae) native to China. The biennial root, Largehead Atractylodes Rhizome (LAR), is the most commonly used Chinese herbal medicine to prevent early pregnancy loss due to miscarriage. From summer 2010 to spring 2012, symptoms of root rot were observed on LAR in Xianfeng county, Enshi city, Hubei Province, China. White mold on the root of LAR could be observed at an early growth stage in the field and the white mold spread over the entire plant after 10 days, which differs from root rot of LAR caused by Fusarium oxysporum and Rhizoctonia solani, neither of which are characterized as having mycelium spreading over the whole plant (4). Where root rot symptoms were present, rhizome yield was reduced by 15% on average, with up to 40% yield loss in some fields. Under humid conditions in mid-June, the disease in the field spread quickly and the rhizomes of LAR were completely rotted. After rainfall and increasing temperature from 16 to 35°C, white mycelium appeared and plants withered within a few weeks. In April 2011 and 2012, a fungus was consistently recovered from symptomatic rhizome samples after they were surface sterilized with 0.1% mercuric chloride solution and plated onto potato dextrose agar (PDA). Pale gray colonies with short aerial mycelia and brown sclerotia formed on PDA after 7 days incubation at 28°C. Binucleate cells were observed using light microscopy and the characteristics were matched with morphological characteristics of a Ceratobasidium sp (3). Genomic DNA of the culture was extracted, and the rDNA-internal transcribed spacer sequence (GenBank Accession No. JQ926741) showed 99% identity to Ceratobasidium sp (GenBank No. H269825.1). Mycelial plugs of the culture taken from PDA were inoculated onto 40 rhizomes of 1-year-old seedlings and plants were incubated with a 16-h photoperiod at 28°C and 90% relative humidity in an artificial climate chamber where they developed typical disease symptoms after 2 days. Ten rhizomes of 1-year-old seedlings and were treated with PDA plugs only. All seedlings inoculated with the pathogen were withered and the rhizomes were completely covered with gray mycelium 2 days after inoculation, which was similar to the symptoms observed in the field. After 7 days, the symptoms were more severe than those observed in the field, with seedlings rotted completely. The main stalk of all inoculated plants was covered with gray mycelia in 4 days, and the stalk became withered, which was similar to the symptoms observed in the field. No symptoms were observed on control seedlings and plants. Koch's postulates were fulfilled by successful reisolation of Ceratobasidium sp. from diseased seedlings. The pathogenicity tests were carried out twice. Ceratobasidium sp. has been reported to cause root rot of canola in Washington (2). It has also been observed on Rehmannia in China (1). To our knowledge, this is the first report of Ceratobasidium sp. causing root rot on LAR. References: (1) B. B. Chen et al. Chin. J. Chin. Material Medica (In Chinese) 9:1137, 2011. (2) K. L. Schroeder et al. Plant Dis. 96:591, 2012. (3) B. Sneh et al. Page 39 in: Identification of Rhizoctonia Species. The American Phytopathological Society, 1991. (4) S. X. Zang et al. J. Agric. Univ. Hebei (In Chinese) 28:73, 2005.

Biomechanical effect of anterior grafting devices on the rotational stability of spinal constructs

In the thoracolumbar spine, frequently strut grafting is used to restore the anterior and middle column defects. Biomechanical stability of the surgical construct may be altered significantly depending on the type of anterior grafting devices. In this study, a biomechanical flexibility test was conducted to compare the stabilizing role of various types of anterior grafting devices, such as a polymethylmethacrylate block, tricortical iliac crest bone graft, one large Harms cage, and two small Harms cages using a calf lumbar corpectomy model. The Harms cage, especially one large cage, improved the axial rotational stability significantly in both anterior and posterior fixation groups as compared with the iliac bone or polymethylmethacrylate. No significant difference in the stabilizing role was found among different grafting devices in lateral bending, flexion, and extension. These results suggest that a more rigid spinal construct can be obtained by using a metal cage with improved friction at the cage-bone interface.

Contrast media of high and low molecular weights in the detection of recurrent herniated disks

PURPOSE

Our goal was to compare contrast enhancement of recurrent herniated disk fragments and scar after intravenous injection of a new high-molecular-weight contrast medium, Gadomer 17 (gadomer), with that after injection of a low-molecular-weight contrast medium, (gadopentetate dimeglumine).

METHODS

Recurrent herniated disks were modeled in dogs by placing a fragment of intervertebral disk cartilage in the epidural space at laminectomy. MR imaging was performed with one of the contrast media at 20 and 50 days and with the other medium at 22 and 52 days. The changes in signal intensity from baseline in the disk fragment and in the adjacent scar tissue was measured at 2, 22, and 45 minutes. Differences were tested for significance with a student t-test.

RESULTS

At 50 days after surgery, signal intensity in the intervertebral disk fragment increased by an average of 0.52 at 2 minutes after injection of gadomer and by an average of 0.90 after injection of gadopentetate. For scar, the increases in signal intensity were 1.41 (gadomer) and 1.62 (gadopentetate). At 22 and 45 minutes after injection, the signal intensity change in the disk fragment continued to be significantly greater after gadopentetate than after gadomer injection. In comparison with the changes at 50 days, both scar and disk fragment tended to show greater signal intensity changes at 20 days. Signal intensity changes in the disk fragments were significantly less after gadomer than after gadopentetate. Signal intensity changes in scar were slightly less with gadomer than with gadopentetate.

CONCLUSION

Greater contrast is achieved between scar and recurrent herniated disk with a higher-molecular-weight contrast medium than with one of lower molecular weight. The difference between the high- and low-molecular-weight contrast media increases with maturation of the scar tissue.

Biomechanical evaluation of anterior and posterior fixations in an unstable calf spine model

STUDY DESIGN

Fresh calf lumbar spines were used to perform flexibility tests in multiple loading directions to compare the stabilizing effects of anterior and posterior rigid instrumentations.

OBJECTIVE

To compare the biomechanical flexibility of anterior and posterior instrumentation constructs using an unstable calf spine model.

SUMMARY OF BACKGROUND DATA

Unstable burst fractures of the thoracolumbar spine can be managed anteriorly or posteriorly. Controversy persists, however, on the merit of anterior fixation versus that of posterior fixation in terms of how much stability can be achieved.

METHODS

Fifteen fresh calf spines (L2-L5) were loaded with pure unconstrained moments in flexion, extension, axial rotation, and lateral bending directions. After removal of L3-L4 disc and endplates to create an 1.5-cm anterior and middle column defect, testing was performed on five specimens after anterior Kaneda rod fixation, anterior University Plate fixation, or posterior ISOLA pedicle screw fixation (AcroMed, Cleveland, OH). Testing was repeated after inserting a polymethylmethacrylate block to stimulate an interbody anterior graft with instrumentation.

RESULTS

All fixation devices provided a significant stabilizing effect in flexion and lateral bending. In extension, all constructs except ISOLA (AcroMed) without graft were stiffer than the intact specimen. In axial rotation with no graft, only the Kaneda device significantly reduced the flexibility from that of the intact specimen. The interbody graft provided additional rigidity to the ISOLA (AcroMed) instrumentation construct in flexion and extension and to the Kaneda construct in lateral bending. There was no significant effect of grafting in axial rotation.

CONCLUSIONS

A short, transpedicular instrumentation, such as ISOLA (AcroMed), provided less rigid fixation in flexion and extension without the anterior structural graft. The Kaneda rod and University plate with grafting provided a significant stabilizing effect in all directions compared with the intact specimen. When no graft was inserted, the Kaneda device was more effective in preventing axial rotation than the other devices. In lateral bending, the University plate provided more rigid fixation than the Kaneda device without grafting.

Biomechanics of transfixation in pedicle screw instrumentation

STUDY DESIGN

The biomechanical role of transfixation in pedicle screw instrumentation was investigated using flexibility tests and finite element analyses.

OBJECTIVE

To assess the stabilizing effect of use and position of transfixators.

SUMMARY OF BACKGROUND DATA

Transfixation is common in pedicle screw instrumentation, however, its biomechanical role and optimal position are not completely understood.

METHODS

Specimens underwent nondestructive flexibility tests using a three-dimensional motion analysis system. Tests compared the intact spine with instrumentation with and without transfixators Rotational angles of the superior vertebra, resulting from the maximum moment of 6.4 Nm, were compared. Three-dimensional finite element models investigated transfixator position. Rotations of the superior vertebra were compared for cases with and without transfixators to determine the position providing the greatest stability.

RESULTS

Biomechanical test showed that only axial rotational stability significantly improved with transfixators compared with instrumentation alone. Pimte element models predicted improvement in lateral bending and axial rotation with transfixators compared with the case with no transfixator. With one transfixator, the greatest improvement in axial rotation stability occurred with the transfixator at the proximal 1/4 position of the rods. When two transfixators were used, the optimal locations were with one transfixator in the middle and the second at the proximal 1/8 position.

CONCLUSIONS

Transfixators improved the stabilizing effects of pedicle screw instrumentation. The greatest axial rotation stability was obtained with two transfixators; one in the middle and the other at the proximal 1/8 position of the longitudinal rods.

Calorimetric characterization of the formation of acrylic type bone cements

The formation of acrylic bone cements upon heating was investigated by differential scanning calorimetry (DSC). The effects of the contents of initiators, accelerator, biocompatibilizer, and crosslinking agents on the rate and the heat of polymerization during DSC heating were studied. The rate and the heat of polymerization (delta H) were characterized by the peak temperature and the area of the DSC exotherm, respectively. It was found that both the rate and heat of polymerization decreased with increasing heating rate. The delta H was increased considerably with increasing benzoyl peroxide (BPO) initiator concentration from 1 to 10% (w/v), whereas the rate of polymerization was reduced significantly. An increase in azobisisobutyronitrile (AIBN) initiator concentration also induced an increase in delta H, but the rate of reaction was not affected considerably. The addition of accelerator promoted the rate of reaction but resulted in a drop in delta H. The rate of polymerization for the system containing BPO initiator was increased quite significantly with the addition of hydroxyethyl methacrylate (HEMA) biocompatibilizer, while the delta H was slightly increased. For the system using AIBN as the initiator, the rate of polymerization was decreased slightly and the delta H dropped significantly with the addition of HEMA. The effect of ethylene glycol dimethacrylate (EGDMA) crosslinking agent was also examined. Polymerization became more rapid with the addition of EGDMA in the bone cement using BPO initiator, while it remained approximately constant for the system using AIBN as the initiator. No systematic change in delta H was observed with the addition of EGDMA in both systems. This study demonstrated that DSC is a potential tool to measure the amount of heat released and also the rate of polymerization for bone cements.

Biomechanical evaluation of anterior thoracolumbar spinal instrumentation

STUDY DESIGN

A biomechanical study was designed to assess relative construct stabilities of modern anterior thoracolumbar instrumentations in a calf spine model with an anterior and middle column defect.

OBJECTIVES

The purpose is to compare the biomechanical stability of various anterior fixation devices in an unstable calf spine model.

SUMMARY OF BACKGROUND DATA

Modern types of anterior thoracolumbar instrumentations evolved to either rods or plates. Biomechanical properties and comparative studies of these instrumentations are lacking.

METHODS

Twenty fresh calf spines (L2-L5) were used for the biomechanical tests. L2 and L5 vertebrae were used to attach the loading and base frames, respectively. Specimens underwent nondestructive biomechanical tests performed using a three-dimensional motion measuring system. In each specimen, three different cases were tested: intact spine, anterior fixation with an interbody graft after total discectomy and endplate excision of L3-L4 disc, anterior fixation only without the graft. Four anterior fixators, University Anterior Plating System, the Kaneda device, the Z-plate, and Texas Scottish Rite Hospital system were used. Each device was tested on five specimens. A polymethylmethacrylate block was inserted into the disc space to simulate the interbody grafting, and a fixation device was implanted with axial compression. Rotational angles of the L3-L4 segment stabilized by a fixation device and graft were normalized by the corresponding angles of the intact specimen to study the overall stabilizing effects.

RESULTS

With the interbody graft and fixation devices, all showed significant stabilizing effects in flexion, extension, and lateral bending. All devices restored axial rotation stability to intact specimen, but only the Kaneda device restored the torsional stability beyond the intact specimen. No statistical differences in stabilizing effects in axial rotation were found between any of the tested devices. When the graft was removed, the Kaneda device significantly decreased the motions in all directions compared with the intact motion, whereas the University plate decreased the motions in flexion, extension, and lateral bending. The Texas Scottish Rite Hospital system was found to reduce the flexion and lateral bending motions significantly, and Z-plate decreased lateral bending motions only. Stabilizing effects of the interbody graft were significant in lateral bendings for all devices. Additionally, the significant stabilizing role of the graft was noted in flexion and extension in Z-plate only. The graft did not significantly reduce the axial rotation motion in any instrumentations.

CONCLUSIONS

Modern anterior instrumentations for the thoracolumbar spine, such as the Kaneda device, Texas Scottish Rite Hospital system, Z-plate, and University plate, restored the stability in all motions when an interbody graft was inserted. The stability of fixation devices revealed that the Kaneda device is the best, particularly in restoring the torsional stability. The information on the relative stability provided by different instrumentations should help the spine surgeon in choosing the appropriate instrumentation for the particular circumstance.