Mutations in the Pectin Methyltransferase QUASIMODO2 Influence Cellulose Biosynthesis and Wall Integrity in Arabidopsis.

Pectins are abundant in the cell walls of dicotyledonous plants, but how they interact with other wall polymers and influence wall integrity and cell growth has remained mysterious. Here, we verified that QUASIMODO2 (QUA2) is a pectin methyltransferase and determined that QUA2 is required for normal pectin biosynthesis. To gain further insight into how pectin affects wall assembly and integrity maintenance, we investigated cellulose biosynthesis, cellulose organization, cortical microtubules, and wall integrity signaling in two mutant alleles of Arabidopsis (Arabidopsis thaliana) QUA2, qua2 and tsd2 In both mutants, crystalline cellulose content is reduced, cellulose synthase particles move more slowly, and cellulose organization is aberrant. NMR analysis shows higher mobility of cellulose and matrix polysaccharides in the mutants. Microtubules in mutant hypocotyls have aberrant organization and depolymerize more readily upon treatment with oryzalin or external force. The expression of genes related to wall integrity, wall biosynthesis, and microtubule stability is dysregulated in both mutants. These data provide insights into how homogalacturonan is methylesterified upon its synthesis, the mechanisms by which pectin functionally interacts with cellulose, and how these interactions are translated into intracellular regulation to maintain the structural integrity of the cell wall during plant growth and development.

Clinical Outcomes Following Primary Anterior Cruciate Ligament Reconstruction with Hamstring Autograft versus Planned Hybrid Graft.

Few studies have compared outcomes between autografts versus hybrid grafts (combination of autograft and allograft) for anterior cruciate ligament reconstruction (ACLR). The purpose of this study was to compare revision rate and patient-reported outcomes following primary ACLR with a hamstring autograft versus a preoperatively planned hybrid autograft-allograft. At a minimum 2-year follow-up, patients who had undergone primary ACLR with a double-stranded semitendinosus and gracilis hamstring autograft (A) or a planned hybrid (H) graft (single-strand semitendinosus with nonirradiated peroneus longus or tibialis posterior allograft) were contacted to fill out a survey containing the Knee Injury and Osteoarthritis Outcome Score (KOOS), Subjective International Knee Documentation Committee (IKDC) score, Single Assessment Numeric Evaluation (SANE), 12-Item Short-Form Health Survey (SF-12), and visual analog scale (VAS) for activity level prior to injury and at follow-up. From this collection of patients, a matched-pair comparison was made between groups, with patients matched by gender, age at the time of surgery, and follow-up time. Revision rate at follow-up was 8.4 and 2.4% in the A and H groups, respectively (p = 0.073). A total of 148 surveys were completed (83 A, 65 H), from which 36 matched pairs were formed. Within the matched pairs, average age at surgery did not differ significantly between groups (A: 35.7 years, H: 36.0 years, p = 0.23). Time to follow-up was 4.3 and 3.7 years in the A and H groups, respectively. Patients with a hybrid graft had significantly higher KOOS Quality of Life subscores (A 69.6, H 79.2, p = 0.028), subjective IKDC scores (A 72.6, H 79.7, p = 0.031), and SANE scores (A 83.2, H 91.4, p = 0.015) at follow-up. Otherwise, no significant differences were found in patient-reported outcome scores between groups. A preoperatively planned hybrid graft, with use of a fresh-frozen, nonirradiated allograft, should be considered as a viable alternative for primary ACLR in older patients.

Effects of plant cell wall matrix polysaccharides on bacterial cellulose structure studied with vibrational sum frequency generation spectroscopy and X-ray diffraction.

The crystallinity, allomorph content, and mesoscale ordering of cellulose produced by Gluconacetobacter xylinus cultured with different plant cell wall matrix polysaccharides were studied with vibrational sum frequency generation (SFG) spectroscopy and X-ray diffraction (XRD). Crystallinity and ordering were assessed as the intensity of SFG signals in the CH/CH2 stretch vibration region (and confirmed by XRD), while Iα content was assessed by the relative intensity of the OH stretch vibration at 3240 cm(-1). A key finding is that the presence of xyloglucan in the culture medium greatly reduced Iα allomorph content but with a relatively small effect on cellulose crystallinity, whereas xylan resulted in a larger decrease in crystallinity with a relatively small decrease in the Iα fraction. Arabinoxylan and various pectins had much weaker effects on cellulose structure as assessed by SFG and XRD. Homogalacturonan with calcium ion reduced the SFG signal, evidently by changing the ordering of cellulose microfibrils. We propose that the distinct effects of matrix polysaccharides on cellulose crystal structure result, at least in part, from selective interactions of the backbone and side chains of matrix polysaccharides with cellulose chains during the formation of the microfibril.

Characterization of starch polymorphic structures using vibrational sum frequency generation spectroscopy.

The polymorphic structures of starch were characterized with vibrational sum frequency generation (SFG) spectroscopy. The noncentrosymmetry requirement of SFG spectroscopy allows for the detection of the ordered domains without spectral interferences from the amorphous phase and also the distinction of the symmetric elements among crystalline polymorphs. The V-type amylose was SFG-inactive due to the antiparallel packing of single helices in crystal unit cells, whereas the A- and B-type starches showed strong SFG peaks at 2904 cm(-1) and 2952-2968 cm(-1), which were assigned to CH stretching of the axial methine group in the ring and CH2 stretching of the exocyclic CH2OH side group, respectively. The CH2/CH intensity ratios of the A- and B-type starches are significantly different, indicating that the conformation of hydroxymethyl groups in these two polymorphs may be different. Cyclodextrin inclusion complexes were also analyzed as a comparison to the V-type amylose and showed that the head-to-tail and head-to-head stacking patterns of cyclodextrin molecules govern their SFG signals and peak positions. Although the molecular packing is different between V-type amylose and cyclodextrin inclusion complexes, both crystals show the annihilation of SFG signals when the functional group dipoles are arranged pointing in opposite directions.

Long-term hardware-related complications of deep brain stimulation.

OBJECTIVE: To determine the incidence of long-term hardware-related complications of deep brain stimulation (DBS). METHODS: The study design is a retrospective chart review of a single-surgeon, single-institution experience with DBS in 84 consecutive cases from 1993 to 1999. Only patients with a minimum follow-up of 1 year were considered. Five patients were excluded because trial stimulation failed to achieve pain relief (n = 4) or because the procedure was aborted owing to hemorrhage (n = 1). Seventy-nine patients received 124 permanent DBS electrode implants. RESULTS: The mean follow-up period was 33 months, and the cumulative follow-up time was 217 patient-years or 310 electrode-years. Overall, 20 patients (25.3%) had 26 hardware-related complications involving 23 (18.5%) of the electrodes. There were 4 lead fractures, 4 lead migrations, 3 short or open circuits, 12 erosions and/or infections, 2 foreign body reactions, and one cerebrospinal fluid leak. The hardware-related complication rate per electrode-year was 8.4%. The most common complications were related to the electrode connectors. A significant finding was a high number of complications involving erosions or infections, which occurred in 7 of 12 instances as a late complication (beyond 12 mo). CONCLUSION: Long-term follow-up reveals that hardware-related complications occur in a significant number of patients. Factors that lead to such complications must be identified and addressed to maximize the important benefits of DBS therapy.