NMR structure of the LCCL domain and implications for DFNA9 deafness disorder.

The LCCL domain is a recently discovered, conserved protein module named after its presence in Limulus factor C, cochlear protein Coch-5b2 and late gestation lung protein Lgl1. The LCCL domain plays a key role in the autosomal dominant human deafness disorder DFNA9. Here we report the nuclear magnetic resonance (NMR) structure of the LCCL domain from human Coch-5b2, where dominant mutations leading to DFNA9 deafness disorder have been identified. The fold is novel. Four of the five known DFNA9 mutations are shown to involve at least partially solvent-exposed residues. Except for the Trp91Arg mutant, expression of these four LCCL mutants resulted in misfolded proteins. These results suggest that Trp91 participates in the interaction with a binding partner. The unexpected sensitivity of the fold with respect to mutations of solvent-accessible residues might be attributed to interference with the folding pathway of this disulfide-containing domain.

Sensitive 1H-31P correlations with 5' methylene protons of DNA via homonuclear double-quantum coherence.

A novel pulse sequence is presented for the correlation of 5' and 5'' protons in DNA with phosphorus. Double-quantum coherence between the methylene protons is used to generate 1H5'-31P and 1H5''-31P cross peaks in an HMQC-type experiment. The resolution for these cross peaks is significantly improved over that of conventional HSQC experiments, as cross peaks between 1H4' and 31P are largely suppressed and a 3D version of the experiment can be performed with little penalty in sensitivity. In addition, sensitivity is favoured by slower relaxation of the double-quantum coherence and a more favourable multiplet fine structure in the acquisition dimension.

A bioabsorbable plug in bone-tendon-bone reconstruction of the anterior cruciate ligament: Introduction of a novel fixation technique.

PURPOSE: Our aim was to compare the fixation strength of a novel plugging technique with that of the conventional interference technique in bone-patellar tendon-bone reconstruction of the anterior cruciate ligament. TYPE OF STUDY: Randomized experimental study. METHODS: Twenty matched pairs of porcine knees were randomly assigned to 2 groups. The bone block of the graft was secured in the femoral drill hole with either the new bioabsorbable poly-L-lactide/D-lactide (PLA 96/4) copolymer plug (plugging technique) (n = 20) or a conventional interference screw (interference technique) (n = 20). Ten pairs were subjected to a single cycle loading test at a rate of 50 mm/min while the remaining 10 pairs underwent a cyclic loading test to further assess the quality of the fixation. The cyclic loading test consisted of 1,500 loading cycles between 50 and 200 N at half-hertz frequency, after which the specimens were loaded to failure at a rate of 50 mm/min. RESULTS: In the single cycle loading test, the average ultimate failure load was 1,061 +/- 342 N in the plugging technique group and 971 +/- 260 N in the interference technique group (P =.57). Significant group differences were found neither in the yield loads nor in the stiffness of the fixations. In the cyclic loading, significant displacement difference was not observed between the 2 fixation techniques. There were neither significant group differences with regard to the ultimate failure load (plugging technique 994 +/- 376 N versus interference technique 1,001 +/- 343 N, P =.97) nor yield load of the fixations in the subsequent single cycle loading. CONCLUSIONS: The results of this study indicate that, in anterior cruciate ligament reconstruction, the new plugging technique is a reasonable alternative for fixation of the femoral site of a bone-patellar tendon-bone graft.

NMR relaxation in multipolar AMX systems under spin-locking conditions

A relaxation network has been calculated for multipolar AMX systems under application of a spin-locking RF field. Systems of this type are of interest in the study of proteins with fractional (2)H enrichment. All possible auto- and cross-correlation terms involving dipolar, quadrupolar, and CSA interactions have been taken into account. The results show the presence of spectral densities at zero frequency for interactions associated with the locked nuclei, which are nonvanishing in the absence of fast motions. In addition, the application of a spin-locking field blocks certain cross-correlation interactions, thereby considerably simplifying the relaxation network. Copyright 2000 Academic Press.

NMR relaxation in multipolar AX systems under spin locking conditions.

A relaxation matrix has been calculated for a multipolar AX spin system under the on-resonance spin-locking condition. Auto- and cross-correlation terms between dipolar, quadrupolar, and CSA interactions are considered. It is shown that the spin-lock leads to many relaxation pathways being blocked, resulting in a considerably simplified relaxation network. The presence of spectral densities at zero frequency, associated with locked nuclei, allows efficient relaxation also in the absence of fast molecular motions.

Development of a bioabsorbable suture anchor.

In this article, the design and properties of a new bioabsorbable suture anchor (SmartAnchor(trade mark)) are described and its properties are compared with those of some commercial anchors. Two comparative experiments were carried out in order to measure (1) the breaking force of suture/anchor attachment for SmartAnchor, MitekGII, and for Ogden anchors; and (2) the fixation force of the following anchors and tacks: SmartAnchor, MitekGII, BankartTack, and Suretac. The average suture/anchor attachment breaking force of SmartAnchor (204, 9 N) was 32% higher in comparison to MitekGII (155, 6 N) and 84% higher in comparison to the Ogden anchor (111, 4). The mean fixation force of the SmartAnchor (195, 5 N) was 40% higher than that of MitekGII (139, 2 N), but the T-test showed no statistical differences between MitekGII and SmartAnchor (p = 0.05). Both tested tacks behaved very similarly in this test. The average fixation force (pull-out force) for both tacks was about 210 N. Therefore, it is evident that the bioabsorbable SmartAnchor has a high enough initial mechanical performance for clinical investigation.

Long-term functional outcome after surgery of chronic ankle instability. A 5-year follow-up study of the modified Evans procedure.

Chronic ankle instability is a rather common consequence of poorly healed rupture of the lateral ligaments of the ankle. In some rare cases, instability symptoms can be caused by general laxity of the joints, but since these cases are normally bilateral, they can easily be distinguished from posttraumatic instability. This report presents the long-term (average follow-up 4.6 years) functional outcome after a modified Evans tenodesis of 48 patients. The follow-up examination consisted of a questionnaire evaluating the subjective assessment of the ankle, and clinical examination measuring ankle stability, range of motion and swelling, and atrophy of the calf muscles. Additionally, the functional recovery of the ankle was assessed by a standardized performance test protocol. According to the subjective assessment, 25 subjects (52%) considered the ankle fully recovered, or at least much better than before surgery. In the performance test, however, only 17 subjects (35%) achieved an excellent or good score. In the performance test protocol, two functional tests, walking down a staircase and balancing on a square beam, best demonstrated the impaired function of the injured ankle. The modified Evans procedure could restore the stability of the ankle to the preinjury level, although the ankle range of motion was significantly impaired, and swelling of the ankle and atrophy of the calf muscles were frequent findings at the follow-up. In conclusion, surgical treatment of chronic ankle instability by the Evans procedure restores the mechanical stability of the joint, but too frequently the function of the ankle does not return to the pre-injury level.

Isokinetic muscle performance after surgery of the lateral ligaments of the ankle.

In this study, we assessed the isokinetic strength and power profile of 138 patients with a surgically treated lateral ligament injury of an ankle. In addition, the outcome predicting factors were analyzed. The measurements were done 6.2+/-0.8 years after the surgery using the Cybex II isokinetic dynamometer. The general strength status of the patients was good, the isokinetic testing showing no or only moderate (always < or = 18%) average strength deficits in the peak torque values of dorsiflexor and plantar flexor muscles of the injured ankle. Of the outcome predicting variables, only the age of the patient in the group with surgery for chronic ankle instability correlated significantly with the isokinetic peak torque deficits: the older the subject, the greater the peak torque deficit in the injured ankle (r(s) = -0.388 with p = 0.015) in ankle dorsiflexion at the speed of 60 degrees/s. In conclusion, patients having surgery for ankle ligament insufficiency, either in acute or chronic phase of the injury, seem to recover well showing no remarkable deficiencies in the isokinetic ankle muscle strengths several years after the repair.

Five-quantum coherence of I = 52 nuclei: 27Al in an Al2O3 single crystal

Optimal conditions were calculated for excitation and detection of the five-quantum coherence of quadrupolar nuclei with I = 52 in single crystals, observed by the two-pulse sequence (theta1)x - tau1 - (theta2)alpha - tau2, where alpha is the phase cycling angle. Variations in the pulse lengths, the relative values of the nutation frequency omega1 = gammaB1, and the quadrupolar frequency omegaQ as well as in the resonance offset were taken into account. In addition, the effect of the pulse length on the intensity of spectral lines was considered. Theoretical results were compared with experiments on 27Al nuclei in an Al2O3 single crystal. Copyright 1998 Academic Press.

14N NMR echo in NH4ClO4 after the pulse sequence (theta1)x-tau-(theta2)y-t.

We have derived a closed-form expression for the solid echo signal of quadrupolar I = 1 nuclei after the pulse sequence (theta1)x-tau-(theta2)y-t for arbitrary values of the RF nutation frequency omega1 = gammaB1 and the quadrupolar frequency omegaQ. In the case of single crystals both the true echo term of this expression and its induction-signal-like terms are important as shown by experiments on 14N nuclei in NH4ClO4 crystal. Conditions for obtaining the maximal echo in powder samples are presented. A very low B1 field together with long RF pulses may distort even the central part of the spectrum, resulting in strange looking apparent spectra.

Five quantum coherence of I=5/2 nuclei: 27Al in polycrystalline AlCl3.

Optimal conditions were calculated for the excitation and detection of the five quantum coherence of quadrupolar nuclei with I = 5/2 in powder samples, observed by the two-pulse sequence (theta1)x - tau1 - (theta2)alpha - tau2, where alpha is the phase cycling angle. We varied the pulse lengths and the relative values of the nutation frequency omega1 = gammaB1 and the quadrupolar frequency omegaQ. Also, the effect of the resonance offset was studied under optimal conditions. Besides, the conditions for obtaining the maximal echo amplitude after the two-pulse sequence with alpha = y were found. Theoretical results were compared with experiments on 27Al nuclei in polycrystalline AlCl3.

Proton double quantum coherence and cross-relaxation in (NH4)2SnBr6.

A proton double quantum coherence signal can be observed exclusively from the T species NH4 groups (with the total spin I = 1) in ammonium compounds at low temperatures by the three-pulse sequence 90x degrees - tpr - 90x degrees - tev - 90x degrees - ta, where tpr and ta are of the magnitude of the inverse line width and tev very short. The usefulness of this pulse sequence, preceded by the additional pulse sequence 90x degrees - t1 -90(-x) degrees - t2 for creating an unbalance between the A and T species magnetizations, was demonstrated by applying it to cross-relaxation studies in (NH4)2SnBr6.

Long-term functional outcome after primary repair of the lateral ligaments of the ankle.

We retrospectively reexamined a total of 100 patients 6 to 8 years after primary repair of ruptured lateral ligaments of the ankle. Fifty-nine percent of the injuries had occurred in sports; the other main causes of the injuries were accidents at work (12%), in traffic (10%), and at home (4%). Almost two-thirds of the sports injuries were sustained in volleyball. The most common type of injury was a combined rupture of the anterior talofibular and the calcaneofibular ligaments (66 patients). According to subjective assessment, 74 patients had excellent or good results. For the anterior drawer sign test, 75 patients showed no sign of instability in their injured ankles. The scores in our performance test protocol of ankle injuries were classified as excellent or good in 65 patients, fair in 27 patients, and poor in 8 patients. The overall long-term results were acceptable in the majority of the patients. Prospective, randomized studies are needed to clarify if nonoperative treatment (i.e., early controlled mobilization) would give similar long-term results.

Double quantum coherence of quadrupolar I = 1 nuclei: 14N in NH4ClO4.

We have calculated optimal conditions for observing the double quantum coherence of quadrupolar nuclei I = 1 in single crystals and powders after the two and three pulse sequences (theta1)x-tau1-(theta2)alpha-tau2 [-(theta3)beta-tau3] Here alpha and beta are the phase-cycling angles, which were incremented properly to select the desired coherence transfer pathways. Experiments for double quantum excitation and detection were performed on the single crystal and powder samples of NH4ClO4. Because of a fast decay of the signal from the powder after the two-pulse sequence, we employed the third pulse to produce an echo related to the double quantum coherence.

Surgery versus functional treatment in ankle ligament tears. A prospective study.

A prospective study was performed to compare surgical treatment (primary repair plus early controlled mobilization) to functional treatment (early controlled mobilization alone) in severe (Grade III) lateral ligament injuries of the ankle. Thirty surgically treated patients were compared with 30 age, height, weight, gender, and sporting activity matched, functionally treated similar patients. In both treatment groups, all but 1 patient had a stable ankle at 9 months. Compared with the functional group, the range of motion of the ankle joint was restricted in the surgical treatment group at 6 weeks but did not normalize during the followup. The functional group showed no restrictions. A specific scoring scale developed for subjective and functional followup evaluation of in injured ankle also was used as an outcome criterion. Nine months after the injury, excellent or good scores were achieved in 87% of the functionally treated patients and 60% of the surgically treated patients, respectively. The results of this study indicated that early mobilization gives better results than surgery plus mobilization in the treatment of the complete tears of the lateral ligaments of the ankle.

A performance test protocol and scoring scale for the evaluation of ankle injuries.

The aim of the study was to introduce and evaluate a standardized test protocol and scoring scale for evaluation of ankle injuries. After evaluation of 11 different functional ankle tests, questionnaire answers, and results of clinical ankle examination, the final test protocol consisted of 3 simple questions describing the subjective assessment of the injured ankle, 2 clinical measurements (range of motion in dorsiflexion, laxity of the ankle joint), 1 ankle test measuring functional stability (walking down a staircase), 2 tests measuring muscle strength (rising on heels and toes), and 1 test measuring balance (balancing on a square beam). Each selected test showed excellent reproducibility when tested with a reference group of 100 uninjured persons. According to the test results of a population of 148 patients with an operatively treated grade III lateral ligament injury of the ankle, each test could significantly differentiate healthy controls and patients with excellent overall healing from those with poor or fair recovery. The final total test score correlated significantly with the isokinetic strength results of the ankle, subjective opinion about the recovery, and subjective-functional assessment. The scale presented is recommended for studies evaluating functional recovery after ankle injury.