Needle-Through-Needle Technique in Lumbar Interlaminar Epidural Steroid Injection: A Case Report.

When performing lumbar epidural steroid injection on obese patients, needle placement can be challenging due to the difficulty in estimating the appropriate needle length to utilize. Often times, the standard 3.5-inch Tuohy needle is too short to reach its target. In our case report, a needle-through-needle technique was attempted in a lumbar interlaminar epidural steroid injection procedure after the initial needle fell short of the epidural space. To avoid removing the initial needle and restarting the procedure using a longer needle, a 20-gauge 6-inch Tuohy needle was inserted into the 17-gauge 3.5-inch Tuohy needle, successfully reaching the epidural space. This technique can facilitate quicker needle placement by avoiding the need for restarting the procedure with a longer needle. Thus, procedural time and radiation exposure may be decreased, as may patient discomfort from repeat needle insertions.

Structural characterization of the C3 domain of cardiac myosin binding protein C and its hypertrophic cardiomyopathy-related R502W mutant.

Human cardiac myosin binding protein C (cMyBP-C), a thick filament protein found within the sarcomere of cardiac muscle, regulates muscle contraction and is essential for proper muscle function. Hypertrophic cardiomyopathy (HCM), a genetic disease affecting 1 in 500 people, is the major cause of death in young athletes. It is caused by genetic mutations within sarcomeric proteins. Forty-two percent of the HCM-related mutations are found in cMyBP-C. Here we present the nuclear magnetic resonance-derived structural ensembles of the wild-type cMyBP-C C3 domain and its HCM-related R502W mutant. The C3 domain adopts an immunoglobulin-like fold, and mutation of the exposed Arg502 to a tryptophan does not perturb its structure, dynamics, or stability. However, the R502W mutation does alter the predicted electrostatic properties of the C3 domain. We hypothesize that this mutation, and other HCM-linked mutations found within the same domain, may directly disrupt the interaction of cMyBP-C with other sarcomeric proteins.

The structure of cardiac troponin C regulatory domain with bound Cd2+ reveals a closed conformation and unique ion coordination.

The amino-terminal domain of cardiac troponin C (cNTnC) is an essential Ca(2+) sensor found in cardiomyocytes. It undergoes a conformational change upon Ca(2+) binding and transduces the signal to the rest of the troponin complex to initiate cardiac muscle contraction. Two classical EF-hand motifs (EF1 and EF2) are present in cNTnC. Under physiological conditions, only EF2 binds Ca(2+); EF1 is a vestigial site that has lost its function in binding Ca(2+) owing to amino-acid sequence changes during evolution. Proteins with EF-hand motifs are capable of binding divalent cations other than calcium. Here, the crystal structure of wild-type (WT) human cNTnC in complex with Cd(2+) is presented. The structure of Cd(2+)-bound cNTnC with the disease-related mutation L29Q, as well as a structure with the residue differences D2N, V28I, L29Q and G30D (NIQD), which have been shown to have functional importance in Ca(2+) sensing at lower temperatures in ectothermic species, have also been determined. The structures resemble the overall conformation of NMR structures of Ca(2+)-bound cNTnC, but differ significantly from a previous crystal structure of Cd(2+)-bound cNTnC in complex with deoxycholic acid. The subtle structural changes observed in the region near the mutations may play a role in the increased Ca(2+) affinity. The 1.4 Å resolution WT cNTnC structure, which is the highest resolution structure yet obtained for cardiac troponin C, reveals a Cd(2+) ion coordinated in the canonical pentagonal bipyramidal geometry in EF2 despite three residues in the loop being disordered. A Cd(2+) ion found in the vestigial ion-binding site of EF1 is coordinated in a noncanonical `distorted' octahedral geometry. A comparison of the ion coordination observed within EF-hand-containing proteins for which structures have been solved in the presence of Cd(2+) is presented. A refolded WT cNTnC structure is also presented.