BTS

BTS is a potent inhibitor of Ca2+-stimulated myosin S1 ATPase (IC50 ~ 5 μM) and reversibly blocks the gliding motility. IC50 value: 5 uM Target: Ca2+-stimulated myosin S1 ATPase BTS also weakens myosin’s interaction with F-actin. BTS is much less effective in suppressing contraction in rat myocardial or rabbit slow twitch muscle and has no effect on platelet myosin II.

References:
[1]. Cheung A, et al. A small-molecule inhibitor of skeletal muscle myosin II. Nat Cell Biol. 2002 Jan;4(1):83-8.

Return of the pulmonary nodule: the radiologist's key role in implementing the 2015 BTS guidelines on the investigation and management of pulmonary nodules.[Pubmed:26781558]

Br J Radiol. 2016;89(1059):20150776.

The British Thoracic Society has published new comprehensive guidelines for the management of pulmonary nodules. These guidelines are significantly different from those previously published, as they use two malignancy prediction calculators to better characterize the risk of malignancy. There are recommendations for a higher nodule size threshold for follow-up (>/=5 mm or >/=80 mm(3)) and a reduction of the follow-up period to 1 year for solid pulmonary nodules; both of these will reduce the number of follow-up CT scans. PET-CT plays a crucial role in characterization also, with an ordinal scale being recommended for reporting. Radiologists will be the key in implementing these guidelines, and routine use of volumetric image-analysis software will be required to manage patients with pulmonary nodules correctly.

Endoscopic stenting as bridge-to-surgery (BTS) in left-sided obstructing colorectal cancer: Experience with conformable stents.[Pubmed:27156171]

Clin Res Hepatol Gastroenterol. 2016 Nov;40(5):638-644.

BACKGROUND: Compared to emergency surgery, self-expandable metallic stents are effective and safe when used as bridge-to-surgery (BTS) in operable patients with acute colorectal cancer obstruction. In this study, we report data on the new conformable colonic stents. OBJECTIVES: To evaluate clinical effectiveness of conformable stents as BTS in patients with acute colorectal cancer obstruction. DESIGN: This was a retrospective study. SETTINGS: The study was conducted at six Italian Endoscopic Units. PATIENTS: Data about patients with acute malignant colorectal obstruction were collected between 2007 and 2012. MAIN OUTCOME MEASURES: All patients were treated with conformable stents as BTS. Technical success, clinical success, rate of primary anastomosis and colostomy, early and late complications were evaluated. RESULTS: Data about 88 patients (62 males) were reviewed in this study. Conformable SEMS were correctly deployed in 86 out of 88 patients, with resolution of obstruction in all treated patients. Tumor resection with primary anastomosis was possible in all patients. A temporary colostomy was performed in 40. Early complications did not occur. Late complications occurred in 11 patients. Stent migration was significantly higher in patients treated with partially-covered stents compared to the uncovered group (35% vs. 0%, P<0.001). Endoscopical re-intervention was required in 12% of patients. One patient with rectal cancer had an anastomotic dehiscence after surgery and he was successfully treated with endoscopic clipping. One year after surgery, all patients were alive and local recurrence have not been documented. LIMITATIONS: This was a retrospective and uncontrolled study. CONCLUSIONS: Preliminary data from this large case series are encouraging, with a high rate of technical and clinical success and low rate of clinically relevant complications. Partially-covered SEMS should be avoided in order to reduce the risk of endoscopic re-intervention.

Skeletal muscle myosin cross-bridge cycling is necessary for myofibrillogenesis.[Pubmed:12673599]

Cell Motil Cytoskeleton. 2003 May;55(1):61-72.

A major stimulus affecting myofibrillogenesis in both embryonic and mature striated muscle is contractile activity. There are two major signals associated with contractile activity: a physiological signal, the transient increase in intracellular calcium, and a physical signal, the transient increase in tension production. However, dissociating these two signals to examine their relative contributions to myofibrillogenesis has proven difficult. In this study, we have used two different myosin inhibitors to determine the importance of myosin cross-bridge cycling in sarcomere assembly. We find that the small-molecule inhibitor 2,3-butanedione monoxime (BDM), which inhibits myosin ATPase, disrupts myofibrillogenesis in amphibian myocytes, consistent with results from avian studies. However, BDM is a weak myosin inhibitor and it is non-specific; concentrations that inhibit contraction and disrupt myofibrillogenesis also disrupt calcium signaling. Therefore, we also used the recently identified skeletal muscle myosin II inhibitor, N-benzyl-p-toluenesulphonamide (BTS), which has high affinity and specificity for skeletal muscle fast myosin. BTS inhibits contraction and results in myofibrillar disruption that phenocopies our results with BDM. However, BTS does not affect either spontaneous or induced calcium transients. Furthermore, BTS is reversible and does not significantly affect the expression levels of myosin or actin. Thus, our convergent results with BDM and BTS suggest that sarcomere assembly depends on active regulation of tension in the forming myofibril.

Mechanism of inhibition of skeletal muscle actomyosin by N-benzyl-p-toluenesulfonamide.[Pubmed:12755615]

Biochemistry. 2003 May 27;42(20):6128-35.

N-Benzyl-p-toluenesulfonamide (BTS) is a small organic molecule that specifically inhibits the contraction of fast skeletal muscle fibers. To determine the mechanism of inhibition by BTS, we performed a kinetic analysis of its effects on the elementary steps of the actomyosin subfragment-1 ATPase cycle. BTS decreases the steady-state acto-S1 ATPase rate approximately 10-fold and increases the actin concentration for half-maximal activation. BTS primarily affects three of the elementary steps of the reaction pathway. It decreases the rate of P(i) release >20-fold in the absence of actin and >100-fold in the presence of actin. It decreases the rate of S1.ADP dissociation from 3.9 to 0.8 s(-)(1) while decreasing the S1.ADP dissociation constant from 2.3 to 0.8 microM. BTS weakens the apparent affinity of S1.ADP for actin, increasing the K(d) from 7.0 to 29.5 microM. ATP binding to S1, hydrolysis, and the affinity of nucleotide-free S1 for actin are unaffected by BTS. Kinetic modeling indicates that the binding of BTS to myosin depends on actin association/dissociation and on nucleotide state. Our results suggest that the reduction of the acto-S1 ATPase rate is due to the inhibition of P(i) release, and the suppression of tension is due to inhibition of P(i) release in conjunction with the decreased apparent affinity of S1.ADP.P(i) and S1.ADP for actin.

A small-molecule inhibitor of skeletal muscle myosin II.[Pubmed:11744924]

Nat Cell Biol. 2002 Jan;4(1):83-8.

We screened a small-molecule library for inhibitors of rabbit muscle myosin II subfragment 1 (S1) actin-stimulated ATPase activity. The best inhibitor, N-benzyl-p-toluene sulphonamide (BTS), an aryl sulphonamide, inhibited the Ca2+-stimulated S1 ATPase, and reversibly blocked gliding motility. Although BTS does not compete for the nucleotide-binding site of myosin, it weakens myosin's interaction with F-actin. BTS reversibly suppressed force production in skinned skeletal muscle fibres from rabbit and frog skin at micromolar concentrations. BTS suppressed twitch production of intact frog fibres with minimum alteration of Ca2+ metabolism. BTS is remarkably specific, as it was much less effective in suppressing contraction in rat myocardial or rabbit slow-twitch muscle, and did not inhibit platelet myosin II. The isolation of BTS and the recently discovered Eg5 kinesin inhibitor, monastrol, suggests that motor proteins may be potential targets for therapeutic applications.