Inhibition of nitric oxide-activated guanylyl cyclase by calmodulin antagonists

Background and purpose:

Nitric oxide (NO) controls numerous physiological processes by activation of its receptor, guanylyl cyclase (sGC), leading to the accumulation of 3′-5′ cyclic guanosine monophosphate (cGMP). Ca²⁺-calmodulin (CaM) regulates both NO synthesis by NO synthase and cGMP hydrolysis by phosphodiesterase-1. We report that, unexpectedly, the CaM antagonists, calmidazolium, phenoxybenzamine and trifluoperazine, also inhibited cGMP accumulation in cerebellar cells evoked by an exogenous NO donor, with IC₅₀ values of 11, 80 and 180 µM respectively. Here we sought to elucidate the underlying mechanism(s).

Experimental approach:

We used cerebellar cell suspensions to determine the influence of CaM antagonists on all steps of the NO-cGMP pathway. Homogenized tissue and purified enzyme were used to test effects of calmidazolium on sGC activity.

Key results:

Inhibition of cGMP accumulation in the cells did not depend on changes in intracellular Ca²⁺ concentration. Degradation of cGMP and inactivation of NO were both inhibited by the CaM antagonists, ruling out increased loss of cGMP or NO as explanations. Instead, calmidazolium directly inhibited purified sGC (IC₅₀= 10 µM). The inhibition was not in competition with NO, nor did it arise from displacement of the haem moiety from sGC. Calmidazolium decreased enzyme V_max and K_m, indicating that it acts in an uncompetitive manner.

Conclusions and implications:

The disruption of every stage of NO signal transduction by common CaM antagonists, unrelated to CaM antagonism, cautions against their utility as pharmacological tools. More positively, the compounds exemplify a novel class of sGC inhibitors that, with improved selectivity, may be therapeutically valuable.     

Effect of sugar positions in ginsenosides and their inhibitory potency on Na+/K+-ATPase activity

Aim:

To determine whether ginsenosides with various sugar attachments may act as active components responsible for the cardiac therapeutic effects of ginseng and sanqi (the roots of Panax ginseng and Panax notoginseng) via the same molecular mechanism triggered by cardiac glycosides, such as ouabain and digoxin.

Methods:

The structural similarity between ginsenosides and ouabain was analyzed. The inhibitory potency of ginsenosides and ouabain on Na⁺/K⁺-ATPase activity was examined and compared. Molecular modeling was exhibited for the docking of ginsenosides to Na⁺/K⁺-ATPase.

Results:

Ginsenosides with sugar moieties attached only to the C-3 position of the steroid-like structure, equivalent to the sugar position in cardiac glycosides, and possessed inhibitory potency on Na⁺/K⁺-ATPase activity. However, their inhibitory potency was significantly reduced or completely abolished when a monosaccharide was linked to the C-6 or C-20 position of the steroid-like structure; replacement of the monosaccharide with a disaccharide molecule at either of these positions caused the disappearance of the inhibitory potency. Molecular modeling and docking confirmed that the difference in Na⁺/K⁺-ATPase inhibitory potency among ginsenosides was due to the steric hindrance of sugar attachment at the C-6 and C-20 positions of the steroid-like structure.

Conclusion:

The cardiac therapeutic effects of ginseng and sanqi should be at least partly attributed to the effective inhibition of Na⁺/K⁺-ATPase by their metabolized ginsenosides with sugar moieties attached only to the C-3 position of the steroid-like structure.     

Can widespread hypersensitivity in carpal tunnel syndrome be substantiated if neck and arm pain are absent?

Recent studies demonstrated that patients with carpal tunnel syndrome (CTS) have signs of thermal and mechanical hyperalgesia in extra‐median territories suggesting an involvement of central pain mechanisms. As previous studies included patients with shoulder/arm symptoms or neck pain, a potential influence of these coexisting disorders cannot be excluded. This study therefore evaluated whether widespread sensory changes (hypoesthesia or hyperalgesia) are present in patients with unilateral CTS in the absence of coexisting disorders. Twenty‐six patients with unilateral CTS with symptoms localised to their hand and 26 healthy controls participated in the study. A comprehensive quantitative sensory testing (QST) protocol including thermal and mechanical detection and pain thresholds was performed over the hands (median, ulnar and radial innervation area), lateral elbows, neck and tibialis anterior muscle. Patients with CTS demonstrated thermal and mechanical hypoesthesia in the hand but not at distant sites. Thermal or mechanical hyperalgesia was not identified at any location with traditional QST threshold testing. However, patients with CTS rated the pain during thermal pain testing significantly higher than healthy participants. This was especially apparent for heat pain ratings which were elevated not only in the affected hand but also in the neck and tibialis anterior muscle. In conclusion, CTS alone in the absence of coexisting neck and arm pain does not account for sensory changes outside the affected hand as determined by traditional QST threshold testing. Elevated pain ratings may however be an early indication of central pain mechanisms.     

Pharmacokinetics of recombinant activated factor VII in trauma patients with severe bleeding

Introduction  

Recombinant activated factor VII (rFVIIa) has been used as adjunctive therapy in trauma patients with severe bleeding. However, its pharmacokinetics profile remains unknown.     

应用分析型超临界流体萃取测定苏合香丸中主要成分

利用分析型超临界流体萃取技术和GC/MS,GC/FID非在线偶合的方法测定了中成药苏合香丸提取物中主要的挥发性组分及其含量。本工作对超临界流体动态萃取过程影响萃取效率的主要因素,如压力、流体流过样品的体积等进行了考察,确定了适宜的操作条件。与传统方法比较,本方法具有更多的优点。     

How do parents experience patching or dichoptic action video gaming as amblyopia treatment? A qualitative study exploring treatment preferences and information needs to facilitate decision-making

Purpose

To explore parents' experiences, preferences and information needs when either patching treatment or dichoptic action video gaming is used as an amblyopia treatment for their child.

Methods

A qualitative study was carried out on parents whose newly diagnosed amblyopic children participated in a randomised controlled trial (RCT) comparing the effects of dichoptic action video gaming versus patching. A purposive heterogenic sample was selected for an additional interview after the study period. Semi-structured interviews were conducted with one or both parents and transcribed verbatim, and a thematic analysis was performed.

Results

Ten families agreed to participate: seven in the patching group and three in the gaming group. Two themes emerged from the data exploring experiences with treatment: (1) factors influencing compliance and (2) burden with treatment. Parents reported creating a routine which improved compliance with patching, as opposed to gaming where parents felt less need to conduct the treatment themselves as it was performed in the outpatient clinic. In both groups, parents experienced an information hiatus regarding the role of refractive error. In deciding the type of treatment to be used, parents preferred to deliberate the choice with the healthcare professional and discuss considerations resulting in shared decisions. The emerging themes were (1) effect and efficiency of treatment, (2) organisational aspects of treatments and (3) their child's traits.

Conclusion

This study provides insight into the experiences of parents whose children underwent different types of amblyopia therapy. Both treatments have their own advantages and disadvantages. For parents, the effectiveness and efficiency of treatment were the most important aspects when deciding the method of management. Parents wish to come to a well-informed, shared decision regarding the type of amblyopia treatment.