A novel technique for post-pyloric feeding tube placement in critically ill patients: a pilot study

Delivery of enteral nutrition in critically ill patients is often hampered by gastric stasis necessitating direct feeding into the small intestine. Current techniques for placement of post-pyloric feeding catheters are complex, time consuming or both, and improvements in feeding tube placement techniques are required. The Cathlocator is a novel device that permits real time localisation of the end of feeding tubes via detection of a magnetic field generated by a small electric current in a coil incorporated in the tip of the tube. We performed a pilot study evaluating the feasibility of the Cathlocator system to guide and evaluate the placement of (1) nasoduodenal feeding tubes, and (2) nasogastric drainage tubes in critically ill patients with feed intolerance due to slow gastric emptying. A prospective study of eight critically ill patients was undertaken in the intensive care unit of a tertiary hospital. The Cathlocator was used to (1) guide the positioning of the tubes post-pylorically and (2) determine whether nasogastric and nasoduodenal tubes were placed correctly. Tube tip position was compared with data obtained by radiology. Data are expressed as median (range). Duodenal tube placement was successful in 7 of 8 patients (insertion time 12.6 min (5.3-34.4)). All nasogastric tube placements were successful (insertion time 3.4 min (0.6-10.0)). The Cathlocator accurately determined the position of both tubes without complication in all cases. The Cathlocator allows placement and location of an enteral feeding tube in real time in critically ill patients with slow gastric emptying. These findings warrant further studies into the application of this technique for placement of post-pyloric feeding tubes.

Steroid receptor/coactivator binding inhibitors: An update

The purpose of this review is to highlight recent developments in small molecules and peptides that block the binding of coactivators to steroid receptors. These coactivator binding inhibitors bind at the coregulator binding groove, also known as Activation Function-2, rather than at the ligand-binding site of steroid receptors. Steroid receptors that have been targeted with coactivator binding inhibitors include the androgen receptor, estrogen receptor and progesterone receptor. Coactivator binding inhibitors may be useful in some cases of resistance to currently prescribed therapeutics. The scope of the review includes small-molecule and peptide coactivator binding inhibitors for steroid receptors, with a particular focus on recent compounds that have been assayed in cell-based models.

Isolation and Pharmacological Characterization of Six Opioidergic Picralima nitida Alkaloids

The seeds of the akuamma tree (Picralima nitida) have been used as a traditional treatment for pain and fever. Previous studies have attributed these effects to a series of indole alkaloids found within the seed extracts; however, these pharmacological studies were significantly limited in scope. Herein, an isolation protocol employing pH-zone-refining countercurrent chromatography was developed to provide six of the akuamma alkaloids in high purity and quantities sufficient for more extensive biological evaluation. Five of these alkaloids, akuammine (1), pseudo-akuammigine (3), akuammicine (4), akuammiline (5), and picraline (6), were evaluated against a panel of >40 central nervous system receptors to identify that their primary targets are the opioid receptors. Detailed in vitro investigations revealed 4 to be a potent kappa opioid receptor agonist, and three alkaloids (1-3) were shown to have micromolar activity at the mu opioid receptor. The mu opioid receptor agonists were further evaluated for analgesic properties but demonstrated limited efficacy in assays of thermal nociception. These findings contradict previous reports of the antinociceptive properties of the P. nitida alkaloids and the traditional use of akuamma seeds as analgesics. Nevertheless, their opioid-preferring activity does suggest the akuamma alkaloids provide distinct scaffolds from which novel opioids with unique pharmacologic properties and therapeutic utility can be developed.

Cefazolin does not accelerate gastric emptying in the critically ill

OBJECTIVE

To evaluate the effect of intravenous cefazolin on gastric emptying measured by the C-13 octanoic acid breath test.

DESIGN

Prospective, double-blind, cross-over, randomised, placebo-controlled trial.

SETTING

Mixed multidisciplinary intensive care unit in a university hospital.

PATIENTS

Fourteen critically ill, mechanically ventilated patients.

INTERVENTIONS

After a 4-h fast patients received either 50 mg cefazolin or 20 ml saline over 20 min immediately prior to measurement of gastric emptying. The next day the study was repeated with the alternative therapy.

MEASUREMENTS AND RESULTS

Breath samples were analysed for the concentration of (13)CO2 by mass spectrometer, and the gastric emptying coefficient (GEC) and half-emptying time (t(50)) were calculated. Results are mean (standard deviation). Data were analysed with the paired t-test (saline vs cefazolin). Two patients were excluded for technical problems. Twelve patients remained (six male/six female), aged 57 (+/-16) years, with an APACHE II score of 20 (+/-8). Both GEC and t(50) were unchanged after administration of cefazolin compared with placebo (t(50) cefazolin, 138 (+/-54) vs saline 122 (+/-46) min, P=0.32; GEC cefazolin 3.27 (+/-0.83) vs saline 3.55 (+/-0.6), P=0.24). Two patients had abnormal t(50) after saline and five after cefazolin. There was no order effect of the study day.

CONCLUSION

In mechanically ventilated patients, cefazolin had no effect on gastric emptying. These data do not support the use of low-dose cefazolin as a pro-kinetic agent in critically ill patients.

NOD1 mediates interleukin-18 processing in epithelial cells responding to Helicobacter pylori infection in mice

The interleukin-1 family members, IL-1β and IL-18, are processed into their biologically active forms by multi-protein complexes, known as inflammasomes. Although the inflammasome pathways that mediate IL-1β processing in myeloid cells have been defined, those involved in IL-18 processing, particularly in non-myeloid cells, are still not well understood. Here we report that the host defence molecule NOD1 regulates IL-18 processing in mouse epithelial cells in response to the mucosal pathogen, Helicobacter pylori. Specifically, NOD1 in epithelial cells mediates IL-18 processing and maturation via interactions with caspase-1, instead of the canonical inflammasome pathway involving RIPK2, NF-κB, NLRP3 and ASC. NOD1 activation and IL-18 then help maintain epithelial homoeostasis to mediate protection against pre-neoplastic changes induced by gastric H. pylori infection in vivo. Our findings thus demonstrate a function for NOD1 in epithelial cell production of bioactive IL-18 and protection against H. pylori-induced pathology.

Discovery of Potent Kappa Opioid Receptor Agonists Derived from Akuammicine

Akuammicine (1), an alkaloid isolated from Picralima nitida, is an agonist of the kappa opioid receptor (κOR). To establish structure-activity relationships (SARs) for this structurally unique κOR ligand, a collection of semisynthetic derivatives was synthesized. Evaluating these derivatives for their ability to activate the κOR and mu opioid receptor (μOR) revealed key SAR trends and identified derivatives with enhanced κOR potency. Most notably, substitutions to the C10 position of the aryl ring led to a > 200-fold improvement in κOR potency and nearly complete selectivity for the κOR. A selection of the most potent ligands was shown to possess differing abilities recruitment of β-Arrestin-2 to the κOR, indicating they have distinct signaling properties from each other and existing κOR ligands. The discovery of these κOR agonists underscores the potential of using natural products to identify new classes of potent and selective ligands and provides new tools to probe the κOR.

Pharmacological characterization of the novel selective kappa opioid receptor agonists 10-Iodo-Akuammicine and 10-Bromo-akuammicine in mice

Akuammicine (AKC), an indole alkaloid, is a kappa opioid receptor (KOR) full agonist with a moderate affinity. 10-Iodo-akuammicine (I-AKC) and 10-Bromo-akuammicine (Br-AKC) showed higher affinities for the KOR with Ki values of 2.4 and 5.1 nM, respectively, and high selectivity for the KOR over other opioid receptors. Both were KOR full agonists. As AKC and derivatives have distinctly different chemical structures from other KOR agonists, herein we investigated whether Br-AKC and I-AKC produced similar pharmacological effects as typical KOR agonists. Br-AKC and I-AKC inhibited compound 48/80-induced scratching in a dose-dependent manner, with ED50 values of 3.0 and 1.3 mg/kg (s.c.), respectively, indicating anti-pruritic activities. Side effects of I-AKC and Br-AKC and their promotion of KOR phosphorylation and internalization were examined using doses in the effective anti-scratch dose range, at 1.9-3.8x ED50 and 1.7-3.3x ED50, respectively. At 5 mg/kg, Br-AKC and I-AKC produced profound conditioned place aversion (CPA). Br-AKC (10 mg/kg), but not I-AKC (5 mg/kg), reduced novelty-induced hyperlocomotion, and Br-AKC impaired rotarod performance more profoundly than I-AKC. Br-AKC, but not I-AKC, caused KOR phosphorylation at S369 in the mouse brain and KOR internalization in the ventral tegmental area. These results indicate that Br-AKC and I-AKC produce anti-scratch effect and CPA, similar to typical KOR agonists. However, there are some differences between the two. In addition, KOR phosphorylation and internalization in mouse brains are not associated with CPA but may be related to hypolocomotion and impaired rotarod performance. This is the first in vivo pharmacological characterization of AKC derivatives.