Serum 1,3-Beta-D-Glucan Values During and After Laparoscopic and Open Intestinal Surgery.

Background1,3-beta-D Glucan (BDG) assay has good accuracy for distinguishing patients with invasive fungal infections from patients without. Some procedures and medications affect BDG levels, resulting in false-positive BDG results. The extent of intestinal surgery on BDG kinetics is unknown. We evaluated the influence of laparoscopic and open intestinal surgery on peri- and postsurgical serum BDG values.MethodsBDG was determined in 346 samples from 50 patients undergoing laparoscopic (24) or open (26) intestinal surgery at the following time points: after insertion of arterial but before skin incision, after skin incision but before dissection of the intestinal mucosa, after completion of anastomosis, after completion of skin sutures, in the evening after surgery, day 2 after surgery, 4-5 days after surgery.ResultsBDG was positive (ie, concentration ≥80 pg/mL) in 54% to 61% of patients during laparoscopic and open surgery (highest rates after completion of skin sutures). BDG was still positive in 12% (open) to 17% (laparoscopic) of patients without any suspected or proven fungal infection or anastomotic leakage 4-5 days after surgery. After completion of gut anastomosis, the BDG increase was higher in open compared with laparoscopic intestinal surgery.ConclusionsThe value of positive BDG tests in the perioperative setting up to 5 days postsurgery seems to be limited due to BDG elevations from intestinal surgical procedures

Nitric oxide activates ATP-sensitive potassium channels in mammalian sensory neurons: action by direct S-nitrosylation

<p>Abstract</p> <p>Background</p> <p>ATP-sensitive potassium (K_ATP) channels in neurons regulate excitability, neurotransmitter release and mediate protection from cell-death. Furthermore, activation of K_ATPchannels is suppressed in DRG neurons after painful-like nerve injury. NO-dependent mechanisms modulate both K_ATPchannels and participate in the pathophysiology and pharmacology of neuropathic pain. Therefore, we investigated NO modulation of K_ATPchannels in control and axotomized DRG neurons.</p> <p>Results</p> <p>Cell-attached and cell-free recordings of K_ATPcurrents in large DRG neurons from control rats (sham surgery, SS) revealed activation of K_ATPchannels by NO exogenously released by the NO donor SNAP, through decreased sensitivity to [ATP]i.</p> <p>This NO-induced K_ATPchannel activation was not altered in ganglia from animals that demonstrated sustained hyperalgesia-type response to nociceptive stimulation following spinal nerve ligation. However, baseline opening of K_ATPchannels and their activation induced by metabolic inhibition was suppressed by axotomy. Failure to block the NO-mediated amplification of K_ATPcurrents with specific inhibitors of sGC and PKG indicated that the classical sGC/cGMP/PKG signaling pathway was not involved in the activation by SNAP. NO-induced activation of K_ATPchannels remained intact in cell-free patches, was reversed by DTT, a thiol-reducing agent, and prevented by NEM, a thiol-alkylating agent. Other findings indicated that the mechanisms by which NO activates K_ATPchannels involve direct S-nitrosylation of cysteine residues in the SUR1 subunit. Specifically, current through recombinant wild-type SUR1/Kir6.2 channels expressed in COS7 cells was activated by NO, but channels formed only from truncated isoform Kir6.2 subunits without SUR1 subunits were insensitive to NO. Further, mutagenesis of SUR1 indicated that NO-induced K_ATPchannel activation involves interaction of NO with residues in the NBD1 of the SUR1 subunit.</p> <p>Conclusion</p> <p>NO activates K_ATPchannels in large DRG neurons via direct S-nitrosylation of cysteine residues in the SUR1 subunit. The capacity of NO to activate K_ATPchannels via this mechanism remains intact even after spinal nerve ligation, thus providing opportunities for selective pharmacological enhancement of K_ATPcurrent even after decrease of this current by painful-like nerve injury.</p

Guidance of block needle insertion by electrical nerve stimulation: a pilot study of the resulting distribution of injected solution in dogs

Little is known regarding the final needle tip location when various intensities of nerve stimulation are used to guide block needle insertion. Therefore, in control and hyperglycemic dogs, the authors examined whether lower-intensity stimulation results in injection closer to the sciatic nerve than higher-threshold stimulation. During anesthesia, the sciatic nerve was approached with an insulated nerve block needle emitting either 1 mA (high-current group, n = 9) or 0.5 mA (low-current group, n = 9 in control dogs and n = 6 in hyperglycemic dogs). After positioning to obtain a distal motor response, the lowest current producing a response was identified, and ink (0.5 ml) was injected. Frozen sections of the tissue revealed whether the ink was in contact with the epineurium of the nerve, distant to it, or within it. In control dogs, the patterns of distribution using high-threshold (final current 0.99 +/- 0.03 mA, mean +/- SD) and low-threshold (final current 0.33 +/- 0.08 mA) stimulation equally showed ink that was in contact with the epineurium or distant to it. One needle placement in the high-threshold group resulted in intraneural injection. In hyperglycemic dogs, all needle insertions used a low-threshold technique (n = 6, final threshold 0.35 +/- 0.08 mA), and all resulted in intraneural injections. In normal dogs, current stimulation levels in the range of 0.33-1.0 mA result in needle placement comparably close to the sciatic nerve but do not correlate with distance from the target nerve. In this experimental design, low-threshold electrical stimulation does not offer satisfactory protection against intraneural injection in the presence of hyperglycemi

Restoration of calcium influx corrects membrane hyperexcitability in injured rat dorsal root ganglion neurons

We have previously shown that a decrease of inward Ca(2+) flux (I(Ca)) across the sensory neuron plasmalemma, such as happens after axotomy, increases neuronal excitability. From this, we predicted that increasing I(Ca) in injured neurons should correct their hyperexcitability. The influence of increased or decreased I(Ca) upon membrane biophysical variables and excitability was determined during recording from A-type neurons in nondissociated dorsal root ganglia after spinal nerve ligation using an intracellular recording technique. When the bath Ca(2+) level was increased to promote I(Ca), the after-hyperpolarization was decreased and repetitive firing was suppressed, which also followed amplification of Ca(2+)-activated K(+) current with selective agents NS1619 and NS309. A decreased external bath Ca(2+) concentration had the opposite effects, similar to previous observations in uninjured neurons. These findings indicate that at least a part of the hyperexcitability of somatic sensory neurons after axotomy is attributable to diminished inward Ca(2+) flux, and that measures to restore I(Ca) may potentially be therapeutic for painful peripheral neuropath

Painful nerve injury increases plasma membrane Ca²⁺-ATPase activity in axotomized sensory neurons

Abstract Background The plasma membrane Ca2+-ATPase (PMCA) is the principal means by which sensory neurons expel Ca2+ and thereby regulate the concentration of cytoplasmic Ca2+ and the processes controlled by this critical second messenger. We have previously found that painful nerve injury decreases resting cytoplasmic Ca2+ levels and activity-induced cytoplasmic Ca2+ accumulation in axotomized sensory neurons. Here we examine the contribution of PMCA after nerve injury in a rat model of neuropathic pain. Results PMCA function was isolated in dissociated sensory neurons by blocking intracellular Ca2+ sequestration with thapsigargin, and cytoplasmic Ca2+ concentration was recorded with Fura-2 fluorometry. Compared to control neurons, the rate at which depolarization-induced Ca2+ transients resolved was increased in axotomized neurons after spinal nerve ligation, indicating accelerated PMCA function. Electrophysiological recordings showed that blockade of PMCA by vanadate prolonged the action potential afterhyperpolarization, and also decreased the rate at which neurons could fire repetitively. Conclusion We found that PMCA function is elevated in axotomized sensory neurons, which contributes to neuronal hyperexcitability. Accelerated PMCA function in the primary sensory neuron may contribute to the generation of neuropathic pain, and thus its modulation could provide a new pathway for peripheral treatment of post-traumatic neuropathic pain.</p

K_ATPchannel subunits in rat dorsal root ganglia: alterations by painful axotomy

Abstract Background ATP-sensitive potassium (KATP) channels in neurons mediate neuroprotection, they regulate membrane excitability, and they control neurotransmitter release. Because loss of DRG neuronal KATP currents is involved in the pathophysiology of pain after peripheral nerve injury, we characterized the distribution of the KATP channel subunits in rat DRG, and determined their alterations by painful axotomy using RT-PCR, immunohistochemistry and electron microscopy. Results PCR demonstrated Kir6.1, Kir6.2, SUR1 and SUR2 transcripts in control DRG neurons. Protein expression for all but Kir6.1 was confirmed by Western blots and immunohistochemistry. Immunostaining of these subunits was identified by fluorescent and confocal microscopy in plasmalemmal and nuclear membranes, in the cytosol, along the peripheral fibers, and in satellite glial cells. Kir6.2 co-localized with SUR1 subunits. Kir6.2, SUR1, and SUR2 subunits were identified in neuronal subpopulations, categorized by positive or negative NF200 or CGRP staining. KATP current recorded in excised patches was blocked by glybenclamide, but preincubation with antibody against SUR1 abolished this blocking effect of glybenclamide, confirming that the antibody targets the SUR1 protein in the neuronal plasmalemmal membrane. In the myelinated nerve fibers we observed anti-SUR1 immunostaining in regularly spaced funneled-shaped structures. These structures were identified by electron microscopy as Schmidt-Lanterman incisures (SLI) formed by the Schwann cells. Immunostaining against SUR1 and Kir6.2 colocalized with anti-Caspr at paranodal sites. DRG excised from rats made hyperalgesic by spinal nerve ligation exhibited similar staining against Kir6.2, SUR1 or SUR2 as DRG from controls, but showed decreased prevalence of SUR1 immunofluorescent NF200 positive neurons. In DRG and dorsal roots proximal to axotomy SLI were smaller and showed decreased SUR1 immunofluorescence. Conclusions We identified Kir6.2/SUR1 and Kir6.2/SUR2 KATP channels in rat DRG neuronal somata, peripheral nerve fibers, and glial satellite and Schwann cells, in both normal state and after painful nerve injury. This is the first report of KATP channels in paranodal sites adjacent to nodes of Ranvier and in the SLI of the Schwann cells. After painful axotomy KATP channels are downregulated in large, myelinated somata and also in SLI, which are also of smaller size compared to controls. Because KATP channels may have diverse functional roles in neurons and glia, further studies are needed to explore the potential of KATP channels as targets of therapies against neuropathic pain and neurodegeneration.</p