Multidisciplinary approach to the diagnosis of Contracaecum magnipapillatum infections in Australian black noddies, Anous minutus (Charadriiformes: Laridae)

We provide the incidental necropsy findings associated with anisakid nematode infections of black noddy terns, Anous minutus Boie, 1844 (Charadriiformes: Laridae), from offshore islands in the southern Great Barrier Reef, Queensland, Australia. Specimens collected from the proventriculi were identified morphologically as Contracaecum magnipapillatum Chapin, 1925 (Rhabditida: Anisakidae), using light and scanning electron microscopy (SEM). The entire nuclear ribosomal DNA internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2) was amplified by polymerase chain reaction (PCR) and sequenced to provide reference sequences for morphologically well-identified voucher specimens. Interestingly, after an alignment with closely related taxa using BLAST, sequences of the ITS1 and ITS2 were 100% identical to the sequences assigned to Contracaecum septentrionale Kreis, 1955, from a razorbill, Alca torda Linnaeus, 1758 (Charadriiformes: Alcidae), from Spain. These results either raise questions about the ITS as a genetic marker for some members of Contracaecum, or the identity of the specimens assigned to C. septentrionale, given that no supporting morphological data was associated with them. We highlight the need for a combined morphological and molecular approach to parasite diagnostics and the use of multiple genetic loci to resolve the molecular taxonomy of cryptic species. Morphological identifications should be taxonomically robust, transparent and precede the deposition of molecular barcodes in public repositories. The gross and histopathological findings of our investigation concur with previous reports of widespread Contracaecum infections in black noddies and support the contention that Contracaecum spp. are an unlikely primary cause of mortality.

Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

Non-isotopic RNA In Situ Hybridization on Embryonic Sections

This unit describes methods for non-isotopic RNA in situ hybridization on embryonic mouse sections. These methods can be used to follow the spatiotemporal dynamics of gene expression in an embryonic tissue of interest. They involve the use of labeled (e.g., digoxygenin, FITC) antisense riboprobes that hybridize to a specific mRNA in the target tissue. The probes are detected using an alkaline phosphatase-conjugated antibody recognizing the label and a chromogenic substrate. This method can be used to: (1) assess the expression of a single gene within a tissue, (2) compare the expression profiles of two genes within a tissue, or (3) compare the distribution of a transcript and protein within a tissue. While this approach is not quantitative, it provides a qualitative assessment of the precise cell types where a gene is expressed, which is not easily achievable with other more quantitative methods such as quantitative PCR.

Efficient delivery of siRNA to cortical neurons using layered double hydroxide nanoparticles

Small interfering RNAs (siRNAs) are capable of targeting and destroying specific mRNAs, making them particularly suited to the treatment of neurodegenerative conditions such as Huntington's Disease where the production of abnormal proteins results in a gain-of-function phenotype. Although a variety of nanoparticle formulations are currently under development as siRNA delivery systems, application of these technologies has been limited by their high cytotoxicity, low drug loading capacity and release, and inability to penetrate cell membranes. Layered double hydroxide (LDH) nanoparticles are now emerging as a potential new drug delivery system as they exhibit low cytotoxicity and are highly biocompatible. Here we present the first study investigating LDH delivery of siRNAs to primary cultured neurons. We show that internalization by neurons is rapid, dose-dependent and saturable, and markedly more efficient than in other cell types. We demonstrate that siRNA-LDH complexes are internalized by clathrin-dependent endocytosis at the cell body and in neurites, with subsequent retrograde transport to the cell body followed by efficient release into the cytoplasm. Finally we show that LDH mediated siRNA delivery effectively silences neuronal gene expression. This study therefore confirms the potential of LDH nanoparticles as a drug delivery system for patients suffering from neurodegenerative disease.

STAT5A/B activity is required in the developing forebrain and spinal cord

Formation of the CNS requires the coordination and integration of processes such as cell proliferation, neuronal differentiation, neuronal migration, axon tract formation and synaptogenesis, all of which must occur at precise times and places during development. Although growth factors are known to play a role in regulating many of these processes, very little is known of the signaling events immediately downstream of ligand-receptor interactions in the developing CNS. Here we present evidence that STAT5, an important mediator of cytokine signaling, is required for some aspects of CNS development. We show that phosphorylated and hence activated forms of STAT5 (pSTAT5) are expressed in a temporally restricted manner in a subset of early-born telencephalic neurons and axons. Accordingly, Stat5 mutants have reduced numbers of interneurons in the cortical marginal zone, suggestive of migration defects. Moreover, corticofugal axons develop aberrantly in Stat5 mutants, indicative of a role for pSTAT5 in axon guidance. Notably, pSTAT5 is also expressed in commissural axons in the embryonic spinal cord, where it is also required for their guidance. Taken together, we provide the first evidence that STAT5 is a key effector molecule in the developing mammalian CNS.

Na,K-ATPase from mice lacking the gamma subunit (FXYD2) exhibits altered Na+ affinity and decreased thermal stability

The gamma subunit of the Na,K-ATPase, a 7-kDa single-span membrane protein, is a member of the FXYD gene family. Several FXYD proteins have been shown to bind to Na,K-ATPase and modulate its properties, and each FXYD protein appears to alter enzyme kinetics differently. Different results have sometimes been obtained with different experimental systems, however. To test for effects of gamma in a native tissue environment, mice lacking a functional gamma subunit gene (Fxyd2) were generated. These mice were viable and without observable pathology. Prior work in the mouse embryo showed that gamma is expressed at the blastocyst stage. However, there was no delay in blastocele formation, and the expected Mendelian ratios of offspring were obtained even with Fxyd2-/- dams. In adult Fxyd2-/- mouse kidney, splice variants of gamma that have different nephron segment-specific expression patterns were absent. Purified gamma-deficient renal Na,K-ATPase displayed higher apparent affinity for Na+ without significant change in apparent affinity for K+. Affinity for ATP, which was expected to be decreased, was instead slightly increased. The results suggest that regulation of Na+ sensitivity is a major functional role for this protein, whereas regulation of ATP affinity may be context-specific. Most importantly, this implies that gamma and other FXYD proteins have their effects by local and not global conformation change. Na,K-ATPase lacking the gamma subunit had increased thermal lability. Combined with other evidence that gamma participates in an early step of thermal denaturation, this indicates that FXYD proteins may play an important structural role in the enzyme complex.

The effect of tracheal intubation and surgical stimulation on median nerve somatosensory evoked potentials during anaesthesia

This study was designed to determine whether alterations in the median nerve somatosensory evoked potentials occur during the stimuli of tracheal intubation and skin incision. Twenty-two patients scheduled for elective surgery and who required tracheal intubation were studied. Median nerve somatosensory evoked potentials were recorded, analysed and stored approximately every 40 seconds. Anaesthesia was induced with thiopentone and vecuronium used for neuromuscular blockade; the trachea was intubated 2 minutes after induction. Fentanyl 1.5 micrograms/kg was administered subsequently. Evoked potential monitoring was continued until at least 2 minutes after surgical incision. Induction of anaesthesia was associated with an increase in evoked potential latency of 0.8 msec and reduction in amplitude of 1.7 microV. Small, statistically insignificant changes occurred between induction of anaesthesia and tracheal intubation. Surgical incision was accompanied by a statistically significant mean decrease in evoked potential latency of 0.5 msec and a statistically significant increase in evoked potential amplitude of 0.6 microV. The fact that surgical stimulation produced an activating effect on evoked potentials suggests that they may be used as a measure of the neurophysiological effects of anaesthesia.