Exploring experimental autoimmune optic neuritis using multimodal imaging.

BACKGROUND: Neuro-axonal injury is a key contributor to non-reversible long-term disability in multiple sclerosis (MS). However, the underlying mechanisms are not yet fully understood. Visual impairment is common among MS patients, in which episodes of optic neuritis (ON) are often followed by structural retinal damage and sustained functional impairment. Alterations in the optic nerve and retina have also been described in experimental autoimmune encephalomyelitis (EAE), a rodent model of MS. Thus, investigating structural anterior visual pathway damage may constitute a unique model for assessing mechanisms and temporal sequence of neurodegeneration in MS. We used a multimodal imaging approach utilizing optical coherence tomography (OCT) and diffusion tensor imaging (DTI) to explore the mechanisms and temporal dynamics of visual pathway damage in the animal model of MS. METHODS: 7 EAE-MOG35-55 and 5 healthy female C57BL/6J mice were used in this study. Ganglion cell complex (GCC) thickness was derived from an OCT volume scan centred over the optic nerve head, while the structure of the optic nerve and tracts was assessed from DTI and co-registered T2-weighted sequences performed on a 7T MRI scanner. Data was acquired at baseline, disease onset, peak of disease and recovery. Linear mixed effect models were used to account for intra-subject, inter-eye dependencies, group and time point. Correlation analyses assessed the relationship between GCC thickness and DTI parameters. Immunofluorescence staining of retina and optic nerve sections was used to assess distribution of marker proteins for microglia and neurodegeneration (nerve filaments). RESULTS: In EAE mice, a significant increase in GCC thickness was observed at disease onset (p < 0.001) followed by a decrease at recovery (p < 0.001) compared to controls. The EAE group had significant GCC thinning at recovery compared to all other time points (p < 0.001 for each). Signal increase on T2-weighted images around the optic nerves indicative of inflammation was seen in most of the EAE mice but in none of the controls. A significant decrease in axial diffusivity (AD) and increase in radial diffusivity (RD) values in EAE optic nerves (AD: p = 0.02, RD: p = 0.01) and tract (AD: p = 0.02, RD: p = 0.006) was observed compared to controls. GCC at recovery was positively correlated with AD (optic nerve: rho = 0.74, p = 0.04, optic tract: rho = 0.74, p = 0.04) and negatively correlated with RD (optic nerve: rho = -0.80, p = 0.02, optic tract: rho = -0.75, p = 0.04). Immunofluorescence analysis indicated the presence of activated microglia in the retina and optic nerves in addition to astrocytosis and axonal degeneration in the optic nerve of EAE mice. CONCLUSION: OCT detected GCC changes in EAE may resemble what is observed in MS-related acute ON: an initial phase of swelling (indicative of inflammatory edema) followed by a decrease in thickness over time (representative of neuro-axonal degeneration). In line with OCT findings, DTI of the visual pathway identifies EAE induced pathology (decreased AD, and increased RD). Immunofluorescence analysis provides support for inflammatory pathology and axonal degeneration. OCT together with DTI can detect retinal and optic nerve damage and elucidate to the temporal sequence of neurodegeneration in this rodent model of MS in vivo.

Effect of fentanyl on the induction dose and minimum infusion rate of propofol preventing movement in dogs.

OBJECTIVE: To determine the effect of fentanyl on the induction dose of propofol and minimum infusion rate required to prevent movement in response to noxious stimulation (MIRNM) in dogs. STUDY DESIGN: Crossover experimental design. ANIMALS: Six healthy, adult intact male Beagle dogs, mean±standard deviation 12.6±0.4 kg. METHODS: Dogs were administered 0.9% saline (treatment P), fentanyl (5 µg kg-1) (treatment PLDF) or fentanyl (10 µg kg-1) (treatment PHDF) intravenously over 5 minutes. Five minutes later, anesthesia was induced with propofol (2 mg kg-1, followed by 1 mg kg-1 every 15 seconds to achieve intubation) and maintained for 90 minutes by constant rate infusions (CRIs) of propofol alone or with fentanyl: P, propofol (0.5 mg kg-1 minute-1); PLDF, propofol (0.35 mg kg-1 minute-1) and fentanyl (0.1 µg kg-1 minute-1); PHDF, propofol (0.3 mg kg-1 minute-1) and fentanyl (0.2 µg kg-1 minute-1). Propofol CRI was increased or decreased based on the response to stimulation (50 V, 50 Hz, 10 mA), with 20 minutes between adjustments. Data were analyzed using a mixed-model anova and presented as mean±standard error. RESULTS: ropofol induction doses were 6.16±0.31, 3.67±0.21 and 3.33±0.42 mg kg-1 for P, PLDF and PHDF, respectively. Doses for PLDF and PHDF were significantly decreased from P (p<0.05) but not different between treatments. Propofol MIRNM was 0.60±0.04, 0.29±0.02 and 0.22±0.02 mg kg-1 minute-1 for P, PLDF and PHDF, respectively. MIRNM in PLDF and PHDF was significantly decreased from P. MIRNM in PLDF and PHDF were not different, but their respective percent decreases of 51±3 and 63±2% differed (p=0.035). CONCLUSIONS AND CLINICAL RELEVANCE: Fentanyl, at the doses studied, caused statistically significant and clinically important decreases in the propofol induction dose and MIRNM.

Optical Coherence Tomography and Magnetic Resonance Imaging in Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorder.

Irreversible disability in multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) is largely attributed to neuronal and axonal degeneration, which, along with inflammation, is one of the major pathological hallmarks of these diseases. Optical coherence tomography (OCT) is a non-invasive imaging tool that has been used in MS, NMOSD, and other diseases to quantify damage to the retina, including the ganglion cells and their axons. The fact that these are the only unmyelinated axons within the central nervous system (CNS) renders the afferent visual pathway an ideal model for studying axonal and neuronal degeneration in neurodegenerative diseases. Structural magnetic resonance imaging (MRI) can be used to obtain anatomical information about the CNS and to quantify evolving pathology in MS and NMOSD, both globally and in specific regions of the visual pathway including the optic nerve, optic radiations and visual cortex. Therefore, correlations between brain or optic nerve abnormalities on MRI, and retinal pathology using OCT, may shed light on how damage to one part of the CNS can affect others. In addition, these imaging techniques can help identify important differences between MS and NMOSD such as disease-specific damage to the visual pathway, trans-synaptic degeneration, or pathological changes independent of the underlying disease process. This review focuses on the current knowledge of the role of the visual pathway using OCT and MRI in patients with MS and NMOSD. Emphasis is placed on studies that employ both MRI and OCT to investigate damage to the visual system in these diseases.

Hyaluronidase modulates bleomycin-induced lung injury detected noninvasively in small rodents by radial proton MRI.

PURPOSE: To assess whether hyaluronic acid, a building block of proteoglycans and extracellular matrix with hydrophilic characteristics, might contribute to magnetic resonance imaging (MRI)-detected proton signals elicited by bleomycin in the lung. To this end, hyaluronidase, which degrades hyaluronic acid, was administered to bleomycin-challenged animals. MATERIALS AND METHODS: Fibrosis was induced by oropharyngeal aspiration (OA) of bleomycin. Mice received bleomycin once daily (0.1 mg/kg) on 6 consecutive days, while rats were given a single dose (2 or 4 mg/kg). Hyaluronidase, budesonide, and the respective vehicles were also administered via OA. Animals were examined using a radial ultrashort echo time sequence. Histology of picrosirius reflecting collagen and tissue gene analysis were performed postmortem. RESULTS: In mice, hyaluronidase induced an increase of high intensity signals by 34 ± 12 µL (means ± SD, P = 0.007), consistent with the ability of the degradation products of hyaluronic acid to provoke acute inflammation. Budesonide was able to resolve hyaluronidase-induced signals or to prevent their formation. Combined administration of budesonide and hyaluronidase to bleomycin-treated rats resulted in an overall decrease (-17.1 ± 7%, P = 0.02) of the MRI-detected bleomycin-induced signals. Moreover, the relative gene expression of hyaluronidase was reduced (-61.8 ± 10.2%, P < 0.001) in fibrotic lungs. CONCLUSION: The present data indicate that hyaluronic acid contributes to the bleomycin-induced responses detected by MRI in the lung.

Adriamycin-induced nephropathy in rats: functional and cellular effects characterized by MRI.

PURPOSE: To assess with magnetic resonance imaging (MRI) adriamycin-induced nephropathy in living rats, an established model for proteinuric renal disease was used. MATERIALS AND METHODS: Functional information of contrast agent clearance was obtained with dynamic contrast-enhanced (DCE) imaging following intravenous Gd-DOTA administration. Perfusion data were obtained with a bolus tracking technique comprising intravenous injection of superparamagnetic iron oxide (SPIO) nanoparticles. Cellular information was derived from anatomical images acquired 24 hours after SPIO. Treatment with the transforming growth factor-ß123 (TGF-ß1,2,3 ) antibody, 1D11, started 1 week after adriamycin. Histology was performed at week 6 post-adriamycin. RESULTS: Tracer washout rates derived by DCE-MRI decreased by 65.5% with respect to baseline at week 6 post-adriamycin. The impaired kidney function agreed with glomerulopathy, nephropathy and fibrosis revealed histologically (picrosirius collagen staining in adriamycin-treated rats increased by 125.8% [P = 0.005] with respect to controls). Perfusion was reduced by 16.1%. Images acquired 24 hours after SPIO presented contrast changes that correlated inversely with the histologically determined iron content (R = -0.74, P = 2.6 × 10(-4) ). In adriamycin-challenged animals, iron was found in macrophages and in sclerotic tubuli, only in areas where macrophages were present. Treatment with 1D11 did not improve the adriamycin-induced renal injury. CONCLUSION: MRI provides longitudinal functional and cellular (macrophage infiltration) information that correlates with nephropathy development in adriamycin-challenged rats.

Lung volume quantified by MRI reflects extracellular-matrix deposition and altered pulmonary function in bleomycin models of fibrosis: effects of SOM230.

Idiopathic pulmonary fibrosis is a progressive and lethal disease, characterized by loss of lung elasticity and alveolar surface area, secondary to alveolar epithelial cell injury, reactive inflammation, proliferation of fibroblasts, and deposition of extracellular matrix. The effects of oropharyngeal aspiration of bleomycin in Sprague-Dawley rats and C57BL/6 mice, as well as of intratracheal administration of ovalbumin to actively sensitized Brown Norway rats on total lung volume as assessed noninvasively by magnetic resonance imaging (MRI) were investigated here. Lung injury and volume were quantified by using nongated or respiratory-gated MRI acquisitions [ultrashort echo time (UTE) or gradient-echo techniques]. Lung function of bleomycin-challenged rats was examined additionally using a flexiVent system. Postmortem analyses included histology of collagen and hydroxyproline assays. Bleomycin induced an increase of MRI-assessed total lung volume, lung dry and wet weights, and hydroxyproline content as well as collagen amount. In bleomycin-treated rats, gated MRI showed an increased volume of the lung in the inspiratory and expiratory phases of the respiratory cycle and a temporary decrease of tidal volume. Decreased dynamic lung compliance was found in bleomycin-challenged rats. Bleomycin-induced increase of MRI-detected lung volume was consistent with tissue deposition during fibrotic processes resulting in decreased lung elasticity, whereas influences by edema or emphysema could be excluded. In ovalbumin-challenged rats, total lung volume quantified by MRI remained unchanged. The somatostatin analog, SOM230, was shown to have therapeutic effects on established bleomycin-induced fibrosis in rats. This work suggests MRI-detected total lung volume as readout for tissue-deposition in small rodent bleomycin models of pulmonary fibrosis.

Antinociceptive and selected physiological effects of morphine and xylazine on tiletamine-zolazepam anesthesia in llamas.

OBJECTIVE: Evaluate antinociception, anesthesia, and recovery in llamas given tiletamine-zolazepam (TZ) with either morphine, xylazine, morphine and xylazine, or saline. STUDY DESIGN: Randomized crossover experimental study. ANIMALS: Six healthy, adult intact male llamas. METHODS: Llamas were given each of four treatments intramuscularly with a 1-week washout: TZ (2 mg kg(-1) ) combined with either morphine (0.5 mg kg(-1) ; M), xylazine (0.15 mg kg(-1) ; X), morphine (0.5 mg kg(-1) ) and xylazine (0.15mg kg(-1) ) (MX), or saline (C). Llamas breathed room air during the experiment. Characteristics of anesthesia, recovery, and selected cardiopulmonary variables were recorded. Antinociception was assessed by clamping a claw at 5-minute intervals. Data were analyzed using a mixed-model anova and Tukey-Kramer test, and are expressed as least squares mean ± SEM. Significance was set at p < 0.05. RESULTS: No llama in the control group demonstrated antinociception. Antinociception was longest with treatment MX, followed by treatments X and M, respectively. Heart rates in llamas given treatments X and MX were significantly lower than with other treatments. The respiratory rate in llamas given treatment C was greater (p < 0.05) than for all other treatments, however, the respiratory rate was not significantly different among treatments X, M and MX. The PaO2 for llamas given MX remained <60 mmHg throughout the 20 minute period of blood gas analysis. Mean arterial blood pressure in llamas in treatment MX was less than for treatments M or C. CONCLUSION AND CLINICAL RELEVANCE: The combination of morphine (0.5 mg kg(-1) ) and xylazine (0.15 mg kg(-1) ) increased the duration of antinociception compared with xylazine alone, in TZ-anesthetized llamas. Treatments X, M and MX were associated with hypoxemia (PaO2 < 60 mmHg).

Intraoperative esophageal washout reduces free intraluminal tumor cells during resection of carcinomas of the esophagus and cardia.

OBJECTIVE: Intraluminally shed viable tumor cells might contribute to anastomotic recurrence in cancer of the esophagus and the cardia. The study aimed to establish a method of esophageal washout and, hence, to reduce intraluminal cancer cells before esophageal anastomosis. METHODS: Forty-eight consecutive patients with esophago-gastric resection for histologically proven cancer of the esophagus or the cardia were included in a prospective, interventional study. Before transection, the esophagus was clamped proximally to the tumor and rinsed with 1:10 diluted povidone-iodine-solution (10 × 30 ml) applied by a transorally inserted 24F-Foley catheter. The first, fifth and tenth portion of the lavage fluid were sent to cytological examination. RESULTS: Intraoperative frozen sections confirmed clear proximal resection margins of the esophagus. The cytological examination of the fluid recovered from the esophageal washout revealed malignant cells in 13/48 patients (27%). The presence of malignant cells was significantly less likely in patients with neoadjuvant treatment than in patients without neoadjuvant treatment: 2/23 (9%) vs. 11/25 (44%) (p = 0.009). Repetitive washout reduced the probability of detectable malignant cells from 13 to 8 (62%) patients after 5, and further to 4 patients (30%) after 10 washout maneuvers. CONCLUSIONS: Free malignant cells may be present in the esophageal lumen following intraoperative manipulation of cancers of the esophagus or cardia. Transoral washout of the esophagus is novel, feasible and enables reduction or even elimination of these tumor cells. The reliability of this procedure raises with increasing washout volume. Esophageal washout might be especially worthwhile in patients who do not receive neoadjuvant therapy.

The effect of fentanyl on the end-tidal sevoflurane concentration needed to prevent motor movement in dogs.

OBJECTIVE: The objectives of this study were to determine the effects of fentanyl on the end-tidal concentration of sevoflurane needed to prevent motor movement (MACNM ) in response to noxious stimulation, and to evaluate if acute tolerance develops. STUDY DESIGN: Randomized cross-over experimental study. ANIMALS: Six healthy, adult (2-3 years old), intact male, mixed-breed dogs weighing 16.2 ± 1.1 kg. METHODS: Six dogs were randomly assigned to receive one of three separate treatments over a 3 week period. After baseline sevoflurane MACNM (MACNM-B) determination, fentanyl treatments (T) were administered as a loading dose (Ld) and constant rate infusion (CRI) as follows: T1-Ld of 7.5 µg kg(-1) and CRI at 3 µg kg(-1) hour(-1); T2-Ld of 15 µg kg(-1) and CRI at 6.0 µg kg (-1) hour(-1); T3-Ld of 30 µg kg(-1) and CRI at 12 µg kg(-1) hour(-1). The MACNM was defined as the minimum end-tidal sevoflurane concentration preventing motor movement. The first post-treatment MACNM (MACNM-I) determination was initiated 90 minutes after the start of the CRI, and a second MACNM (MACNM - II) determination was initiated 3 hours after MACNM-I was established. RESULTS: The overall least square mean MACNM-B for all groups was 2.66%. All treatments decreased (p < 0.05) MACNM, and the decrease from baseline was 22%, 35% and 41% for T1, T2 and T3, respectively. Percentage change in T1 differed (p < 0.05) from T2 and T3; however, T2 did not differ from T3. MACNM-I was not significantly different from MACNM-II within treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Fentanyl doses in the range of 3-12 µg kg(-1) hour(-1) significantly decreased the sevoflurane MACNM. Clinically significant tolerance to fentanyl did not occur under the study conditions.

The effect of ketamine on the MACBAR of sevoflurane in dogs.

OBJECTIVE: To determine the effect of intravenous ketamine on the minimum alveolar concentration of sevoflurane needed to block autonomic response (MAC(BAR)) to a noxious stimulus in dogs. STUDY DESIGN: Randomized, crossover, prospective design. ANIMALS: Eight, healthy, adult male, mixed-breed dogs, weighing 11.2-16.1 kg. METHODS: Dogs were anesthetized with sevoflurane on two occasions, 1 week apart, and baseline MAC(BAR) (B-MAC(BAR)) was determined on each occasion. MAC(BAR) was defined as the mean of the end-tidal sevoflurane concentrations that prevented and allowed an increase (≥15%) in heart rate or invasive mean arterial pressure in response to a noxious electrical stimulus (50 V, 50 Hz, 10 ms). Dogs then randomly received either a low-dose (LDS) or high-dose series (HDS) of ketamine, and treatment MAC(BAR) (T-MAC(BAR)) was determined. The LDS had an initial loading dose (LD) of 0.5 mg kg(-1) and constant rate infusion (CRI) at 6.25 µg kg(-1) minute(-1), followed, after T-MAC(BAR) determination, by a second LD (1 mg kg(-1)) and CRI (12.5 µg kg(-1) minute(-1)). The HDS had an initial LD (2 mg kg(-1)) and CRI (25 µg kg(-1) minute(-1)) followed by a second LD (3 mg kg(-1)) and CRI (50 µg kg(-1) minute(-1)). Data were analyzed with a mixed-model anova and are presented as LSM ± SEM. RESULTS: The B-MAC(BAR) was not significantly different between treatments. Ketamine at 12.5, 25, and 50 µg kg(-1) minute(-1) decreased sevoflurane MAC(BAR), and the maximal decrease (22%) occurred at 12.5 µg kg(-1) minute(-1). The percentage change in MAC(BAR) was not correlated with either the log plasma ketamine or norketamine concentration. CONCLUSIONS AND CLINICAL RELEVANCE: Ketamine at clinically relevant doses of 12.5, 25, and 50 µg kg(-1) minute(-1) decreased sevoflurane MAC(BAR), although the reduction was neither dose-dependent nor linear.