Horizontal connectivity in V1: Prediction of coherence in contour and motion integration.

This study demonstrates the functional importance of the Surround context relayed laterally in V1 by the horizontal connectivity, in controlling the latency and the gain of the cortical response to the feedforward visual drive. We report here four main findings: 1) a centripetal apparent motion sequence results in a shortening of the spiking latency of V1 cells, when the orientation of the local inducer and the global motion axis are both co-aligned with the RF orientation preference; 2) this contextual effects grows with visual flow speed, peaking at 150-250°/s when it matches the propagation speed of horizontal connectivity (0.15-0.25 mm/ms); 3) For this speed range, the axial sensitivity of V1 cells is tilted by 90° to become co-aligned with the orientation preference axis; 4) the strength of modulation by the surround context correlates with the spatiotemporal coherence of the apparent motion flow. Our results suggest an internally-generated binding process, linking local (orientation /position) and global (motion/direction) features as early as V1. This long-range diffusion process constitutes a plausible substrate in V1 of the human psychophysical bias in speed estimation for collinear motion. Since it is demonstrated in the anesthetized cat, this novel form of contextual control of the cortical gain and phase is a built-in property in V1, whose expression does not require behavioral attention and top-down control from higher cortical areas. We propose that horizontal connectivity participates in the propagation of an internal "prediction" wave, shaped by visual experience, which links contour co-alignment and global axial motion at an apparent speed in the range of saccade-like eye movements.

Pathology influences blood pressure change following vagal stimulation in an animal intubation model.

PURPOSE: The haemodynamic response to critical care intubation is influenced by the use of sedation and relaxant drugs and the activation of the vagal reflex. It has been hypothesized that different disease states may have a contrasting effect on the cardiovascular response to vagal stimulation. Our objective was to determine whether the blood pressure response to vagal stimulation was modified by endotoxaemia or hypovolaemia. METHODS: New Zealand White rabbits were anaesthetised with urethane before tracheotomy. The exposed left Vagus nerve of randomised groups of control (n = 11), endotoxin (n = 11, 1 mg/kg), hypovolaemia 40% (n = 8) and hypovolaemia 20% (n = 8) rabbits were subjected to 10 Hz pulsed electrical stimulations of 25 s duration every 15 min. Haemodynamic parameters were recorded from a catheter in the right carotid artery connected to an iWorx monitor. Serum catecholamines were measured every 30 min using reverse-phase ion-pairing liquid chromatography. The change in blood pressure after vagal stimulation was compared to controls for one hour after the first death in the experimental groups. RESULTS: 29% of the rabbits died in the hypovolaemia 40% group and 27% in the endotoxin group. One rabbit died in the hypovolaemia 40% group before vagal stimulation and was excluded. Following electrical stimulation of the Vagus nerve there was a fall in blood pressure in control rabbits. Blood pressure was conserved in the hypovolaemic rabbits compared to controls (p<0.01). For the endotoxaemic rabbits, there was a non-significant trend for the mean blood pressure to decrease more than the controls. Serum catecholamines were significantly raised in both the hypovolaemic and endotoxaemic rabbits. CONCLUSIONS: Pathology may contribute to modifications in blood pressure when vagal activation occurs. Patients who are either already vasoconstricted, or not vasoplegic, may be less at risk from intubation-related vagally mediated reductions in blood pressure than those with vasodilatory pathologies.

Myocardial fibrosis in a horse with polymorphic ventricular tachycardia observed during general anesthesia.

Ventricular dysrhythmias are more commonly associated with myocardial disease than are supraventricular dysrhythmias. Management of arrhythmias under general anesthesia is difficult because of the dysrhythmogenic effects of the anesthetic drugs. This report describes a severe ventricular dysrhythmia observed in a pony under general anesthesia, with a severe and old myocardial fibrosis found on postmortem examination.

Bilateral Polydactyly in a foal.

The following case report describes the diagnosis and surgery of bilateral polydactyly of unknown origin in a colt. A 7-month-old Berber colt was referred for cosmetic and curative excision of supernumerary digits. Radiographic examination revealed bilateral polydactyly and welldeveloped first carpal bones. Surgery consisted of an osteotomy of both second metacarpal bones combined with an amputation of the supernumerary digits. The follow-up at 18 months after surgery revealed a sound horse with an excellent cosmetic outcome.

Preoperative immunosuppressive therapy and surgery as a treatment for anal furunculosis.

OBJECTIVES: To evaluate the efficacy of combining preoperative immunosuppressive therapy with surgical excision for treatment of anal furunculosis (AF) in dogs. STUDY DESIGN: Retrospective study. ANIMALS: Dogs (n=25) with stages 1-4 AF. METHODS: Preoperative immunosuppressive therapy was either cyclosporine A (CyA) alone or in combination with ketoconazole (Group 1; n=18), or azathioprine combined with prednisolone (Group 2; n=7). Surgical excision of residual draining tracts, cryptectomy, and anal sacculectomy were performed. Only dogs with postoperative clinical follow-up exceeding 9 months were retained for the study. RESULTS: Both immunosuppressive protocols were effective in reducing progression of AF. Subsequent draining tracts excision, cryptectomy, and anal sacculectomy were bilateral (12 dogs) or unilateral (13 dogs of which 4 had bilateral anal sacculectomy). Postoperative recovery was uneventful, except for 2 dogs that had wound breakdown. Recurrence was not observed in any of the dogs that had bilateral surgical excision and or in 9 dogs that had unilateral excision. CONCLUSION: Preoperative immunosuppressive therapy, combined with bilateral surgical resection of affected tissue consistently, resulted in resolution of AF. Four dogs that had recurrence had unilateral excision despite initial bilateral involvement, suggesting that all diseased tissue should be excised. CLINICAL RELEVANCE: These preliminary results suggest that immunosuppressive therapy before surgical excision for AF yields minimizes recurrence in dogs.

Successful engraftment of cultured autologous mesenchymal stem cells in a surgically repaired soft palate defect in an adult horse.

The objective of this study was to graft autologous mesenchymal stem cells (MSCs) at the site of surgical repair of a soft palate defect in an adult horse in an attempt to improve wound healing and to investigate whether the transplanted MSCs would integrate into the soft palate structure and participate in regeneration. Bone marrow was collected from an adult horse with a full-thickness soft palate defect. The MSCs were isolated, cultured in monolayers, and labeled with 5-bromo-2-desoxymidine (BrdU) and chloromethylbenzamido-DiI-derived (cm-DiI) before transplantation. The soft palate defect was repaired by mandibular symphysiotomy, and the labeled MSCs were injected into the repaired soft palate. Postmortem examination revealed that 90% of the soft palate defect had been sutured. Staining by BrdU and cm-DiI was intense in the soft palate tissue. Labeled MSCs were detected in tissue slices from the injection sites. The cells were organized in a manner similar to that in native soft palate tissue, indicating successful engraftment.

Analgesic comparison of meloxicam or ketoprofen for orthopedic surgery in dogs.

OBJECTIVE: To compare the safety and efficacy of 2 analgesic protocols (preoperative meloxicam or intraoperative ketoprofen administration) during the first 24 hours after orthopedic surgery in dogs. STUDY DESIGN: Double-blind, prospective randomized clinical trial. ANIMALS: Sixty client-owned dogs. METHODS: Dogs with surgical orthopedic disorders were randomly separated into 2 groups: 30 dogs were administered 0.2 mg/kg meloxicam intravenously (IV) immediately before induction and 30 dogs were administered 2 mg/kg ketoprofen IV, 30 minutes before the end of surgery. Pain was assessed with a visual analog scale (VAS) and a cumulative pain score (CPS) preoperatively and at 30 minutes, 1, 2, 3, 4, 6, 8, and 24 hours after extubation. Selected serum biochemical variables were measured before and 24 hours after surgery and, buccal mucosal bleeding time (BMBT) and whole blood clotting time (WBCT) were measured before and 8 hours after surgery. Dogs were anesthetized with propofol and maintained on halothane in oxygen. Any complications were documented for 7 days after surgery. Results were compared between the 2 groups for significant differences in VAS scores (2-sample t-test) and in CPS (Wilcoxon's 2-sample test). Moreover, results were analyzed for significant differences in area under the curve (AUC) for VAS (2-sample t-test) and CPS (Wilcoxon's 2-sample test) among groups. To assess the effects of treatments on biochemical and coagulation functions, pre- and postoperative mean values of BMBT and WBCT were compared within both treatment groups (paired t-tests) and between both groups (2-sample t-test). RESULTS: No significant differences in pain response or coagulation were found between meloxicam- and ketoprofen-treated dogs. In both groups, alkaline phosphatase and alanine aminotransferase concentrations were significantly increased compared with baseline. No serious complications occurred. CONCLUSIONS: Preoperative administration of meloxicam is a safe and effective method of controlling postoperative pain for up to 24 hours in dogs undergoing orthopedic surgery. CLINICAL RELEVANCE: Analgesia after administration of preoperative meloxicam was comparable with administration of ketoprofen at the end of the surgery.