Chloroplast-to-nucleus retrograde signalling controls intercellular trafficking via plasmodesmata formation.

The signalling pathways that regulate intercellular trafficking via plasmodesmata (PD) remain largely unknown. Analyses of mutants with defects in intercellular trafficking led to the hypothesis that chloroplasts are important for controlling PD, probably by retrograde signalling to the nucleus to regulate expression of genes that influence PD formation and function, an idea encapsulated in the organelle-nucleus-PD signalling (ONPS) hypothesis. ONPS is supported by findings that point to chloroplast redox state as also modulating PD. Here, we have attempted to further elucidate details of ONPS. Through reverse genetics, expression of select nucleus-encoded genes with known or predicted roles in chloroplast gene expression was knocked down, and the effects on intercellular trafficking were then assessed. Silencing most genes resulted in chlorosis, and the expression of several photosynthesis and tetrapyrrole biosynthesis associated nuclear genes was repressed in all silenced plants. PD-mediated intercellular trafficking was changed in the silenced plants, consistent with predictions of the ONPS hypothesis. One striking observation, best exemplified by silencing the PNPase homologues, was that the degree of chlorosis of silenced leaves was not correlated with the capacity for intercellular trafficking. Finally, we measured the distribution of PD in silenced leaves and found that intercellular trafficking was positively correlated with the numbers of PD. Together, these results not only provide further support for ONPS but also point to a genetic mechanism for PD formation, clarifying a longstanding question about PD and intercellular trafficking. This article is part of the theme issue 'Retrograde signalling from endosymbiotic organelles'.

Combined Qualitative and Quantitative Assessment of Low-Attenuation Renal Lesions Improves Identification of Renal Malignancy on Noncontrast Computed Tomography.

OBJECTIVE: The objective of this study was to assess renal lesions measuring less than 20 Hounsfield units (HU) on noncontrast computed tomography (NCT). METHODS: Twenty-one (18.1%) of 116 consecutive pathologically proven renal cell carcinomas measured less than 20 HU on NCT and were compared with 40 confirmed benign cysts also measuring less than 20 HU. All lesions were assessed qualitatively (heterogeneous or homogenous) by 3 blinded readers and quantitatively with commercially available textural analysis software. Finally, a combined assessment was performed. RESULTS: Qualitative assessment performed well (sensitivity, 76%-90%; specificity, 70%-88%). Quantitative assessment revealed mean positive pixels as having the highest performance (area under the curve, 0.912; sensitivity, 90%; specificity, 80% at a cutoff value of 21). The combined assessment, using the mean positive pixel cutoff, improved the sensitivity (reader 1, 100%; reader 2, 95%; and reader 3, 95%). CONCLUSION: Qualitative and quantitative assessments have relatively good performance, but the combination can nearly eliminate renal cell carcinomas being missed on NCT.

A rare case of type 2 entrapment of the median nerve after posterior elbow dislocation with MRI and ultrasound correlation.

A 9-year-old boy sustained an ulnohumeral dislocation with a medial epicondyle fracture and experienced incomplete post-traumatic median nerve palsy in addition to post-traumatic stiffness following closed reduction and cast immobilization. When his motor palsy and stiffness did not improve, MRI and ultrasound were obtained, which demonstrated entrapment of the median nerve in an osseous tunnel at the fracture site, compatible with type 2 median nerve entrapment. Subsequently, the patient underwent surgery to mobilize the medial epicondyle and free the median nerve, resulting in improved range of motion, near complete restoration of motor function, and complete restoration of sensory function in the median nerve distribution within 6 months of surgery. Median nerve entrapment, particularly intraosseous, is a rare complication of posterior elbow dislocation and medial epicondyle fracture that may result in significant, sometimes irreversible, nerve damage if there is a delay in diagnosis and treatment. A high degree of clinical suspicion with early imaging is indicated in patients with persistent stiffness or nerve deficits following reduction of an elbow dislocation. Intra-articular entrapment diagnosed on ultrasound has been reported and intraosseous entrapment diagnosed clinically and on MR neurography have been reported; however, to our knowledge, this is the first reported case of intraosseous (type 2) median nerve entrapment clearly visualized and diagnosed on traditional MRI and ultrasound. The use of ultrasound for diagnosing median nerve entrapment is an accurate, accessible, and non-invasive imaging option for patients presenting with suspected nerve entrapment following elbow dislocation.

Acute Appendicitis Involving a De Garengeot Hernia.

We present a case of appendicitis within a De Garengeot hernia. The patient presented to the emergency department with 4 days of worsening abdominal pain. Computed tomography examination revealed an inflamed appendix within a femoral hernia. The patient underwent appendectomy and repair of the femoral defect. Pathological examination was consistent with acute appendicitis. De Garengeot hernia is a rare phenomenon, with less than 5% of femoral hernias containing the appendix and 0.08% to 0.13% containing an incarcerated acute appendicitis.

The effect of nicotine on sign-tracking and goal-tracking in a Pavlovian conditioned approach paradigm in rats.

RATIONALE: Nicotine (NIC) potently increases operant responding for non-NIC reinforcers, and this effect may depend on drug-mediated increases in incentive motivation. According to this hypothesis, NIC should also potently increase approach to Pavlovian-conditioned stimuli associated with rewards. OBJECTIVE: The present studies explored the effects of NIC on Pavlovian-conditioned approach responses. METHOD: To do so, liquid dippers were used to deliver an unconditioned stimulus (US; 0.1 ml sucrose) after presentation of a conditioned stimulus (CS; 30 s illumination of a stimulus light)-both the CS and US were presented in receptacles equipped to monitor head entries. RESULTS: In experiment 1, the CS and US were presented in the same receptacle, but NIC pretreatment (0.4 mg/kg base) did not increase conditioned approach responses. Delivery of the sucrose US was then shifted to receptacle in a different location. All rats learned to approach the new US location (goal-tracking) at similar rates. Approach to the CS receptacle (sign-tracking) declined for saline-pretreated rats, but NIC pretreatment increased sign-tracking. In experiment 2, NIC pretreatment increased sign-tracking when the CS and US were spatially separated during acquisition. In experiment 3, NIC pretreatments were replaced with saline, but the effect of NIC persisted for an additional 24 test sessions. CONCLUSION: The findings suggest that NIC increases incentive motivation and that this effect is long-lasting, persisting beyond the pharmacological effects of NIC.