Plant circadian clock control of Medicago truncatula nodulation via regulation of nodule cysteine-rich peptides.

Legumes house nitrogen-fixing endosymbiotic rhizobia in specialized polyploid cells within root nodules, which undergo tightly regulated metabolic activity. By carrying out expression analysis of transcripts over time in Medicago truncatula nodules, we found that the circadian clock enables coordinated control of metabolic and regulatory processes linked to nitrogen fixation. This involves the circadian clock-associated transcription factor LATE ELONGATED HYPOCOTYL (LHY), with lhy mutants being affected in nodulation. Rhythmic transcripts in root nodules include a subset of nodule-specific cysteine-rich peptides (NCRs) that have the LHY-bound conserved evening element in their promoters. Until now, studies have suggested that NCRs act to regulate bacteroid differentiation and keep the rhizobial population in check. However, these conclusions came from the study of a few members of this very large gene family that has complex diversified spatio-temporal expression. We suggest that rhythmic expression of NCRs may be important for temporal coordination of bacterial activity with the rhythms of the plant host, in order to ensure optimal symbiosis.

Spontaneous celiac artery dissection.

BACKGROUND: Spontaneous celiac artery dissection is a rare visceral artery dissection that typically presents with acute abdominal or flank pain. CASE REPORT: We describe a case of a 54-year old previously healthy male who presented to the Emergency Department with subacute back pain and was found to have a spontaneous celiac artery dissection. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Emergency medicine physicians frequently consider acute aortic dissection in patients presenting to the Emergency Department with acute chest, back, and/or upper abdominal pain. Less commonly thought of are variations of arterial dissection, including those involving the celiac artery. Given readily available diagnostic imaging modalities and therapeutic interventions, it remains important to consider visceral arterial dissection, and to recognize the varied clinical manifestations of this rare clinical entity.

What is the risk of diagnostic endoscopic retrograde cholangiopancreatography before cholecystectomy?

Many surgeons prefer to perform endoscopic retrograde cholangiopancreatography (ERCP) before cholecystectomy, specifically in patients at significant risk of having biliary pathology. However, a preoperative diagnostic ERCP, without the use of an endoscopic ultrasound or magnetic retrograde cholangiopancreatoscopy, remains controversial. This is the result of the risk of either performing an unnecessary procedure and/or the development of post-ERCP pancreatitis (PEP). We performed a retrospective review of all surgeon-performed ERCPs at our institution between July 2011 and May 2013. This was done to examine patients who had pericholecystectomy ERCP. We had 550 ERCPs performed at our institution during this time period, 169 of which were pericholecystectomy procedures. We divided the 169 patients who had a diagnostic procedure (Diagnostic group) from those who had known biliary pathology before intervention (Therapeutic group). As a result, 34 patients (20.1%) were placed in the Diagnostic group and 135 patients (79.9%) in the Therapeutic group. Of the 34 Diagnostic patients, four (11.8%) developed PEP. Fifteen (44.1%) had unnecessary procedures, two of which had PEP (2.9%). Of the 135 ERCPs in the Therapeutic group, 18 patients (13.4%) developed PEP. Five of the 11 who had unnecessary procedures developed PEP. Based on the low incidence of complications, diagnostic ERCP has an acceptable rate of pancreatitis and/or unnecessary procedures when performed in highly selected patients and before cholecystectomy when compared with patients undergoing therapeutic ERCP. However, more aggressive use of diagnostic imaging before ERCP should be adopted given the number of unnecessary procedures performed.