Saccharomyces cerevisiae is dimorphic and switches from a yeast form to a pseudohyphal (PH) form when starved for nitrogen. PH cells are elongated, bud in a unipolar manner, and invade the agar substrate. We assessed the requirements for actin in mediating the dramatic morphogenetic events that accompany the transition to PH growth. Twelve “alanine scan” alleles of the single yeast actin gene (ACT1) were tested for effects on filamentation, unipolar budding, agar invasion, and cell elongation. Someact1 mutations affect all phenotypes, whereas others affect only one or two aspects of PH growth. Tests of intragenic complementation among specific act1 mutations support the phenotypic evidence for multiple actin functions in filamentous growth. We present evidence that interaction between actin and the actin-binding protein fimbrin is important for PH growth and suggest that association of different actin-binding proteins with actin mediates the multiple functions of actin in filamentous growth. Furthermore, characterization of cytoskeletal structure in wild type and act1/act1 mutants indicates that PH cell morphogenesis requires the maintenance of a highly polarized actin cytoskeleton. Collectively, this work demonstrates that actin plays a central role in fungal dimorphism.
SUMMARY: A prospective comparative study of 0.5 Tesla cine‐magnetic resonance arteriography (MRA) versus standard arteriography (SA) was performed in 42 patients with clinical suspicion of atheromatous renal artery stenosis (ARAS), all of whom had chronic renal failure (average creatinine for 42 patients was 269.2±103.4 μmol/L). MRA was performed on a Philips 0.5 Tesla T5 release III, (London, UK) using T1 gradient echo cine, and 3D phase contrast. SA was performed as an aortic flush, with or without selective renal studies, via the femoral artery. Intravenous digital subtraction angiography was performed (instead of a flush procedure) in two patients with severe femoral atheroma. One radiologist reported the MRA's, another reported the SA's; both were blinded to the results of other scans. MRA correctly identified the number of renal arteries in 31 of the 42 patients (75%); accessory arteries could not be visualized. Using SA as the gold standard‘, MRA had a sensitivity of 90% and a specificity of 54%, with regard to detection of significant (>50%) ARAS lesions. MRA had a negative predictive value of 70%, and a positive predictive value of 82%. MRA was well tolerated by all patients, oral sedation being needed for just three. We conclude that 0.5 Tesla MRA has only limited usefulness as a non‐invasive screening test for ARAS, demonstrating fair sensitivity, comparable to other screening methods, in the context of significant renal impairment. However, specificity was poor, due to seven false positives. Improving the signal to noise ratio by using signal‐enhancing media, or using a more powerful magnet, are likely to yield more accurate information.
Summary A 56-year-old man who received a live-related renal transplant in 1988 was started in 1995 on the selective angiotensin II antagonist losartan (Dupont-Merke) to treat worsening hypertension. Two months later because of pulmonary oedema, loop diuretics were started. Within two weeks, serum creatinine had increased from 245 to 571 mumol/l, and the patient became oliguric. A systolic bruit was noted over the graft. Renal angiography showed a 90% stenosis of the transplant renal artery. Losartan was withdrawn, with prompt improvement in renal function. A successful percutaneous transluminal angioplasty performed a few days later resulted in further improvement in renal function accompanied by a significant diuresis.
Aorto-enteric fistulas (AEFs) and para-anastomotic aneurysms (PAAs) are uncommon complications of open aortic surgery (0.5-2.5%) and (0.2-15%), respectively. AEF if untreated is often fatal and surgical management is associated with mortality up to 90%. The risk of PAA rupture carries a mortality of 58%. We present our experience in ten patients with the endovascular treatment of these complications to define the role of endovascular repair in this high-risk group.This is a retrospective review of patients presenting acutely with complications of open aortic surgery. From January 2003 to March 2006, ten patients, all males with a mean age of 73 years presented through the Accident and Emergency department and were assessed with contrast enhanced CT. Five patients presented with secondary AEFs. Three patients with PAAs. Another patient presented with a secondary mycotic aneurysm of the thoracic aorta following open repair of abdominal aortic aneurysm and finally a patient with a femoral pseudoaneurysm. The mean time from the original procedure to presentation was 50 months. All patients were offered endovascular management after stabilisation as they were deemed as high-risk surgical patients.No intra-procedural complications were recorded. The in-hospital 30-day mortality was 1 (10%) patient due to multiple organ failure. One patient died six months later due to an unrelated event. The average in-hospital stay was 5.4 days; median follow-up period was 28 months. All patients were repeatedly admitted after discharge due to septic episodes for which they received IV antibiotics. Repeated cultures for all patients were only positive on four occasions.Endovascular stent-graft repair of AEF and PAAs is a viable alternative to open surgery. It is likely to be associated with less mortality and morbidity and in-hospital stay. It should be considered as an alternative in high-risk patients. Persistence of the infection remains a problem, however, in our experience; it can be well controlled through long-term antibiotics.
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