Some transcription factors bind DNA motifs containing direct or inverted sequence repeats. Preference for each of these DNA topologies is dictated by structural constraints. Most prokaryotic ...regulators form symmetric oligomers, which require operators with a dyad structure. Binding to direct repeats requires breaking the internal symmetry, a property restricted to a few regulators, most of them from the AraC family. The KorA family of transcriptional repressors, involved in plasmid propagation and stability, includes members that form symmetric dimers and recognize inverted repeats. Our structural analyses show that ArdK, a member of this family, can form a symmetric dimer similar to that observed for KorA, yet it binds direct sequence repeats as a non-symmetric dimer. This is possible by the 180° rotation of one of the helix-turn-helix domains. We then probed and confirmed that ArdK shows affinity for an inverted repeat, which, surprisingly, is also recognized by a non-symmetrical dimer. Our results indicate that structural flexibility at different positions in the dimerization interface constrains transcription factors to bind DNA sequences with one of these two alternative DNA topologies.
Horizontal gene transfer (HGT) is a major force driving bacterial evolution. Because of their ability to cross inter-species barriers, bacterial plasmids are essential agents for HGT. This ability, ...however, poses specific requisites on plasmid physiology, in particular the need to overcome a multilevel selection process with opposing demands. We analyzed the transcriptional network of plasmid R388, one of the most promiscuous plasmids in Proteobacteria. Transcriptional analysis by fluorescence expression profiling and quantitative PCR revealed a regulatory network controlled by six transcriptional repressors. The regulatory network relied on strong promoters, which were tightly repressed in negative feedback loops. Computational simulations and theoretical analysis indicated that this architecture would show a transcriptional burst after plasmid conjugation, linking the magnitude of the feedback gain with the intensity of the transcriptional burst. Experimental analysis showed that transcriptional overshooting occurred when the plasmid invaded a new population of susceptible cells. We propose that transcriptional overshooting allows genome rebooting after horizontal gene transfer, and might have an adaptive role in overcoming the opposing demands of multilevel selection.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Plasmids, when transferred by conjugation in natural environments, must overpass restriction-modification systems of the recipient cell. We demonstrate that protein ArdC, encoded by broad host range ...plasmid R388, was required for conjugation from Escherichia coli to Pseudomonas putida. Expression of ardC was required in the recipient cells, but not in the donor cells. Besides, ardC was not required for conjugation if the hsdRMS system was deleted in P. putida recipient cells. ardC was also required if the hsdRMS system was present in E. coli recipient cells. Thus, ArdC has antirestriction activity against the HsdRMS system and consequently broadens R388 plasmid host range. The crystal structure of ArdC was solved both in the absence and presence of Mn2+. ArdC is composed of a non-specific ssDNA binding N-terminal domain and a C-terminal metalloprotease domain, although the metalloprotease activity was not needed for the antirestriction function. We also observed by RNA-seq that ArdC-dependent conjugation triggered an SOS response in the P. putida recipient cells. Our findings give new insights, and open new questions, into the antirestriction strategies developed by plasmids to counteract bacterial restriction strategies and settle into new hosts.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Gray scale ultrasound has an important diagnostic role in native kidney disease. Low cost, absence of ionizing radiation and nephrotoxicity, short performance time, and repeatability even at the ...bedside, are the major advantages of this technique. The introduction of contrast enhancement ultrasound (CEUS) in daily clinical practice has significantly reduced the use of contrast enhancement computed tomography (CECT) and contrast enhancement magnetic resonance (CEMR), especially in patients with renal disease. Although there are many situations in which CECT and CEMRI are primarily indicated, their use may be limited by the administration of the contrast medium, which may involve a risk of renal function impairment, especially in the elderly, and in patients with acute kidney injury (AKI) and moderate to severe chronic kidney disease (CKD). In these cases, CEUS can be a valid diagnostic choice. To date, numerous publications have highlighted the role of CEUS in the study of parenchymal micro-vascularization and renal pathology by full integration with second level imaging methods (CECT and CEMRI) both in patients with normal renal function and with diseased kidneys. The aim of this review is to offer an updated overview of the limitations and potential applications of CEUS in native kidney disease.
High-flow priapism is a rare condition in children, usually due to a perineal trauma.
We present a case of traumatic highflow priapism investigated by Doppler ultrasound and managed by angiography ...and selective embolization of a branch of the internal pudendal artery.
A 13-year-old gymnast underwent perineal trauma during training and developed a high-flow priapism. The first ultrasound (immediately after the trauma) showed the presence of an inhomogeneous area of 3 x 2 cm associated with an anechoic vascularized area (pseudoaneurysm) in the right corpus cavernosum. On the left side there was a similar finding, but of smaller size. After 3 weeks the pseudoaneurysm on the left was completely obliterated while the right one was still present. Angiography and superselective catheterization of a branch of the left pudendal artery and its embolization with microspheres and with metal microcoils were performed. After the procedure, ultrasound showed that the right pseudoaneurysm was completely obliterated and there were no more branches reaching it. The cavernous arteries were both pervious.
Selective arterial embolization is a safe treatment that can also be used in pediatric patients.
Background:
Ureteropelvic junction obstruction (UPJO) is one of the most frequent causes of congenital hydronephrosis. It is essential to distinguish UPJO which needs surgical treatment. fMRU ...combines high quality morphological details of the kidney and excretory pathways with functional data.
Objective
This study aims to introduce a new radiological score based on fMRU findings to be able to differentiate surgical from non-surgical kidneys.
Materials and Methods
We retrospectively selected patients with hydronephrosis due to UPJO who underwent fMRU (January 2009–June 2018). A multidisciplinary team identified a list of fMRU morpho-functional predictive variables to be included in the analysis. To evaluate the role of different independent variables in predicting the outcome, a multivariable logistic regression model has been performed; the outcome variable was the surgical intervention. For each predictive variable, Odds Ratio and 95% Confidence Intervals were calculated. The likelihood ratio test was used to assess the significance of the variables. Using the regression model, we assigned a numerical value to each predictive variable, rounding up the beta-coefficients. The cut-off value of the total score was obtained from the ROC curve analysis.
Results
A total of 192 patients were enrolled, corresponding to 200 pathological kidneys. All of them underwent fMRU; 135 were surgically treated, while 65 underwent ultrasound or MRU follow-up. Predictive variables significantly associated with surgery resulted to be the urographic phase, the presence of abnormal vessels, and a baseline anterior-posterior pelvic diameter >23 mm. Beta coefficients of the logistic regression model were then converted in scores. The ROC curve of the score showed high sensitivity (84.3%) and specificity (81.3%) with a cut-off > 2.5.
Conclusions
We propose a new fMRU score able to identify surgical vs. non-surgical kidneys with UPJO.
Polymers can serve as an effective matrix to stabilize gold nanoparticles. These materials offer a continuous light-activated supply of subnanoclusters, which are composed of a few atoms. We report ...an efficient approach to enhance the catalytic activity of gold subnanoclusters by in situ feeding of these species through the generation of hot carriers via 5d–6s6p interband transitions on PEG-stabilized Au nanoparticles.
Polymers can serve as an effective matrix to stabilize gold nanoparticles. These materials offer a continuous light-activated supply of subnanoclusters, which are composed of a few atoms. We report ...an efficient approach to enhance the catalytic activity of gold subnanoclusters by in situ feeding of these species through the generation of hot carriers via 5d–6s6p interband transitions on PEG-stabilized Au nanoparticles.
Abstract Objective To determine whether small, incidentally detected testicular lesions can be safely followed up, by assessing growth rate and volume threshold for benign vs. malignant lesions. ...Methods This retrospective observational study includes a consecutive series of 130 testicular incidentalomas < 1 cm and with negative tumour markers identified from October 2001 to November 2022, which were initially followed up with ultrasound. A total of 39 cases proceeded to surgery during the study period, either due to lesion growth ( n = 28) or patient preference/recommendation by the referring urologist ( n = 11). For the lesions that were growing, specific growth rate (SGR) and doubling time (DT) were calculated assuming an exponential growth pattern. In addition, the velocity of increase of the average diameter (∆D av ) and of the maximum diameter (∆D max ) were calculated. Results Of the 130 nodules that were initially followed up, six disappeared, eight were reduced in size, eighty-eight were stable, and twenty-eight increased in size. For operated nodules all 18 malignant tumours, 8/9 benign tumours, and 2/12 surgically proved non-neoplastic lesions were growing. The best cut-off values of the growth indicators to differentiate between malignant and non-malignant histology were 3.47 × 10 −3 %volume/day, ≤ 179 days, > 10 × 10 −3 mm/day, and > 5 × 10 −3 mm/day for SGR, DT, ∆D max , ∆D av , respectively. Conclusions Malignant and non-malignant small incidentalomas can be effectively differentiated based on growing parameters, even though overlap exists. An increase of the maximum diameter of about 1 mm and 2 mm in three months and in six months, respectively, suggests malignancy. Clinical relevance statement Growing parameters allow an educated assessment of benign and malignant small testicular incidentalomas. Non-aggressive management is justified and safe when follow-up includes self-examination and tumour marker assessment to reduce the risk of interval tumour growth. Key Points Small, non-palpable and asymptomatic testicular nodules < 1 cm are unexpectedly discovered during scrotal ultrasound . Growth indicators estimate the potential malignancy, even though overlap with non-malignant lesions exists . Non-growing incidentalomas can be safely followed up .
Ultrasonography (US) is highly dependent on operators’ skills. It is not only a matter of correct scan techniques; there are anatomical structures and variants, as well as artifacts, which can ...produce images difficult to interpret and which, if not properly understood, can be causes of errors.
This paper will review relatively common US pitfalls and artifacts that can be encountered in trauma patients and will offer tips to recognize and avoid them.
Normal anatomical structures and anatomical variants can mimic fluid collections or perisplenic lesions. Examination along multiple scan planes, real-time observation of movements or repetition of the study after the patient has drunk some fluid or after placing a finger on her/his body wall can help proper identification. The term artifact in US imaging refers to display phenomena not properly representing the imaged structures. This can result in images suggesting fracture lines within organs or at their borders, lung consolidations, or pleural effusions, and abdominal fluid collections. Their knowledge is the first step to recognize them; then, use of multiple scan planes or repetition of the study after voiding or changes of equipment setting can make them disappear or clarify their nature.
We present possible anatomic pitfalls and artifacts that may affect correct interpretation of US images in patients with abdominal trauma and suggest how to avoid or to clarify them during the examination. Knowing their existence, their appearances, and the reasons why they are produced is important for proper use of this diagnostic technique.
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