Diversity and strength of internal outward-oriented promoters in group IIC-attC introns

Integrons are genetic elements that incorporate mobile gene cassettes by site-specific recombination and express them as an operon from a promoter (Pc) located upstream of the cassette insertion site. Most gene cassettes found in integrons contain only one gene followed by an attC recombination site. We have recently shown that a specific lineage of group IIC introns, named group IIC-attC introns, inserts into the bottom strand sequence of attC sites. Here, we show that S.ma.I2, a group IIC-attC intron inserted in an integron cassette array of Serratia marcescens, impedes transcription from Pc while allowing expression of the following antibiotic resistance cassette using an internal outward-oriented promoter (Pout). Bioinformatic analyses indicate that one or two putative Pout, which have sequence similarities with the Escherichia coli consensus promoters, are conserved in most group IIC-attC intron sequences. We show that Pout with different versions of the −35 and −10 sequences are functionally active in expressing a promoterless chloramphenicol acetyltransferase (cat) reporter gene in E. coli. Pout in group IIC-attC introns may therefore play a role in the expression of one or more gene cassettes whose transcription from Pc would otherwise be impeded by insertion of the intron

Functional characterization of Tn1331 gene cassettes

Objectives: The transposon Tn1331 possesses a region including three antibiotic resistance genes with the structure aac(60)-Ib-attC-aadA1-attI1*-blaOXA-9-attC, which potentially includes four gene cas-settes. Experimental data on the mobility of fusion cassettes as well as those on mobility of cassettes in a genetic environment such as Tn1331, which lacks an integrase gene, are limited. Therefore, experi-ments using pJHCMW1, a plasmid harbouring this transposon, in the presence of IntI1 supplied in trans were carried out to define which cassettes are mobile in vivo. Methods: In vivo excision of resistance genes was investigated in Escherichia coli cells harbouring pJHCMW1 and in a recombinant clone that included the intI1 gene under the control of the Ptac pro-moter. Plasmid DNA was purified and subjected to PCR analysis, and DNA sequencing of PCR products was performed to determine whether excision had occurred. Results and conclusions: In vivo recombination experiments showed that the fused aadA1-attI1*-blaOXA-9-attC gene cassette was excised in the presence of IntI1. The excision of a DNA fragment including aadA1-attI1 * was also detected but at a lower frequency. The analysis of the latter recombina-tion reaction showed that, although attI1 * includes only a small fraction of the complete attI1 sequence, it is still used as a substrate by IntI1, albeit in a very inefficient manner

The potassium regulator patiromer affects serum and stool electrolytes in patients receiving hemodialysis.

© 2020 International Society of Nephrology Hyperkalemia is a common and an important cause of death in maintenance hemodialysis patients. Here we investigated the effect of patiromer, a synthetic cation exchanger, to regulate potassium homeostasis. Serum and stool electrolytes were measured in 27 anuric patients with hyperkalemia receiving hemodialysis (mainly 2 mEq/L dialysate) during consecutive two weeks of no-treatment, 12 weeks of treatment with patiromer (16.8g once daily), and six weeks of no treatment. The serum potassium decreased from a mean of 5.7 mEq/L pre-treatment to 5.1 mEq/L during treatment and rebounded to 5.4 mEq/L post-treatment. During the treatment phase, serum calcium significantly increased (from 8.9 to 9.1 mg/dL) and serum magnesium significantly decreased (from 2.6 to 2.4 mg/dL) compared to pre-treatment levels. For each one mEg/L increase in serum magnesium, serum potassium increased by 1.07 mEq/L. Stool potassium significantly increased during treatment phase from pre-treatment levels (4132 to 5923 μg/g) and significantly decreased post-treatment to 4246 μg/g. For each one μg/g increase in stool potassium, serum potassium significantly declined by 0.05 mEq/L. Stool calcium was significantly higher during the treatment phase (13017 μg/g) compared to pre-treatment (7874 μg/g) and post-treatment (7635 μg/g) phases. We estimated that 16.8 g of patiromer will increase fecal potassium by 1880 μg/g and reduce serum potassium by 0.5 mEq/L. Thus, there is a complex interaction between stool and blood potassium, calcium and magnesium during patiromer treatment. Long term consequence of patiromer-induced changes in serum calcium and magnesium remains to be studied

Risk for chronic kidney disease in the general population: Italian reports for World Kidney Days 2007-2009

The prevalence of chronic kidney disease (CKD) has rapidlyincreased in recent decades in many countries, leading toconsistent economic implications. Considering the fact thatpatients surviving to CKD often develop end-stage renal disease,the number of patients requiring replacement therapyreached 169/million population (pmp) in Italy in 2004 and342 pmp in the Unites States. Furthermore, CKD weighs onpatients survival with a considerably increased cardiovascular(CV) morbidity and mortality