Modification of conservative treatment of heterotopic cervical pregnancy by Foley catheter balloon fixation with cerclage sutures at the level of the external cervical os: a case report

<p>Abstract</p> <p>Introduction</p> <p>Conservative treatment of a heterotopic cervical pregnancy was performed with a modification of the fixation of a Foley catheter at the level of the external cervical os, followed by the ligature of the descending cervical branches of the uterine arteries and systemic methotrexate application.</p> <p>Case presentation</p> <p>A 34-year-old Caucasian woman was diagnosed with double gestation after 6 weeks of <it>in vitro </it>fertilization treatment. A gynecological examination and color Doppler ultrasound scan revealed intra-uterine and cervical gestational sacs both containing live fetuses. A Foley catheter balloon was inserted into the cervical canal, inflated and fixed by a cerclage suture at the level of the external cervical os, followed by ligation of the descending cervical branches of the uterine arteries. Systemic methotrexate was applied. Three days after removal of the Foley catheter, an evacuation of the intra-uterine gestational sac was performed. Hemorrhage from the implantation site was controlled immediately and a pregnancy termination was successfully performed. The procedure was uneventful and our patient was discharged with a preserved uterus.</p> <p>Conclusions</p> <p>Conservative treatment of cervical pregnancy using a Foley catheter balloon is more efficacious if the Foley catheter balloon is attached in the correct position with a cerclage suture at the level of the external os, followed by ligation of the descending cervical branches of the uterine arteries, thereby exerting maximal pressure on the bleeding vessels.</p

Zinc-finger recombinase activities in vitro

Zinc-finger recombinases (ZFRs) are chimaeric proteins comprising a serine recombinase catalytic domain linked to a zinc-finger DNA binding domain. ZFRs can be tailored to promote site-specific recombination at diverse ‘Z-sites’, which each comprise a central core sequence flanked by zinc-finger domain-binding motifs. Here, we show that purified ZFRs catalyse efficient high-specificity reciprocal recombination between pairs of Z-sites in vitro. No off-site activity was detected. Under different reaction conditions, ZFRs can catalyse Z-site-specific double-strand DNA cleavage. ZFR recombination activity in Escherichia coli and in vitro is highly dependent on the length of the Z-site core sequence. We show that this length effect is manifested at reaction steps prior to formation of recombinants (binding, synapsis and DNA cleavage). The design of the ZFR protein itself is also a crucial variable affecting activity. A ZFR with a very short (2 amino acids) peptide linkage between the catalytic and zinc-finger domains has high activity in vitro, whereas a ZFR with a very long linker was less recombination-proficient and less sensitive to variations in Z-site length. We discuss the causes of these phenomena, and their implications for practical applications of ZFRs

Purification and in vitro characterization of zinc finger recombinases

Zinc finger recombinases (ZFRs) are designer site-specific recombinases that have been adapted for a variety of genome editing purposes. Due to their modular nature, ZFRs can be customized for targeted sequence recognition and recombination. There has been substantial research on the in vivo properties and applications of ZFRs; however, in order to fully understand and customize them, it will be necessary to study their properties in vitro. Experiments in vitro can allow us to optimize catalytic activities, improve target specificity, measure and minimize off-target activity, and characterize key steps in the recombination pathway that might be modified to improve performance. Here, we present a straightforward set of protocols for the expression and purification of ZFRs, an assay system for catalytic proficiency in vitro and bandshift assays for detection of sequence-specific DNA interactions