An individually-controlled multi-tined expandable electrode using active-cannula-based shape morphing for on-demand conformal radiofrequency ablation lesions

Being minimally invasive and highly effective, radiofrequency ablation (RFA) is widely used for small size malignant tumors treatment. However, in clinical practice, a large number of tumors are found in irregular shape, while the current RFA devices are hard to control their morphologic appearance of RFA lesions on demand, which usually ends up excessively ablating the tissues and often brings excessively irreversible damage to the organs’ functions. Here, we introduce active cannulas for each of individually-controlled sub-electrodes to achieve an on-demand shape morphing and thus conformal RFA lesion. The shape as well as the length of inserted sub-electrode can be precisely controlled by tuning the expanded length of the active stylet and relative position of the active cannula. Furthermore, owing to independent movement and energy control of each sub-electrodes, our electrode is shown to be not only efficient enough to accomplish accurate trajectory to target tissue in a single insertion, but also adaptive enough to ablate target tissues with diverse morphologic appearances and locations. Potentially, our RFA electrode is a better choice in the future clinical practice for minimally invasive treatments of malignant tumors of which preferred treatment is conformal ablation. Corresponding author(s) Email: [email protected]

A DREaMR system to simplify combining mutations with rescue transgenes in Aedes aegypti

In most experimental animals, it is challenging to combine mutations and rescue transgenes and to use bipartite systems to assess gene expression. To circumvent the difficulties in combining multiple genetic elements, we developed the DREaMR ( Drug-on, REporter, Mutant, Rescue) system. Using Drosophila white as the initial model, we demonstrated that introduction of a single insertion by CRISPR/Cas9 created a null mutation, a tagged rescue construct, which could be induced with doxycycline, and which allowed assessment of protein expression. To create a DREaMR in an organism in which combining multiple genetic elements is more problematic than in Drosophila, we tested the mosquito, Aedes aegypti—the insect vector for dengue, yellow fever, Zika and other viral diseases. We generated a DREaMR allele in the kh gene, which permitted us to induce expression of the rescue construct, and detect expression of Kh. Thus, this system avoids the need to perform genetic crosses to introduce an inducible rescue transgene in a mutant background, or to combine driver and reporter lines to examine expression of the targeted protein. We propose that DREaMR provides a system that can be applied to additional mosquito vectors as well as other organisms in which CRISPR/Cas9 is effective.

Whether sutures reduce the graft laceration caused by interference screw in anterior cruciate ligament reconstruction? A biomechanical study in vitro

Background Interference screw is commonly used for graft fixation in anterior cruciate ligament (ACL) reconstruction. However, previous studies had reported that the insertion of interference screws significantly caused graft laceration. The purposes of this study were to (1) quantitatively evaluate the graft laceration from one single insertion of PEEK interference screws; and (2) determine whether different types of sutures reduced the graft laceration after one single insertion of interference screws in ACL reconstruction. Methods The in-vitro ACL reconstruction model was created using porcine tibias and bovine extensor digitorum tendons of bovine hind limbs. The ends of grafts were sutured using three different sutures, including the bioabsorbable, Ethibond and ultra-high molecular weight polyethylene (UHMWPE) sutures. Poly-ether-ether-ketone (PEEK) interference screws were used for tibial fixation. This study was divided into five groups (n = 10 in each group): the non-fixed group, the non-sutured group, the absorbable suture group, the Ethibond suture group and the UHMWPE suture group. Biomechanical tests were performed using the mode of pull-to-failure loading tests at 10 mm/min. Tensile stiffness (newtons per millimeter), energy absorbed to failure (in joules) and ultimate load (newtons) were recorded for analysis. Results All prepared tendons and bone specimens showed similar characteristics (length, weight, and pre-tension of the tendons, tibial bone mineral density) among all groups (P > 0.05). The biomechanical tests demonstrated that PEEK interference screws significantly caused the graft laceration (P < 0.05). However, all sutures (the bioabsorbable, Ethibond and UHMWPE sutures) did not reduce the graft laceration in ACL reconstruction (P > 0.05). Conclusions Our biomechanical study suggested that the ultimate failure load of grafts was reduced of approximately 25 % after one single insertion of a PEEK interference screw in ACL reconstruction. Suturing the ends of the grafts using different sutures (absorbable, Ethibond and UHMWPE sutures) did not decrease the graft laceration caused by interference screws.

Simultaneous Gene Expression and Multi-Gene Silencing in Zea Mays Using Maize Dwarf Mosaic Virus

Background: Maize dwarf mosaic virus (MDMV), a member of the genus Potyvirus, infects maize and is non-persistently transmitted by aphids. Several plant viruses have been developed as tools for gene expression and gene silencing in plants. The capacity of MDMV for both gene expression and gene silencing were examined.Results: Infectious clones of an Ohio isolate of MDMV, MDMV-OH5, were obtained, and engineered for gene expression only, and for simultaneous marker gene expression and virus-induced gene silencing (VIGS) of three endogenous maize target genes. Single gene expression in single insertion constructs and simultaneous expression of green fluorescent protein (GFP) and silencing of three maize genes in a double insertion construct was demonstrated. Constructs with GFP inserted in the N-terminus of HCPro were more stable than those with insertion at the N-terminus of CP in our study. Unexpectedly, the construct with two insertion sites also retained insertions at a higher rate than single-insertion constructs. Engineered MDMV expression and VIGS constructs were transmissible by aphids (Rhopalosiphum padi). Conclusions: These results demonstrate that MDMV-based vector can be used as a tool for simultaneous gene expression and multi-gene silencing in maize.

piRNA Clusters Need a Minimum Size to Control Transposable Element Invasions

piRNA clusters are thought to repress transposable element (TE) activity in mammals and invertebrates. Here, we show that a simple population genetics model reveals a constraint on the size of piRNA clusters: The total size of the piRNA clusters of an organism must exceed 0.2% of a genome to repress TE invasions. Moreover, larger piRNA clusters accounting for up to 3% of the genome may be necessary when populations are small, transposition rates are high, and TE insertions are recessive. If piRNA clusters are too small, the load of deleterious TE insertions that accumulate during a TE invasion may drive populations extinct before an effective piRNA-based defense against the TE can be established. Our findings are solely based on three well-supported assumptions: 1) TEs multiply within genomes, 2) TEs are mostly deleterious, and 3) piRNA clusters act as transposon traps, where a single insertion in a cluster silences all TE copies in trans. Interestingly, the piRNA clusters of some species meet our observed minimum size requirements, whereas the clusters of other species do not. Species with small piRNA clusters, such as humans and mice, may experience severe fitness reductions during invasions of novel TEs, which is possibly even threatening the persistence of some populations. This work also raises the important question of how piRNA clusters evolve. We propose that the size of piRNA clusters may be at an equilibrium between evolutionary forces that act to expand and contract piRNA clusters.

piRNA clusters need a minimum size to control transposable element invasions

AbstractpiRNA clusters are thought to repress transposable element activity in mammals and invertebrates. Here we show that a simple population genetics model reveals a constraint on the size of piRNA clusters: the total size of the piRNA clusters of an organism ought to exceed 0.2% of a genome. Larger piRNA clusters accounting for up to 3% of the genome may be necessary when populations are small, transposition rates are high and TE insertions recessive. If piRNA clusters are too small the load of deleterious TE insertions accumulating during a TE invasion may drive populations extinct before an effective piRNA based defence against the TE can be established. Our finding is solely based on three well supported assumptions: i) TEs multiply withing genomes, ii) TEs are mostly deleterious and iii) piRNA clusters act as transposons traps, where a single insertion in a cluster silences all TE copies in trans. Interestingly, piRNA clusters of some species meet our minimum size requirements while clusters of other species don’t. Species with small piRNA clusters, such as humans and mice, may experience severe fitness reductions during invasions of novel TEs, possibly even threatening the persistence of some populations. This work also raises the important question of how piRNA clusters evolve. We propose that the size of piRNA clusters may be at an equilibrium between evolutionary forces that act to expand and contract piRNA clusters.