Local Transposition Research Articles

Modern reconstruction techniques for oral and pharyngeal defects after tumor resection

Several techniques have been developed to reconstruct oral and pharyngeal defects following surgery, in order to restore function and cosmesis. These are primary closure, skin grafts, local transposition of skin, mucosa and/or muscle, regional flaps and free vascularized flaps. Because of the 'bulky', pedicled nature and problems with the donor area of locoregional flaps, and consequently frequently unsatisfactory functional results, free vascularized flaps have gained popularity during the last decade. The authors review the current options available to give physicians, who are not experienced in the field of reconstruction in the head and neck, an impression of the range of techniques available for reconstruction of oral and pharyngeal defects following tumor resection. For reconstruction of oral cavity and pharyngeal defects, fasciocutaneous (e.g. radial forearm and anterolateral thigh flaps) and myocutaneous free flaps (e.g. rectus abdominis and latissimus dorsi) have proven to be very reliable. Free vascularized osteocutaneous flaps (e.g. fibula and iliac crest) permit reconstructive options for bony defects of the mandible or maxilla that can be adapted to a variety of defects. Depending on the site, size and involved tissues of the surgical defect and patient factors, a variety of reconstructive options are available. For both soft tissue and bony defects of the upper aerodigestive tract, microvascular free flaps provide good functional outcomes.

Postburn contracture treatment: A healthcare project in Bangladesh

Over the last 6 years, a health care program aimed at the surgical correction of postburn contractures has taken place in Faridpur, Bangladesh. People in this rural region are very poor and often cannot afford medical treatment. Often secondary flexion contractures of the face and chin as well as the upper and lower extremity impede daily functioning and have an enormous psycho-social impact. The application of basic plastic surgical principles such as local transposition of skin flaps as well as skin grafts restores function dramatically and results in stable skin cover. It is quite challenging – both for the surgeon and the anaesthesiologist – to perform these operations within a rather limited infrastructure. In Bangladesh, there is a monumental need for correction of postburn contractures for the social needs of the patient as well as for functional purposes. Future actions should be directed to the training of surgeons and the development of specialized hospitals to demonstrate social as well as political commitment to health care programs.

Two-stage reconstruction of the auricle in congenital microtia using autogenous costal cartilage

The current authors reconstructed the auricles of congenital microtia patients with a two-stage method using autogenous costal cartilage. In the first stage, lobule rotation, fabrication of the cartilage framework, and implantation of the framework were performed. In the second stage, elevation of the auricle using transplantation of the costal cartilage and two local transposition flaps, formation of the tragus, and deepening of the concha were performed. A total of 125 consecutive patients were treated, ranging from seven to 53 years old, from 1990 to 2003. Sixty-nine patients were males and 56 patients were females. Unilateral microtia was present in 114 patients (right 73, left 41), bilateral in 11 patients. Ninety-four cases were the classic sausage-shaped lobule type deformity; the remaining 42 cases presented concha-type deformity. The follow-up period was 6 months to 10 years. One hundred and eighteen cases presented acceptable ear contour after ear reconstruction. Unfavourable results were blunted convolution of the reconstructed ear because of thick fibrous tissue in six cases, mild absorption of carved cartilage by infection in two cases, deformation of the constructed helix occurred in four cases, less projection of the elevated ear in three cases, and hypertrophic scars in three cases. Our procedure produced acceptable contour of the reconstructed auricle with fewer complications than conventional procedures. In addition, careful meticulous manipulation is necessary to create natural contour of the ear and to reduce complications in all stages.

The vascular anatomy of the lumbrical muscles in the hand

The lumbrical muscles are located in the midpalm, dorsal to the palmar aponeurosis. The main function of these muscles is an indirect contribution to interphalangeal joint extension by decreasing the flexor effect of the flexor digitorum profundus muscle. Due to their minor biomechanical functions and suitable constructions, these muscles have been preferred in reconstructive surgery as local transposition flaps or pedicled flaps. Despite the surgical and clinical importance, vascular anatomical studies of these muscles are not well represented in the current literature. This study was performed in the Department of Anatomy of the Faculty of Medicine of the Ege University. Thirty-four cadaver hands, injected with red-coloured latex were used, and we aimed to describe the morphometry and vascular anatomy of the lumbrical muscles. We measured the length and width of the muscles, after removing their epimisium, and the diameter and length of the arteries to the muscles. The outcomes of our study determined that the length and width of the lumbrical muscles were reduced significantly from radial towards ulnar sides. The lumbrical muscles were supplied from both their palmar and dorsal surfaces by both superficial and deep palmar arches and/or their branches. We also described the level of entry of the dominant arteries for each lumbrical muscle and measured the size of the vessels and muscles to guide some surgical approaches. This anatomical study could guide for some surgical approaches and reduce the deficiency about the vascular anatomical patterns of the lumbrical muscles in the literature.

Optimizing Communications of Dynamic Data Redistribution on Symmetrical Matrices in Parallelizing Compilers

Dynamic data redistribution is used to enhance data locality and algorithm performance by reducing interprocessor communication in many parallel scientific applications on distributed memory multicomputers. Since the redistribution is performed at runtime, there is a performance tradeoff between the efficiency of the new data decomposition for a subsequent phase of an algorithm and the cost of redistributing data among processors. In this paper, we present a processor replacement scheme to minimize the cost of interprocessor data exchange during runtime. The main idea of the proposed technique is to develop a replacement function for reordering logical processors in the destination phase. Based on the replacement function, a realigned sequence of destination processors can be derived and is then used to perform data decomposition in the receiving phase. Together with local matrix and compressed CRS vectors transposition schemes, the interprocessor communication can be eliminated during runtime. A significant improvement of this approach is that the realignment of data can be performed without interprocessor communication for special cases. The second contribution of the present technique is that the complicated communication sets generation could be simplified by applying local matrix transposition. Consequently, the indexing cost could be reduced significantly. The proposed techniques can be applied in both dense and sparse applications. A generalized symmetric redistribution algorithm is also presented in this work. To analyze the efficiency of the proposed technique, the theoretical analysis proves that up to (p-1)/p data transmission cost can be saved. For general cases, the symmetric redistribution algorithm saves 1/p communication overheads compared with the traditional method. Experimental results also show that the proposed techniques provide superior performance in most data redistribution instances

Remarkable Site Specificity of Local Transposition Into the Hsp70 Promoter of Drosophila melanogaster

Heat-shock genes have numerous features that ought to predispose them to insertional mutagenesis via transposition. To elucidate the evolvability of heat-shock genes via transposition, we have exploited a local transposition technique and Drosophila melanogaster strains with EPgy2 insertions near the Hsp70 gene cluster at 87A7 to produce numerous novel EPgy2 insertions into these Hsp70 genes. More than 50% of 45 independent insertions were made into two adjacent nucleotides in the proximal promoter at positions -96 and -97, and no insertions were into a coding or 3'-flanking sequence. All inserted transposons were in inverse orientation to the starting transposon. The frequent insertion into nucleotides -96 and -97 is consistent with the DNase hypersensitivity, absence of nucleosomes, flanking GAGA-factor-binding sites, and nucleotide sequence of this region. These experimental insertions recapitulated many of the phenotypes of natural transposition into Hsp70: reduced mRNA expression, less Hsp70 protein, and decreased inducible thermotolerance. The results suggest that the distinctive features of heat-shock promoters, which underlie the massive and rapid expression of heat-shock genes upon heat shock, also are a source of evolutionary variation on which natural selection can act.

The treatment of chronic osteomyelitis: A 10 year audit

Despite modern surgical techniques and advanced antimicrobial therapy, osteomyelitis remains a difficult and challenging problem. A 10 year audit study from 1990 to 2000 was carried out to assess the outcome of treatment of chronic osteomyelitis. A total of 41 patients with chronic osteomyelitis (26 male, 15 female with an age range of 10-76 years, mean 45.3 years) underwent extirpation and reconstruction with muscle interposition. The duration of osteomyelitis ranged from 1 to 69 years (mean 16.6 years) and many patients had undergone multiple attempted procedures prior to definitive treatment. Thirty-seven patients underwent free microvascular muscle transfer and four patients underwent local transposition muscle flaps. Two of the 41 patients developed recurrent sepsis at 12 months (4.4% recurrence rate). These were treated successfully with elevation of the flap and curettage of the remaining infection and debris and re-insetting of the flap. Only one patient in the series required a below knee amputation and this was as a result of persistent intractable bone pain rather than recurrence of the osteomyelitis.

The Posterior Neuromuscular Compartment of the Deltoid

The aim of this study was to define a posterior neuromuscular compartment of the deltoid with adequate innervation and circulation for use as a local transposition flap as well as a functional flap to restore shoulder and elbow function. The nerve supply and blood supply to the posterior one third of the deltoid was studied in 20 cadaveric shoulders. A posterior neuromuscular compartment of the deltoid with adequate circulation and innervation was identified. It was feasible to transpose it for local coverage about the shoulder and to restore shoulder abduction and elbow extension. A posterior neuromuscular functional compartment of the deltoid has been identified.

Reconstruction of the Lower Eyelid by Third Eyelid Lateral Advancement and Local Transposition Cutaneous Flap After “En Bloc” Resection of Squamous Cell Carcinoma in 5 Cats

To describe a novel technique for blepharoplasty to cover a tissue defect involving >/=50% of the lower eyelid. Prospective clinical study. Five cats with lower eyelid squamous cell carcinoma (SCC). En bloc resection of SCC by removing >/=50% of the lower lid with either the medial or lateral canthus was performed without other adjunctive treatment for SCC. The lid defect was reconstructed with a transposition skin flap derived from the frontal (medial defect) or temporal (lateral defect) region. The third eyelid was advanced laterally without dissection from its insertion; its outer conjunctival layer was removed, and the skin flap was sutured with single interrupted sutures dorsally over the nictitating membrane, ventrally to the cutaneous edge of the surgical wound and medially or laterally (depending on the canthus removed) to the skin of the remaining lower lid. Satisfactory cosmetic and functional results were achieved and the Schirmer tear tests were normal. In 2 cats, the skin flap needed monthly hair trimming to avoid corneal lesions. After en bloc resection of SCC involving >/=50% of the lower eyelid, reconstruction can be achieved by relocation of the third eyelid and use of a cutaneous transposition flap sutured to the scarified external surface of the third eyelid. Eyelid apposition and lacrimal function were preserved. Blepharoplasty using a cutaneous transposition flap sutured to the scarified surface of a relocated third eyelid should be considered for reconstruction of lower eyelid defects with >/=50% tissue loss of the lid margin.

Insertion-Sequence-Mediated Mutations Isolated During Adaptation to Growth and Starvation in Lactococcus lactis

We studied the activity of three multicopy insertion sequence (IS) elements in 12 populations of Lactococcus lactis IL1403 that evolved in the laboratory for 1000 generations under various environmental conditions (growth or starvation and shaken or stationary). Using RFLP analysis of single-clone representatives of each population, nine IS-mediated mutations were detected across all environmental conditions and all involving IS981. When it was assumed that these mutations were neutral, their frequency was higher under shaken than under stationary conditions, possibly due to oxygen stress. We characterized seven of the nine mutations at the molecular level and studied their population dynamics where possible. Two were simple insertions into new positions and the other five were recombinational deletions (of <1->10 kb) among existing and new copies of IS981; in all but one case these mutations disrupted gene functions. The best candidate beneficial mutations were two deletions of which similar versions were detected in two populations each. One of these two parallel deletions, affecting a gene involved in bacteriophage resistance, showed intermediate rearrangements and may also have resulted from increased local transposition rates.

Promiscuous Target Interactions in the mariner Transposon Himar1

We have previously characterized the early intermediates of mariner transposition. Here we characterize the target interactions that occur later in the reaction. We find that, in contrast to the early transposition intermediates, the strand transfer complex is extremely stable and difficult to disassemble. Transposase is tightly bound to the transposon ends constraining rotation of the DNA at the single strand gaps in the target site flanking the element on either side. We also find that although the cleavage step requires Mg2+ or Mn2+ as cofactor, the strand transfer step is also supported by Ca2+, suggesting that the structure of the active site changes between cleavage and insertion. Finally, we show that, in contrast to the bacterial cut and paste transposons, mariner target interactions are promiscuous and can take place either before or after cleavage of the flanking DNA. This is similar to the behavior of the V(D)J system, which is believed to be derived from an ancestral eukaryotic transposon. We discuss the implications of promiscuous target interactions for promoting local transposition and whether this is an adaptation to facilitate the invasion of a genome following horizontal transfer to a new host species.

The use of fillet limb to reconstruct huge defect post trunk tumor excision

Post girdle excision (forequarter amputation and hemi‐pelvectomy) for bone or soft tissue tumours result in extensive defects exposing bone and major neurovascular structures. Large flaps are necessary to reconstruct the defect and protect the underlying structures. Total thigh flap was first described in 1956 by Georgiade et al. for the treatment of large trochanteric ulcers with osteomyelitis of femur. Free fillet flaps from the amputated limb provides a large amount of soft tissue coverage without additional donor site morbidity and hence it is ideal in major reconstruction for these trunk defect. We had five patients with major excision of girdle tumour with two forequarter amputation, three hemipelvectomy (two osteosarcoma, three soft tissue sarcoma). Four fillet limbs were used (two upper limbs, two lower limbs, one multiple local transposition flaps). The clinical course, morbidity and mortality were discussed in this paper.

Characterization of Sleeping Beauty transposition and its application to genetic screening in mice.

The use of mutant mice plays a pivotal role in determining the function of genes, and the recently reported germ line transposition of the Sleeping Beauty (SB) transposon would provide a novel system to facilitate this approach. In this study, we characterized SB transposition in the mouse germ line and assessed its potential for generating mutant mice. Transposition sites not only were clustered within 3 Mb near the donor site but also were widely distributed outside this cluster, indicating that the SB transposon can be utilized for both region-specific and genome-wide mutagenesis. The complexity of transposition sites in the germ line was high enough for large-scale generation of mutant mice. Based on these initial results, we conducted germ line mutagenesis by using a gene trap scheme, and the use of a green fluorescent protein reporter made it possible to select for mutant mice rapidly and noninvasively. Interestingly, mice with mutations in the same gene, each with a different insertion site, were obtained by local transposition events, demonstrating the feasibility of the SB transposon system for region-specific mutagenesis. Our results indicate that the SB transposon system has unique features that complement other mutagenesis approaches.

Transposon mutagenesis of the mouse germline.

Sleeping Beauty is a synthetic "cut-and-paste" transposon of the Tc1/mariner class. The Sleeping Beauty transposase (SB) was constructed on the basis of a consensus sequence obtained from an alignment of 12 remnant elements cloned from the genomes of eight different fish species. Transposition of Sleeping Beauty elements has been observed in cultured cells, hepatocytes of adult mice, one-cell mouse embryos, and the germline of mice. SB has potential as a random germline insertional mutagen useful for in vivo gene trapping in mice. Previous work in our lab has demonstrated transposition in the male germline of mice and transmission of novel inserted transposons in offspring. To determine sequence preferences and mutagenicity of SB-mediated transposition, we cloned and analyzed 44 gene-trap transposon insertion sites from a panel of 30 mice. The distribution and sequence content flanking these cloned insertion sites was compared to 44 mock insertion sites randomly selected from the genome. We find that germline SB transposon insertion sites are AT-rich and the sequence ANNTANNT is favored compared to other TA dinucleotides. Local transposition occurs with insertions closely linked to the donor site roughly one-third of the time. We find that approximately 27% of the transposon insertions are in transcription units. Finally, we characterize an embryonic lethal mutation caused by endogenous splicing disruption in mice carrying a particular intron-inserted gene-trap transposon.

Total lower lip reconstruction

Ten cases of total lower lip reconstruction are reviewed. The total lip defects resulted from tumor resection (n=6), trauma (n=3), and noma (n=1). There were concomitant chin and mandible defects in three and four patients. The planning and choice of operative methods depended on the quality of the surrounding tissue and the patient's age, sex, occupation, and general health. Local procedures and tissue transposition from the head and neck region were used in eight cases; distant flaps were necessary in two cases. All patients achieved satisfactory functional and esthetic results. The author's experience and evaluation of various surgical methods are presented with special regard to the combined use of local and distant tissue to achieve an optimal outcome.

An analysis using the hobo genetic system reveals that combinatorial signaling by the Dpp and Wg pathways regulates dpp expression in leading edge cells of the dorsal ectoderm in Drosophila melanogaster.

Our laboratory has contributed to the development of a genetic system based upon the hobo transposable element in Drosophila melanogaster. We recently reported that hobo, like the better-known P element, is capable of local transposition. In that study, we mobilized a hobo enhancer trap vector and generated two unique alleles of decapentaplegic (dpp), a transforming growth factor-beta family member with numerous roles during development. Here we report a detailed study of one of those alleles (dpp(F11)). To our knowledge, this is the first application of the hobo genetic system to understanding developmental processes. First, we demonstrate that lacZ expression from the dpp(F11) enhancer trap accurately reflects dpp mRNA accumulation in leading edge cells of the dorsal ectoderm. Then we show that combinatorial signaling by the Wingless (Wg) pathway, the Dpp pathway, and the transcriptional coactivator Nejire (CBP/p300) regulates dpp(F11) expression in these cells. Our analysis of dpp(F11) suggests a model for the integration of Wg and Dpp signals that may be applicable to other developmental systems. Our analysis also illustrates several new features of the hobo genetic system and highlights the value of hobo, as an alternative to P, in addressing developmental questions.

Timing and targeting of P-element local transposition in the male germline cells of Drosophila melanogaster.

The P element in Drosophila melanogaster preferentially transposes into nearby sites. The local insertions display a preferential orientation toward the starting element. We investigated the mechanism of the P-element local transposition by isolating and characterizing local insertions in the male germline. We designed a genetic screen employing a marker gene that is carried in the P element and is dose sensitive. This dose effect allows isolation of flies containing newly transposed P elements in the presence of the starting element. A rapid molecular screen with PCR was used to identify 45 local insertions located within an approximately 40-kb genomic region on both sides of the starting element. Our system permits the isolation of the cluster progeny derived from a single insertion event, but none was isolated. The data suggest that local transposition occurs in the meiotic cell cycle. Nearly all of the local insertions were located within the promoter regions of the genes that were active in the male germline cells, suggesting that local insertions target predominantly active promoters. Our analysis shows that local transposition of the P element is highly regulated, displaying a cell-type specificity and a target specificity.

Population dynamics of an Ac-like transposable element in self- and cross-pollinating arabidopsis.

Theoretical models predict that the mating system should be an important factor driving the dynamics of transposable elements in natural populations due to differences in selective pressure on both element and host. We used a PCR-based approach to examine the abundance and levels of insertion polymorphism of Ac-III, a recently identified Ac-like transposon family, in natural populations of the selfing plant Arabidopsis thaliana and its close outcrossing relative, Arabidopsis lyrata. Although several insertions appeared to be ancient and shared between species, there is strong evidence for recent activity of this element family in both species. Sequences of the regions flanking insertions indicate that all Ac-III transposons segregating in natural populations are in noncoding regions and provide no evidence for local transposition events. Transposon display analysis suggests the presence of slightly higher numbers of insertion sites per individual but fewer total polymorphic insertions in the self-pollinating A. thaliana than A. lyrata. Element insertions appear to be segregating at significantly lower frequencies in A. lyrata than A. thaliana, which is consistent with a reduction in transposition rate, reduction in effective population size, or reduced efficacy of natural selection against element insertions in selfing populations.

Prefabricated and Prelaminated Flaps for Head and Neck Reconstruction

Flap prefabrication and prelamination are evolving, new techniques that are useful in reconstructing complex defects of the head and neck. Flap prefabrication involves the introduction of a new blood supply by means of a vascular pedicle transfer into a volume of tissue. After a period of neovascularization, this volume of tissue may be transferred, based only on its implanted vascular pedicle. The transfer may be local transposition or by microsurgical transfer. Flap prelamination refers to a technique in which additional tissue is added to an existing flap (without manipulation of its axial blood supply) to make a multilayered flap that may be used for complex, three-dimensional multilayered reconstructions. This technique may be used locally or at a distance, requiring microvascular transfer. Examples of each are described in this article.

Dynamics of the hobo transposable element in transgenic lines of Drosophila melanogaster.

The impact of the hobo transposable element in global reorganization of the Drosophila melanogaster genome has been investigated in transgenic lines generated by injection of hobo elements into the Hikone strain, which lacked them. In the present extensive survey, the chromosomal distribution of hobo insertion sites in the line 28 was found to be homogeneous and similar for all chromosomal arms, except 3L, when compared with other transgenic lines. However, some original features were observed in this line at the genetic and chromosomal levels. Several hotspots of insertion sites were observed on the X, second and third chromosomes. Five sites with a high frequency of hobo insertions were present on the 3L arm in most individuals tested, suggesting the action of selection for hobo element in some sites. The presence of doublets or triplet was also observed, implying that hobo inserts can show local jumps or insertions in preferred regions. This local transposition occurred independently in 11 specific genomic regions in many individuals and generations. The dynamics of this phenomenon were analysed across generations. These results support the use of the hobo system as an important tool in fundamental and applied Drosophila genetics.