Nuclear gene targeting in Chlamydomonas using engineered zinc-finger nucleases

The unicellular green alga Chlamydomonas reinhardtii is a versatile model for fundamental and biotechnological research. A wide range of tools for genetic manipulation have been developed for this alga, but specific modification of nuclear genes is still not routinely possible. Here, we present a nuclear gene targeting strategy for Chlamydomonas that is based on the application of zinc-finger nucleases (ZFNs). Our approach includes (i) design of gene-specific ZFNs using available online tools, (ii) evaluation of the designed ZFNs in a Chlamydomonas in situ model system, (iii) optimization of ZFN activity by modification of the nuclease domain, and (iv) application of the most suitable enzymes for mutagenesis of an endogenous gene. Initially, we designed a set of ZFNs to target the COP3 gene that encodes the light-activated ion channel channelrhodopsin-1. To evaluate the designed ZFNs, we constructed a model strain by inserting a non-functional aminoglycoside 3'-phosphotransferase VIII (aphVIII) selection marker interspaced with a short COP3 target sequence into the nuclear genome. Upon co-transformation of this recipient strain with the engineered ZFNs and an aphVIII DNA template, we were able to restore marker activity and select paromomycin-resistant (Pm-R) clones with expressing nucleases. Of these Pm-R clones, 1% also contained a modified COP3 locus. In cases where cells were co-transformed with a modified COP3 template, the COP3 locus was specifically modified by homologous recombination between COP3 and the supplied template DNA. We anticipate that this ZFN technology will be useful for studying the functions of individual genes in Chlamydomonas.

Intentional left subclavian artery coverage without revascularization during TEVAR

At present, endovascular therapy is a well-established treatment for different types of thoracic aortic pathologies. There is growing evidence, that thoracic endovascular aortic repair (TEVAR) has advantages over open repair with regard to perioperative morbidity and mortality in the treatment of thoracic aortic aneurysms. However, in up to 50% of TEVAR procedures the proximal end of the stent-graft will (partly) cover the origin of the left subclavian artery (LSA) in order to achieve a save sealing zone. Intracranial stroke and paraplegia are feared complications and might be associated with LSA exclusion from the circulation. Unfortunately, no reliable technique is available to assess the individual risk of stroke and paraplegia in case of LSA coverage, so that the indication for LSA revascularization continues to be matter of assuming and guessing. The quality of available evidence on necessity or superfluity to revascularize the LSA is very low and studies report, to some extent, controversial outcome after intentional LSA coverage. In the light of the devastating consequences for patients in case of neurological complications due to LSA coverage the question of prophylactic LSA revascularization remains a significant problem which is elucidated and discussed in this manuscript.

Thoracoabdominal aneurysms and changes in adjacent vertebral bodies

AIM

The aim of this study was to assess if chronic intermittent pressure of a thoracoabdominal aortic aneurysm (TAAA) induces structural changes in vertebral bodies and if eroded vertebral bones can still be found after the extermination of syphilis.

METHODS

A retrospective analysis of computed tomography (CT) scans of patients with TAAA was performed. In the anatomical regions were the TAAA was in close contact with the vertebral bodies, the vertebral body alteration was distinguished into 4 categories. Category 0: no changes; 1: discrete changes, minimal asymmetry; 2: obvious asymmetry of the vertebral body with sustained cortical layer; 3: severe destruction of the vertebral body with loss of the cortical layer.

RESULTS

Eighty-six CT scans of patients (mean age 63; range 25-82 years) with TAAA pathology were examined (24 female, 62 male). The mean aneurysm diameter was 6.5 cm (4.3-14 cm). The results for scoring were: category 0: 33 patients; category 1: 46 patients; category 2: 5 patients and category 3: 2 patients. One of the category 3 patients suffered from acute spinal cord compression with complete paraplegia. In total, 62% of patients showed some degree of changes at vertebral bodies adjacent to the TAAA.

CONCLUSION

Intermittent pressure by either dissecting or non-dissecting TAAAs may induce structural changes in the vertebral bodies of the spine. Severe destruction of the bone is a rare, but existing complication.

[Aortic aneurysm 2012: open, hybrid or total endovascular repair?]

During the past two decades, minimally invasive endovascular procedures have changed therapeutic strategies. Such techniques have now become the method of choice for practically all vascular and aortic pathologies. This development is especially apparent in the treatment of aortic aneurysms. The purpose of this report is to provide a critical review about the current standard of care of abdominal and thoracic aorta based on an electronic Medline literature search. For elective infrarenal aneurysms, endovascular aneurysm repair (EVAR) has become a widely accepted alternative to open repair in cases with appropriate morphology. Currently, fenestrated (FEVAR) or branched endografts offer promising short- and mid-term results in juxtarenal aneurysms, however, these techniques are complex, technically challenging, and expensive. The alternative chimney or sandwich graft technique are becoming more common because they are feasible using standard endografts. Thoracic endovascular aortic repair (TEVAR) is already the gold standard for some descending pathologies. Complex thoracoabdominal aneurysms still require open surgery in centres of excellence, whereby, total endovascular repair or hybrid procedures have proved to be feasible in such specialist centres for selected patients.

Phototropin influence on eyespot development and regulation of phototactic behavior in Chlamydomonas reinhardtii

The eyespot of Chlamydomonas reinhardtii is a light-sensitive organelle important for phototactic orientation of the alga. Here, we found that eyespot size is strain specific and downregulated in light. In a strain in which the blue light photoreceptor phototropin was deleted by homologous recombination, the light regulation of the eyespot size was affected. We restored this dysfunction in different phototropin complementation experiments. Complementation with the phototropin kinase fragment reduced the eyespot size, independent of light. Interestingly, overexpression of the N-terminal light, oxygen or voltage sensing domains (LOV1+LOV2) alone also affected eyespot size and phototaxis, suggesting that aside from activation of the kinase domain, they fulfill an independent signaling function in the cell. Moreover, phototropin is involved in adjusting the level of channelrhodopsin-1, the dominant primary receptor for phototaxis within the eyespot. Both the level of channelrhodopsin-1 at the onset of illumination and its steady state level during the light period are downregulated by phototropin, whereas the level of channelrhodopsin-2 is not significantly altered. Furthermore, a light intensity-dependent formation of a C-terminal truncated phototropin form was observed. We propose that phototropin is a light regulator of phototaxis that desensitizes the eyespot when blue light intensities increase.

Primary and secondary amputation in critical limb ischemia patients: different aspects

The TASC II working group reports on primary amputation incidence rates vary between 12 and 50 per 100,000 per year. The primary amputation rate does not only depend on co-morbidities like diabetes and PAD, but also on local factors like the regional availability of vascular surgeons and interventional radiologists and their case load. Further-more, several studies could show that increasing revascularisation rates have drastically reduced amputation rates in the US, with a 50% decrease in amputation rates during a 10 year study period and a corresponding increase in surgical and endovascular revascularisation rates. An analysis of national and state US databases confirmed a drop in major amputations and open surgical revascularisations, in favour of an increase in endovascular interventions. The same study observed an increase in minor amputations during the same period. However, it remains unclear whether this trend is a consequence of the increased usage of endovascular procedures in high-risk patients who are unfit for open surgery or of earlier endovascular intervention in less critical lesions. This review gives an overview of the incidence, indication, amputation-level finding and outcome of major amputations performed in critical limb ischemia (CLI) patients.

Reliability of constant-load treadmill testing in patients with intermittent claudication

AIM

Constant-load treadmill testing is frequently used to estimate walking ability of patients with peripheral arterial disease and to assess changes in functional capacity following therapeutic interventions or through disease progression. The value of this test has frequently been disputed based on doubts concerning its reproducibility. The aim of this study was to investigate the reliability of treadmill testing at a speed of 3 km/h and a constant inclination of 12%.

METHODS

Sixty-eight patients with stable peripheral arterial disease who were familiar with treadmill testing underwent two sessions of walking exercise at 3 km/h and 12% inclination within three weeks. Initial claudication distance (ICD) and maximum walking distance (MWD) on the treadmill as well as reported walking distances on level ground at individual speed were recorded.

RESULTS

Correlation coefficients of 0.8 and within-subject variation coefficients of 15% for ICD and 13% for MWD demonstrated low variability of walking distances between visits. No learning effects were observed. Intra-class correlation coefficients of 0.78 for ICD and 0.83 for MWD proved good reproducibility of treadmill testing. Correlation of measured and reported walking distances was poor.

CONCLUSION

Constant-load treadmill testing at 3km/h and 12% inclination is a well reproducible method to investigate walking capacity of patients with stable intermittent claudication who are familiar with this test method. From treadmill walking distances, no conclusions should be drawn concerning the actual walking range of the patient.

Technical challenges and anatomic anomalies encountered during aortic surgery

Since the introduction of endovascular techniques for the treatment of aortic pathologies, clinical application of these lesser invasive procedures has increased exponentially during the last two decades and changed daily vascular practice completely. Starting in the infra-renal aorta, the indications for endovascular repair have gradually extended to the suprarenal aorta, aortic arch, descending and thoracoabdominal aorta. In addition, other pathologies than aneurysms have been treated by endovascular means, including dissection, traumatic injuries, penetrating aortic ulcer, intramural hematoma and aorto bronchial fistula. With increased application, short-term and longer-term technical failures have developed, in the majority of cases managed by repeat endovascular techniques. However, these complications cannot always be solved by endotechniques, requiring conversion to open surgery. At present there are additional reasons why open surgical repair remains a mainstay in the treatment of complex aortic diseases. Younger patients might choose for traditional surgery because of the unknown durability of complex endovascular reconstructions. Patients with connective tissue disease suffer from vulnerable aortic tissue in which endografts might behave different as compared to degenerative aneurysms. Therefore, the modern vascular surgeon should not only be trained in endovascular procedures but also master the wide spectrum of open surgical techniques. Besides anatomical knowledge and standard vascular handling, the surgeon must be familiar with unusual variations and unexpected situations.

XANES Studies at N and C K-Edge of Compounds in the Ternary System Si-C-N

We report on XANES-investigations at the nitrogen and carbon K-edge of Si-C-N containing solid phases prepared by the reaction of silicon tetrachloride with bis(trimethylsilyl)carbodiimide and annealing the reaction product at temperatures between room temperature (RT) and 1600°C. From the spectra it is possible to evidence the evolution of four phase regions and their different structural increments. We can relate the observed changes of atomic excitations to chemical and structural effects. By that means proposed structural models for the different phases are testified.

Organic electrospun nanofibers as vehicles toward intelligent pheromone dispensers: characterization by laboratory investigations

Organic nanofibers have a history of technical application in various independent fields, including medical technology, filtration technology, and applications of pharmaceuticals via inhalation into the lungs. Very recently, in a joint effort with polymer chemists, agricultural applications have been added to this list of priorities. The aim is finding novel approaches to insect control. Pheromones, dispensed in a quantifiable way, are being used here in disrupting the mating communication between male and female pest insects, e.g. the European grapevine moth Lobesia botrana (Lepidoptera: Tortricidae), where current dispenser technology does not fully meet the high expectations of growers and environmentalists with respect to longevity of constant release, self decomposition, mechanical distribution, renewability as well as sustainability of resources. The methodology of electrospinning is exhaustively covered by Greiner and Wendorff (2007), with technical details reported by Hellmann et al. (2009), Hein et al. (2011), and Hummel et al. (2010). Wind tunnel studies were run within a tunnel with adjustable laminar flow and 0.5 m/sec air velocity. Mass losses of the electrospun fiber bundles were determined with a sensitive analytical balance 2-3 times per week and recorded as time vs. mass change. CLSA experiments were performed with a self developed glass apparatus (Lindner, 2010) based on various suggestions of previous authors. Microgram quantities of volatile pheromone (E,Z)-7,9-Dodecadienylacetate were absorbed on a filter of rigorously purified charcoal and desorbed by repeated micro extraction with a suitable solvent mixture. Aliquots of the solution were subjected to temperature programmed capillary GLC. Retention times were used for identification, whereas the area covered by the pheromone peak originating from a FID detector signal was integrated and compared with a carefully calibrated standard peak. Since these signals were usually in the low nanogram range, several replications were averaged for statistical improvement. - Thermogravimetric analysis between ambient temperature and 500 degrees C provided a series of degradation curves where the diagram contained information on the evaporation of pheromone alone, polymer fiber alone and pheromone included in the fiber.- Microscopic investigations resulted in pictures of nanofibers from which the overall morphology and the fiber dimensions could be quantified. Organic nanofibers loaded with the grapevine moth pheromone have been well characterized by 5 different lab methods, followed by field bioassays reported elsewhere in these communications volumes (HUMMEL et al., 2011). This comprehensive analytical approach to fiber characterization is new and will be further refined. The federal agency JKI Berlin subjected the pheromone loaded organic fibers to various independent toxicological and ecotoxicological tests and found no adverse side effects.

Organic nanofibers containing insect pheromone disruptants: a novel technical approach to controlled release dispensers with potential for process mechanization

Beginning fifty years ago, the search for suitable dispensers containing insect pheromones grew with the availability of these synthetic biotechnical tools. Many economic entomologists and application engineers dearly wish they had the "smart, intelligent and ideal dispenser". More or less suitable approximations are available commercially, but none so far meets all demands. Under economic strictures, novel inexpensive systems would be advantageous with release characteristics tailored to the specific life histories of pest insects, the plants considered and the numerous requirements of growers alike. Simultaneously, their field distribution should be mechanizable and be accomplished by one (or very few) application runs. The dispensers should be biodegradable, biocompatible, sustainably applicable, and they should be based on renewable resources. This report presents first results of a novel organic, electrospun nanofiber dispenser with dimensions in the upper nanometer range. Its load of pheromone can be adjusted to be sufficient for 7 weeks of constant disruptive action in vineyards and can be directed against the European Grape Vine Moth Lobesia botrana (Lepidoptera: Tortricidae) which here serves as a readily available model. Mating disruption in L. botrana and the related Eupoecilia ambiguella is a well studied and developed engineering process. Equally, nanofiber production by electrospinning (for a comprehensive review see Greiner and Wendorff, 2007A, B) is well known and already has numerous applications in filtration technology, air conditioning, and medical wound dressing. Our goal was to bring together and successfully mate these (partly incompatible) technologies via technical tricks of a proprietary nature. Even though the lifetime and effectiveness of currently available nanofibers still must be doubled, the rather complicated system of their production and analysis is known well enough to identify the parameters that need future adjustment. Another challenge is the mechanical distribution of the fibers in the vineyards by suitable machinery. Also, in this respect, certain technical leads are available for future development.

Angiography catheter based bleeding complication at the access site related to neurofibromatosis I

Neurofibromatosis Type I (NF-I) is one of the most common inherited human diseases with an incidence of 1/3000. Besides the cardinal features, all organs or body structures as well as several arterial regions can occasionally be affected. We present an unusual case of an access-site hematoma following percutaneous transluminal coronary angioplasty in a patient suffering from NF-1. After exposure of the vessels, excessive bleeding from surrounding proliferations of supposedly neurofibromatous or ganglioneuromatous tissue was identified as the sole source of the hematoma. Patients with neurofibromatosis are at considerable risk of obtaining catheter interventions over the years. In this group, we strongly recommend an ultrasound examination of the arterial segment where the arterial access is planned. In case of suspicious findings an alternative approach should be preferred to avoid bleeding complications.

[Intraoperative neuromonitoring for prevention of neurological complications in aortic surgery]

AIM

Stroke and paraplegia are devastating complications of thoracic and thoracoabdominal aortic surgery. The aim of this study was to analyse the value of transcranial Doppler ultrasound (TCD), electroencephalogram (EEG) and motor-evoked potentials (MEP) in preventing neurological complications. Moreover, the principles, technology and surgical protocols are described.

PATIENTS AND METHODS

In 2009, 22 patients (4 females, 18 males) underwent thoracic or thoracoabdominal open aortic repair. We performed 2 arches with descending aortic replacement, 5 arches with TAAA repair, 2 type II, 9 type III, 3 type IV and one type V TAAA aortic repair. In 6 patients, the neuromonitoring included TCD, EEG and MEPs. In 15 patients only MEP monitoring was necessary. In one patient who was operated on in an emergency setting, neuromonitoring was not performed. The surgical approach was a left thoracotomy in 3 and a left thoracolaparotomy in 19 patients. The surgical protocol included cerebrospinal fluid drainage (n=22), moderate (n=19) or deep hypothermia (n=2), and extracorporeal circulation (n=21) with retrograde aortic perfusion and selective cerebral and/or viscerorenal perfusion.

RESULTS

In 21 patients, the neuromonitoring could be established successfully. Using TCD and EEG, a relevant cerebral ischaemia during supraaortic clamping was excluded. With a mean distal arterial pressure of 60 mmHg, the MEPs remained adequate in 15 patients (68.2%). Increasing of the blood pressure restored the MEPs in one patient. In 5 patients (22.7%), a reimplantation of segmental arteries (n=4) or of the left subclavian artery (n=1) re-established spinal cord perfusion, as indicated by restored MEPs. We had no absent MEPs at the end of the procedures. Delayed paraparesis developed in 2 patients with a haemodynamic instability during the postoperative course. Paraplegia was not observed.

CONCLUSION

TCD, EEG and MEPs are reliable techniques to unmask cerebral or spinal cord ischaemia during aortic surgery. Immediate operative strategies based on neuromonitoring information prevent neurological complications in aortic surgery.

Marfan Syndrome: when to operate TAA(A)s?

Marfan Syndrome is a heritable disorder of connective tissue leading to aortic aneurysms and other cardiovascular complications associated with reduced life expectancy. Marfan patients with thoracic aortic aneurysms (TAAs) or with thoracoabdominal aortic aneurysms (TAAAs) should be treated by means of open surgery, requiring an extensive protocol, including extracorporeal circulation, neuromonitoring and adjunctive modalities to provide organ protection. Then, open surgical repair of TAA(A)s are associated with excellent results. However, in the last time a gradual change to endovascular treatment in Marfan patients is observable. Particularly in patients with an increased surgical risk due to redo sternotomy or thoracotomy, endovascular treatment might be an alternative due to its less invasive approach. Consequently, thoracic endovascular aortic repair comprises a therapeutic alternative in individual situations even in Marfan patients, when the landing zones are safe and appropriate. In cases of failed endovascular therapy, however, conversion to open surgery remains still an option with acceptable results, although the distal and proximal clamping positions change inappropriate with larger extensions due to the aortic stent.

[Retroperitoneal bronchogenic cyst treated by laparoscopic surgery]

The diagnosis of primary retroperitoneal cystic tumors is very infrequent in surgical pathology. We report the case of a 51-year-old woman presenting with an incidental left-sided retroperitoneal mass (32 x 24 mm in diameter) suspected of being an adrenal tumor. Intraoperatively the tumor was identified as a cystic lesion filled with mucous secretion and laparoscopically completely resected. The diagnosis was histopathologically confirmed as a bronchogenic cyst. In this article the laparoscopic removal of such a rare benign congenital aberration resulting from an abnormal budding of the tracheobronchial tree is presented.

Pancreatic graft survival despite partial vascular graft thrombosis due to splenocephalic anastomoses

Thrombotic complications following pancreas transplantation are still the most common cause of nonimmunologic graft loss. The aim of this study was to analyze pancreatic graft function after partial arterial graft thrombosis and the investigation of the pancreatic arterial anatomy with regard to intraparenchymal anastomoses. We retrospectively analyzed the data for 175 consecutive pancreas transplants performed between January 2002 and October 2007. Selective Y-graft angiography was performed in 10 and rubber-milk injection in 5 fresh pancreas specimens. Thrombosis of one leg of the Y-graft was diagnosed in 18 (10.3%) patients. Only one of these patients with thrombosis of the splenic artery required exogenous insulin. Sufficient graft perfusion was demonstrated in all of the remaining grafts. One graft was lost due to acute rejection. In all specimens angiography showed an excellent perfusion of the pancreaticoduodenal arcade, even after selective cannulation of the splenic artery. Arterial collaterals between the gastroduodenal, splenic artery and the superior mesenteric artery were demonstrated. Our results demonstrate that global perfusion of the pancreatic graft and sufficient graft function is sustained after the thrombotic occlusion of one branch of the Y-graft by a complex system of intraparenchymal anastomoses. These anatomical findings may have consequences for resection strategies in pancreas surgery.

Lack of obvious influence of PLLA nanofibers on the gene expression of BMP-2 and VEGF during growth and differentiation of human mesenchymal stem cells

Growth factors like bone morphogenetic protein 2 (BMP-2) and vascular endothelial growth factor (VEGF) play an important role in bone remodeling and fracture repair. Therefore, with respect to tissue engineering, an artificial graft should have no negative impact on the expression of these factors. In this context, the aim of this study was to analyze the impact of poly(L-lactic acid) (PLLA) nanofibers on VEGF and BMP-2 gene expression during the time course of human mesenchymal stem cell (hMSC) differentiation towards osteoblasts. PLLA matrices were seeded with hMSCs and cultivated over a period of 22 days under growth and osteoinductive conditions, and analyzed during the course of culture, with respect to gene expression of VEGF and BMP-2. Furthermore, BMP-2–enwoven PLLA nanofibers were used in order to elucidate whether initial down-regulation of growth factor expression could be compensated. Although there was a great interpatient variability with respect to the expression of VEGF and BMP-2, PLLA nanofibers tend to result in a down-regulation in BMP-2 expression during the early phase of cultivation. This effect was diminished in the case of VEGF gene expression. The initial down-regulation was overcome when BMP-2 was directly incorporated into the PLLA nanofibers by electrospinning. Furthermore, the incorporation of BMP-2 into the PLLA nanofibers resulted in an increase in VEGF gene expression. Summarized, the results indicate that the PLLA nanofibers have little effect on growth factor production. An enhancement in gene expression of BMP-2 and VEGF can be achieved by an incorporation of BMP-2 into the PLLA nanofibers.