Dorsal hindbrain ablation results in rerouting of neural crest migration and changes in gene expression, but normal hyoid development

Our previous studies have shown that hindbrain neural tube cells can regulate to form neural crest cells for a limited time after neural fold removal (Scherson, T., Serbedzija, G., Fraser, S. E. and Bronner-Fraser, M. (1993). Development 188, 1049-1061; Sechrist, J., Nieto, M. A., Zamanian, R. T. and Bronner-Fraser, M. (1995). Development 121, 4103-4115). In the present study, we ablated the dorsal hindbrain at later stages to examine possible alterations in migratory behavior and/or gene expression in neural crest populations rostral and caudal to the operated region. The results were compared with those obtained by misdirecting neural crest cells via rhombomere rotation. Following surgical ablation of dorsal r5 and r6 prior to the 10 somite stage, r4 neural crest cells migrate along normal pathways toward the second branchial arch. Similarly, r7 neural crest cells migrate primarily to the fourth branchial arch. When analogous ablations are performed at the 10- 12 somite stage, however, a marked increase in the numbers of DiI/Hoxa-3-positive cells from r7 are observed within the third branchial arch. In addition, some DiI-labeled r4 cells migrate into the depleted hindbrain region and the third branchial arch. During their migration, a subset of these r4 cells up-regulate Hoxa-3, a transcript they do not normally express. Krox20 transcript levels were augmented after ablation in a population of neural crest cells migrating from r4, caudal r3 and rostral r3. Long-term survivors of bilateral ablations possess normal neural crest-derived cartilage of the hyoid complex, suggesting that misrouted r4 and r7 cells contribute to cranial derivatives appropriate for their new location. In contrast, misdirecting of the neural crest by rostrocaudal rotation of r4 through r6 results in a reduction of Hoxa-3 expression in the third branchial arch and corresponding deficits in third arch-derived structures of the hyoid apparatus. These results demonstrate that neural crest/tube progenitors in the hindbrain can compensate by altering migratory trajectories and patterns of gene expression when the adjacent neural crest is removed, but fail to compensate appropriately when the existing neural crest is misrouted by neural tube rotation

Rhombomere of origin determines autonomous versus environmentally regulated expression of Hoxa3 in the avian embryo

We have investigated the pattern and regulation of Hoxa3 expression in the hindbrain and associated neural crest cells in the chick embryo, using whole mount in situ hybridization in conjunction with DiI labeling of neural crest cells and microsurgical manipulations. Hoxa3 is expressed in the neural plate and later in the neural tube with a rostral border of expression corresponding to the boundary between rhombomeres (r) 4 and 5. Initial expression is diffuse and becomes sharp after boundary formation. Hoxa3 exhibits uniform expression within r5 after formation of rhombomeric borders. Cell marking experiments reveal that neural crest cells migrating caudally, but not rostrally, from r5 and caudally from r6 express Hoxa3 in normal embryo. Results from transposition experiments demonstrate that expression of Hoxa3 in r5 neural crest cells is not strictly cell-autonomous. When r5 is transposed with r4 by rostrocaudal rotation of the rhomobomeres, Hoxa3 is expressed in cells migrating lateral to transposed r5 and for a short time, in condensing ganglia, but not by neural crest within the second branchial arch. Since DiI-labeled cells from transposed r5 are present in the second arch, Hoxa3-expressing neural crest cells from r5 appear to down-regulate their Hoxa3 expression in their new environment. In contrast, when r6 is transposed to the position of r4 after boundary formation, Hoxa3 is maintained in both migrating neural crest cells and those positioned within the second branchial arch and associated ganglia. These results suggest that Hoxa3 expression is cell-autonomous in r6 and its associated neural crest. Our results suggest that neural crest cells expressing the same Hox gene are not eqivalent; they respond differently to environmental signals and exhibit distinct degrees of cell autonomy depending upon their rhombomere of origin

Outcomes of elective liver surgery worldwide: a global, prospective, multicenter, cross-sectional study

Background: The outcomes of liver surgery worldwide remain unknown. The true population-based outcomes are likely different to those vastly reported that reflect the activity of highly specialized academic centers. The aim of this study was to measure the true worldwide practice of liver surgery and associated outcomes by recruiting from centers across the globe. The geographic distribution of liver surgery activity and complexity was also evaluated to further understand variations in outcomes. Methods: LiverGroup.org was an international, prospective, multicenter, cross-sectional study following the Global Surgery Collaborative Snapshot Research approach with a 3-month prospective, consecutive patient enrollment within January–December 2019. Each patient was followed up for 90 days postoperatively. All patients undergoing liver surgery at their respective centers were eligible for study inclusion. Basic demographics, patient and operation characteristics were collected. Morbidity was recorded according to the Clavien–Dindo Classification of Surgical Complications. Country-based and hospital-based data were collected, including the Human Development Index (HDI). (NCT03768141). Results: A total of 2159 patients were included from six continents. Surgery was performed for cancer in 1785 (83%) patients. Of all patients, 912 (42%) experienced a postoperative complication of any severity, while the major complication rate was 16% (341/2159). The overall 90-day mortality rate after liver surgery was 3.8% (82/2,159). The overall failure to rescue rate was 11% (82/ 722) ranging from 5 to 35% among the higher and lower HDI groups, respectively. Conclusions: This is the first to our knowledge global surgery study specifically designed and conducted for specialized liver surgery. The authors identified failure to rescue as a significant potentially modifiable factor for mortality after liver surgery, mostly related to lower Human Development Index countries. Members of the LiverGroup.org network could now work together to develop quality improvement collaboratives

Hybrid PWM Techniques for a DCM-232 Three-Phase Transformerless Inverter with Reduced Leakage Ground Current

Pulse Width Modulation (PWM) strategies are crucial for controlling DC–AC power converters. In particular, transformerless inverters require specific PWM techniques to improve efficiency and to deal with leakage ground current issues. In this paper, three hybrid PWM methods are proposed for a DCM-232 three-phase topology. These methods are based on the concepts of carrier-based PWM and space vector modulation. Calculations of time intervals for active and null vectors are performed in a conventional way, and the resulting waveforms are compared with a carrier signal. The digital signals obtained are processed using Boolean functions, generating ten signals to control the DCM-232 three-phase inverter. The performance of the three proposed PWM methods is evaluated considering the reduction in leakage ground current and efficiency. The proposed modulation techniques have relevant performances complying with international standards, which make them suitable for transformerless three-phase photovoltaic (PV) inverter markets. To validate the proposed hybrid PWM strategies, numerical simulations and experimental tests were performed

Symbiotic Co-Culture of <i>Scenedesmus</i> sp. and <i>Azospirillum brasilense</i> on N-Deficient Media with Biomass Production for Biofuels

The treatment of nitrogen-deficient agriculture wastewater, arising from the vegetable and fruit processing, is a significant problem that limits the efficiency of its biological treatment. This study evaluates the effectiveness of the symbiotic co-culture of Azospirillum brasilense and Scenedesmus sp., under two nitrogen levels (8.23 mg L&#8722;1 and 41.17 mg L&#8722;1) and mixing systems (aeration and magnetic stirring), aiming to simultaneously use the N-deficient media for their growth while producing biomass for biofuels. Microalgae growth and biomass composition, in terms of protein, carbohydrate and fatty acid contents, were evaluated at the end of the exponential growth phase (15 days after inoculation). Results show that the symbiotic co-culture of microalgae-bacteria can be effectively performed on nitrogen-deficient media and has the potential to enhance microalgae colony size and the fatty acid content of biomass for biofuels. The highest biomass concentration (103 &#177; 2 mg&#183;L&#8722;1) was obtained under aeration, with low nitrogen concentration, in the presence of A. brasilense. In particular, aeration contributed to, on average, a higher fatty acid content (48 &#177; 7% dry weight (DW)) and higher colony size (164 &#177; 21 &#181;m2) than mechanical stirring (with 39 &#177; 2% DW and 134 &#177; 21 &#181;m2, respectively) because aeration contribute to better mass transfer of gases in the culture. Also, co-culturing contributed in average, to higher colony size (155 &#177; 21 &#181;m2) than without A. brasilense (143 &#177; 21 &#181;m2). Moreover, using nitrogen deficient wastewater as the culture media can contribute to decrease nitrogen and energy inputs. Additionally, A. brasilense is approved and already extensively used in agriculture and wastewater treatment, without known environmental or health issues, simplifying the biomass processing for the desired application

Symbiotic Co-Culture of Scenedesmus sp. and Azospirillum brasilense on N-Deficient Media with Biomass Production for Biofuels

© 2019 by the authors. The treatment of nitrogen-deficient agriculture wastewater, arising from the vegetable and fruit processing, is a significant problem that limits the efficiency of its biological treatment. This study evaluates the effectiveness of the symbiotic co-culture of Azospirillum brasilense and Scenedesmus sp., under two nitrogen levels (8.23 mg L -1 and 41.17 mg L -1 ) and mixing systems (aeration and magnetic stirring), aiming to simultaneously use the N-deficient media for their growth while producing biomass for biofuels. Microalgae growth and biomass composition, in terms of protein, carbohydrate and fatty acid contents, were evaluated at the end of the exponential growth phase (15 days after inoculation). Results show that the symbiotic co-culture of microalgae-bacteria can be effectively performed on nitrogen-deficient media and has the potential to enhance microalgae colony size and the fatty acid content of biomass for biofuels. The highest biomass concentration (103 ± 2 mg. L -1 ) was obtained under aeration, with low nitrogen concentration, in the presence of A. brasilense. In particular, aeration contributed to, on average, a higher fatty acid content (48 ± 7% dry weight (DW)) and higher colony size (164 ± 21 μm 2 ) than mechanical stirring (with 39 ± 2% DW and 134 ± 21 μm 2 , respectively) because aeration contribute to better mass transfer of gases in the culture. Also, co-culturing contributed in average, to higher colony size (155 ± 21 μm 2 ) than without A. brasilense (143 ± 21 μm 2 ). Moreover, using nitrogen deficient wastewater as the culture media can contribute to decrease nitrogen and energy inputs. Additionally, A. brasilense is approved and already extensively used in agriculture and wastewater treatment, without known environmental or health issues, simplifying the biomass processing for the desired application.status: publishe