The Experts below are selected from a list of 2430 Experts worldwide ranked by ideXlab platform
Iris A Perez - One of the best experts on this subject based on the ideXlab platform.
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children with congenital central hypoventilation syndrome do not wake up to ventilator alarms
Sleep and Breathing, 2021Co-Authors: Shreya Mathur, Thomas G Keens, Iris A Perez, Eric Laifman, Sheila Kun, Sally Davidson L WardAbstract:Purpose Congenital Central Hypoventilation Syndrome (CCHS) requires lifelong ventilatory support during sleep. Subjects with CCHS are vulnerable to sleep disturbances associated with treatments, monitoring alarms, and care they receive. We hypothesized that sleep would be disrupted in patients with CCHS due to ventilatory support and other treatments at night. Methods An anonymous survey of patients with CCHS, age up to 17 years was conducted through REDCAP. Subjects were recruited in person, by flyer, email, and social media. Data collected included demographics, PHOX2B genotype, ventilatory support, treatments, nursing, and sleep parameters. Results We received 23 responses (35% female, 8.1 years ± 5.6). PHOX2B genotypes were 20/24 ParM (2), 20/25 ParM (4), 20/26 ParM (2), 20/27 ParM (9), ≥ 20/28 ParM (2), and NParM (2). Two subjects did not indicate the PHOX2B genotype. 13/23 were ventilated by PPV via tracheostomy, 7 by NIPPV, 2 by diaphragm pacing, and 1 did not indicate. Additional treatments received at night included suctioning (9), aerosol (1), G-tube feeding (2), and none (11). Only 9 received nursing at night. 13 used pulse oximetry for monitoring, and 9 used both pulse oximetry and end tidal CO2 monitor. 17/23 rarely woke up due to ventilator or monitor alarms. 11/23 usually or sometimes woke up at least once a night; only 2/11 woke up due to alarms. 5/17 who rarely woke up to the alarms had night nursing. Conclusion Most subjects with CCHS did not awaken to ventilator or monitoring alarms and a majority of these patients did not have nighttime nursing. (Mathur et al. in Sleep 43(Supplement_1):A333, 2020).
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the genetics of congenital central hypoventilation syndrome clinical implications
The application of clinical genetics, 2018Co-Authors: John Bishara, Thomas G Keens, Iris A PerezAbstract:Congenital central hypoventilation syndrome (CCHS) is a rare genetic disorder of the autonomic nervous system (ANS) and respiratory control. This disorder, formerly referred to as Ondine's curse, is due to a mutation in the PHOX2B gene that affects the development of the neural crest cells. CCHS has an autosomal dominant pattern of inheritance. Majority of the patients have a polyalanine repeat mutation (ParM) of the PHOX2B, while a small group has non-ParM (NParM). Knowledge of the patient's PHOX2B gene mutation helps predict a patient's clinical presentation and outcome and aids in anticipatory management of the respiratory and ANS dysfunction.
Matin Qaim - One of the best experts on this subject based on the ideXlab platform.
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the economics behind an ecological crisis livelihood effects of oil palm expansion in sumatra indonesia
Human Ecology, 2018Co-Authors: Christoph Kubitza, Vijesh V Krishna, Zulkifli Alamsyah, Matin QaimAbstract:While the negative ecological effects of the rapid expansion of oil palm in Southeast Asia are far-reaching and relatively widely studied, the socioeconomic consequences have received much less attention in the literature. We examine whether local farmers in Indonesia benefit from cultivating oil palm. We also look at the impact dynamics and possible spillover effects on other farmers. Our analysis builds on panel data collected from 680 farm households in Jambi Province, Sumatra. We show that oil palm cultivation has significant positive effects on farmers’ livelihoods. The economic gains allow farm households to increase their consumption. Oil palm has lower labor requirements than alternative crops. Hence, oil palm farmers can cultivate larger areas and also reallocate saved labor time to non-farm economic activities, which contributes to additional secondary gains. Policies aimed at regulating further oil palm area expansion will have to account for the economic benefits of this crop for the local population.
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land markets property rights and deforestation insights from indonesia
World Development, 2017Co-Authors: Vijesh V Krishna, Christoph Kubitza, Unai Pascual, Matin QaimAbstract:Summary We examine the emergence of land markets and their effects on forest land appropriation by farm households in Jambi Province, Sumatra, using micro-level data covering land use and land transactions for a period of more than 20 years (1992–2015). Based on a theoretical model of land acquisition by a heterogeneous farming population, different hypotheses are developed and empirically tested. Farm households involved in forest land appropriation differ from those involved in land market purchases in terms of migration status and other socioeconomic characteristics. In principle, these differences provide opportunities for market-induced deforestation. However, the appropriated forest land is not extensively traded, which we attribute to the lack of de jure property right protection and the resulting undervaluation in the market. While the de facto property right protection under customary law provides sufficient security within the village community, the sense of external tenure security is low when the land cannot be formally titled. Clearing forests for trading in the land market is, therefore, financially less lucrative for farm households than engaging in own cultivation of plantation crops, such as oil palm and rubber. We conclude that land markets did not have significant effects on deforestation. On the other hand, the emergence of land markets alone has also not been able to deter forest appropriation by local farm households.
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Oil Palm Adoption, Household Welfare, and Nutrition Among Smallholder Farmers in Indonesia
World Development, 2017Co-Authors: Manfred Euler, Vijesh Krishna, Hermanto Siregar, Stefan Schwarze, Matin QaimAbstract:Oil palm is one of the most rapidly expanding crops throughout the humid tropics. In Indonesia, the expansion is largely driven by smallholder farmers. While recent research has studied effects for the environment and climate change, socioeconomic impacts in the small farm sector have hardly been analyzed. Here, we address this research gap by analyzing effects of oil palm adoption on farm household living standards and nutrition in Sumatra. Using survey data and econometric models, we estimate average impacts, impact pathways, and impact heterogeneity. Results show that oil palm adoption improves household living standards and nutrition. Mean impacts on food and non-food expenditures, as well as on calorie consumption and dietary quality, are all positive and significant. A sizeable part of the total effects is attributable to oil palm adopters expanding their farm size rather than realizing higher profits per hectare. Oil palm has lower labor requirements than alternative crops (especially rubber), so that adopting farmers are able to manage larger land areas. Labor saved through switching from rubber to oil palm is also used to increase off-farm incomes. Impact heterogeneity is analyzed with quantile regressions. We find positive effects of oil palm adoption across the entire expenditure distribution. However, the absolute gains in total expenditures and non-food expenditures are larger for the better-off, suggesting that oil palm may contribute to rising inequality.
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oil palm adoption household welfare and nutrition among smallholder farmers in indonesia
Research Papers in Economics, 2015Co-Authors: Michael Euler, Stefan Schwarze, Hermanto Siregar, Vijesh V Krishna, Matin QaimAbstract:The recent expansion of oil palm in Indonesia is largely smallholder-driven. However, its socio-economic implications are under-examined. Analyzing farm-household data from Jambi Province, Sumatra, oil palm adoption is found to have positive consumption and nutrition effects. However, these effects are largely due to farm size expansion that is associated with oil palm adoption. Potential heterogeneity of effects among oil palm adopters is examined using quantile regressions. While nutrition effects of oil palm adoption are found to be homogenous across quantiles, the effects on non-food expenditure are expressed more strongly at the upper end of the expenditure distribution.
Stefan Schwarze - One of the best experts on this subject based on the ideXlab platform.
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Oil Palm Adoption, Household Welfare, and Nutrition Among Smallholder Farmers in Indonesia
World Development, 2017Co-Authors: Manfred Euler, Vijesh Krishna, Hermanto Siregar, Stefan Schwarze, Matin QaimAbstract:Oil palm is one of the most rapidly expanding crops throughout the humid tropics. In Indonesia, the expansion is largely driven by smallholder farmers. While recent research has studied effects for the environment and climate change, socioeconomic impacts in the small farm sector have hardly been analyzed. Here, we address this research gap by analyzing effects of oil palm adoption on farm household living standards and nutrition in Sumatra. Using survey data and econometric models, we estimate average impacts, impact pathways, and impact heterogeneity. Results show that oil palm adoption improves household living standards and nutrition. Mean impacts on food and non-food expenditures, as well as on calorie consumption and dietary quality, are all positive and significant. A sizeable part of the total effects is attributable to oil palm adopters expanding their farm size rather than realizing higher profits per hectare. Oil palm has lower labor requirements than alternative crops (especially rubber), so that adopting farmers are able to manage larger land areas. Labor saved through switching from rubber to oil palm is also used to increase off-farm incomes. Impact heterogeneity is analyzed with quantile regressions. We find positive effects of oil palm adoption across the entire expenditure distribution. However, the absolute gains in total expenditures and non-food expenditures are larger for the better-off, suggesting that oil palm may contribute to rising inequality.
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Exploring yield gaps in smallholder oil palm production systems in eastern Sumatra, Indonesia
Agricultural Systems, 2016Co-Authors: Manfred Euler, Zakky Fathoni, Munir P. Hoffmann, Stefan SchwarzeAbstract:Oil palm (Elaeis guineensis) has become the most important oil crop throughout the world. The growing palm oil production was mainly based on the expansion of cultivated area into forest areas, causing serious environmental and social concerns. Increasing yields on existing plantations is a potential pathway to reduce the undesired ecological impacts of oil palm agriculture while enhancing its social benefits. Although oil palm production is still dominated by large private estates, smallholder farmers are increasingly engaging in its cultivation. While there is some evidence that smallholders' palm oil yields show large variations and are often far below plantation standards, empirical studies on their agronomic performance are scarce. Based on crop modeling analysis and farm household survey data from Sumatra, Indonesia, this paper quantifies smallholder yield gaps relative to exploitable yield levels and analyses smallholders' production constraints. Results show that oil palm smallholdings offer a tremendous potential for future yield increases, because they obtain, on average, only around 50% of the cumulative exploitable yield over a 20 year plantation life cycle. In particular, we find yield gaps to be largest during the most productive phase of oil palm. Our results indicate that farmers do not adapt their labor and fertilizer inputs to the higher resource demand of the palm. In general, significant determinants of yield gaps are management practices such as fertilizer dosage, length of harvesting intervals and plant mortality. Supported smallholders perform relatively better compared to independent farmers. In summary, our study shows that there is large potential to increase productivity of smallholder oil palm systems in Sumatra. In order to exploit this opportunity, farmers' awareness about the changing management requirements of oil palm over the plantation life cycle needs to be enhanced.
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oil palm adoption household welfare and nutrition among smallholder farmers in indonesia
Research Papers in Economics, 2015Co-Authors: Michael Euler, Stefan Schwarze, Hermanto Siregar, Vijesh V Krishna, Matin QaimAbstract:The recent expansion of oil palm in Indonesia is largely smallholder-driven. However, its socio-economic implications are under-examined. Analyzing farm-household data from Jambi Province, Sumatra, oil palm adoption is found to have positive consumption and nutrition effects. However, these effects are largely due to farm size expansion that is associated with oil palm adoption. Potential heterogeneity of effects among oil palm adopters is examined using quantile regressions. While nutrition effects of oil palm adoption are found to be homogenous across quantiles, the effects on non-food expenditure are expressed more strongly at the upper end of the expenditure distribution.
Thomas G Keens - One of the best experts on this subject based on the ideXlab platform.
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children with congenital central hypoventilation syndrome do not wake up to ventilator alarms
Sleep and Breathing, 2021Co-Authors: Shreya Mathur, Thomas G Keens, Iris A Perez, Eric Laifman, Sheila Kun, Sally Davidson L WardAbstract:Purpose Congenital Central Hypoventilation Syndrome (CCHS) requires lifelong ventilatory support during sleep. Subjects with CCHS are vulnerable to sleep disturbances associated with treatments, monitoring alarms, and care they receive. We hypothesized that sleep would be disrupted in patients with CCHS due to ventilatory support and other treatments at night. Methods An anonymous survey of patients with CCHS, age up to 17 years was conducted through REDCAP. Subjects were recruited in person, by flyer, email, and social media. Data collected included demographics, PHOX2B genotype, ventilatory support, treatments, nursing, and sleep parameters. Results We received 23 responses (35% female, 8.1 years ± 5.6). PHOX2B genotypes were 20/24 ParM (2), 20/25 ParM (4), 20/26 ParM (2), 20/27 ParM (9), ≥ 20/28 ParM (2), and NParM (2). Two subjects did not indicate the PHOX2B genotype. 13/23 were ventilated by PPV via tracheostomy, 7 by NIPPV, 2 by diaphragm pacing, and 1 did not indicate. Additional treatments received at night included suctioning (9), aerosol (1), G-tube feeding (2), and none (11). Only 9 received nursing at night. 13 used pulse oximetry for monitoring, and 9 used both pulse oximetry and end tidal CO2 monitor. 17/23 rarely woke up due to ventilator or monitor alarms. 11/23 usually or sometimes woke up at least once a night; only 2/11 woke up due to alarms. 5/17 who rarely woke up to the alarms had night nursing. Conclusion Most subjects with CCHS did not awaken to ventilator or monitoring alarms and a majority of these patients did not have nighttime nursing. (Mathur et al. in Sleep 43(Supplement_1):A333, 2020).
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the genetics of congenital central hypoventilation syndrome clinical implications
The application of clinical genetics, 2018Co-Authors: John Bishara, Thomas G Keens, Iris A PerezAbstract:Congenital central hypoventilation syndrome (CCHS) is a rare genetic disorder of the autonomic nervous system (ANS) and respiratory control. This disorder, formerly referred to as Ondine's curse, is due to a mutation in the PHOX2B gene that affects the development of the neural crest cells. CCHS has an autosomal dominant pattern of inheritance. Majority of the patients have a polyalanine repeat mutation (ParM) of the PHOX2B, while a small group has non-ParM (NParM). Knowledge of the patient's PHOX2B gene mutation helps predict a patient's clinical presentation and outcome and aids in anticipatory management of the respiratory and ANS dysfunction.
David Popp - One of the best experts on this subject based on the ideXlab platform.
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microtubule like properties of the bacterial actin homolog ParM r1
Journal of Biological Chemistry, 2012Co-Authors: David Popp, Akihiro Narita, Robert Robinson, Lin Jie Lee, Marten LarssonAbstract:In preparation for mammalian cell division, microtubules repeatedly probe the cytoplasm to capture chromosomes and assemble the mitotic spindle. Critical features of this microtubule system are the formation of radial arrays centered at the centrosomes and dynamic instability, leading to persistent cycles of polymerization and depolymerization. Here, we show that actin homolog, ParM-R1 that drives segregation of the R1 multidrug resistance plasmid from Escherichia coli, can also self-organize in vitro into asters, which resemble astral microtubules. ParM-R1 asters grow from centrosome-like structures consisting of interconnected nodes related by a pseudo 8-fold symmetry. In addition, we show that ParM-R1 is able to perform persistent microtubule-like oscillations of assembly and disassembly. In vitro, a whole population of ParM-R1 filaments is synchronized between phases of growth and shrinkage, leading to prolonged synchronous oscillations even at physiological ParM-R1 concentrations. These results imply that the selection pressure to reliably segregate DNA during cell division has led to common mechanisms within diverse segregation machineries.
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structure and filament dynamics of the psk41 actin like ParM protein implications for plasmid dna segregation
Journal of Biological Chemistry, 2010Co-Authors: David Popp, Akihiro Narita, Yuichiro Maeda, Anthony J Brzoska, Ronald A Skurray, Neville Firth, Umesh Ghoshdastider, Robert Robinson, Maria A SchumacherAbstract:Type II plasmid partition systems utilize ParM NTPases in coordination with a centromere-binding protein called ParR to mediate accurate DNA segregation, a process critical for plasmid retention. The Staphylococcus aureus pSK41 plasmid is a medically important plasmid that confers resistance to multiple antibiotics, disinfectants, and antiseptics. In the first step of partition, the pSK41 ParR binds its DNA centromere to form a superhelical partition complex that recruits ParM, which then mediates plasmid separation. pSK41 ParM is homologous to R1 ParM, a known actin homologue, suggesting that it may also form filaments to drive partition. To gain insight into the partition function of ParM, we examined its ability to form filaments and determined the crystal structure of apoParM to 1.95 Å. The structure shows that pSK41 ParM belongs to the actin/Hsp70 superfamily. Unexpectedly, however, pSK41 ParM shows the strongest structural homology to the archaeal actin-like protein Thermoplasma acidophilum Ta0583, rather than its functional homologue, R1 ParM. Consistent with this divergence, we find that regions shown to be involved in R1 ParM filament formation are not important in formation of pSK41 ParM polymers. These data are also consonant with our finding that pSK41 ParM forms 1-start 10/4 helices very different from the 37/17 symmetry of R1 ParM. The polymerization kinetics of pSK41 ParM also differed from that of R1 ParM. These results indicate that type II NTPases utilize different polymeric structures to drive plasmid segregation.
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molecular mechanism of bundle formation by the bacterial actin ParM
Biochemical and Biophysical Research Communications, 2010Co-Authors: David Popp, Akihiro Narita, Mitsusada Iwasa, Yuichiro Maeda, Robert RobinsonAbstract:The actin homolog ParM plays a microtubule-like role in segregating DNA prior to bacterial cell division. Fluorescence and cryo-electron microscopy have shown that ParM forms filament bundles between separating DNA plasmids in vivo. Given the lack of ParM bundling proteins it remains unknown how ParM bundles form at the molecular level. Here we show using time-lapse TIRF microscopy, under in vitro molecular crowding conditions, that ParM-bundle formation consists of two distinct phases. At the onset of polymerization bundle thickness and shape are determined in the form of nuclei of short helically disordered filaments arranged in a liquid-like lattice. These nuclei then undergo an elongation phase whereby they rapidly increase in length. At steady state, ParM bundles fuse into one single large aggregate. This behavior had been predicted by theory but has not been observed for any other cytomotive biopolymer, including F-actin. We employed electron micrographs of ParM rafts, which are 2-D analogs of 3-D bundles, to identify the main molecular interfilament contacts within these suprastructures. The interface between filaments is similar for both parallel and anti-parallel orientations and the distribution of filament polarity is random within a bundle. We suggest that the interfilament interactions are not due to the interactions of specific residues but rather to long-range, counter ion mediated, electrostatic attractive forces. A randomly oriented bundle ensures that the assembly is rigid and that DNA may be captured with equal efficiency at both ends of the bundle via the ParR binding protein.
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protofilament formation of ParM mutants
Journal of Molecular Biology, 2009Co-Authors: David Popp, Akihiro Narita, Toshiro Oda, Mitsusada Iwasa, Kayo Maeda, Yuichiro MaedaAbstract:ParM, an actin homolog, forms left-handed two-start helical filaments that segregate DNA in bacteria prior to cell division. Our recent atomic model obtained from electron microscopy (EM) reconstructions of negatively stained ParM filaments implied that two salt bridges (Glu35-Lys258 and Asp63-Arg262) may be key inter-filament contacts that stabilize the left-handed ParM helix. We made mutations of these amino acids and probed the inter-strand interface of our model experimentally by EM and X-ray fiber diffraction. We found that several mutations, such as ParM single mutants Asp258 and Asp262 and double mutant Asp258/Arg262, were incapable of forming straight filaments in aqueous buffers and appeared ragged and unstructured. However, in the presence of crowding agents, straight filaments or filament bundles formed, which allowed us to elucidate the structure of these mutant filaments. Centrifugation of filaments also resulted in a pellet of straightened filaments that could be oriented in glass capillaries and gave detailed X-ray diffraction patterns. Both EM and X-ray diffraction showed that filaments formed from these ParM mutants were not double-stranded helical filaments but single protofilaments, indicating that these residues are important for formation of the ParM helix. Our data also confirm a major prediction of crowding theory, namely that molecular crowding shifts the equilibrium of even severely impaired, unstructured cytoskeletal polymers toward their structured native and functional state. ParM is the first example of a helical actin homolog that can be induced to form protofilaments.
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molecular structure of the ParM polymer and the mechanism leading to its nucleotide driven dynamic instability
The EMBO Journal, 2008Co-Authors: David Popp, Akihiro Narita, Toshiro Oda, Tetsuro Fujisawa, Hiroshi Matsuo, Yasushi Nitanai, Mitsusada Iwasa, Kayo Maeda, Hirofumi Onishi, Yuichiro MaedaAbstract:ParM is a prokaryotic actin homologue, which ensures even plasmid segregation before bacterial cell division. In vivo, ParM forms a labile filament bundle that is reminiscent of the more complex spindle formed by microtubules partitioning chromosomes in eukaryotic cells. However, little is known about the underlying structural mechanism of DNA segregation by ParM filaments and the accompanying dynamic instability. Our biochemical, TIRF microscopy and high-pressure SAX observations indicate that polymerization and disintegration of ParM filaments is driven by GTP rather than ATP and that ParM acts as a GTP-driven molecular switch similar to a G protein. Image analysis of electron micrographs reveals that the ParM filament is a left-handed helix, opposed to the right-handed actin polymer. Nevertheless, the intersubunit contacts are similar to those of actin. Our atomic model of the ParM-GMPPNP filament, which also fits well to X-ray fibre diffraction patterns from oriented gels, can explain why after nucleotide release, large conformational changes of the protomer lead to a breakage of intra- and interstrand interactions, and thus to the observed disintegration of the ParM filament after DNA segregation.
