The Experts below are selected from a list of 332556 Experts worldwide ranked by ideXlab platform
Ingrid E Scheffer - One of the best experts on this subject based on the ideXlab platform.
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Ectopic Posterior Pituitary Lobe and Periventricular Heterotopia: Cerebral Malformations with the Same Underlying Mechanism?
2015Co-Authors: Anne L Mitchell, Paul Q. Thomas, Margaret Zacharin, Ingrid E SchefferAbstract:with growth hormone deficiency and is part of the spectrum associated with septo-optic dysplasia. Some cases of septo-optic dysplasia are caused by homozygous mutations in the homeobox gene HESX1, whereas heterozygous mutations are associated with milder pheno-types. To date, HESX1 is the only gene associated with ectopic posterior pituitary lobe. We describe an association between ectopic posterior pituitary lobe and periventricular heterotopia in four children without classic features of septo-optic dysplasia and suggest possible mecha-nisms on the basis of a review of pituitary embryology and recent molecular genetic advances. METHODS: Among 20 children with ectopic posterior pituitary lobe, four had associated periventricular heterotopia. We herein review the clinical and MR imaging findings of these four children. Mutation screening of HESX1 was performed in two. RESULTS: All four children had growth hormone deficiency. None had visual or neurologic disturbances. MR images showed a range of pituitary appearances, with scattered discrete periventricular heterotopia in each case. Other abnormalities were limited to small suprasellar lipomas and callosal dysgenesis. A heterozygous HESX1 mutation was present in one case. CONCLUSION: The coexistence of ectopic posterior pituitary lobe and periventricular hete
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ectopic posterior pituitary lobe and periventricular heterotopia cerebral malformations with the same Underlying Mechanism
American Journal of Neuroradiology, 2002Co-Authors: Anne L Mitchell, Paul Q. Thomas, Margaret Zacharin, Ingrid E SchefferAbstract:BACKGROUND AND PURPOSE: Ectopic posterior pituitary lobe often occurs in children with growth hormone deficiency and is part of the spectrum associated with septo-optic dysplasia. Some cases of septo-optic dysplasia are caused by homozygous mutations in the homeobox gene HESX1, whereas heterozygous mutations are associated with milder phenotypes. To date, HESX1 is the only gene associated with ectopic posterior pituitary lobe. We describe an association between ectopic posterior pituitary lobe and periventricular heterotopia in four children without classic features of septo-optic dysplasia and suggest possible Mechanisms on the basis of a review of pituitary embryology and recent molecular genetic advances. METHODS: Among 20 children with ectopic posterior pituitary lobe, four had associated periventricular heterotopia. We herein review the clinical and MR imaging findings of these four children. Mutation screening of HESX1 was performed in two. RESULTS: All four children had growth hormone deficiency. None had visual or neurologic disturbances. MR images showed a range of pituitary appearances, with scattered discrete periventricular heterotopia in each case. Other abnormalities were limited to small suprasellar lipomas and callosal dysgenesis. A heterozygous HESX1 mutation was present in one case. CONCLUSION: The coexistence of ectopic posterior pituitary lobe and periventricular heterotopia suggests they have a common Underlying genetic basis that is due to gene expression at different locations and stages of development. The presence of a heterozygous HESX1 mutation in one case suggests this gene is important in the development of both ectopic posterior pituitary lobe and periventricular heterotopia and supports their place in the spectrum of septo-optic dysplasia. Further analysis of HESX1 and other genes in related developmental pathways will elucidate their roles in the development of both malformations.
Hailong Li - One of the best experts on this subject based on the ideXlab platform.
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the Underlying Mechanism of calcium peroxide pretreatment enhancing methane production from anaerobic digestion of waste activated sludge
Water Research, 2019Co-Authors: Dongbo Wang, Dandan He, Qiuxiang Xu, Xiaoming Li, Qilin Wang, Bingjie Ni, Qi Yang, Hailong LiAbstract:Abstract Recent investigations verified that calcium peroxide (CaO2) could be used to pretreat waste activated sludge to promote methane yield from anaerobic digestion. However, the Underlying Mechanism of how CaO2 pretreatment promotes methane production is unclear. This work therefore aims to provide insights into such systems. Experimental results showed that with an increase of CaO2 dosage from 0 to 0.14 g/g VSS (volatile suspended solids) the methane yield increased linearly from 146.3 to 215.9 mL/g VSS. Further increases of CaO2 resulted in decreases in methane yield. CaO2 pretreatment promoted the disintegration of sludge and the degradation of sludge recalcitrant organics (especially humus and lignocellulose), thereby providing more substrates for subsequent methane production. Ultraviolet absorption spectroscopy indicated that CaO2 enhanced the cleavage of unsaturated conjugated bonds and reduced the aromaticity of humus and lignocellulose. Fourier transform infrared spectroscopy showed that CaO2 changed the structures and functional groups of humus and lignocellulose, making them transform to be biodegradable. GC/MS analyses exhibited that the degradation products of humus and lignocellulose included several types of small molecular organics such as ester-like, acid-like, and alcohol-like substances. Further investigation demonstrated that substantial methane could be produced from these degradation products. It was also found that the presence of recalcitrant organics was detrimental to anaerobes relevant to anaerobic digestion, and the degradation of such recalcitrant organics mitigated their inhibitions to the anaerobes. Model-based analysis suggested that CaO2 pretreatment increased the maximum methane yield and methane production rate, which were consistent with the analysis above.
Anuya Nisal - One of the best experts on this subject based on the ideXlab platform.
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silk fibroin sophorolipid gelation deciphering the Underlying Mechanism
Biomacromolecules, 2016Co-Authors: Parul Dubey, Sugam Kumar, V K Aswal, Sapna Ravindranathan, P R Rajamohanan, Asmita Prabhune, Anuya NisalAbstract:Silk fibroin (SF) protein, produced by silkworm Bombyx mori, is a promising biomaterial, while sophorolipid (SL) is an amphiphilic functional biosurfactant synthesized by nonpathogenic yeast Candida bombicola. SL is a mixture of two forms, acidic (ASL) and lactonic (LSL), which when added to SF results in accelerated gelation of silk fibroin. LSL is known to have multiple biological functionalities and hence hydrogels of these green molecules have promising applications in the biomedical sector. In this work, SANS, NMR, and rheology are employed to examine the assembling properties of individual and mixed SLs and their interactions with SF to understand the Mechanism that leads to rapid gelation. SANS and NMR studies show that ASL assembles to form charged micelles, while LSL forms micellar assemblies and aggregates of a mass fractal nature. ASL and LSL together form larger mixed micelles, all of which interact differently with SF. It is shown that preferential binding of LSL to SF causes rapid unfolding ...
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Silk Fibroin-Sophorolipid Gelation: Deciphering the Underlying Mechanism
2016Co-Authors: Parul Dubey, Sugam Kumar, V K Aswal, Sapna Ravindranathan, P R Rajamohanan, Asmita Prabhune, Anuya NisalAbstract:Silk fibroin (SF) protein, produced by silkworm Bombyx mori, is a promising biomaterial, while sophorolipid (SL) is an amphiphilic functional biosurfactant synthesized by nonpathogenic yeast Candida bombicola. SL is a mixture of two forms, acidic (ASL) and lactonic (LSL), which when added to SF results in accelerated gelation of silk fibroin. LSL is known to have multiple biological functionalities and hence hydrogels of these green molecules have promising applications in the biomedical sector. In this work, SANS, NMR, and rheology are employed to examine the assembling properties of individual and mixed SLs and their interactions with SF to understand the Mechanism that leads to rapid gelation. SANS and NMR studies show that ASL assembles to form charged micelles, while LSL forms micellar assemblies and aggregates of a mass fractal nature. ASL and LSL together form larger mixed micelles, all of which interact differently with SF. It is shown that preferential binding of LSL to SF causes rapid unfolding of the SF chain leading to the formation of intermolecular beta sheets, which trigger fast gelation. Based on the observations, a Mechanism for gelation of SF in the presence of different sophorolipids is proposed
Donald M Bers - One of the best experts on this subject based on the ideXlab platform.
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sarcoplasmic reticulum ca2 release causes myocyte depolarization Underlying Mechanism and threshold for triggered action potentials
Circulation Research, 2000Co-Authors: Klaus Schlotthauer, Donald M BersAbstract:Spontaneous sarcoplasmic reticulum (SR) Ca(2+) release causes delayed afterdepolarizations (DADs) via Ca(2+)-induced transient inward currents (I:(ti)). However, no quantitative data exists regarding (1) Ca(2+) dependence of DADs, (2) Ca(2+) required to depolarize the cell to threshold and trigger an action potential (AP), or (3) relative contributions of Ca(2+)-activated currents to DADs. To address these points, we evoked SR Ca(2+) release by rapid application of caffeine in indo 1-AM-loaded rabbit ventricular myocytes and measured caffeine-induced DADs (cDADs) with whole-cell current clamp. The SR Ca(2+) load of the myocyte was varied by different AP frequencies. The cDAD amplitude doubled for every 88+/-8 nmol/L of Delta[Ca(2+)](i) (simple exponential), and the Delta[Ca(2+)](i) threshold of 424+/-58 nmol/L was sufficient to trigger an AP. Blocking Na(+)-Ca(2+) exchange current (I(Na/Ca)) by removal of [Na](o) and [Ca(2+)](o) (or with 5 mmol/L Ni(2+)) reduced cDADs by >90%, for the same Delta[Ca(2+)](i). In contrast, blockade of Ca(2+)-activated Cl(-) current (I(Cl(Ca))) with 50 micromol/L niflumate did not significantly alter cDADs. We conclude that DADs are almost entirely due to I(Na/Ca), not I(Cl(Ca)) or Ca(2+)-activated nonselective cation current. To trigger an AP requires 30 to 40 micromol/L cytosolic Ca(2+) or a [Ca(2+)](i) transient of 424 nmol/L. Current injection, simulating I(ti)s with different time courses, revealed that faster I:(ti)s require less charge for AP triggering. Given that spontaneous SR Ca(2+) release occurs in waves, which are slower than cDADs or fast I(ti)s, the true Delta[Ca(2+)](i) threshold for AP activation may be approximately 3-fold higher in normal myocytes. This provides a safety margin against arrhythmia in normal ventricular myocytes.
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sarcoplasmic reticulum ca2 release causes myocyte depolarization Underlying Mechanism and threshold for triggered action potentials
Circulation Research, 2000Co-Authors: Klaus Schlotthauer, Donald M BersAbstract:Abstract —Spontaneous sarcoplasmic reticulum (SR) Ca 2+ release causes delayed afterdepolarizations (DADs) via Ca 2+ -induced transient inward currents ( I ti ). However, no quantitative data exists regarding (1) Ca 2+ dependence of DADs, (2) Ca 2+ required to depolarize the cell to threshold and trigger an action potential (AP), or (3) relative contributions of Ca 2+ -activated currents to DADs. To address these points, we evoked SR Ca 2+ release by rapid application of caffeine in indo 1-AM–loaded rabbit ventricular myocytes and measured caffeine-induced DADs (cDADs) with whole-cell current clamp. The SR Ca 2+ load of the myocyte was varied by different AP frequencies. The cDAD amplitude doubled for every 88±8 nmol/L of Δ[Ca 2+ ] i (simple exponential), and the Δ[Ca 2+ ] i threshold of 424±58 nmol/L was sufficient to trigger an AP. Blocking Na + -Ca 2+ exchange current ( I Na/Ca ) by removal of [Na] o and [Ca 2+ ] o (or with 5 mmol/L Ni 2+ ) reduced cDADs by >90%, for the same Δ[Ca 2+ ] i . In contrast, blockade of Ca 2+ -activated Cl – current ( I Cl(Ca) ) with 50 μmol/L niflumate did not significantly alter cDADs. We conclude that DADs are almost entirely due to I Na/Ca , not I Cl(Ca) or Ca 2+ -activated nonselective cation current. To trigger an AP requires 30 to 40 μmol/L cytosolic Ca 2+ or a [Ca 2+ ] i transient of 424 nmol/L. Current injection, simulating I ti s with different time courses, revealed that faster I ti s require less charge for AP triggering. Given that spontaneous SR Ca 2+ release occurs in waves, which are slower than cDADs or fast I ti s, the true Δ[Ca 2+ ] i threshold for AP activation may be ≈3-fold higher in normal myocytes. This provides a safety margin against arrhythmia in normal ventricular myocytes.
Anne L Mitchell - One of the best experts on this subject based on the ideXlab platform.
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Ectopic Posterior Pituitary Lobe and Periventricular Heterotopia: Cerebral Malformations with the Same Underlying Mechanism?
2015Co-Authors: Anne L Mitchell, Paul Q. Thomas, Margaret Zacharin, Ingrid E SchefferAbstract:with growth hormone deficiency and is part of the spectrum associated with septo-optic dysplasia. Some cases of septo-optic dysplasia are caused by homozygous mutations in the homeobox gene HESX1, whereas heterozygous mutations are associated with milder pheno-types. To date, HESX1 is the only gene associated with ectopic posterior pituitary lobe. We describe an association between ectopic posterior pituitary lobe and periventricular heterotopia in four children without classic features of septo-optic dysplasia and suggest possible mecha-nisms on the basis of a review of pituitary embryology and recent molecular genetic advances. METHODS: Among 20 children with ectopic posterior pituitary lobe, four had associated periventricular heterotopia. We herein review the clinical and MR imaging findings of these four children. Mutation screening of HESX1 was performed in two. RESULTS: All four children had growth hormone deficiency. None had visual or neurologic disturbances. MR images showed a range of pituitary appearances, with scattered discrete periventricular heterotopia in each case. Other abnormalities were limited to small suprasellar lipomas and callosal dysgenesis. A heterozygous HESX1 mutation was present in one case. CONCLUSION: The coexistence of ectopic posterior pituitary lobe and periventricular hete
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ectopic posterior pituitary lobe and periventricular heterotopia cerebral malformations with the same Underlying Mechanism
American Journal of Neuroradiology, 2002Co-Authors: Anne L Mitchell, Paul Q. Thomas, Margaret Zacharin, Ingrid E SchefferAbstract:BACKGROUND AND PURPOSE: Ectopic posterior pituitary lobe often occurs in children with growth hormone deficiency and is part of the spectrum associated with septo-optic dysplasia. Some cases of septo-optic dysplasia are caused by homozygous mutations in the homeobox gene HESX1, whereas heterozygous mutations are associated with milder phenotypes. To date, HESX1 is the only gene associated with ectopic posterior pituitary lobe. We describe an association between ectopic posterior pituitary lobe and periventricular heterotopia in four children without classic features of septo-optic dysplasia and suggest possible Mechanisms on the basis of a review of pituitary embryology and recent molecular genetic advances. METHODS: Among 20 children with ectopic posterior pituitary lobe, four had associated periventricular heterotopia. We herein review the clinical and MR imaging findings of these four children. Mutation screening of HESX1 was performed in two. RESULTS: All four children had growth hormone deficiency. None had visual or neurologic disturbances. MR images showed a range of pituitary appearances, with scattered discrete periventricular heterotopia in each case. Other abnormalities were limited to small suprasellar lipomas and callosal dysgenesis. A heterozygous HESX1 mutation was present in one case. CONCLUSION: The coexistence of ectopic posterior pituitary lobe and periventricular heterotopia suggests they have a common Underlying genetic basis that is due to gene expression at different locations and stages of development. The presence of a heterozygous HESX1 mutation in one case suggests this gene is important in the development of both ectopic posterior pituitary lobe and periventricular heterotopia and supports their place in the spectrum of septo-optic dysplasia. Further analysis of HESX1 and other genes in related developmental pathways will elucidate their roles in the development of both malformations.
