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71.
The inner ear and cochleovestibular ganglion (CVG) derive from a specialized region of head ectoderm termed the otic placode. During embryogenesis, the otic placode invaginates into the head to form the otic vesicle (OV), the primordium of the inner ear and CVG. Non-autonomous cell signaling from the hindbrain to the OV is required for inner ear morphogenesis and neurogenesis. In this study, we show that neuroepithelial cells (NECs), including neural crest cells (NCCs), can contribute directly to the OV from the neural tube. Using Wnt1-Cre, Pax3(Cre/+) and Hoxb1(Cre/+) mice to label and fate map cranial NEC lineages, we have demonstrated that cells from the neural tube incorporate into the otic epithelium after otic placode induction has occurred. Pax3(Cre/+) labeled a more extensive population of NEC derivatives in the OV than did Wnt1-Cre. NEC derivatives constitute a significant population of the OV and, moreover, are regionalized specifically to proneurosensory domains. Descendents of Pax3(Cre/+) and Wnt1-Cre labeled cells are localized within sensory epithelia of the saccule, utricle and cochlea throughout development and into adulthood, where they differentiate into hair cells and supporting cells. Some NEC derivatives give rise to neuroblasts in the OV and CVG, in addition to their known contribution to glial cells. This study defines a dual cellular origin of the inner ear from sensory placode ectoderm and NECs, and changes the current paradigm of inner ear neurosensory development. 相似文献
72.
Aggarwal S Yurlova L Snaidero N Reetz C Frey S Zimmermann J Pähler G Janshoff A Friedrichs J Müller DJ Goebel C Simons M 《Developmental cell》2011,21(3):445-456
The insulating layers of myelin membrane wrapped around axons by oligodendrocytes are essential for the rapid conduction of nerve impulses in the central nervous system. To fulfill this function as an electrical insulator, myelin requires a unique lipid and protein composition. Here we show that oligodendrocytes employ a barrier that functions as a physical filter to generate the lipid-rich myelin-membrane sheets. Myelin basic protein (MBP) forms this molecular sieve and restricts the diffusion of proteins with large cytoplasmic domains into myelin. The barrier is generated from MBP molecules that line the entire sheet and is, thus, intimately intertwined with the biogenesis of the polarized cell surface. This system might have evolved in oligodendrocytes in order to generate an anisotropic membrane organization that facilitates the assembly of highly insulating lipid-rich membranes. 相似文献
73.
Aggarwal S 《Nature biotechnology》2011,29(12):1083-1089
74.
Parkash R Aggarwal DD Kalra B Ranga P 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2011,158(4):531-541
Drosophila busckii is more abundant under colder and drier montane habitats in the western Himalayas as compared to Drosophila melanogaster but the mechanistic basis of such climatic adaptations is largely unknown. We tested the hypothesis whether genetic variation or phenotypic plasticity of cuticular traits confer adaptive protection against desiccation stress in two melanic Drosophila species living under drier montane localities. For D. melanogaster, changes in melanisation are known to be associated with reduced water loss but there are no data on D. busckii. We investigated changes in body melanisation, cuticular lipids, desiccation resistance, water loss, extractable hemolymph volume (%), and dehydration tolerance in six sympatric populations of D. busckii and D. melanogaster over an altitudinal range of 640-2236 m. D. busckii is a melanic species but changes in cuticular water loss are negatively correlated with cuticular lipid mass and not with body melanisation. In D. melanogaster, there are no plastic effects (14-28 °C) for cuticular lipid mass but variation in body melanisation is associated with desiccation-related traits. Effects of organic solvents (hexane or chloroform: methanol), developmental plasticity and seasonal variation in cuticular lipids affect body water loss in D. busckii but no such changes occur in D. melanogaster. Thus, sympatric populations of D. busckii and D. melanogaster have evolved different water balance mechanisms under shared environmental conditions in the western Himalayas. Multiple measures of desiccation resistance in these species show clinal variation with altitude, consistent with adaptation to increased desiccation stress. 相似文献
75.
Agricultural biotechnology for crop improvement in a variable climate: hope or hype? 总被引:2,自引:0,他引:2
Developing crops that are better adapted to abiotic stresses is important for food production in many parts of the world today. Anticipated changes in climate and its variability, particularly extreme temperatures and changes in rainfall, are expected to make crop improvement even more crucial for food production. Here, we review two key biotechnology approaches, molecular breeding and genetic engineering, and their integration with conventional breeding to develop crops that are more tolerant of abiotic stresses. In addition to a multidisciplinary approach, we also examine some constraints that need to be overcome to realize the full potential of agricultural biotechnology for sustainable crop production to meet the demands of a projected world population of nine billion in 2050. 相似文献
76.
Connor Brennan Adeeti Aggarwal Rui Pei David Sussillo Alex Proekt 《PLoS computational biology》2023,19(1)
The relationship between neuronal activity and computations embodied by it remains an open question. We develop a novel methodology that condenses observed neuronal activity into a quantitatively accurate, simple, and interpretable model and validate it on diverse systems and scales from single neurons in C. elegans to fMRI in humans. The model treats neuronal activity as collections of interlocking 1-dimensional trajectories. Despite their simplicity, these models accurately predict future neuronal activity and future decisions made by human participants. Moreover, the structure formed by interconnected trajectories—a scaffold—is closely related to the computational strategy of the system. We use these scaffolds to compare the computational strategy of primates and artificial systems trained on the same task to identify specific conditions under which the artificial agent learns the same strategy as the primate. The computational strategy extracted using our methodology predicts specific errors on novel stimuli. These results show that our methodology is a powerful tool for studying the relationship between computation and neuronal activity across diverse systems. 相似文献
77.
Biphasic transport of water and dimethyl sulfoxide (Me(2)SO), a common cryoprotective agent (CPA), in algal cells was induced and measured on a cryoperfusion stage. A two-step experimental protocol provided data for the volumetric response of Chlorococcum (C.) texanum to impermeable and permeable solutes. First, the cells were exposed to a 500-mOsm sucrose solution, causing immediate shrinkage of the cell to a minimum equilibrium volume. Then an isoosmotic 200-mOsm/300-mOsm CPA/sucrose solution was introduced to the cells, resulting in increased cell volume to a new equilibrium state. Experiments were conducted at temperatures between -3 and 23 degrees C. Cell volumes were measured off-line by computer analysis of video images. A network thermodynamic model was fit to the transient volume data to determine permeabilities of C. texanum to water and Me(2)SO over the full temperature range, and results were calculated with two numeric methods. Biphasic transport was found to be slower at colder temperatures, with water entering the cell faster than Me(2)SO. Experimental results were also compared with data from similar experiments using methanol (MeOH) as the CPA. MeOH influx was calculated to be a magnitude larger than that of water. Additionally, MeOH permeability was at least three orders of magnitude greater than Me(2)SO permeability, and the difference in these solute permeabilities increased as temperature decreased. 相似文献
78.
Janke A Gullberg A Hughes S Aggarwal RK Arnason U 《Journal of molecular evolution》2005,61(5):620-626
Based on morphological analyses, extant members of the order Crocodylia are divided into three families, Alligatoridae, Crocodylidae,
and Gavialidae. Gavialidae includes one species, the gharial, Gavialis gangeticus. In this study we have examined crocodilian relationships in phylogenetic analyses of seven mitochondrial genomes that have
been sequenced in their entirety. The analyses did not support the morphologically acknowledged separate position of the gharial
in the crocodilian tree. Instead the gharial joined the false gharial (Tomistoma schlegelii) on a common branch that was shown to constitute a sister group to traditional Crocodylidae (less Tomistoma). Thus, the analyses suggest the recognition of only two Crocodylia families, Alligatoridae and Crocodylidae, with the latter
encompassing traditional Crocodylidae plus Gavialis/Tomistoma. A molecular dating of the divergence between Alligatoridae and Crocodylidae suggests that this basal split among recent
crocodilians took place ≈140 million years before present, at the Jurassic/Cretaceous boundary. The results suggest that at
least five crocodilian lineages survived the mass extinction at the KT boundary.
[Reviewing Editor: Dr. Nicolas Galtier] 相似文献
79.
Thermal preconditioning protocols for cardiac cells were identified which produce elevated HSP70 levels while maintaining high cell viability. Bovine aortic endothelial cells were heated with a water bath at temperatures ranging from 44 to 50 degrees C for periods of 1-30 min. Thermal stimulation protocols were determined which induce HSP70 expression levels ranging from 2.3 to 3.6 times the control while maintaining cell viabilities greater than 90%. An Arrhenius injury model fit to the cell damage data yielded values of A = 1.4 X 10(66) s(-1) and Ea = 4.1 X 10(5) J/mol. Knowledge of the injury parameters and HSP70 kinetics will enhance dosimetry guideline development for thermal stimulation of heat shock proteins expression in cardiac tissue. 相似文献
80.
Nair DT Johnson RE Prakash L Prakash S Aggarwal AK 《Structure (London, England : 1993)》2005,13(10):1569-1577
Human DNA polymerase iota (hPoliota), a member of the Y family of DNA polymerases, differs in remarkable ways from other DNA polymerases, incorporating correct nucleotides opposite template purines with a much higher efficiency and fidelity than opposite template pyrimidines. We present here the crystal structure of hPoliota bound to template G and incoming dCTP, which reveals a G.C + Hoogsteen base pair in a DNA polymerase active site. We show that the hPoliota active site has evolved to favor Hoogsteen base pairing, wherein the template sugar is fixed in a cavity that reduces the C1'-C1' distance across the nascent base pair from approximately 10.5 A in other DNA polymerases to 8.6 A in hPoliota. The rotation of G from anti to syn is then largely in response to this curtailed C1'-C1' distance. A G.C+ Hoogsteen base pair suggests a specific mechanism for hPoliota's ability to bypass N(2)-adducted guanines that obstruct replication. 相似文献