Propulsion and Space Vehicle Systems Analysis Program Tensor I, volume I Technical report no. 341

Computer program for space vehicle and propulsion systems analysi

Cell-type-specific metabolic labeling, detection and identification of nascent proteomes in vivo

A big challenge in proteomics is the identification of cell-type-specific proteomes in vivo. This protocol describes how to label, purify and identify cell-type-specific proteomes in living mice. To make this possible, we created a Cre-recombinase-inducible mouse line expressing a mutant methionyl-tRNA synthetase (L274G), which enables the labeling of nascent proteins with the non-canonical amino acid azidonorleucine (ANL). This amino acid can be conjugated to different affinity tags by click chemistry. After affinity purification (AP), the labeled proteins can be identified by tandem mass spectrometry (MS/MS). With this method, it is possible to identify cell-type-specific proteomes derived from living animals, which was not possible with any previously published method. The reduction in sample complexity achieved by this protocol allows for the detection of subtle changes in cell-type-specific protein content in response to environmental changes. This protocol can be completed in ~10 d (plus the time needed to generate the mouse lines, the desired labeling period and MS analysis

Influence of Grazing on Soil Microbial Communities on a Mixed Grass Prairie Ecosystem

The grazing of ungulates is the predominant use for much of the world\u27s semiarid rangelands. Grazing these lands can result in significant changes not only in the vegetation community but also in the soil physical, chemical and biological properties. Changes in soil physical and chemical properties and the plant community can potentially lead to changes in soil microbial communities which may have long-term ramifications for nutrient cycling and carbon (C) sequestration. The objective of this research was to ascertain the influence of three long-term grazing treatments on soil microbial communities

Febrile Convulsions as a Problem in Waiting Times

A simple hypothesis on the occurrence of febrile convulsions is posed. This is (1) that certain children are genetically predisposed, and (2) that for such children, the probability of the first attack occurring in year 1, 2, etc., is essentially constant up to the end of the period during which the attacks can take place. These assumptions lead to a probability model which agrees well with data on age at first attack in the Town of Tecumseh, Mich. It appears that susceptibility does not gradually diminish, but rather disappears abruptly. The calculation yields an estimate of the proportion of children, among those susceptible, who will have at least one attack before they exceed the age of suceptibility. Penetrance of the condition, measured in this way, is nearly complete: 93.8% will have manifested the condition by age 7. The population frequency of the susceptible type of child is found to be 3.90%. If one assumes the simple dominant mode of inheritance of Frantzen et al. to be correct, this estimate of population frequency leads to an estimate of the gene frequency. This is approximately p = 0.02. The homozygote would therefore have a frequency of 4 per 10,000. Some speculations on verifying this theory of inheritance by identifying the homozygote are given. RÉSUMÉ On Émet une hypothÈse simple sur la survenue des convulsions fÉbriles, À savoir (1) que certains enfants sont gÉnÉtiquement prÉdisposÉs et (2) que pour ces enfants la probabilitÉ d'apparition de la premiÈre crise dans la premiÈre, la seconde annÉe, etc. est essentiellement constante jusqu'À la fin de la pÉriode pendant laquelle les crises peuvent survenir. De telles suppositions conduisent ÀÉtablir un modÈle de probabilite qui concorde bien avec les donnÉes sur l'Âge de la premiÈre crise, dans la ville de Techumseh, dans le Michigan. Il en ressort que cette prÉdisposition ne diminue pas progressivement, mais au contraire, disparaÎt brusquement. Les calculs permettent d'estimer la proportion d'enfants prÉdisposÉs qui auront au moins une crise, avant d'avoir dÉpassÉ l'Âge limite de la prÉdisposition. La pÉnÉtrance de cette condition, ainsi ÉvaluÉe, est presque complÈte: 93.8% des enfants auront manifestÉ cette condition À l'Âge de 7 ans. La frÉquence des enfants prÉdisposÉs dans la population est de 3.90%. Si l'on considÈre que le mode d'hÉrÉditÉ dominante simple de Frantzen est valable, cette estimation de la frÉquence dans la population conduit À une Évaluation de la frÉquence du gÈne. Celle-ci est approximativement de p = 0.02; l'homozygote aurait done une frÉquence de 4/10.000. Les possibilitÉs de vÉrifier cette thÉorie des modalitÉs hÉrÉditaires par l'identification de l'homozygote sont discutÉes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65705/1/j.1528-1157.1972.tb05265.x.pd

Impact of Grazing Management Strategies on Carbon Sequestration in a Semi-Arid Rangeland, USA

The effects of 12 years of grazing management strategies on carbon (C) distribution and sequestration were assessed on a semi-arid mixed-grass prairie in Wyoming, USA. Five grazing treatments were evaluated: non-grazed exclosures; continuous, season-long grazing at a light (22 steer-days ha-1) stocking rate; and, rotationally-deferred, short-duration rotation, and continuous, season-long grazing, all three at a heavy stocking rate (59 steer-days ha-1). Non-grazed exclosures exhibited a large buildup of dead plant material (72% of total aboveground plant matter) and forb biomass represented a large component (35%) of the plant community. Stocking rate, but not grazing strategy, changed plant community composition and decreased surface litter. Light grazing decreased forbs and increased cool-season mid-grasses, resulting in a highly diversified plant community and the highest total production of grasses. Heavy grazing increased warm-season grasses at the expense of the cool-season grasses, which decreased total forage production and opportunity for early season grazing. Compared to the exclosures, all grazing treatments resulted in significantly higher levels of C (6000-9000 kg ha-1) in the surface 15 cm of the soil. Higher levels of soil C with grazing are likely the result of faster litter decomposition and recycling, and redistribution of C within the 0-60 cm plant-soil system. Grazing at an appropriate stocking rate had beneficial effects on plant composition, forage production, and soil C sequestration. Without grazing, deterioration of the plant-soil system is indicated

Inhibitory top-down projections from zona incerta mediate neocortical memory

Top-down projections convey a family of signals encoding previous experiences and current aims to the sensory neocortex, where they converge with external bottom-up information to enable perception and memory. Whereas top-down control has been attributed to excitatory pathways, the existence, connectivity, and information content of inhibitory top-down projections remain elusive. Here, we combine synaptic two-photon calcium imaging, circuit mapping, cortex-dependent learning, and chemogenetics in mice to identify GABAergic afferents from the subthalamic zona incerta as a major source of top-down input to the neocortex. Incertocortical transmission undergoes robust plasticity during learning that improves information transfer and mediates behavioral memory. Unlike excitatory pathways, incertocortical afferents form a disinhibitory circuit that encodes learned top-down relevance in a bidirectional manner where the rapid appearance of negative responses serves as the main driver of changes in stimulus representation. Our results therefore reveal the distinctive contribution of long-range (dis)inhibitory afferents to the computational flexibility of neocortical circuits

Subcellular sequencing of single neurons reveals the dendritic transcriptome of GABAergic interneurons

Although mRNAs are localized in the processes of excitatory neurons, it is still unclear whether interneurons also localize a large population of mRNAs. In addition, the variability in the localized mRNA population within and between cell-types is unknown. Here we describe the unbiased transcriptomic characterization of the subcellular compartments of hundreds of single neurons. We separately profiled the dendritic and somatic transcriptomes of individual rat hippocampal neurons and investigated mRNA abundances in the soma and dendrites of single glutamatergic and GABAergic neurons. We found that, like their excitatory counterparts, interneurons contain a rich repertoire of ~4000 mRNAs. We observed more cell type-specific features among somatic transcriptomes than their associated dendritic transcriptomes. Finally, using cell-type specific metabolic labelling of isolated neurites, we demonstrated that the processes of Glutamatergic and, notably, GABAergic neurons were capable of local translation, suggesting mRNA localization and local translation is a general property of neurons