Sem. Bot. at the University of Nebraska

The Sem. Bot. (Seminarium Botanicum or Botanical Seminar) began in 1886 as an association of seven students (two Juniors, two Sophomores, and three Freshmen) at the University of Nebraska. They collected plants, campaigned against the “Lits and Philistines” (literary and classical studies), and controlled the Science Club and several debating societies. “Show me a Lit” was their rallying cry. Charles Bessey was a force in organizing and developing the Sem. Bot

Discriminating between viable and membrane-damaged cells of the plant pathogen Xylella fastidiosa.

Xylella fastidiosa is a plant pathogenic bacterium with devastating consequences to several crops of economic importance across the world. While this pathogen has been studied for over a century in the United States, several aspects of its biology remain to be investigated. Determining the physiological state of bacteria is essential to understand the effects of its interactions with different biotic and abiotic factors on cell viability. Although X. fastidiosa is culturable, its slow growing nature makes this technique cumbersome to assess the physiological state of cells present in a given environment. PMA-qPCR, i.e. the use of quantitative PCR combined with the pre-treatment of cells with the dye propidium monoazide, has been successfully used in a number of studies on human pathogens to calculate the proportion of viable cells, but has less frequently been tested on plant pathogens. We found that the use of a version of PMA, PMAxx, facilitated distinguishing between viable and non-viable cells based on cell membrane integrity in vitro and in planta. Additional experiments comparing the number of culturable, viable, and total cells in planta would help further confirm our initial results. Enhancers, intended to improve the efficacy of PMAxx, were not effective and appeared to be slightly toxic to X. fastidiosa

Cisternal Organization of the Endoplasmic Reticulum during Mitosis

The endoplasmic reticulum (ER) of animal cells is a single, dynamic, and continuous membrane network of interconnected cisternae and tubules spread out throughout the cytosol in direct contact with the nuclear envelope. During mitosis, the nuclear envelope undergoes a major rearrangement, as it rapidly partitions its membrane-bound contents into the ER. It is therefore of great interest to determine whether any major transformation in the architecture of the ER also occurs during cell division. We present structural evidence, from rapid, live-cell, three-dimensional imaging with confirmation from high-resolution electron microscopy tomography of samples preserved by high-pressure freezing and freeze substitution, unambiguously showing that from prometaphase to telophase of mammalian cells, most of the ER is organized as extended cisternae, with a very small fraction remaining organized as tubules. In contrast, during interphase, the ER displays the familiar reticular network of convolved cisternae linked to tubules

Role of disclinations in determining the morphology of deformable fluid interfaces

We study the equilibrium shapes of vesicles, with an in-plane nematic order, using a Monte-Carlo scheme and show that highly curved shapes, like tubes and discs, with a striking similarity to the structures engendered by certain curvature sensing peripheral membrane proteins, can be spontaneously generated by anisotropic directional curvature with nematic disclinations playing and important role. We show that the coupling between nematic order and local curvature could lead to like defects moving towards each other and unlike defects moving away, in turn leading to tube formation. Thermally induced defect pair production lead to branched tubular structures. It is also shown that helical arrangement of the membrane tubes, with nematic field spiraling around it, is a dominant soft mode of the system.Comment: 6 Figures; Soft Matter, Advance Article 201

Formation of the postmitotic nuclear envelope from extended ER cisternae precedes nuclear pore assembly

During mitosis, the nuclear envelope merges with the endoplasmic reticulum (ER), and nuclear pore complexes are disassembled. In a current model for reassembly after mitosis, the nuclear envelope forms by a reshaping of ER tubules. For the assembly of pores, two major models have been proposed. In the insertion model, nuclear pore complexes are embedded in the nuclear envelope after their formation. In the prepore model, nucleoporins assemble on the chromatin as an intermediate nuclear pore complex before nuclear envelope formation. Using live-cell imaging and electron microscope tomography, we find that the mitotic assembly of the nuclear envelope primarily originates from ER cisternae. Moreover, the nuclear pore complexes assemble only on the already formed nuclear envelope. Indeed, all the chromatin-associated Nup 107–160 complexes are in single units instead of assembled prepores. We therefore propose that the postmitotic nuclear envelope assembles directly from ER cisternae followed by membrane-dependent insertion of nuclear pore complexes

A 3D analysis of yeast ER structure reveals how ER domains are organized by membrane curvature

Electron tomography of continuous ER domains during budding shows that reticulons and Yop1 stabilize rather than generate membrane curvature in this organelle

Racial, Ethnic, and Sex Disparities in Patients With STEMI and Cardiogenic Shock

OBJECTIVES: The aim of this study was to evaluate the combined impact of race, ethnicity, and sex on in-hospital outcomes using data from the National Inpatient Sample. BACKGROUND: Cardiogenic shock (CS) is a major cause of mortality following ST-segment elevation myocardial infarction (STEMI). Early revascularization reduces mortality in such patients. Mechanical circulatory support (MCS) devices are increasingly used to hemodynamically support patients during revascularization. Little is known about racial, ethnic, and sex disparities in patients with STEMI and CS. METHODS: The National Inpatient Sample was queried from January 2006 to September 2015 for hospitalizations with STEMI and CS. The associations between sex, race, ethnicity, and outcomes were examined using complex-samples multivariate logistic or generalized linear model regressions. RESULTS: Of 159,339 patients with STEMI and CS, 57,839 (36.3%) were women. In-hospital mortality was higher for all women (range 40% to 45.4%) compared with men (range 30.4% to 34.7%). Women (adjusted odds ratio [aOR]: 1.11; 95% confidence interval [CI]: 1.06 to 1.16; p \u3c 0.001) as well as Black (aOR: 1.18; 95% CI: 1.04 to 1.34; p = 0.011) and Hispanic (aOR: 1.19; 95% CI: 1.06 to 1.33; p = 0.003) men had higher odds of in-hospital mortality compared with White men, with Hispanic women having the highest odds of in-hospital mortality (aOR: 1.46; 95% CI: 1.26 to 1.70; p \u3c 0.001). Women were older (age: 69.8 years vs. 63.2 years), had more comorbidities, and underwent fewer invasive cardiac procedures, including revascularization, right heart catheterization, and MCS. CONCLUSIONS: There are significant racial, ethnic, and sex differences in procedural utilization and clinical outcomes in patients with STEMI and CS. Women are less likely to undergo invasive cardiac procedures, including revascularization and MCS. Women as well as Black and Hispanic patients have a higher likelihood of death compared with White men

ER sliding dynamics and ER–mitochondrial contacts occur on acetylated microtubules

Movement of the ER and mitochondria is coupled by limited interactions of the ER with a subset of posttranslationally modified microtubules

The endogenous caspase-8 inhibitor c-FLIPL regulates ER morphology and crosstalk with mitochondria

Components of the death receptors-mediated pathways like caspase-8 have been identified in complexes at intracellular membranes to spatially restrict the processing of local targets. In this study, we report that the long isoform of the cellular FLICE-inhibitory protein (c-FLIPL), a well- known inhibitor of the extrinsic cell death initiator caspase-8, localizes at the endoplasmic reticulum (ER) and mitochondria-associated membranes (MAMs). ER morphology was disrupted and ER Ca2+-release as well as ER-mitochondria tethering were decreased in c-FLIP-/- mouse embryonic fibroblasts (MEFs). Mechanistically, c-FLIP ablation resulted in enhanced basal caspase-8 activation and in caspase-mediated processing of the ER-shaping protein reticulon-4 (RTN4) that was corrected by re-introduction of c-FLIPL and caspase inhibition, resulting in the recovery of a normal ER morphology and ER-mitochondria juxtaposition. Thus, the caspase-8 inhibitor c-FLIPL emerges as a component of the MAMs signaling platforms, where caspases appear to regulate ER morphology and ER-mitochondria crosstalk by impinging on ER-shaping proteins like the RTN4