Modeling Vegetation-Erosion Dynamics using Differential Equations with Human Factors

The effects of soil erosion are often devastating. Plants can reduce erosion by slowing runoff and reinforcing soil using its roots. In this project, we investigate the dynamic relationship between vegetation and erosion processes. We assume an inverse relationship between vegetation density and soil erosion: that is, an increase in vegetation cover reverses soil degradation and a decrease in vegetation cover intensifies the problem of erosion. We also assume that human activities (like logging, road-building) affect both vegetation development and resilience against erosion. Our model for the vegetation-erosion dynamics is a two-dimensional nonlinear system of differential equations with logistic growth on both variables. Equilibrium and nullcline analysis methods are applied to determine all possible dynamic scenarios between vegetation and erosion. The resulting parameter conditions can be used to analyze bifurcations on the vegetation and erosion dynamics

The Histamine H4 Receptor Mediates Inflammation and Pruritus in Th2-Dependent Dermal Inflammation

The role of histamine H4 receptor (H4R) was investigated in a T-helper type 2 (Th2)-cell-mediated mouse skin inflammation model that mimics several of the features of atopic dermatitis. Treatment with two specific H4R antagonists before challenge with FITC led to a significant reduction in ear edema, inflammation, mast cell, and eosinophil infiltration. This was accompanied by a reduction in the levels of several cytokines and chemokines in the ear tissue. Upon ex vivo antigen stimulation of lymph nodes, H4R antagonism reduced lymphocyte proliferation and IL-4, IL-5, and IL-17 levels. One explanation for this finding is that lymph nodes from animals dosed with the H4R antagonist, JNJ 7777120, contained a lower number of FITC-positive dendritic cells. The effect of H4R antagonism on dendritic cell migration in vivo may be an indirect result of the reduction in tissue cytokines and chemokines or a direct effect on chemotaxis. In addition to anti-inflammatory effects, JNJ 7777120 also significantly inhibited the pruritus shown in the model. Therefore, the dual effects of H4R antagonists on pruritus and Th2-cell-mediated inflammation point to their therapeutic potential for the treatment of Th2-mediated skin disorders, including atopic dermatitis

Development of Low-Cost Micromanipulation Systems for Small Extraterrestrial Samples

The analysis of microscale to mm-scale astromaterials often involves the transfer of samples from storage or collection substrates to analytical substrates. These transfers are accomplished by hand (via tweezers or fine-tipped needles) or by utilizing micromanipulation instruments. Freehand manipulation of small particles is extremely challenging due to involuntary hand tremors on the order of 100m and due to the triboelectric charging induced by frequent contact between the manipulation tool and the support substrate. Months or years of practice may be required before an investigator develops the necessary experience to confidently transfer a 10-20m particle in this manner. Handling even mm-sized particles with fine-tipped tweezers can be challenging, due to the inability to precisely control the force with which grains are being held. Mechanical, hydraulic, and motorized/electrical micromanipulators enable the precise handling of microscale samples and are often utilized in laboratories where frequent small sample preparation is required. However, the price of such instruments (~ $10,000 to$100,000) makes them cost-prohibitive for some institutions. Graduate students or early-career scientists interested in conducting research on interplanetary dust particles, Itokawa particles returned by Hayabusa, or future samples returned by OSIRIS-REx or Hayabusa2 may experience difficulty in justifying the expense of a micromanipulator to their advisors or principle investigators. Johnson Space Centers Astromaterials Acquisition and Curation Office and the Lunar and Planetary Institute conduct annual training for early career scientists and for investigators that require experience with handling of small extraterrestrial samples. In support of this training, we have been developing low-cost mechanical alternatives to expensive micromanipulators that training participants can implement in their respective facilities

Enrichment for chemoresistant ovarian cancer stem cells from human cell lines

Cancer stem cells (CSCs) are defined as a subset of slow cycling and undifferentiated cells that divide asymmetrically to generate highly proliferative, invasive, and chemoresistant tumor cells. Therefore, CSCs are an attractive population of cells to target therapeutically. CSCs are predicted to contribute to a number of types of malignancies including those in the blood, brain, lung, gastrointestinal tract, prostate, and ovary. Isolating and enriching a tumor cell population for CSCs will enable researchers to study the properties, genetics, and therapeutic response of CSCs. We generated a protocol that reproducibly enriches for ovarian cancer CSCs from ovarian cancer cell lines (SKOV3 and OVCA429). Cell lines are treated with 20 µM cisplatin for 3 days. Surviving cells are isolated and cultured in a serum-free stem cell media containing cytokines and growth factors. We demonstrate an enrichment of these purified CSCs by analyzing the isolated cells for known stem cell markers Oct4, Nanog, and Prom1 (CD133) and cell surface expression of CD177 and CD133. The CSCs exhibit increased chemoresistance. This method for isolation of CSCs is a useful tool for studying the role of CSCs in chemoresistance and tumor relapse

Lessons in photoprotection from nature’s sunscreens : an investigation of photoactive motifs in synthetic molecules

At present there are only a few UVA (315-400 nm) absorbers available for sunscreen formulations even though such compounds are essential for effective protection against the harms of solar radiation. The four major aims of this research are 1) to understand how the naturally occurring photoprotective motif (N/O=C-C=C-N-) can be scaffolded into synthetic molecules, 2) to propose new molecules for the global bank of UVA filters that is available to sunscreen manufacturers, 3) to characterise how a subset of molecules disperse excess energy after they are energetically excited by light, and 4) to investigate a natural product pathway in bacteria to produce new ‘natural’ and ‘unnatural’ sunscreens. These aims are achieved by a combination of experiment and theory, covering the natural product molecules, synthetic analogues and new hybrid sunscreens. • In Chapter 1 an introduction is presented with reference to photochemical theory. • In Chapter 2, the materials and methods used are in this work are detailed with reference to all relevant spectra in the Appendix. • Both Chapters 3 and 5 refer to MAAs, a family of molecules characteristic of high UV marine environments. In Chapter 3 it is studied how sunscreen active ingredients absorb light and then relax from excite d energetic states by dispersing excess energy in primarily non - radiative ways. In Chapter 5, the modification of a biosynthetic pathway of exemplar MAA, shinorine , is explored. • In Chapter 4, it is shown how new hybrid molecules, designed by combining avobenzone and cinnamate moti fs , match or exceed the photostability of industry standard avobenzone in polar, non - protic solvents. A complete picture of sunscreening ability must consider the long - and short - term behaviour of molecules during and after interaction with light. The longer time studies in solar - like conditions track the fate of molecules on the minute to hour timescale; while ultrafast transient absorption spectroscop ies on the femto - to nanosecond scale are used to track the energy flow shortly after photoexcitation , complemented by computational models. In short, this work contributes to the understanding of sunscreening molecules and adds new compounds to our photoprotectant library. The techniques used to quantify photoprotection could be extended towards near - to - life conditions. The synthetic methods could be optimised to further improve the yields and scope . The molecular biology approach could be expanded to include a range of control s , an improved understanding of the limits of detection and other enzymes of interest

Trichostatin A Inhibits Corneal Haze \u3cem\u3ein vitro\u3c/em\u3e and \u3cem\u3ein vivo\u3c/em\u3e

PURPOSE. Trichostatin A (TSA), a histone deacetylase inhibitor, has been shown to suppress TGF- –induced fibrogenesis in many nonocular tissues. The authors evaluated TSA cytotoxicity and its antifibrogenic activity on TGF- –driven fibrosis in the cornea with the use of in vitro and in vivo models. METHODS. Human corneal fibroblasts (HSFs) were used for in vitro studies, and New Zealand White rabbits were used for in vivo studies. Haze in the rabbit cornea was produced with photorefractive keratectomy (PRK) using excimer laser. Trypan blue exclusion and MTT assays evaluated TSA cytotoxicity to the cornea. Density of haze in the rabbit eye was graded with slit lamp biomicroscopy. Real-time PCR, immunoblotting, or immunocytochemistry was used to measure -smooth muscle actin (SMA), fibronectin, and collagen type IV mRNA or protein levels. TUNEL assay was used to detect cell death. RESULTS. TSA concentrations of 250 nM or less were noncytotoxic and did not alter normal HSF morphology or proliferation. TGF- 1 treatment of HSF significantly increased mRNA and protein levels of SMA (9-fold), fibronectin (2.5-fold), and collagen type IV (2-fold). TSA treatment showed 60% to 75% decreases in TGF- 1–induced SMA and fibronectin mRNA levels and 1.5- to 3.0-fold decreases in protein levels but had no effect on collagen type IV mRNA or protein levels in vitro. Two-minute topical treatment of TSA on rabbit corneas subjected to 9 D PRK significantly decreased corneal haze in vivo. CONCLUSIONS. TSA inhibits TGF- 1–induced accumulation of extracellular matrix and myofibroblast formation in the human cornea in vitro and markedly decreases haze in rabbit cornea in vivo

Investigating Astromaterials Curation Applications for Dexterous Robotic Arms

The Astromaterials Acquisition and Curation office at NASA Johnson Space Center is currently investigating tools and methods that will enable the curation of future astromaterials collections. Size and temperature constraints for astromaterials to be collected by current and future proposed missions will require the development of new robotic sample and tool handling capabilities. NASA Curation has investigated the application of robot arms in the past, and robotic 3-axis micromanipulators are currently in use for small particle curation in the Stardust and Cosmic Dust laboratories. While 3-axis micromanipulators have been extremely successful for activities involving the transfer of isolated particles in the 5-20 micron range (e.g. from microscope slide to epoxy bullet tip, beryllium SEM disk), their limited ranges of motion and lack of yaw, pitch, and roll degrees of freedom restrict their utility in other applications. For instance, curators removing particles from cosmic dust collectors by hand often employ scooping and rotating motions to successfully free trapped particles from the silicone oil coatings. Similar scooping and rotating motions are also employed when isolating a specific particle of interest from an aliquot of crushed meteorite. While cosmic dust curators have been remarkably successful with these kinds of particle manipulations using handheld tools, operator fatigue limits the number of particles that can be removed during a given extraction session. The challenges for curation of small particles will be exacerbated by mission requirements that samples be processed in N2 sample cabinets (i.e. gloveboxes). We have been investigating the use of compact robot arms to facilitate sample handling within gloveboxes. Six-axis robot arms potentially have applications beyond small particle manipulation. For instance, future sample return missions may involve biologically sensitive astromaterials that can be easily compromised by physical interaction with a curator; other potential future returned samples may require cryogenic curation. Robot arms may be combined with high resolution cameras within a sample cabinet and controlled remotely by curator. Sophisticated robot arm and hand combination systems can be programmed to mimic the movements of a curator wearing a data glove; successful implementation of such a system may ultimately allow a curator to virtually operate in a nitrogen, cryogenic, or biologically sensitive environment with dexterity comparable to that of a curator physically handling samples in a glove box

Meca500 Robotic Arm Developments Towards Astromaterials Curation Applications

As a part of the ongoing efforts to develop new curation tools and techniques for astromaterials within the Astromaterials Acquisition and Curation office at NASAs Johnson Space Center, we are developing a variety of manually and electrically controlled micromanipulation systems. Most current techniques require manual manipulation, and in some cases the manipulation task is being done entirely freehand. The motorized systems avail-able are restricted to three degrees of freedom and use proprietary control systems. For example, the MicroSupport AxisPro manipulation system currently used in microscale particle experiments is limited in its range of motion, as it can only move the manipulators in a three axis Cartesian range over a predetermined area above microscope slides. While having an efficient user interface, the control system is proprietary and prevents custom development and optimization to extend the viable applications of the system. In order to address some of these limitations, we have been testing robotic designs with multiple degrees of freedom and of a variety of designs. We are currently investigating the Meca500 robotic arm by Mecademic as a potential manipulation system to overcome some of these obstacles