2010 Presentations

SACNAS 2010 Abstracts

Expression of Clostridial Autolysins and Their Role in Toxin Release
Juan Ruiz, Wei Jen Lin

Clostridium botulinum is an anaerobic, Gram-positive bacteria that is responsible for the disease botulism, a deadly neurological and paralyzing disease. Due to the severe consequence that the botulinum neurotoxin (BoNT) poses to human and animal health, it is a major concern to public health officials and national defense agencies.  The BoNT toxin is produced during cell growth but the mechanism through which the toxin is released is not known, but can occur through lysis of the cell.  Our previous studies show that autolysins, which hydrolyze cell walls, may have caused cell leakage during early growth phases and led to the release of the toxin.   In this study, we investigated the role of these autolysins in relationship to the early release of the toxin.  The genomic sequence analysis showed thirty-four autolysins in C. botulinum, of which one-third are expressed in early growth phase based on our microarray study.  The first autolysin we chose to clone and characterize is the lysozyme CBO3274 which cleaves cell wall peptidoglycan.  The microarray study showed that this gene was found to be up-regulated during mid-log growth phase when toxin release was first detected.  The gene was amplified by PCR and then cloned to a cloning vector.  After verification of the gene sequence, the DNA was sub-cloned to an expression vector for expression and purification from an E. coli strain.  Purified clostridial lysozyme will be added back to Clostridium strains and examined for its role in the release of the toxin during early growth phases.


Sensor based on Single-mode–Multi-mode–Single-mode (SMS) Fiber Structure 
Michael Medrano and Ertan Salik

We investigated the sensitivity of an optical fiber sensor. An optical fiber is a thin thread of glass, and there are many different mechanisms for optical fiber sensors. The sensor we investigated is fabricated by splicing a short piece of multimode fiber between two pieces of single- mode fiber using a fusion splicer. This Single-mode–Multi-mode–Single-mode (SMS) structure works much like a modal Mach- Zehnder interferometer; light that travels in the single mode fiber splits its power into two modes of the multimode fiber. As light transitions back into the single-mode fiber, interference occurs. As stress or temperature is varied in and around the sensor, the effective refractive indices of the modes and to a lesser degree- the length of the path each mode travels must change, resulting in a change in relative phase of the modes and ultimately the transmission of light through the sensor.

Two sensors were created- both with a multimode fiber length of 10 cm. We used spontaneous emission of a semiconductor optical amplifier as the light source. Transmission was monitored with an optical spectrum analyzer. We placed the sensors on two fiber holders mounted on translation stages in order to determine the sensitivity to stress. Temperature sensitivity was determined by placing each sensor in a water- bath. We independently monitored the temperature with platinum-resistor type temperature probe.

The sensor showed sensitivity to both temperature and stress. However, sensitivity depends on the measurement wavelength. At a critical wavelength for the SMS structures, we confirmed that sensitivity was the highest. We predict about 1 microstrain stress resolution, and about 0.01 Kelvin temperature resolution. Because of the sinusoidal nature of the sensor response, the range of stress values and temperature values is rather limited, which requires further work.

MgO Composite Paints: Protecting Humans Against Harmful Bacteria
Authors: Jeanaye Mason, David I Zuniga, Daniel E Murrieta, Cal Poly Pomona
Mentors: Winny Dong, Tanya Faltens, Chemicals & Materials Engineering, Cal Poly Pomona


Traditional magnesium oxide (MgO) is an ionic crystalline solid with high bactericidal effectiveness. Other forms of MgO, amorphous MgO xerogels and aerogels can be synthesized via the sol-gel process. These novel structures are highly porous, giving them a greater surface area and concentration of structural defects than crystalline MgO. Increasing these two factors is expected to increase the bactericidal effectiveness of MgO.

In this work, we investigated the synthesis and properties of paints containing MgO xerogels and aerogels, which are of interest for aerospace and household applications.  We have found that MgO reacts with water-based paint, causing it to prematurely solidify.  To avoid this solidification, we investigated two anti-drying agents including glycerin and methanol.

We found that addition of 45-53wt% of glycerin to a paint of composition (list the wt% of each component in our paint) is effective in preventing solidification of the paint.

X-ray diffraction (XRD) analysis of the MgO paint composite indicates that MgO reacts with water in the paint to yield magnesium hydroxide (Mg(OH)2). In previous work, finely ground MgO powder suspended in aqueous solution was shown to maintain bactericidal effectiveness.  In these previous studies, possible structural changes resulting from MgO reacting with water were not investigated. 

Future work will focus on evaluating the bactericidal effectiveness of different magnesium oxides and hydroxides, the kinetics of the MgO reaction with water, and the incorporation of MgO into acrylic or oil based paints.     

OBESITY 2010 Abstract

The Effect of Resveratrol on the Differentiation of hMSCs 
Lindsay Peltz, Jessica Gomez, Negar Atashpanjeh, Frances Alencastro, and Yuanxiang Zhao

Resveratrol is a natural phytoalexin found in plants. It is a potent antioxidant and inflammatory suppressant that has been shown to extend lifespan in C. elegansDrosophila, fish, and mice. It has also been implicated to have anti-tumorigenic and anti-adipogenesis effects in animal or animal cell models. All of these attributes may potentially apply to humans as well. However, very limited research has been conducted using human cells. We have studied the effect of short- and long-term resveratrol exposure on human adipogenesis, osteogenesis, and adult stem cell self-renewal by using human mesenchymal stem cells (hMSCs) as our in vitro cell model. hMSCs are multipotent adult stem cells that normally reside in multiple tissues including bone marrow and adipose tissue. They can differentiate into many different mature cell types, including but not limited to adipocytes, osteoblasts, chrondrocytes, and neurons upon receiving appropriate external stimuli. Our study demonstrated that Resveratrol had dosage dependent effect on the development of hMSCs. At concentrations greater than 10uM Resveratrol was found to be toxic to hMSCs. At concentrations equal or higher than 5uM, it inhibited both osteogenic and adipogenic differentiation of hMSCs, whereas at concentrations equal or less than 1uM it significantly promoted osteogenic differentiation of hMSCs but slightly inhibited adipogenic differentiation of these cells. Our results suggest that Resveratrol could be a beneficial non-dietary supplement for treating human conditions including obesity and osteoporosis, however, cautions need to be taken on the recommended daily dosage of synthetic Resveratrol in order to achieve a balanced outcome.

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