A microfluidic device for studying multiple distinct strains.

The study of cell responses to environmental changes poses many experimental challenges: cells need to be imaged under changing conditions, often in a comparative manner. Multiwell plates are routinely used to compare many different strains or cell lines, but allow limited control over the environment dynamics. Microfluidic devices, on the other hand, allow exquisite dynamic control over the surrounding conditions, but it is challenging to image and distinguish more than a few strains in them. Here we describe a method to easily and rapidly manufacture a microfluidic device capable of applying dynamically changing conditions to multiple distinct yeast strains in one channel. The device is designed and manufactured by simple means without the need for soft lithography. It is composed of a Y-shaped flow channel attached to a second layer harboring microwells. The strains are placed in separate microwells, and imaged under the exact same dynamic conditions. We demonstrate the use of the device for measuring protein localization responses to pulses of nutrient changes in different yeast strains.

A murine model for the study of molecular pathogenesis of radiation proctitis.

PURPOSE: To establish a novel mouse brachytherapy model with which to study the role of inflammation in the pathogenesis of radiation proctitis. METHODS AND MATERIALS: The distal rectums of BALB/c and C57BL/6 mice were irradiated with three to five fractions of 5.5 to 8 Gy. Tissues were harvested and evaluated for histopathology, using the radiation injury score (RIS). Cytokine mRNA expression was assessed using real-time PCR. RESULTS: Fifty percent of the mice treated with 22 Gy delivered in four fractions of 5.5 Gy died as a result of anorectal stenosis and distal bowel obstruction prior to the time of scheduled sacrifice, with a latency period of 4 to 10 weeks for the BALB/c and 3 to 4 weeks for the C57BL/6 mice. The RISs were 7, 12, and 8 at 2, 6, and 11 weeks, respectively, in the BALB/c mice and was 8.7 in the C57BL/6 mice on week 6. A 100- to 300-fold increase in interleukin-1beta (IL-1beta) (p = 0.04) and IL-6 mRNA (p = 0.07) and a 5- to 6-fold increase in transforming growth factor (TGF) and tumor necrosis factor-alpha mRNA expression levels (p < 0.001 and p = 0.01) were observed at 2 to 6 weeks after radiation. Cytokine mRNA tissue expression correlated positively with radiation dose (p < 0.0001). The RIS correlated well with IL-1beta and IL-6 mRNA levels in the BALB/c mice and with IL-1beta, IL-6, and TGF mRNA levels in C57BL/6 mice. Analysis of receiver operating characteristic curve showed that IL-1beta and IL-6 have the largest area under the curve and therefore are good markers of radiation proctitis (p < 0.001). CONCLUSIONS: Radiation-induced proctitis was associated with a dose-dependent, characteristic proinflammatory cytokine response pattern in a novel mouse model suitable for interventional studies.