ABSTRACT
An effort to understand the development of breast cancer motivates the study of mammary gland cells and their interactions with the extracellular matrix. A mixture of mammary gland epithelial cells (normal murine mammary gland), collagen, and fluorescent beads was loaded into microchannels and observed via four-dimensional imaging. Collagen concentrations of 1.3, 2, and 3 mg/mL were used. The displacements of the beads were used to calculate strains in the 3D matrix. To ensure physiologically relevant materials properties for analysis, the collagen was characterized using independent tensile testing with strain rates in the range of those measured in the cell-gel constructs. 3D elastic theory for an isotropic material was employed to calculate the stress. The technique presented adds to the field of measuring cell-generated stresses by providing the capability of measuring 3D stresses locally around a single cell and using physiologically relevant materials properties for analysis. The highest strains were observed in the most compliant matrix. Additionally, the stresses fluctuated over time due to the cells' interaction with the collagen matrix.
Subject(s)
Collagen , Mammary Glands, Animal/cytology , Tissue Scaffolds/chemistry , Animals , Biocompatible Materials/chemistry , Biocompatible Materials/metabolism , Cell Line , Cells , Collagen/chemistry , Collagen/metabolism , Epithelial Cells/cytology , Extracellular Matrix/chemistry , Extracellular Matrix/metabolism , Female , Gels/chemistry , Gels/metabolism , Mechanical Phenomena , Mice , Tissue Engineering/methodsABSTRACT
Collagen is a key structural component of extracellular matrix and its mechanical properties, particularly its stiffness, have been shown to influence cell function. This study explores the mechanical behavior of type I collagen gels at low rates relevant to that of cell motion. The Young's modulus, E, was obtained for collagen samples of concentrations 1.3, 2 and 3 mg/ml at varying crosshead displacement rates: 0.01, 0.1 and 1 mm/min. Local strain measurement in the gage section were used for both the strain and strain rate determination. The power law models for the modulus at these low strain rates show that the values converge as the displacement rate approaches a quasistatic state. This study provides data that was unavailable in the past on the Young's modulus of collagen at rates relevant to the cell.
Subject(s)
Collagen/physiology , Elastic Modulus/physiology , Movement/physiology , Animals , Collagen/chemistry , Dogs , Materials Testing , Models, Biological , Models, Theoretical , Osmolar Concentration , Rats , Stress, Mechanical , Tensile Strength/physiology , Time Factors , Tissue Scaffolds/chemistryABSTRACT
Microfluidics has shown promise as a new platform for assisted reproduction. To assess the potential of microfluidics for fertilization, we studied sperm and fluid motion in microchannels to better understand the flow characteristics in a microfluidic device, how sperm interacted with this flow, and how sperm-oocyte attachment occurs in the device. There is a threshold fluid velocity where sperm transition from traveling with the fluid to a regime in which the sperm can move independently of the flow. A significant population of sperm remained in the inlet well area. Based on the lack of progressive forward movement, it was presumed that these sperm may have defects. Also of extreme interest was the tendency of sperm to travel along surface contours. These observations provide an improved understanding of sperm motion in microchannels and provide a basis for improved device designs that take advantage of the sperm/flow and sperm/geometry interactions.
Subject(s)
Fertilization in Vitro/instrumentation , Fertilization in Vitro/methods , Microfluidic Analytical Techniques/instrumentation , Microfluidics/instrumentation , Sperm Motility/physiology , Animals , Cattle , Equipment Design , Male , Oocytes/physiology , Sperm-Ovum Interactions/physiologySubject(s)
Brain Ischemia , Cerebral Infarction , Factor V , Smoking/adverse effects , Spherocytosis, Hereditary/complications , Adult , Brain Ischemia/etiology , Brain Ischemia/pathology , Brain Ischemia/physiopathology , Cerebral Infarction/etiology , Cerebral Infarction/pathology , Cerebral Infarction/physiopathology , Humans , Male , Risk Factors , Tomography, X-Ray ComputedABSTRACT
A new method for ascites filtration and reinfusion, which uses a single Cuprophan filter and is performed in the dialysis unit, is reported. Thirty-one procedures were performed in 17 patients with cirrhosis and massive ascites. A mean volume of 8.6 L of ascitic fluid was removed; from this volume, 5 L were ultrafiltered and a concentrated ascitic fluid was reinfused (x = 359.8 mL). The whole procedure was completed in a mean time of 248 minutes. No relevant method-related complications were detected. Moreover, no significant changes in blood urea nitrogen (BUN), creatinine, plasma and urinary electrolytes, or platelet count were found, even in the case of repeated procedures (two to nine times). The reinfused fluid contained a mean value of albumin of 4.7 g/dL and significant amounts of globulins and complement. The overall cost of the materials used in the procedure ($49.46) offered competitive advantages with respect to other types of frequently used methods. In conclusion, we present a safe, effective, and time- and cost-saving technique for ascites reinfusion that represents an advantageous alternative to more complicated and expensive methods or to the currently used medical therapy.
