Mean Cell Thickness Research Articles

Measuring Absolute Cell Volume Using Quantitative-Phase Digital Holographic Microscopy and a Low-Cost, Open-Source, and 3D-Printed Flow Chamber

Although cell volume is a critical cell parameter and acute changes of its regulation mechanisms can reveal pathophysiological states, its accurate measurement remains difficult. On the other hand, custom-made devices are now possible through the application of 3D printing that meet the needs of certain specific applications. Therefore, in this article we describe the development of a low-cost, open-source, and 3D-printed flow chamber optimized to perform non-invasive accurate measurements of important cell biophysical parameters. This measurement development includes the absolute cell volume, mean cell thickness, and whole-cell refractive index using quantitative-phase digital holographic microscopy. Specifically, this advancement makes it possible to develop a flow chamber that preserves cell viability while exhibiting a fast washout process for the two-liquid decoupling procedure - an experimental procedure allowing to separately measure the intracellular refractive index and cell thickness from the quantitative-phase signal - characterized by a homogeneous return of the extracellular refractive index over the entire imaging slit toward the known value of the last perfusion solution. Such a fast washout process has been extensively characterized by monitoring the time required to obtain a stabilization of the quantitative-phase signal following the perfusion of the two liquids. A more rapid quantitative-phase signal stabilization time results in fewer cell changes, including important cell position and shape modifications. These changes likely take place over the washout process time and ultimately result in important artefacts to all cell biophysical measurements. The proposed flow chamber has been used to perform measurements of the whole-cell refractive index, mean cell thickness, and absolute cell volume of three cell types in culture during resting state, and hypo-osmotic and hyper-osmotic challenges. For a typical cell body, these biophysical parameters are measured with a precision of 0.0006, 100 nm, and 50 µm3 respectively. Finally, the design files of the flow chamber will be shared with the scientific community through an open-source model.

Avoiding initial hypothermia does not improve liver graft quality in a porcine donation after circulatory death (DCD) model of normothermic perfusion.

BackgroundNormothermic machine perfusion (NMP) of liver grafts donated after circulatory death (DCD) has shown promise in large animal and clinical trials. Following procurement, initial flush with a cold preservation solution is the standard of care. There is concern that initial cooling followed by warming may exacerbate liver injury, and the optimal initial flush temperature has yet to be identified. We hypothesize that avoidance of the initial cold flush will yield better quality liver grafts.MethodsTwenty-four anaesthetized pigs were withdrawn from mechanical ventilation and allowed to arrest. After 60-minutes of warm ischemia to simulate a DCD procurement, livers were flushed with histidine-tryptophan-ketoglutarate (HTK) at 4°C, 25°C or 35°C (n = 4 per group). For comparison, an adenosine-lidocaine crystalloid solution (AD), shown to have benefit at warm temperatures in heart perfusions, was also used (n = 4 per group). During 12-hours of NMP, adenosine triphosphate (ATP), lactate, transaminase levels, and histological injury were determined. Bile production and hemodynamics were monitored continuously.ResultsATP levels recovered substantially following 1-hour of NMP reaching pre-ischemic levels by the end of NMP with no difference between groups. There was no difference in peak aspartate aminotransferase (AST) or in lactate dehydrogenase (LDH). Portal vein resistance was lowest in the 4°C group reaching significance after 2 hours (0.13 CI -0.01,0.277, p = 0.025). Lactate levels recovered promptly with no difference between groups. Comparison to AD groups showed no statistical difference in the abovementioned parameters. On electron microscopy the HTK4°C group had the least edema with mean cell thickness of 2.92μm (p = 0.41) while also having the least sinusoidal dilatation with a mean diameter of 5.36μm (p = 0.04). For AD, the 25°C group had the lowest mean cell thickness at 3.14μm (p = 0.09).ConclusionsAvoidance of the initial cold flush failed to demonstrate added benefit over standard 4°C HTK in this DCD model of liver perfusion.

Refractive index measurement in viable cells using quantitative phase‐amplitude microscopy and confocal microscopy

The refractive index (RI) of cellular material provides fundamental biophysical information about the composition and organizational structure of cells. Efforts to describe the refractive properties of cells have been significantly impeded by the experimental difficulties encountered in measuring viable cell RI. In this report we describe a procedure for the application of quantitative phase microscopy in conjunction with confocal microscopy to measure the RI of a cultured muscle cell specimen. The experimental strategy involved calculation of cell thickness by using confocal optical sectioning procedures, construction of a phase map of the same cell using quantitative phase microscopy, and selection of cellular regions of interest to solve for the cell RI. Mean cell thickness and phase values for six cell regions (five cytoplasmic and one nuclear) were determined. The average refractive index calculated for cytoplasmic and nuclear regions was 1.360 +/- 0.004. The uncertainty in the final RI value represents the technique measurement error. The methodology we describe for viable cell RI measurement with this prototype cell has broad generic application in the study of cell growth and functional responses. The RI value we report may be used in optical analyses of cultured cell structure and morphology.

Thickness measurements on cell monolayers using CR-39 detectors

Interpretation of radiation effects on living cells requires the determination of the absorbed dose. Dosimetry in cell monolayers irradiated by charged particles needs the knowledge of the mean cell thickness. Thickness measurement was made utilising the energy alteration of alpha particles traversing the cell monolayers. The reduced energy was determined from diameters or lengths of etched tracks produced by the penetrating alpha particles in CR-39. The experiments were performed using 3T3 cells grown directly on the CR-39 surface. The reliability of the method has been studied by means of a detailed error analysis. The total thickness errors are composed of the measurement uncertainty and the fluctuations of the cell thickness within the monolayers.

Induction and Rejoining of DNA Double-Strand Breaks in Chinese Hamster V79-4 Cells Irradiated with Characteristic Aluminum K and Copper L Ultrasoft X Rays

Characteristic aluminum K (AlK) (energy of 1.5 keV) and copper L (CuL) (energy of approximately 0.96 keV) ultrasoft X rays have been used to investigate the effectiveness of the numerous low-energy secondary electrons produced by low-linear energy transfer (LET) ionizing radiation. Cellular inactivation and induction and rejoining of DNA double-strand breaks (DSBs) in Chinese hamster V79-4 cells irradiated as monolayers with these ultrasoft X radiations have been studied under aerobic and anaerobic conditions. The mean cell thickness, determined by confocal laser scanning fluorescence microscopy, was used to calculate the mean dose to the nucleus of the irradiated cells. Relative to 60Co gamma rays, the relative biological effectiveness (RBE) for cellular inactivation at 10% survival is 1.7 +/- 0.1 and 2.3 +/- 0.3 for AIK and CuL ultrasoft X rays, respectively. The RBE values for induction of DSBs of 2.5 +/- 0.2 and 3.0 +/- 0.3 for AlK and CuL X rays, respectively, were determined after irradiation at 277 K using the technique of pulsed-field gel electrophoresis. Induction of DSBs is linearly dependent on dose. Oxygen enhancement ratios of 1.9 and 2.1 for cellular inactivation and DSB induction, respectively, were obtained with AIK X rays. These values are less than those for 60Co gamma radiation. The repair kinetics for rejoining of DSBs after a dose of 15 Gy is similar for both X-ray energies and 60Co gamma rays with a first half-life of 18-22 +/- 5 min. From these studies, it is suggested that induction of DSBs by low-LET radiations such as 60Co gamma rays reflects clustered damage produced predominantly by low-energy electron "track ends," which represent about 30% of the total dose.

The Blood Picture of Pyridoxine Deficiency in the Monkey

Abstract 1. Pyridoxine deficiency in the monkey results in a severe anemia characterized by hypochromia, increase in mean diameter, decrease in mean cell thickness, dehydration, the appearance of "target" cells and increased resistance to hemolysis. 2. The administration of pyridoxine results in restoration of hematologic values to normal, correction of dehydration and disappearance of "target" cells. 3. Further evidence is offered relating "target" cells to dehydration and, in addition, possibly to hepatic damage. 4. A delayed macrocytic anemia which was not corrected by low doses of vitamin B12, folic acid or iron is described in control animals. This anemia occurred chronologically one to two years later than the induced anemia of pyridoxine deficiency and is not necessarily related. The cause of this anemia is unknown. 5. Normal hematologic data on twenty-one M. rhesus monkeys is presented.