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The purpose of this thesis is to design a physical microchannel model for micro-Couette blood flow that provides constant and controlled conditions to study and analyze Red Blood Cell (RBC) aggregation. The innovation of this work is that the Couette blood flow is created by the motion of a second fluid with different properties, thereby entraining the blood. The experimental work is coupled with three-dimensional numerical simulations performed using a research Computational Fluid Dynamic (CFD) Solver, Nek5000, based on the spectral element method, while the experiments are conducted using a micro Particle Image Velocimetry (μPIV) system with a double frame CCD camera and an inverted laser imaging microscope. The design of the channel (150 × 33 μm and 170 × 64 μm microchannels) is based on several parameters determined numerically, such as the velocity and viscosity ratios and the degree of miscibility between the fluids, and the resulting configurations are fabricated in the laboratory using standard photolithography methods. The microchannel designed numerically is then tested experimentally, first, with a Newtonian fluid (glycerol), then with RBC suspensions to be compared to the simulations results. It was found that, numerically, using a velocity ratio of 4 between the two fluids, a third of the channel thickness corresponds to the blood layer. Within that range, it can be concluded, that the velocity profile of the blood layer is approximately linear as confirmed by experimental tests, resulting in the desired profile to study RBC aggregation in controlled conditions. The effect of several parameters, such as the hematocrit and the shear rate, on the RBC aggregates and the velocity profile is investigated, through experiments on the RBC suspensions. The final goal of this research is to ensure the compatibility of the results between the experiments and the Newtonian numerical model for several ranges of shear rate with the future intention of finding an accurate method to be able to quantitatively analyze aggregates and determine the number of RBC in each aggregate depending on the flow conditions (the shear rate).

The main function of the cardiovascular system is to deliver a sufficient quantity of oxygenated blood to the tissues, cells, and organs of the body in order to provide the cells with essential nutrients for metabolism and for the removal of waste products. All cells require and utilize oxygen. Oxygen is transported to various cells and tissues via red blood cells flowing through the microcirculation of an organism. Measurement of oxygen transport in the microcirculation has shown that about ten times more oxygen appears to leave the blood of arterioles than can be accounted for by diffusion. One possibility to explain the high oxygen loss is an increased release of oxygen due to exposure of blood to light. In the present in vitro study the release of oxygen from red blood cells was measured during exposure of the sample to light by monitoring the change in PO2 of the suspension during light exposure. A PO2 electrode was calibrated using PBS solution and utilized to monitor the change in current in the present study. Red blood cell suspensions were made using blood withdrawn from male Sprague-Dawley rats. The red blood cell suspension was placed in a closed sample chamber and exposed to light for 5 minutes. A method to correct for the drift of the PO2 electrode and temperature change during the experiment was implemented. The calculated change in PO2 of the RBC suspension due to light exposure was small. The change of PO2 in the sample chamber during light exposure was an average of 1.60 ± 0.9 mmHg (SEM). The contribution of photo-dissociation of oxygen from oxygenated hemoglobin molecules to the observed oxygen loss per RBC can account for only about 0.01% of the observed in vivo results. Therefore, light-associated oxygen release is negligible. These findings disprove the hypothesis of the present study, in which light exposure does not have a significant effect on oxygen release and thus rules out this possible explanation for the discrepancy between experiment and theory.

Anemia of prematurity is characterized by a progressive decline in hemoglobin level during the first month of life. Unlike term newborns, preterm infants become anemic and often require red blood cell transfusions. Various factors contribute to the development of this anemia. These include short infant red blood cell (RBC) lifespan, decline in erythropoiesis rate after birth, and blood losses caused by repeated phlebotomies. The objectives of this work were to develop novel models to evaluate fetal and neonatal erythropoiesis, and to study in vivo adult and neonatal RBC survival in low birth weight preterm anemic infants. The model developed to evaluate fetal erythropoiesis was based on the in utero growth of the fetus over time. Neonatal erythropoiesis rate was estimated using a hemoglobin (Hb) mass-balance based method that has the advantage of not relying on specific structural pharmacodynamic model assumptions to describe the Hb production, but instead utilizes simple mass balance principles and nonparametric regression analysis to quantify the amount of Hb produced and the Hb production rate during the first month of life. To study RBC survival, two separate models, one describing the elimination of neonatal RBCs produced under non-steady state conditions, and the second describing the elimination of adult RBCs produced under steady state conditions were developed and applied to the RBC survival data obtained from low birth weight anemic preterm infants. The proposed mathematical models and its implementation provides a flexible framework to study both in utero non-steady state (non-SS) fetal erythropoiesis and neonatal erythropoiesis in newborn infants.

The purpose of this thesis is to design a physical microchannel model for micro-Couette blood flow that provides constant and controlled conditions to study and analyze Red Blood Cell (RBC) aggregation. The innovation of this work is that the Couette blood flow is created by the motion of a second fluid with different properties, thereby entraining the blood. The experimental work is coupled with three-dimensional numerical simulations performed using a research Computational Fluid Dynamic (CFD) Solver, Nek5000, based on the spectral element method, while the experiments are conducted using a micro Particle Image Velocimetry (μPIV) system with a double frame CCD camera and an inverted laser imaging microscope. The design of the channel (150 × 33 μm and 170 × 64 μm microchannels) is based on several parameters determined numerically, such as the velocity and viscosity ratios and the degree of miscibility between the fluids, and the resulting configurations are fabricated in the laboratory using standard photolithography methods. The microchannel designed numerically is then tested experimentally, first, with a Newtonian fluid (glycerol), then with RBC suspensions to be compared to the simulations results. It was found that, numerically, using a velocity ratio of 4 between the two fluids, a third of the channel thickness corresponds to the blood layer. Within that range, it can be concluded, that the velocity profile of the blood layer is approximately linear as confirmed by experimental tests, resulting in the desired profile to study RBC aggregation in controlled conditions. The effect of several parameters, such as the hematocrit and the shear rate, on the RBC aggregates and the velocity profile is investigated, through experiments on the RBC suspensions. The final goal of this research is to ensure the compatibility of the results between the experiments and the Newtonian numerical model for several ranges of shear rate with the future intention of finding an accurate method to be able to quantitatively analyze aggregates and determine the number of RBC in each aggregate depending on the flow conditions (the shear rate).

Flavonoids are of great interest for their antioxidant and health-promoting activities. Ascorbate (vitamin C) has antioxidant activities but also sometimes displays pro-oxidant activities <i>in vitro</i> and reportedly <i>in vivo</i>. This research investigated to what extent flavonoids moderate oxidative stress from vitamin C <i>in vivo</i>.<p>Dietary experiments were conducted in two phases using adult male Wistar rats. First, all animals were maintained for two weeks on a control flavonoid-free diet with the dietary requirement (27 IU) of vitamin E/kg diet. In the subsequent four weeks, the animals were treated in four groups (8 rats/group), being fed the following diets: flavonoid-free control (C), ascorbate-supplemented (7.55 mmol/kg diet) (A), flavonoid-supplemented (2.67 mmol/kg diet) (F) and flavonoids (2.67 mmol/kg diet) plus ascorbate (7.55 mmol/kg diet)-supplemented (T). Measurements were done on in vivo biomarkers of oxidative stress, tissue antioxidants and on tissue in vitro susceptibility to oxidative stress.<p>In the combined feeding of ascorbate plus flavonoids, endogenous thiobarbituric acid reactive substances (TBARS) increased in liver by 114%. No effects of dietary ascorbate or flavonoids were seen on endogenous TBARS in brain or heart, or on plasma thiols or erythrocyte fragility.<p><i>In vitro</i>, the susceptibility to TBARS formation of liver homogenate (incubated for 60 min at 37ºC in air) showed a significant 60% increase in ascorbate-fed animals compared to control, but no increase in animals fed ascorbate plus flavonoids, suggesting that the additional feeding of flavonoids helped to prevent the increase produced by ascorbate-feeding. Incubation of liver mitochondria with 300 µM ascorbate in vitro produced a large (2-7 fold) increase in TBARS, but there was no difference among mitochondria from the different feeding groups.<p>The ability of flavonoid-feeding in protecting against oxidative stress from ascorbate in vivo could not be demonstrated in this study, even showing pro-oxidant effects of flavonoids in combination with ascorbate in liver. However, in vitro tests in liver suggest a protective effect of flavonoid-feeding against susceptibility to oxidative stress from ascorbate. Further investigations are needed in order to resolve the differences observed in vitro and in vivo and to determine the endogenous effects of specific flavonoids under ascorbate-induced oxidative stress.

Introduction The ocular surface provides a unique opportunity to study hemodynamics since the vessels can be visualized directly, without treatment and non-invasively. The availability of instruments to measure various hemodynamic parameters on the ocular surface in an objective manner are lacking. The quantification of red blood cell velocity, blood oxygen saturation and conjunctival redness on the ocular surface using novel, validated techniques has the potential of providing useful information about vascular physiology. The specific aims of each chapter are as follows: Chapter 3: The objective was to design, develop and validate a system that would non-invasively quantify the red blood cell velocity in the conjunctival vessels. A tool was developed to automatically analyze video sequences of conjunctival vessels, digitally imaged with high enough magnification to resolve movement of the blood within the vessel. Chapter 4: The objective was to: a) design and develop a method in order to non-invasively quantify the changes in blood oxygen saturation (SO2) in the conjunctival vessels and demonstrate reliability of the measures and, b) demonstrate the application of the method by showing a response to an isocapnic hyperoxic provocation and compare those values to the results from a valid instrument. Chapter 5: The aim of this experiment was to examine variations in ocular redness levels, red blood cell velocities and oxygen saturation levels over time in clinically healthy participants and also to compare differences between two age groups. Chapter 6: The aim of this experiment was to examine the ocular redness levels, red blood cell velocities and oxygen saturation levels in clinically healthy participants when a topical ophthalmic decongestant was instilled onto the eye and to demonstrate the validity of the use of two novel techniques. Chapter 7: The aim of this experiment was to examine ocular redness, red blood cell velocity and oxygen saturation in participants who were habitual soft contact lens wearers (study) compared to those that did not (control) and also to compare differences in silicone (SH) and non-silicone hydrogel wearers. Methods Chapter 3: Simulations representing moving RBCs within a vessel and the random variation of each cell in terms of speed, shape and intensity were created in order to evaluate the performance of the algorithm. For each vessel, a signal that correlated to blood cell position was extracted from each frame, and the inter-frame displacement was estimated through a modified dynamic time warping (DTW) algorithm. This provided the red blood cell velocity over time in each point of the vessels. Thus, from these estimates, the mean red blood cell velocity for each vessel was easily evaluated. The true mean velocity from the simulation with the one estimated by the algorithm was compared and the system accuracy was determined. Chapter 4: a) Conjunctival vessels were imaged with two narrow-band interference filters with O2-sensitive and O2-insensitive peak transmissions using a Zeiss slit lamp at 32x magnification. Optical densities were calculated from vascular segments using the average reflected intensities inside and outside the vessels. Optical density ratios were used to calculate relative oxygen saturation values. Video images of the bulbar conjunctiva were recorded at three times of the day. Measurement repeatability was assessed over location at each time and across consecutive frames. b) Subjects initially breathed air for 10 minutes followed by pure oxygen (O2) for 20 minutes, and then air for a final 10 minute period using a sequential re-breathing circuit. Simultaneously, SO2 values measured with a pulse oximeter ear clip and finger clip were recorded. The validity of the dual wavelength method was demonstrated by comparing the values to those from the ear clip pulse oximeter. Chapter 5: Participants attended eight separate visits over the course of a day. Levels of bulbar conjunctival redness, red blood cell velocity and blood oxygen saturation were measured on a vessel of interest. Chapter 6: Participants attended three separate visits during an allotted 60 minute session. Bulbar conjunctival redness, red blood cell velocity and blood oxygen saturation were measured on a vessel of interest, pre-insertion, just after insertion and, 10 minutes after insertion of a topical ocular decongestant. Significant differences between the three measures were assessed and correlations between the three parameters were reported. Chapter 7: Participants were measured 8 times over the course of a day with their contact lenses in place. Bulbar conjunctival redness, red blood cell velocity and blood oxygen saturation were measured. Results Chapter 3: Results for the simulated videos demonstrated a very good concordance between the estimated and actual velocities supporting its validity. The mean relative error for the modified Dynamic Time Warping (DTW) method is 6%. Chapter 4: The intraclass correlations (ICCs) between the three locations at each time point were 0.93, 0.56 and 0.86 respectively. Measurements across 5 consecutive frames showed no significant difference for all subjects (ICC = 0.96). The ICCs between the two methods at each time point were 0.45, 0.10 and 0.11 respectively. a) There was no significant difference in SO2 between the three locations measured using the dual wavelength method for all subjects. There was also no significant difference between the three locations at any of the time points for the dual wavelength method. b) In response to isocapnic hyperoxic provocation using the dual wavelength method, blood oxygen saturation was increased from control values and subsequently recovered after withdrawal of hyperoxia. Blood oxygen saturation values recorded from the ear clip and finger clip of the pulse oximeter also showed an increase from control values and subsequently recovered after withdrawal of hyperoxia. SO2 comparison between the dual wavelength method and the ear-clip pulse oximeter method did not show a significant difference. The interaction between the two methods and time on SO2 was not significant. Chapter 5: From baseline, the group mean redness and oxygen saturation did not change significantly over time. There was a significant difference in the group mean red blood cell velocity values over time. There was no significant difference between age strata for all three measures. Chapter 6: After drop instillation redness values decreased significantly. There was no change in red blood cell velocity and oxygen saturation over time. There was a moderate significant correlation between SO2 and red blood cell velocity just after drop insertion. Chapter 7: When comparing the study and control groups, no significant difference in redness or SO2 over time was found. RBC velocity over time was found to be significantly different between groups. When comparing the two study groups (SH vs. hydrogel) no significant difference across either measure over time was found. Conclusions Chapter 3: Signal displacement estimation through the DTW algorithm can be used to estimate mean red blood cell velocity. Successful application of the algorithm in the estimation of RBC velocity in conjunctival vessels was demonstrated. Chapter 4: The application of the dual wavelength method was demonstrated and optical density ratios can be used in a reliable manner for relative oxygen saturation measurements. This valid method promises to enable the study of conjunctival O2 saturation under various experimental and physiological conditions. Chapter 5: The results of this study support the theory of metabolic regulation. The lack of any significant change across time for redness and oxygen saturation along with significant changes in red blood cell velocity substantiates this notion. Chapter 6: This study supports the literature regarding metabolic regulation of the microvasculature during the use of various stimuli. The results demonstrated that oxygen saturation levels remain stable even when a significant decrease in ocular redness is measured. The novel techniques used in this experiment demonstrated the expected action of the decongestant further contributing to their application and validity. Chapter 7: In summary, the participants in the study group were habitual contact lens wearers that had lower RBC velocities when compared to the control group supporting the notion that contact lenses initiate a hypoxic response. The lack of change in SO2 in either group supports the theory of metabolic regulation.

Introduction The ocular surface provides a unique opportunity to study hemodynamics since the vessels can be visualized directly, without treatment and non-invasively. The availability of instruments to measure various hemodynamic parameters on the ocular surface in an objective manner are lacking. The quantification of red blood cell velocity, blood oxygen saturation and conjunctival redness on the ocular surface using novel, validated techniques has the potential of providing useful information about vascular physiology. The specific aims of each chapter are as follows: Chapter 3: The objective was to design, develop and validate a system that would non-invasively quantify the red blood cell velocity in the conjunctival vessels. A tool was developed to automatically analyze video sequences of conjunctival vessels, digitally imaged with high enough magnification to resolve movement of the blood within the vessel. Chapter 4: The objective was to: a) design and develop a method in order to non-invasively quantify the changes in blood oxygen saturation (SO2) in the conjunctival vessels and demonstrate reliability of the measures and, b) demonstrate the application of the method by showing a response to an isocapnic hyperoxic provocation and compare those values to the results from a valid instrument. Chapter 5: The aim of this experiment was to examine variations in ocular redness levels, red blood cell velocities and oxygen saturation levels over time in clinically healthy participants and also to compare differences between two age groups. Chapter 6: The aim of this experiment was to examine the ocular redness levels, red blood cell velocities and oxygen saturation levels in clinically healthy participants when a topical ophthalmic decongestant was instilled onto the eye and to demonstrate the validity of the use of two novel techniques. Chapter 7: The aim of this experiment was to examine ocular redness, red blood cell velocity and oxygen saturation in participants who were habitual soft contact lens wearers (study) compared to those that did not (control) and also to compare differences in silicone (SH) and non-silicone hydrogel wearers. Methods Chapter 3: Simulations representing moving RBCs within a vessel and the random variation of each cell in terms of speed, shape and intensity were created in order to evaluate the performance of the algorithm. For each vessel, a signal that correlated to blood cell position was extracted from each frame, and the inter-frame displacement was estimated through a modified dynamic time warping (DTW) algorithm. This provided the red blood cell velocity over time in each point of the vessels. Thus, from these estimates, the mean red blood cell velocity for each vessel was easily evaluated. The true mean velocity from the simulation with the one estimated by the algorithm was compared and the system accuracy was determined. Chapter 4: a) Conjunctival vessels were imaged with two narrow-band interference filters with O2-sensitive and O2-insensitive peak transmissions using a Zeiss slit lamp at 32x magnification. Optical densities were calculated from vascular segments using the average reflected intensities inside and outside the vessels. Optical density ratios were used to calculate relative oxygen saturation values. Video images of the bulbar conjunctiva were recorded at three times of the day. Measurement repeatability was assessed over location at each time and across consecutive frames. b) Subjects initially breathed air for 10 minutes followed by pure oxygen (O2) for 20 minutes, and then air for a final 10 minute period using a sequential re-breathing circuit. Simultaneously, SO2 values measured with a pulse oximeter ear clip and finger clip were recorded. The validity of the dual wavelength method was demonstrated by comparing the values to those from the ear clip pulse oximeter. Chapter 5: Participants attended eight separate visits over the course of a day. Levels of bulbar conjunctival redness, red blood cell velocity and blood oxygen saturation were measured on a vessel of interest. Chapter 6: Participants attended three separate visits during an allotted 60 minute session. Bulbar conjunctival redness, red blood cell velocity and blood oxygen saturation were measured on a vessel of interest, pre-insertion, just after insertion and, 10 minutes after insertion of a topical ocular decongestant. Significant differences between the three measures were assessed and correlations between the three parameters were reported. Chapter 7: Participants were measured 8 times over the course of a day with their contact lenses in place. Bulbar conjunctival redness, red blood cell velocity and blood oxygen saturation were measured. Results Chapter 3: Results for the simulated videos demonstrated a very good concordance between the estimated and actual velocities supporting its validity. The mean relative error for the modified Dynamic Time Warping (DTW) method is 6%. Chapter 4: The intraclass correlations (ICCs) between the three locations at each time point were 0.93, 0.56 and 0.86 respectively. Measurements across 5 consecutive frames showed no significant difference for all subjects (ICC = 0.96). The ICCs between the two methods at each time point were 0.45, 0.10 and 0.11 respectively. a) There was no significant difference in SO2 between the three locations measured using the dual wavelength method for all subjects. There was also no significant difference between the three locations at any of the time points for the dual wavelength method. b) In response to isocapnic hyperoxic provocation using the dual wavelength method, blood oxygen saturation was increased from control values and subsequently recovered after withdrawal of hyperoxia. Blood oxygen saturation values recorded from the ear clip and finger clip of the pulse oximeter also showed an increase from control values and subsequently recovered after withdrawal of hyperoxia. SO2 comparison between the dual wavelength method and the ear-clip pulse oximeter method did not show a significant difference. The interaction between the two methods and time on SO2 was not significant. Chapter 5: From baseline, the group mean redness and oxygen saturation did not change significantly over time. There was a significant difference in the group mean red blood cell velocity values over time. There was no significant difference between age strata for all three measures. Chapter 6: After drop instillation redness values decreased significantly. There was no change in red blood cell velocity and oxygen saturation over time. There was a moderate significant correlation between SO2 and red blood cell velocity just after drop insertion. Chapter 7: When comparing the study and control groups, no significant difference in redness or SO2 over time was found. RBC velocity over time was found to be significantly different between groups. When comparing the two study groups (SH vs. hydrogel) no significant difference across either measure over time was found. Conclusions Chapter 3: Signal displacement estimation through the DTW algorithm can be used to estimate mean red blood cell velocity. Successful application of the algorithm in the estimation of RBC velocity in conjunctival vessels was demonstrated. Chapter 4: The application of the dual wavelength method was demonstrated and optical density ratios can be used in a reliable manner for relative oxygen saturation measurements. This valid method promises to enable the study of conjunctival O2 saturation under various experimental and physiological conditions. Chapter 5: The results of this study support the theory of metabolic regulation. The lack of any significant change across time for redness and oxygen saturation along with significant changes in red blood cell velocity substantiates this notion. Chapter 6: This study supports the literature regarding metabolic regulation of the microvasculature during the use of various stimuli. The results demonstrated that oxygen saturation levels remain stable even when a significant decrease in ocular redness is measured. The novel techniques used in this experiment demonstrated the expected action of the decongestant further contributing to their application and validity. Chapter 7: In summary, the participants in the study group were habitual contact lens wearers that had lower RBC velocities when compared to the control group supporting the notion that contact lenses initiate a hypoxic response. The lack of change in SO2 in either group supports the theory of metabolic regulation.

Flavonoids are of great interest for their antioxidant and health-promoting activities. Ascorbate (vitamin C) has antioxidant activities but also sometimes displays pro-oxidant activities <i>in vitro</i> and reportedly <i>in vivo</i>. This research investigated to what extent flavonoids moderate oxidative stress from vitamin C <i>in vivo</i>.<p>Dietary experiments were conducted in two phases using adult male Wistar rats. First, all animals were maintained for two weeks on a control flavonoid-free diet with the dietary requirement (27 IU) of vitamin E/kg diet. In the subsequent four weeks, the animals were treated in four groups (8 rats/group), being fed the following diets: flavonoid-free control (C), ascorbate-supplemented (7.55 mmol/kg diet) (A), flavonoid-supplemented (2.67 mmol/kg diet) (F) and flavonoids (2.67 mmol/kg diet) plus ascorbate (7.55 mmol/kg diet)-supplemented (T). Measurements were done on in vivo biomarkers of oxidative stress, tissue antioxidants and on tissue in vitro susceptibility to oxidative stress.<p>In the combined feeding of ascorbate plus flavonoids, endogenous thiobarbituric acid reactive substances (TBARS) increased in liver by 114%. No effects of dietary ascorbate or flavonoids were seen on endogenous TBARS in brain or heart, or on plasma thiols or erythrocyte fragility.<p><i>In vitro</i>, the susceptibility to TBARS formation of liver homogenate (incubated for 60 min at 37ºC in air) showed a significant 60% increase in ascorbate-fed animals compared to control, but no increase in animals fed ascorbate plus flavonoids, suggesting that the additional feeding of flavonoids helped to prevent the increase produced by ascorbate-feeding. Incubation of liver mitochondria with 300 µM ascorbate in vitro produced a large (2-7 fold) increase in TBARS, but there was no difference among mitochondria from the different feeding groups.<p>The ability of flavonoid-feeding in protecting against oxidative stress from ascorbate in vivo could not be demonstrated in this study, even showing pro-oxidant effects of flavonoids in combination with ascorbate in liver. However, in vitro tests in liver suggest a protective effect of flavonoid-feeding against susceptibility to oxidative stress from ascorbate. Further investigations are needed in order to resolve the differences observed in vitro and in vivo and to determine the endogenous effects of specific flavonoids under ascorbate-induced oxidative stress.

This study explored the effects of dietary unsaturated fatty acids on feline lipid metabolism. It was hypothesized that high dietary linoleic acid (18:2n-6, LA) would enhance conversion to arachidonic acid (20:4n-6), enrichment of dietary long chain n-3 FA (LCn-3FA) would affect lipid parameters, and n-3 FAs incorporation may blunt n-6 FA incorporation. Twenty-nine cats were randomized into groups (n = 9, 10, 10), and fed for 28 days with blood collections on days 0, 14, and 28. Experimental diets consisted of a commercial diet, supplemented with 8g oil/100g kibble. Oil supplements and subsequent diets were: high-oleic sunflower (H diet) with 82% oleic acid (18:1n-9), Menhaden fish (M diet) with LCn-3FA, and safflower (S diet) with 75% 18:2n-6. Dietary 20:4n-6 content was: 0.03 for H and S, and 0.09 for M (g FA/kg diet). Nonesterified fatty acid (NEFA), triacylglycerol (TG), total cholesterol (TC), lipoproteincholesterol (LP-C), plasma phospholipid (PL) FAs, red blood cell membrane (RBC) FAs, and ∆5 and ∆6 desaturase indices were measured. Statistical analyses were performed with SAS PROC MIXED with p < 0.05 determining significance. Neither TC nor NEFA showed significant effects. Diet M resulted in significant TG lowering, despite typically low feline TGs. Similarly, pre-β LP-C (i.e. TG-rich VLDL) was decreased in diet M. Plasma PL FAs revealed significant accumulations of the following: 18:1n-9 in diet H, 18:2n-6 in diet S, and LCn-3FA in diet M. Despite high dietary 18:2n-6, plasma PL 20:4n-6 was not increased in diet S over diets H or M. Increased docosadienoic acid (20:2n-6) in diet S demonstrated that 18:2n-6 chain elongation occurred in deference to its ∆6 desaturation further substantiating low feline ∆6 desaturase activity. Interestingly, no diet M blunting of 20:4n-6 incorporation occurred because fish oil supplementation provided additional 20:4n-6. Tissue 20:4n-6 content appears to be diet-dependent. Accumulation of eicosapentaenoic acid (20:5n-3), but low affinity for docosahexaenoic acid (22:6n-3) occurred in diet M RBC membranes. After 28 days, plasma PLs reflect dietary intake more readily than RBC membranes. Fish oil supplementation resulted in plasma PL LCn-3FA enrichment and lowered plasma TG concentrations, both of which may have physiological significance in cats.