The method development process in liquid chromatography (LC) involves optimization of a variety of method parameters including stationary phase chemistry, column temperature, initial and final mobile phase compositions, and gradient time when gradient mobile phases are used. Here, a general simulation program to predict the results (i.e., retention time, peak width and peak shape) of LC separations, with the ability to study various complex chromatographic conditions is described. The simulation program is based on the Craig distribution model where the column is divided into discrete distance (Δz) and time (Δt) segments in a grid and is based on parameterization with either the linear solvent strength or Neue-Kuss models for chromatographic retention. This algorithm is relatively simple to understand and produces results that agree well with closed form theory when available. The set of simulation programs allows for the use of any eluent composition profile (linear and nonlinear), any column temperature, any stationary phase composition (constant or non-constant), and any composition and shape of the injected sample profile. The latter addition to our program is particularly useful in characterizing the solvent mismatch effect in comprehensive two-dimensional liquid chromatography (2D-LC), in which there is a mismatch between the first dimension (1D) effluent and second dimension (2D) initial mobile phase composition. This solvent mismatch causes peak distortion and broadening. The use of simulations can provide a better understanding of this phenomenon and a guide for the method development for 2D-LC. Another development that is proposed to have a great impact on the enhancement of 2D-LC methods is the use of continuous stationary phase gradients. When using rapid mobile phase gradients in the second dimension separation with diode array detection (DAD), refractive index changes cause large backgrounds such as an injection ridge (from solvent mismatch) and sloping baselines which can be problematic for achieving accurate quantitation. Use of a stationary phase gradient may enable the use of an isocratic mobile phase in the 2D, thus minimizing these background signals. Finally, our simulator can be used as an educational tool. Unlike commercially available simulators, our program can capture the evolution of the chromatogram in the form of movies and/or snapshots of the analyte distribution over time and/or distance to facilitate a better understanding of the separation process under complicated circumstances. We plan to make this simulation program publically available to all chromatographers and educators to aid in more efficient method development and chromatographic training.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

The endocrine heart synthesises and secretes two polypeptide hormones: the natriuretic peptides (NP) atrial natriuretic factor (ANF) and B-type natriuretic peptide (BNP). The biological actions of these hormones serve both acutely and chronically to reduce systemic blood pressure and hemodynamic load to the heart, thus contributing to the maintenance of cardiorenal homeostasis. Considerable effort has been focused on the elucidation of the mechanistic underlying ANF and BNP gene expression and secretion but much remains to be determined regarding specific molecular events involved in the cardiocyte secretory function. These hormones are produced by the atrial muscle cells (cardiocytes), which display a dual secretory/muscle phenotype. In contrast, ventricular cardiocytes display mainly a muscle phenotype. Comparatively little information is available regarding the genetic background for this important phenotypic difference with particular reference to the endocrine function of the heart. We postulated that comparison of gene expression profiles between atrial and ventricular muscles would help identify transcripts that underlie the phenotypic differences associated with the endocrine function of the heart as well as identify signaling pathways involved in its regulation. The cardiac atrial and ventricular transcriptomes were analyzed using oligonucleotide microarrays under normal or chronically induced aortocaval shunt volume-overload conditions. Transcriptional differences were validated by RT-PCR and transcripts of interest were knocked-down by RNAi. Comparison of gene expression profiles in the rat heart revealed a total of 1415 differentially expressed genes between normal atrial and ventricular tissues. Functional classification and pathway analysis identified numerous transcripts involved in mechanosensing, vesicle trafficking, hormone secretion, and G protein signaling. Volume-overloaded animals exhibited a progressive increase in cardiac mass over the four-week time course, an increase in expression of known hypertrophic genes, as well as the differential expression of 700 genes within the atria. Volume-overload specifically downregulated the accessory protein for heterotrimeric G protein signaling RASD1 in the atria. In vitro, knockdown of RASD1 in the atrial-derived HL-1 cells, significantly increased ANF secretion, demonstrating a previously unknown negative modulator role for RASD1. The data developed in this investigation provides insight into the expression profiles of genes particularly centered on the secretory function of the heart under normal and chronic hemodynamic overload conditions. Genome-wide expression profile analysis identified RASD1 as being differentially expressed between cardiac tissues as well as being modulated by chronic volume overload. RASD1 emerges as a tonic inhibitor of ANF secretion. The novel function identified herein for RASD1 in the atria is of considerable interest given the fact that secretory impairment of the cardiac natriuretic hormones can negatively impact cardiovascular homeostasis.

The endocrine heart synthesises and secretes two polypeptide hormones: the natriuretic peptides (NP) atrial natriuretic factor (ANF) and B-type natriuretic peptide (BNP). The biological actions of these hormones serve both acutely and chronically to reduce systemic blood pressure and hemodynamic load to the heart, thus contributing to the maintenance of cardiorenal homeostasis. Considerable effort has been focused on the elucidation of the mechanistic underlying ANF and BNP gene expression and secretion but much remains to be determined regarding specific molecular events involved in the cardiocyte secretory function. These hormones are produced by the atrial muscle cells (cardiocytes), which display a dual secretory/muscle phenotype. In contrast, ventricular cardiocytes display mainly a muscle phenotype. Comparatively little information is available regarding the genetic background for this important phenotypic difference with particular reference to the endocrine function of the heart. We postulated that comparison of gene expression profiles between atrial and ventricular muscles would help identify transcripts that underlie the phenotypic differences associated with the endocrine function of the heart as well as identify signaling pathways involved in its regulation. The cardiac atrial and ventricular transcriptomes were analyzed using oligonucleotide microarrays under normal or chronically induced aortocaval shunt volume-overload conditions. Transcriptional differences were validated by RT-PCR and transcripts of interest were knocked-down by RNAi. Comparison of gene expression profiles in the rat heart revealed a total of 1415 differentially expressed genes between normal atrial and ventricular tissues. Functional classification and pathway analysis identified numerous transcripts involved in mechanosensing, vesicle trafficking, hormone secretion, and G protein signaling. Volume-overloaded animals exhibited a progressive increase in cardiac mass over the four-week time course, an increase in expression of known hypertrophic genes, as well as the differential expression of 700 genes within the atria. Volume-overload specifically downregulated the accessory protein for heterotrimeric G protein signaling RASD1 in the atria. In vitro, knockdown of RASD1 in the atrial-derived HL-1 cells, significantly increased ANF secretion, demonstrating a previously unknown negative modulator role for RASD1. The data developed in this investigation provides insight into the expression profiles of genes particularly centered on the secretory function of the heart under normal and chronic hemodynamic overload conditions. Genome-wide expression profile analysis identified RASD1 as being differentially expressed between cardiac tissues as well as being modulated by chronic volume overload. RASD1 emerges as a tonic inhibitor of ANF secretion. The novel function identified herein for RASD1 in the atria is of considerable interest given the fact that secretory impairment of the cardiac natriuretic hormones can negatively impact cardiovascular homeostasis.

The endocrine heart synthesises and secretes two polypeptide hormones: the natriuretic peptides (NP) atrial natriuretic factor (ANF) and B-type natriuretic peptide (BNP). The biological actions of these hormones serve both acutely and chronically to reduce systemic blood pressure and hemodynamic load to the heart, thus contributing to the maintenance of cardiorenal homeostasis. Considerable effort has been focused on the elucidation of the mechanistic underlying ANF and BNP gene expression and secretion but much remains to be determined regarding specific molecular events involved in the cardiocyte secretory function. These hormones are produced by the atrial muscle cells (cardiocytes), which display a dual secretory/muscle phenotype. In contrast, ventricular cardiocytes display mainly a muscle phenotype. Comparatively little information is available regarding the genetic background for this important phenotypic difference with particular reference to the endocrine function of the heart. We postulated that comparison of gene expression profiles between atrial and ventricular muscles would help identify transcripts that underlie the phenotypic differences associated with the endocrine function of the heart as well as identify signaling pathways involved in its regulation. The cardiac atrial and ventricular transcriptomes were analyzed using oligonucleotide microarrays under normal or chronically induced aortocaval shunt volume-overload conditions. Transcriptional differences were validated by RT-PCR and transcripts of interest were knocked-down by RNAi. Comparison of gene expression profiles in the rat heart revealed a total of 1415 differentially expressed genes between normal atrial and ventricular tissues. Functional classification and pathway analysis identified numerous transcripts involved in mechanosensing, vesicle trafficking, hormone secretion, and G protein signaling. Volume-overloaded animals exhibited a progressive increase in cardiac mass over the four-week time course, an increase in expression of known hypertrophic genes, as well as the differential expression of 700 genes within the atria. Volume-overload specifically downregulated the accessory protein for heterotrimeric G protein signaling RASD1 in the atria. In vitro, knockdown of RASD1 in the atrial-derived HL-1 cells, significantly increased ANF secretion, demonstrating a previously unknown negative modulator role for RASD1. The data developed in this investigation provides insight into the expression profiles of genes particularly centered on the secretory function of the heart under normal and chronic hemodynamic overload conditions. Genome-wide expression profile analysis identified RASD1 as being differentially expressed between cardiac tissues as well as being modulated by chronic volume overload. RASD1 emerges as a tonic inhibitor of ANF secretion. The novel function identified herein for RASD1 in the atria is of considerable interest given the fact that secretory impairment of the cardiac natriuretic hormones can negatively impact cardiovascular homeostasis.

The endocrine heart synthesises and secretes two polypeptide hormones: the natriuretic peptides (NP) atrial natriuretic factor (ANF) and B-type natriuretic peptide (BNP). The biological actions of these hormones serve both acutely and chronically to reduce systemic blood pressure and hemodynamic load to the heart, thus contributing to the maintenance of cardiorenal homeostasis. Considerable effort has been focused on the elucidation of the mechanistic underlying ANF and BNP gene expression and secretion but much remains to be determined regarding specific molecular events involved in the cardiocyte secretory function. These hormones are produced by the atrial muscle cells (cardiocytes), which display a dual secretory/muscle phenotype. In contrast, ventricular cardiocytes display mainly a muscle phenotype. Comparatively little information is available regarding the genetic background for this important phenotypic difference with particular reference to the endocrine function of the heart. We postulated that comparison of gene expression profiles between atrial and ventricular muscles would help identify transcripts that underlie the phenotypic differences associated with the endocrine function of the heart as well as identify signaling pathways involved in its regulation. The cardiac atrial and ventricular transcriptomes were analyzed using oligonucleotide microarrays under normal or chronically induced aortocaval shunt volume-overload conditions. Transcriptional differences were validated by RT-PCR and transcripts of interest were knocked-down by RNAi. Comparison of gene expression profiles in the rat heart revealed a total of 1415 differentially expressed genes between normal atrial and ventricular tissues. Functional classification and pathway analysis identified numerous transcripts involved in mechanosensing, vesicle trafficking, hormone secretion, and G protein signaling. Volume-overloaded animals exhibited a progressive increase in cardiac mass over the four-week time course, an increase in expression of known hypertrophic genes, as well as the differential expression of 700 genes within the atria. Volume-overload specifically downregulated the accessory protein for heterotrimeric G protein signaling RASD1 in the atria. In vitro, knockdown of RASD1 in the atrial-derived HL-1 cells, significantly increased ANF secretion, demonstrating a previously unknown negative modulator role for RASD1. The data developed in this investigation provides insight into the expression profiles of genes particularly centered on the secretory function of the heart under normal and chronic hemodynamic overload conditions. Genome-wide expression profile analysis identified RASD1 as being differentially expressed between cardiac tissues as well as being modulated by chronic volume overload. RASD1 emerges as a tonic inhibitor of ANF secretion. The novel function identified herein for RASD1 in the atria is of considerable interest given the fact that secretory impairment of the cardiac natriuretic hormones can negatively impact cardiovascular homeostasis.

No description available.

No description available.