Exercise is the act of increasing metabolic rate for the purpose of enhancing physical fitness. Exercise can be one of the most stressful physiological responses that the body undertakes. With exercise, there are increases in metabolic rate, heart rate, blood flow (hyperemia), respiration, and heat production. The increased metabolic requirement during exercise is well met by an increased blood flow (functional hyperemia) and oxygen supply to the exercising tissue, which is regulated by multiple local and systemic mechanisms. The local mechanisms (factors) are responsible for mediating the muscle homeostasis and vascular conductance to match the increased metabolic requirement, whereas the systemic mechanisms are responsible for the maintenance of blood pressure and global cardiovascular homeostasis, including the increase in and redistribution of cardiac output, which is mainly mediated by sympathetic activation. For instance, the substantial decreases in vascular resistance and resultant large increase in blood flow during exercise require higher blood pressure and more cardiac output, such that the metabolically active muscle can be perfused with adequate blood flow. This book will provide an overview of the cardiovascular responses to exercise under physiological conditions as well as some pathological circumstances.

This book reviews important aspects of polycystic kidney diseases, the latest scientific understanding of the diseases and syndromes, along with the therapies being developed. Cystic kidney diseases comprise a spectrum of genetic syndromes defined by renal cyst formation and expansion with variable extrarenal manifestations. The most prevalent disorder is the autosomal dominant polycystic kidney disease (ADPKD). It is the most common monogenetic disorder in humans and accounts for 4.4% of end-stage renal disease (ESRD) cases in the U.S. Patients inevitably progress to ESRD and require renal replacement therapy in the form of dialysis or transplantation. Through advancements in genomics and proteomics approaches, novel genes responsible for cystic diseases have been identified, further expanding our understanding of basic mechanisms of disease pathogenesis. The hallmark among all cystic genetic syndromes is the formation and growth of fluid-filled cysts, which originate from tubular epithelia of nephron segments. Cysts are the disease, and treatment strategies are being developed to target prevention or delay of cyst formation and expansion at an early stage, however no such therapy is currently approved.

This book reviews important aspects of polycystic kidney diseases, the latest scientific understanding of the diseases and syndromes, along with the therapies being developed. Cystic kidney diseases comprise a spectrum of genetic syndromes defined by renal cyst formation and expansion with variable extrarenal manifestations. The most prevalent disorder is the autosomal dominant polycystic kidney disease (ADPKD). It is the most common monogenetic disorder in humans and accounts for 4.4% of end-stage renal disease (ESRD) cases in the U.S. Patients inevitably progress to ESRD and require renal replacement therapy in the form of dialysis or transplantation. Through advancements in genomics and proteomics approaches, novel genes responsible for cystic diseases have been identified, further expanding our understanding of basic mechanisms of disease pathogenesis. The hallmark among all cystic genetic syndromes is the formation and growth of fluid-filled cysts, which originate from tubular epithelia of nephron segments. Cysts are the disease, and treatment strategies are being developed to target prevention or delay of cyst formation and expansion at an early stage, however no such therapy is currently approved.

The liver is a vital organ involved in numerous metabolic processes such as cholesterol and bile acid metabolism, biliary lipid secretion, and bile formation. Cholesterol balance across the liver has a crucial effect on influencing plasma total and LDL cholesterol levels and biliary cholesterol concentrations. Cholesterol and bile acid biosyntheses are primarily modulated by negative feedback regulatory mechanisms through the sterol regulatory element-binding protein isoform 2 (SREBP-2) and the farnesoid X receptor (FXR) pathways, respectively. The conversion of cholesterol to bile acids in the liver can balance the fecal excretion of bile acids, which is an important route for the removal of cholesterol from the body. Bile formation begins in the bile canaliculi, and maintenance of the enterohepatic circulation of bile acids results in a continuous secretion of bile. Hepatic secretion of biliary lipids is determined mainly by a group of ATP-binding cassette (ABC) transporters that are located on the canalicular membrane of hepatocytes, which are regulated by various nuclear receptors. Bile acids promote bile flow by their osmotic effects. Also, they are essential for the intestinal absorption of cholesterol, fatty acids, and fat-soluble vitamins and play an important role in aiding the digestion of dietary fat. Bile acids function as signaling molecules and anti-inflammatory agents to regulate lipid, glucose, and energy metabolism by rapidly activating nuclear receptors and cell signaling pathways. This eBook summarizes the progress in the molecular and cellular mechanisms of cholesterol and bile acid metabolism and the physical-chemistry of biliary lipids, with emphasis on biliary lipid metabolism that is regulated by nuclear receptors in the hepatobiliary system.

The blood-brain barrier (BBB) is a complex and dynamic structure that protects the brain from cells within the vasculature, from the immune system and from pathogens. This barrier is present in arterioles, capillaries and venules and is formed at the level of adjacent endothelial cells, which are coupled to astrocytes, microglia, neurons and pericytes. The structure of this endothelial barrier is unique among endothelia of other organ systems and is composed of complexes made up of tight, gap and adherens junctions. In addition, it is the responsibility of the surrounding cellular elements to maintain the integrity of the junctional complexes and restrict the entry of substances from the blood into the brain. Changes in permeability of the BBB during physiologic and pathophysiologic conditions involve alterations in specific transporters at the level of the endothelium, activation of specific cellular second messenger pathways and/or the dissolution of the junctional complexes composing the BBB. This book focuses on various aspects that account for the formation and maintenance of the BBB, and on disease states that compromise this barrier.