Abstract: Patients with end-stage renal disease present with an immunodeficient state paradoxically coexisting with signs of activation of immune system cells and that is accentuated rather than corrected by replacement dialysis therapy. The mechanisms of this immune system dysregulation presently under consideration are a reduced bioavailability of interleukin-2 secondary to its overconsumption by activated T cells; a downregulation of phagocyte adhesion molecules and opsonin receptors following their overexpression during dialysis with complement-activating membranes; an increased production of the cytokines interleukin-1, tumor necrosis factor-alpha, and interleukin-6 by activated monocytes and of soluble CD23 by B lymphocytes; and last, but far from least, the presence of uremic toxins. Perspectives of research are aimed at elucidating the respective role of the T helper cell subpopulations (Th-1 and Th-2) and the influence of the progression of chronic renal failure on the naturally occurring cytokine inhibitors, with the hope of better defining the rationale of strategies of immunomodulation that could be beneficial to patients with end-stage renal disease.

Abstract: Hypertension in pregnancy is still a leading cause of morbidity and mortality in mother and fetus. This review of the literature from 1991 to 1992 focuses on research relating to the causes of preeclampsia and the pathogenesis of the marked vasoconstriction so characteristic of this disease. Reports hypothesizing primary roles for endothelial cell dysfunction, aberrations in prostaglandin synthesis, fatty acid and antioxidant metabolism, as well as for dietary calcium deficiency and the renin-angiotensin system are analyzed; articles regarding clinical trials whose origins derive from some of these hypotheses, such as low-dose aspirin and calcium supplementation to prevent preeclampsia, are appraised. The review concludes by examining several controversies regarding management of pregnant women with chronic hypertension, including the proper way to measure blood pressure in pregnancy, the diastolic level at which treatment with antihypertensive medications should commence, and the choice of drugs that are safe and preferable for use during gestation.

Abstract: Ischemia-reperfusion injury occurs in many organs and is the underlying cause of many disease processes, including myocardial infarction, stroke, and acute renal failure, which in total are responsible for the majority of deaths seen in developed countries. Most of the injury seen with this process is associated with the reperfusion phase in which the blood flow to the ischemic tissues is reinstituted. This reperfusion phase is associated with the formation of reactive oxygen species (ROS) in the tissues, and the sources of these oxidants are both the neutrophil as well as parenchymal cells such as endothelium. In the kidney as well as other organs, antioxidant therapy is protective, suggesting an important role for these agents. However, there is emerging evidence that ROS are not solely responsible for the reperfusion injury. In many of the kidney models of ischemia-reperfusion, antioxidants are only partially effective in ameliorating the functional and morphologic alterations. Furthermore, in vitro, ROS do not appear to be primarily involved in the killing of renal tubular epithelial cells, which is the morphologic hallmark of acute renal failure. Thus, reperfusion injury, like other types of tissue injury, appears to be mediated by more than one class of inflammatory mediator.

Abstract: The standard concept of the renin-angiotensin system is that renin is secreted by the juxtaglomerular cells of the kidney into the circulation, where it cleaves angiotensin to release angiotensin I. The angiotensin I is converted to angiotensin II by a converting enzyme located on the plasma membrane of the endothelial cell. The released angiotensin II binds to receptors on target cells to initiate a series of intracellular actions that result in a specific cell function. The kidney was conceived to secrete renin with the circulatory angiotensin II returning to the kidney to alter renal function. It is now clear that all the components of the renin-angiotensin system can be synthesized within the kidney. In fact, angiotensin II is formed in very high concentrations in the renal interstitial space. Local angiotensin II production can have profound influences on renal function, ie, alter glomerular hemodynamics, reduce sodium excretion, and constrict small arterioles. In certain disease states, the local action of angiotensin II may have harmful effects on the kidney, and blockade of the renin-angiotensin system can be beneficial to the kidney.

Abstract: Structural changes of the heart and blood vessels participate in the long-term regulation of the cardiovascular system. In hypertension and myocardial dysfunction, the adaptive process of cardiac and vascular remodeling may contribute to the pathophysiology and complications of these diseases. Recent investigations have enhanced our understanding of the cellular and molecular biology of vascular smooth muscle and cardiac myocyte growth. Mechanical and neurohormonal factors can independently stimulate hypertrophy-hyperplasia in vascular and cardiac myocytes. Increased pressure-stretch of cardiac myocyte and vascular smooth muscle cells can activate protooncogene expressions that may mediate the growth response. Vasoactive substances also regulate cardiovascular growth. In general, endogenous vasoconstrictors (eg, angiotensin, endothelin) act as growth promoters, and endogenous vasodilators (eg, nitric oxide, prostacyclin, atrial natriuretic peptide) act as growth inhibitors of vascular smooth muscle and, possibly, cardiac myocytes. Recent data have demonstrated that the vasoconstrictive agents, such as angiotensin, activate protooncogenes and autocrine growth factors that mediate vascular growth. Furthermore, the development of vascular hypertrophy versus hyperplasia is dependent on the relative activation of endogenous proliferative growth factor (eg, platelet-derived growth factor, basic fibroblast growth factor) versus antiproliferative factor (eg, transforming growth factor-beta) by the growth stimulus. Taken together, these data demonstrate that complex interactions of local mediators, which participate in the pathophysiology of cardiovascular diseases, control cardiovascular growth.

Abstract: The natriuretic peptide system is a complicated system comprising at least three endogenous peptides, atrial natriuretic peptide, brain natriuretic peptide, and C-type natriuretic peptide and three receptors, the atrial natriuretic peptide-A receptor (guanylyl cyclase A), the atrial natriuretic peptide-B receptor (guanylyl cyclase B), and the clearance receptor. The accumulated evidence indicates that this system is implicated in the control of blood pressure, body fluid homeostasis, and vascular remodeling as both cardiac hormone and local regulator.

Abstract: The sympathetic nervous system plays an important role in the regulation of arterial pressure, and increased sympathetic nervous system activity has been implicated as a primary precursor of hypertension in both humans and animal models of the disease. To date, the mechanism that potentiates the increase in sympathetic nervous system activity has not been fully elucidated. Imbalances in several neurotransmitters and neuromodulators are present during the development of hypertension, and these directly and indirectly contribute to increased release of noradrenaline onto the postsynaptic targets of the sympathetic nerves. In sodium chloride-sensitive hypertensive subjects, dietary sodium chloride increases sympathetic nervous system activity both directly and indirectly. Bidirectional interactions among the immune system and the sympathetic nervous system also appear to play a role in the development of hypertension. Finally, recent studies suggest that insulin-glucose excess and nitric oxide deficiency may increase the sympathetic nervous system's contribution to some forms of hypertension.

Abstract: Proteinuria (protein excretion > 300 mg/d) is an independent risk factor for the development of cardiovascular disease and renal failure The finding of persistent proteinuria in otherwise asymptomatic patients often precedes the development of arterial hypertension and renal failure When proteinuria is accompanied by arterial hypertension, blood pressure control can decrease the quantity of protein excretion but not the incidence of proteinuria In this sense, converting enzyme inhibitors seem to possess a higher capacity to reduce proteinuria Nevertheless, the effects of reducing proteinuria on renal function and cardiovascular risk remain to be elucidated Microalbuminuria (urine albumin excretion oscillating between 30 and 300 mg/d) seems to be a predictor of cardiovascular disease in diabetic and nondiabetic subjects and has been established as a predictor for the development of diabetic nephropathy Blood pressure levels and urinary albumin excretion correlate positively, and antihypertensive therapy of any kind decreases the quantity of albumin present in the urine The role of increased albumin excretion in essential hypertension and in renal failure remains to be elucidated

Abstract: Recent advances in our understanding of the regulation of parathyroid hormone secretion in vivo and in vitro are reviewed. The use of assays specific for immunoreactive intact parathyroid hormone has greatly improved our capacity to study parathyroid hormone dynamics in vivo. Such studies have empha

Abstract: FK506, a new macrolide immunosuppressant agent, is approximately 100 times more potent than cyclosporine. Early clinical trials demonstrated FK506 to be effective in reversing refractory rejection in liver, kidney, and heart transplantation. Like cyclosporine, FK506 has significant nephrotoxicity. The clinical presentation and morphology of FK506 nephrotoxicity are identical to those of cyclosporine. Many animal and in vitro studies suggest that FK506 may be less nephrotoxic than cyclosporine. Studies in humans after transplantation have not confirmed this advantage. FK506 has pursued the same pattern in drug development as cyclosporine, with progressive dose reductions over the years. Studies from this early developmental period suggest that the nephrotoxicity of FK506 and cyclosporine in clinical use are approximately equivalent. Further refinement in the clinical use of FK506 will likely reduce its toxicity further. Appropriate studies conducted at that stage will determine which drug possesses less nephrotoxicity.

Abstract: Despite several decades of research interest and productivity, many aspects of hyponatremia and hypo-osmolar disorders remain incompletely understood. Among these aspects are questions relating to the morbidity and mortality actually attributable to hyponatremia, possible hormonal and gender-associated risk factors underlying susceptibility to neurologic complications from hyponatremic encephalopathy, the stimuli to arginine vasopressin secretion in some atypical subsets of patients with the syndrome of inappropriate antidiuretic hormone secretion and other hyponatremic disorders, the contributions of natriuresis and natriuretic peptides to hyponatremic states, the pathologic determinants of brain demyelination that sometimes follow rapid correction of hyponatremia, and appropriate treatment guidelines for patients with acute and chronic hyponatremia. The recent literature confirms that acceptable answers to these questions and others are still not available, and a better understanding of basic issues regarding the pathophysiology of hyponatremia is needed. Several recent advances stand out as being likely to enhance our future understanding of hyponatremia and hypo-osmolar states. First are studies of cellular mechanisms of volume regulation in kidney and brain tissue in response to changes in osmolality. Many, though clearly not all, clinical observations can be better understood by considering them in the conceptual framework provided by knowledge of cell and body fluid compartment volume regulation. Second is the elucidation of several important protein structures via complementary DNA cloning, including the arginine vasopressin V1 and V2 receptors, several organic osmolyte transporters, and the CHIP28 water channel. Future application of these new tools to carefully designed and executed physiologic studies will likely add considerable new knowledge to our understanding of hyponatremia. Third is the development and increasing application of nuclear magnetic resonance spectroscopy and imaging methods that will allow more detailed analyses of acute changes in brain metabolism during hyponatremia and following correction. Finally, the recent development of nonpeptide antagonists to arginine vasopressin V1 and V2 receptors should enable clinical studies to assess more accurately the contribution of arginine vasopressin-induced antidiuresis to hyponatremia and more importantly holds the promise of more effective therapies for hyponatremic patients.

Abstract: The majority of hemodialysis patients die from cardiovascular disease. However, the contribution of myocardial infarction to mortality is relatively minor, despite the fact that coronary artery disease is common in uremic patients. Hypertension seems to be the major risk factor for the development of atherosclerosis in hemodialysis patients, although abnormalities of the lipid spectrum, characterized by an increase in triglycerides and very low density lipoprotein levels and a decrease in high-density lipoprotein levels, are frequent in hemodialysis patients. The existence of left ventricular (LV) hypertrophy is a serious risk factor for morbidity and mortality in hemodialysis patients. LV hypertrophy can present as a dilated cardiomyopathy or as concentric or asymmetric septal hypertrophy. Loss of myocardial contractility by coronary artery disease or carnitine deficiency can lead to systolic LV dysfunction with a compensatory dilated cardiomyopathy. Furthermore, the presence of a hypercirculation in uremic patients, resulting from anemia, the arteriovenous fistula, or fluid overload, can also lead to a dilated cardiomyopathy. Systolic LV dysfunction occurs when the increase in LV wall thickness is inadequate for the increase in LV radius, which might be caused by increased levels of parathyroid hormone. LV diastolic dysfunction, resulting from an increase in LV mass due to the effects of hypertension or to uremic interstitial fibrosis, can both lead to pulmonary edema and hypotensive periods during hemodialysis and is a severe risk factor for mortality in hemodialysis patients. Therefore, in uremic patients, anemia should be corrected and hypertension adequately treated early in the development of renal failure. Chronic fluid overload should be prevented by adequate estimation of optimal dry weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract: This review discusses the role of the sympathetic nervous system in the pathogenesis and maintenance of human hypertension. Three points are emphasized: first, there are mechanisms by which the sympathetic nervous system can contribute to the long-term regulation of vascular resistance and arterial pressure in addition to the moment-to-moment regulation of arterial pressure; second, the microneurographic method for direct intraneural recording of sympathetic nerve activity in humans has provided mounting evidence for increased sympathetic neural activity in human essential and renovascular hypertension; and third, there are both peripheral reflex and humoral mechanisms that may contribute to sympathetic overactivity in human hypertension.

Abstract: The cellular and molecular mechanisms whereby hypertension causes vascular and cardiac disease are beginning to be understood. Angiotensin II, perhaps because so many probes to explore its action are available, is emerging as a central pathogenetic factor in the development of both vascular and cardiac hypertrophy. It is clear that this peptide has direct growth effects on vascular smooth muscle cells and cardiocytes as well as indirect effects by stimulating the synthesis of growth factors or potentiating their effects. However, the details of its action need clarification. Abnormalities in endothelium-derived relaxing factor regulation are a new pathogenetic mechanism of hypertension and are also likely to be intimately involved in the development of hypertensive cardiovascular disease. In the clinical arena, converting enzyme inhibitors are emerging as the best antihypertensive agents, and new therapeutic trials and further support to the suspicion that, when in doubt, it is better to treat.

Abstract: The sodium pump Na,K-ATPase, a heterodimer of an alpha catalytic subunit and a beta glycoprotein subunit, is regulated by a wide array of hormonal, autocrine, and paracrine factors. Both short-term acute adjustments of activity and long-term adjustments of sodium pump pool size are important determinants of cellular Na,K-ATPase activity. Phosphorylation and dephosphorylation are implicated in the acute regulation of activity. Although there is not yet any direct demonstration of phosphorylation in vivo, in vitro studies on purified enzyme directly demonstrate that phosphorylation decreases Na,K-ATPase activity. In addition, it is likely that phosphorylation of other proteins regulates sodium pump activity and cellular distribution. In regard to long-term regulation, recent demonstration of differential translatability of alpha and beta mRNAs and differential stability of newly synthesized alpha and beta subunits suggests that beta subunit is synthesized in excess over alpha subunit and that the excess is rapidly degraded. The isoform composition of alpha beta heterodimers has been shown to affect enzymatic properties, and tissue-specific heterodimer patterns are emerging from regulation studies. In regard to Na,K-ATPase and hypertension, there is continued interest in the significance of the uncoupling of dopamine inhibition of proximal tubule Na,K-ATPase activity in hypertensive rat strains. The uncoupling has been shown to be specific to the proximal tubule, which has been shown to express DA1 dopamine receptors, and both receptor and postreceptor defects are implicated. Questions remaining include how activation of dopamine receptors is coupled to decreased sodium transporter expression in the proximal tubule (short- and long-term regulation) in normotensive rats, the precise nature of the defect in hypertension, and whether a similar defect is observed in human hypertensive patients.

Abstract: Posttransplantation liver disease due to non-A, non-B hepatitis (NANBH) is an important cause of morbidity and mortality in renal transplant recipients. The cloning of the hepatitis C virus (HCV), which is the major cause of parenterally transmitted NANBH, and the development of tests to detect HCV

Abstract: Recent progress in cellular and molecular biology has had a great impact on our understanding of parathyroid hormone-vitamin D physiology and of the pathogenesis of secondary hyperparathyroidism in chronic renal failure and made possible the development of new therapeutic approaches for management o

Abstract: The inherent variability of blood pressure means that the accuracy of a small number of clinic readings in estimating the true blood pressure is limited. In many patients, a clinic visit provokes an increase in blood pressure such that they may be misclassified as being hypertensive (white coat hypertension). This applies to about 20% of hypertensives. Ambulatory monitoring has the potential to overcome these limitations. The white coat effect may still occur in patients taking antihypertensive medications, although in some cases medication may lower the clinic pressure without affecting the ambulatory pressure. The diurnal rhythm of blood pressure is another major source of variability and is influenced by both extrinsic and intrinsic factors. Its pathologic significance is unclear. Antihypertensive medication generally lowers the set point of blood pressure but has relatively little effect on variability.

Abstract: A variety of techniques have been used by different investigators to characterize blood pressure responses to changes in sodium balance. Despite the arbitrary nature of the definition of salt sensitivity, many of these studies have demonstrated consistency in the factors associated with the heterogeneous responses to the methods used. This review surveys current approaches to the assessment of blood pressure responsivity to alterations in sodium and extracellular fluid balance in normotensive as well as hypertensive humans. In addition, new observations related to the possible mechanisms involved are highlighted.

Abstract: The risk of posttransplantation lymphoproliferative disorder (PTLD) has increased with the use of new, highly potent immunosuppressive agents. Monoclonal anti-T-cell antibodies such as OKT3 have been associated with a particularly high risk of these frequently fatal Epstein-Barr virus (EBV)-related B-cell neoplasms. OKT3 is a powerful mitogen, raising the possibility that T-cell activation and cytokine release may facilitate the development of PTLD. Interleukin-6 and interleukin-10 have recently been shown to play major roles in B-cell neoplasia in general, and particularly in EBV-induced B-cell transformation and outgrowth. The development of PTLD after treatment with OKT3 might be mediated by the release of those cytokines. On the other hand, OKT3-related PTLD may simply be the result of the profound T-cell depletion induced by the drug, and the mechanisms for lymphomagenesis may be no different than those operative in PTLDs arising in other immunosuppressed patients. A clearer understanding of the relevant mechanisms will require further work with in vivo models of the disease and may have significant implications for the design of new immunosuppressive agents.

Abstract: A wealth of evidence shows that nitric oxide can modulate the autoregulation of renal blood flow, the glomerular surface area available for filtration, the glomerulotubular feedback response, and the release of renin. From an integrative point of view, inhibition of nitric oxide synthesis will alter the function of all of these homeostatic mechanisms and impair the pressure-induced natriuresis secondary to increases in intrarenal vascular resistance and tubular sodium reabsorption. These effects, along with an elevation of both total peripheral resistance and vascular tone of the capacitance vessels, are the most likely determinants of the volume-dependent elevation of blood pressure (ie, salt-sensitive hypertension) that occurs during partial inhibition of nitric oxide synthesis. This observation has important physiological and pathologic implications because it shows for the first time that the blockade of a single endogenous vasodilator substance can produce a sustained increase in blood pressure that can be influenced by changes in blood volume. Because of these characteristics, this review emphasizes in particular the characteristics of the nitric oxide synthesis pathway and briefly describes several known methods of increasing the biologic activity of nitric oxide; these methods eventually may be modified and used as therapeutic interventions in humans with deficient nitric oxide synthesis.

Abstract: Atherosclerotic cardiovascular disease is a significant cause of morbidity and mortality in patients with chronic renal failure. It is unclear, however, if atherosclerosis in fact occurs at a higher incidence compared with the nonuremic population matched for age, hypertension, and diabetes mellitus or if it occurs at an accelerated rate following the onset of end-stage renal disease. The extent of true atherosclerotic lesions, versus clinically diagnosed "atherosclerosis," in patients with chronic renal failure is equally unclear. Potentially, the uremic state per se, the dialysis treatment, and factors unrelated to renal failure may participate in atherogenesis. The relative contribution of each of these factors is unknown. In this review, we discuss the pathology of "atherosclerotic" lesions in patients with chronic renal failure and the putative factors involved in atherogenesis in this population and describe the results of available studies examining the issue of accelerated atherosclerosis in uremia.

Abstract: In the past year, major advances have been made in understanding the role of endothelin peptides in renal homeostasis. Numerous cells in the kidney secrete endothelin, which binds to two receptor subtypes on neighboring cells in an autocrine or paracrine mode. Endothelin is a potent vasoconstrictor of the renal vasculature that reduces renal blood flow and glomerular filtration rate. Endothelin also affects renal sodium and water handling. Finally, we may have to extend our concept of the renal actions of endothelin to include its growth factor actions.

Abstract: Phosphate retention plays a major role in the pathogenesis of hyperparathyroidism at all stages of renal insufficiency. Dietary phosphate restriction is mandatory only for adults and is not advised for children because of the recommended diet allowance. Dietary restriction is usually not sufficient, and phosphate binders are almost always necessary when the glomerular filtration rate falls below 40 mL/min. Because long-term administration of aluminum phosphate binders is associated with risk of aluminum intoxication despite the use of so-called "safe doses", alternative phosphate binders should be used. Magnesium hydroxide and carbonate can be used only for dialysis patients because a low dialysate magnesium concentration is necessary to prevent the hazards of hypermagnesemia. Therefore, the major alternative is the use of alkaline salts of calcium. The most recently proposed salt, acetate, has a higher phosphate-binding capacity than carbonate but exposes patients to the same incidence of hypercalcemia despite the use of half the dose of elemental calcium. These salts should be taken with meals in order to complex more dietary phosphate and decrease calcium absorption and therefore the risk of hypercalcemia. Oral calcium alone, without 1 alpha OH-vitamin D3 derivatives, can prevent hyperphosphatemia and hyperparathyroidism in most uremic patients before dialysis and in about half of the patients dialyzed with a dialysate calcium of 1.5 to 1.65 mmol/L. 1 alpha OH-vitamin D3 derivatives, which increase intestinal absorption of phosphate, should be used only when hyperphosphatemia has been prevented by oral calcium and diet and when plasma parathyroid hormone levels increase above three times the upper limit of normal. To decrease hypercalcemic risk, patients should be given 1 alpha OH-vitamin D3 derivatives, preferably at night, as an intermittent bolus (intravenous or oral). In dialysis patients, the dialysate concentration of calcium may have to be further decreased in order to prevent hypercalcemia when high doses of oral calcium are necessary to control hyperphosphatemia.

Abstract: Diabetes mellitus is the leading cause of irreversible renal failure in the United States, Japan, and industrialized Europe. Of those diabetic patients begun on uremia therapy, 80% are treated with hemodialysis and 12% with peritoneal dialysis. Continuous ambulatory peritoneal dialysis is proposed b

Abstract: Neuropeptide Y is a vasoactive peptide and is widely distributed throughout the central and peripheral nervous systems. Neuropeptide Y is co-released with noradrenaline by perivascular nerve endings. At high concentrations, it has a direct vasoconstrictor effect. In addition, it enhances the vascular effect of various agonists, including noradrenaline and angiotensin II. Moreover, neuropeptide Y has an inhibitory effect on renin secretion. This peptide may have an important role in cardiovascular regulation.

Abstract: The family of Na(+)- and Cl(-)-dependent, 12 transmembrane domain transporter proteins now includes transporters for neurotransmitter molecules in the brain and for substances important in extraneuronal tissues, including adrenal, kidney, and gut. Transported substrates include monoamine and amino acid neurotransmitters and nonperturbing osmolytes. A common protein topology is predicted and features intracellular N- and C-termini possessing phosphorylation sites and at least one large extramembranous loop with N-linked glycosylation. Using the rat dopamine transporter as a template, molecular modeling of putative transmembrane domains coupled with amino acid sequence conservation analysis indicates amino acid residues potentially involved in substrate and/or ion recognition. Targeting such residues with site-directed mutagenesis will help clarify substrate and ion binding sites and should facilitate rational design of therapeutics to combat depression, locomotor disorders, and substance abuse.