Erythropoietin and myocardial protection: what's new?

Erythropoietin (EPO), the principal hematopoietic cytokine produced by the kidney and the liver in fetuses, regulates mammalian erythropoiesis and exhibits diverse cellular effects in non-hematopoietic tissues. The introduction of recombinant human EPO (rhEPO) has marked a significant advance in the management of anemia associated with chronic renal failure. At the same time, experimental studies have unveiled its potential cardioprotective actions. As with other preconditioning agents, administration of exogenous rhEPO can confer myocardial protection against ischemia-reperfusion injury, in terms of reduction in cellular apoptosis and necrosis as well as improvement in myocardial functional recovery. The purpose of this study is to review current information regarding the various protocols used to investigate the effects of rhEPO administration as well as its cardioprotective properties. We also address the potential mechanisms underlying the protective effects of EPO. A better understanding of these mechanisms is essential for the development of clinical applications and the design of novel therapeutical strategies.     

Urolithiasis/nephrolithiasis: what's it all about?

Urolithiasis (urinary tract calculi or stones) and nephrolithiasis (kidney calculi or stones) are well-documented common occurrences in the general population of the United States. The etiology of this disorder is multifactorial and is strongly related to dietary lifestyle habits or practices. Proper management of calculi that occur along the urinary tract includes investigation into causative factors in an effort to prevent recurrences. Urinary calculi or stones are the most common cause of acute ureteral obstruction. Approximately 1 in 1,000 adults in the United States are hospitalized annually for treatment of urinary tract stones, resulting in medical costs of approximately dollar 2 billion per year (Ramello, Vitale, & Marangella, 2000; Tanagho & McAninch, 2004).     

Oral tolerance: is it all retinoic acid?

Oral tolerance has been argued to depend on "special" presentation of antigen in the gut. New studies support this idea by showing that the catalysis of vitamin A into retinoic acid (RA) in gut-associated dendritic cells (DCs) enhances the transforming growth factor (TGF)-beta-dependent conversion of naive T cells into regulatory T (T reg) cells and also directs T reg cell homing to the gut. These results reveal new tolerance mechanisms that will aid the use of T reg cells in the clinic.     

Proteinuria: is it all in the foot?

Despite significant advances in our understanding of the molecular structure and composition of the glomerular filtration barrier, the mechanisms underlying the presence of excess protein in the urine (proteinuria) in acquired human kidney diseases remain elusive. In a study appearing in this issue of the JCI, Sever and associates use a combination of biochemical, genetic, and in vivo approaches in mice to demonstrate a pivotal role of cathepsin L and its substrate the GTPase dynamin, in the induction of proteinuria and associated foot process effacement in glomerular podocytes (see the related article beginning on page 2095).     

Is it tonotopy after all?

In this functional MRI study the frequency-dependent localization of acoustically evoked BOLD responses within the human auditory cortex was investigated. A blocked design was employed, consisting of periods of tonal stimulation (random frequency modulations with center frequencies 0.25, 0.5, 4.0, and 8.0 kHz) and resting periods during which only the ambient scanner noise was audible. Multiple frequency-dependent activation sites were reliably demonstrated on the surface of the auditory cortex. The individual gyral pattern of the superior temporal plane (STP), especially the anatomy of Heschl's gyrus (HG), was found to be the major source of interindividual variability. Considering this variability by tracking the frequency responsiveness to the four stimulus frequencies along individual Heschl's gyri yielded medio-lateral gradients of responsiveness to high frequencies medially and low frequencies laterally. It is, however, argued that with regard to the results of electrophysiological and cytoarchitectonical studies in humans and in nonhuman primates, the multiple frequency-dependent activation sites found in the present study as well as in other recent fMRI investigations are no direct indication of tonotopic organization of cytoarchitectonical areas. An alternative interpretation is that the activation sites correspond to different cortical fields, the topological organization of which cannot be resolved with the current spatial resolution of fMRI. In this notion, the detected frequency selectivity of different cortical areas arises from an excess of neurons engaged in the processing of different acoustic features, which are associated with different frequency bands. Differences in the response properties of medial compared to lateral and frontal compared to occipital portions of HG strongly support this notion.