Intracellular targets in heme protein-induced renal injury

Intracellular targets in heme protein-induced renal injury. We examined two potential intracellular targets in the glycerol model of acute renal failure, namely, the mitochondrion and the nucleus. Within three hours, alterations in mitochondrial function are already apparent. With either glutamate/malate or succinate/rotenone, state 3 and uncoupled respirations were decreased at three hours, and at 24 hours, such decrements were quite pronounced; in the presence of glutamate/malate, state 2 respiration was also depressed at 24 hours, while with succinate/rotenone state 2 was increased. Marked ultrastructural changes were observed in mitochondria studied at three hours, including the novel finding of degenerate mitochondria in autophagic vacuoles. Since the heme content in mitochondria was increased some tenfold within three hours, mitochondrial function was studied after exposure to concentrations of heme that reproduced such contents of heme: mitochondria initially displayed increased respiration, and subsequently, a persistent decline in oxygen consumption until oxygen consumption was virtually undetectable. With higher concentrations of heme, the early increase in oxygen consumption was blunted and the progressive decline in oxygen consumption was hastened. The antioxidant iron chelator, deferoxamine, prevented the early rise in oxygen consumption but did not prevent or delay the subsequent decline. We also assessed nuclear damage as a potential lesion in the glycerol model. DNA laddering was not observed at any time point. At 3 and 24 hours there was DNA injury by the TUNEL technique in the distal nephron but not in the proximal nephron. The 8-hydroxydeoxyguanosine/deoxyguanosine content was increased in the glycerol kidneys at 24 hours but not at three hours. At neither time point was evidence of apoptosis observed by light or electron microscopy. In studies undertaken in cell culture models, heme, at concentrations of 10 μM, failed to evince any such changes in LLC-PK1 cells, a cell line from the proximal tubule, or in MDCK cells, a cell line derived from the distal tubule. At concentrations of 50 μM, heme induced approximately 20% positivity in MDCK cells but none in LLC-PK1 cells by the TUNEL technique. We conclude that mitochondria and nuclei are prominent targets for injury in the glycerol model of acute renal failure. The presence of TUNEL-positive cells in the distal nephron but not at proximal sites in vivo underscores the increasing appreciation of the distinct responses of these nephron sites to nephrotoxic insults

Cyclic ADP-ribose metabolism in rat kidney: High capacity for synthesis in glomeruli

Cyclic ADP-ribose metabolism in rat kidney: High capacity for synthesis in glomeruli. Recent discovery of cyclic ADP-ribose (cADPR) as an agent that triggers Ca2+ release from intracellular stores, through ryanodine receptor channel, is an important new development in the investigation of intracellular signaling mechanisms. We determined the capacity of kidney and its components for synthesis of cADPR from β-NAD, that is catalyzed by enzyme ADP-ribosyl cyclase, and enzymatic inactivation that is catalyzed by cADPR-glycohydrolase. Little or no activity of ADP-ribosyl cyclase was found in extracts from the whole rat kidney, renal cortex, outer and inner medulla. On the other hand, incubation of β-NAD with similar extracts from rat liver, spleen, heart, and brain resulted in biosynthesis of cADPR. In addition, extracts from suspension of proximal tubules or microdissected proximal convoluted tubules virtually lacked ADP-ribosyl cyclase activity. In sharp contrast to proximal tubules and cortex, extracts from glomeruli had high ADP-ribosyl cyclase activity, similar to that found in non-renal tissues. Authenticity of cADPR biosynthesized in glomeruli was documented by several criteria such as HPLC analysis, effect of inhibitors and homologous desensitization of Ca2+-release bioassay. On the other hand, the activity of cADPR-glycohydrolase was similar in extracts from glomeruli and in extracts from kidney cortex. Mesangial cells and vascular smooth muscle cells grown in primary culture displayed considerable ADPR-ribose cyclase activity. Our results show that extracts from glomeruli, unlike extracts from renal tissue zones and proximal tubules, have a singularly high capacity for synthesis of cADPR. We surmise that cADPR-triggered Ca2+-releasing system can serve as an intracellular signaling pathway that may be operant in regulations of glomerular cell functions

Evolution of cardiac and renal impairment detected by high-field cardiovascular magnetic resonance in mice with renal artery stenosis

BACKGROUND: Renal artery stenosis (RAS) promotes hypertension and cardiac dysfunction. The 2-kidney, 1-clip mouse model in many ways resembles RAS in humans and is amenable for genetic manipulation, but difficult to evaluate noninvasively. We hypothesized that cardiovascular magnetic resonance (CMR) is capable of detecting progressive cardiac and renal dysfunction in mice with RAS and monitoring the progression of the disease longitudinally. METHODS: RAS was induced at baseline in eighteen mice by constricting the renal artery. Nine additional animals served as normal controls. CMR scans (16.4 T) were performed in all mice one week before and 2 and 4 weeks after baseline. Renal volumes and hemodynamics were assessed using 3D fast imaging with steady-state precession and arterial spin labelling, and cardiac function using CMR cine. Renal hypoxia was investigated using blood oxygen-level dependent (BOLD) MR. RESULTS: Two weeks after surgery, mean arterial pressure was elevated in RAS mice. The stenotic kidney (STK) showed atrophy, while the contra-lateral kidney (CLK) showed hypertrophy. Renal blood flow (RBF) and cortical oxygenation level declined in the STK but remained unchanged in CLK. Moreover, cardiac end-diastolic and stroke volumes decreased and myocardial mass increased. At 4 weeks, STK RBF remained declined and the STK cortex and medulla showed development of hypoxia. Additionally, BOLD detected a mild hypoxia in CLK cortex. Cardiac end-diastolic and stroke volumes remained reduced and left ventricular hypertrophy worsened. Left ventricular filling velocities (E/A) indicated progression of cardiac dysfunction towards restrictive filling. CONCLUSIONS: CMR detected longitudinal progression of cardiac and renal dysfunction in 2K, 1C mice. These observations support the use of high-field CMR to obtain useful information regarding chronic cardiac and renal dysfunction in small animals

Ecological specialization to fluctuating resources prevents long-distance migratory raptors from becoming sedentary on islands.

Background The adaptive transition between behavioral strategies, such as the shift from migratoriness to sedentariness, remains an outstanding question in evolutionary ecology. Density-dependent variation in the age of first breeding has been proposed as a feasible mechanism through which long-lived migratory birds with deferred sexual maturity should become sedentary to persist on islands. Although this pattern seems to hold for most raptors and herons, a few exceptions have been identified. One of these exceptions is the Eleonora's falcon, a long-distance migratory bird, which shows one of the most peculiar adaptations in the timing of reproduction and food requirements among raptors. Methodology/Principal Findings Here, we compiled data concerning demography, banding recoveries and satellite tracking of Eleonora's falcons to discuss likely explanations for the exceptional behavior of this insular long-distance migratory species. Conclusions/Significance New data reveal that Eleonora's falcons do return to the natal colonies in their first year and young birds are able to breed. However, in contrast to previous hypothesis, the highly specialized strategy of this and other ecologically similar species, as well as the virtual lack of food during winter at breeding areas prevent them from becoming sedentary on islands. Although the ultimate mechanisms underlying the process of sedentarization remain poorly understood, the evidence provided reveal the existence of important trade-offs associated with ecological specialization that may become particularly relevant in the present context of global change

Utjecaj mangana na sinaptičku transmisiju

In the course of our investigations of the influence of metal ions on synaptic transmission and acetilcholine output, we have noticed that manganese ions cause a block of ganglionic transmission when added to the fluid perfusing the superior cervical ganglion.Dodatak mangana tekućini, kojom se vrši perfuzija izoliranog gornjeg vratnog simpatičnog ganglija mačke, izaziva smanjenje kontrakcija membrane niktitans na stimulaciju predganglijskih vlakana vratnog simpatikusa. Stimulacija postganglijskih vlakana izaziva normalne kontrakcije membrane usprkos prisutnosti manganovih iona. Kalcijevi ioni imaju antagonističke djelovanje na blokadu sinaptičke transmisije izazvanu dodatkom manganovih iona. Mangan izaziva sinaptičku blokadu u koncentraciji od 100 mikrograma na 1 ml

Diagnosis of Partial Body Radiation Exposure in Mice Using Peripheral Blood Gene Expression Profiles

In the event of a terrorist-mediated attack in the United States using radiological or improvised nuclear weapons, it is expected that hundreds of thousands of people could be exposed to life-threatening levels of ionizing radiation. We have recently shown that genome-wide expression analysis of the peripheral blood (PB) can generate gene expression profiles that can predict radiation exposure and distinguish the dose level of exposure following total body irradiation (TBI). However, in the event a radiation-mass casualty scenario, many victims will have heterogeneous exposure due to partial shielding and it is unknown whether PB gene expression profiles would be useful in predicting the status of partially irradiated individuals. Here, we identified gene expression profiles in the PB that were characteristic of anterior hemibody-, posterior hemibody- and single limb-irradiation at 0.5 Gy, 2 Gy and 10 Gy in C57Bl6 mice. These PB signatures predicted the radiation status of partially irradiated mice with a high level of accuracy (range 79–100%) compared to non-irradiated mice. Interestingly, PB signatures of partial body irradiation were poorly predictive of radiation status by site of injury (range 16–43%), suggesting that the PB molecular response to partial body irradiation was anatomic site specific. Importantly, PB gene signatures generated from TBI-treated mice failed completely to predict the radiation status of partially irradiated animals or non-irradiated controls. These data demonstrate that partial body irradiation, even to a single limb, generates a characteristic PB signature of radiation injury and thus may necessitate the use of multiple signatures, both partial body and total body, to accurately assess the status of an individual exposed to radiation

Automated processing pipeline for neonatal diffusion MRI in the developing Human Connectome Project

The developing Human Connectome Project is set to create and make available to the scientific community a 4-dimensional map of functional and structural cerebral connectivity from 20 to 44 weeks post-menstrual age, to allow exploration of the genetic and environmental influences on brain development, and the relation between connectivity and neurocognitive function. A large set of multi-modal MRI data from fetuses and newborn infants is currently being acquired, along with genetic, clinical and developmental information. In this overview, we describe the neonatal diffusion MRI (dMRI) image processing pipeline and the structural connectivity aspect of the project. Neonatal dMRI data poses specific challenges, and standard analysis techniques used for adult data are not directly applicable. We have developed a processing pipeline that deals directly with neonatal-specific issues, such as severe motion and motion-related artefacts, small brain sizes, high brain water content and reduced anisotropy. This pipeline allows automated analysis of in-vivo dMRI data, probes tissue microstructure, reconstructs a number of major white matter tracts, and includes an automated quality control framework that identifies processing issues or inconsistencies. We here describe the pipeline and present an exemplar analysis of data from 140 infants imaged at 38-44 weeks post-menstrual age