A FURTHER STUDY OF THE REGENERATED EPITHELIUM IN CHRONIC URANIUM NEPHRITIS. AN ANATOMICAL INVESTIGATION OF ITS FUNCTION

Zebrafish exposure to environmentally relevant concentration of depleted uranium impairs progeny development at the molecular and histological levels

Uranium is an actinide naturally found in the environment. Anthropogenic activities lead to the release of increasing amounts of uranium and depleted uranium (DU) in the environment, posing potential risks to aquatic organisms due to radiological and chemical toxicity of this radionucleide. Although environmental contaminations with high levels of uranium have already been observed, chronic exposures of non-human species to levels close to the environmental quality standards remain scarcely characterized. The present study focused on the identification of the molecular pathways impacted by a chronic exposure of zebrafish to 20 μg/L of DU during 10 days. The transcriptomic effects were evaluated by the use of the mRNAseq analysis in three organs of adult zebrafish, the brain the testis and the ovaries, and two developmental stages of the adult fish progeny, two-cells embryo and four-days larvae. The results highlight generic effects on the cell adhesion process, but also specific transcriptomic responses depending on the organ or the developmental stage investigated. The analysis of the transgenerational effects of DU-exposure on the four-day zebrafish larvae demonstrate an induction of genes involved in oxidative response (cat, mpx, sod1 and sod2), a decrease of expression of the two hatching enzymes (he1a and he1b), the deregulation of the expression of gene coding for the ATPase complex and the induction of cellular stress. Electron microscopy analysis of skeletal muscles on the four-days larvae highlights significant histological impacts on the ultrastructure of both the mitochondria and the myofibres. In addition, the comparison with the transcriptomic data obtained for the acetylcholine esterase mutant reveals the induction of protein-chaperons in the skeletal muscles of the progeny of fish chronically exposed to DU, pointing towards long lasting effects of this chemical in the muscles. The results presented in this study support the hypothesis that a chronic parental exposure to an environmentally relevant concentration of DU could impair the progeny development with significant effects observed both at the molecular level and on the histological ultrastructure of organs. This study provides a comprehensive transcriptomic dataset useful for ecotoxicological studies on other fish species at the molecular level. It also provides a key DU responsive gene, egr1, which may be a candidate biomarker for monitoring aquatic pollution by heavy metals.

Mitochondrial energetic metabolism perturbations in skeletal muscles and brain of zebrafish (Danio rerio) exposed to low concentrations of waterborne uranium

Anthropogenic release of uranium (U), originating from the nuclear fuel cycle or military activities, may considerably increase U concentrations in terrestrial and aquatic ecosystems above the naturally occurring background levels found throughout the environment. With a projected increase in the world-wide use of nuclear power, it is important to improve our understanding of the possible effects of this metal on the aquatic fauna at concentrations commensurate with the provisional drinking water guideline value of the World Health Organization (15 μg U/L). The present study has examined the mitochondrial function in brain and skeletal muscles of the zebrafish, Danio rerio, exposed to 30 and 100 μg/L of waterborne U for 10 and 28 days. At the lower concentration, the basal mitochondrial respiration rate was increased in brain at day 10 and in muscles at day 28. This is due to an increase of the inner mitochondrial membrane permeability, resulting in a decrease of the respiratory control ratio. In addition, levels of cytochrome c oxidase subunit IV (COX-IV) increased in brain at day 10, and those of COX-I increased in muscles at day 28. Histological analyses performed by transmission electron microscopy revealed an alteration of myofibrils and a dilatation of endomysium in muscle cells. These effects were largest at the lowest concentration, following 28 days of exposure.

DETERMINATION OF THE QUANTITY OF SECRETING TISSUE IN THE LIVING KIDNEY

1. Under the strain induced by the administration of urea, it is possible to demonstrate the relation between the degree of anatomical damage in the kidney and the degree of defect in the urea-excreting capacity induced by uranium. 2. The closest correlation between structure and function was obtained when the ratio between the urea content of the urine and of the blood was used as the measure of function.

CELLULAR MECHANISMS OF RENAL SECRETION. A STUDY BY THE EXTRAVITAL METHOD : I. THE STRUCTURAL PHASE OF THE SECRETORY MECHANISM

1. The secretion of neutral red reproduces those variations which are observed in the mitochondrial apparatus of the renal tubule cells of animals living under native conditions. The tubular absorptive processes concerned with water, salts and sugars do not produce these effects. 2. The changes in the mitochondria consist of both structural and constituent alterations. These have been shown to be not merely phenomena concomitant with secretion, but a determining factor in one part of this process; namely, in the concentration of the dye within the cell.

STRUCTURAL AND FUNCTIONAL TRANSFORMATIONS IN THE TUBULAR EPITHELIUM OF THE DOG'S KIDNEY IN CHRONIC BRIGHT'S DISEASE AND THEIR RELATION TO MECHANISMS OF RENAL COMPENSATION AND FAILURE

1. The wall of the proximal convolution in chronic canine nephritis is composed of various types of epithelial cells which can be recognized as definite structural types from their cytological characteristics. 2. The function of these cell types, as tested by their reaction to the administration of trypan blue, varies with their structural constitution. 3. As a result of the varied cellular content of its wall the abnormal proximal convolution handles trypan blue by mechanisms which differ both quantitatively and qualitatively from those of the normal convolution. 4. A distinguishing characteristic of the decompensated kidney in chronic canine nephritis is the inability of its epithelium to concentrate trypan blue within its cells and to prevent diffusion of the dye from the lumen into the tubule wall. 5. It follows: (a) (from conclusion 3), that it cannot be assumed that the renal mechanisms concerned with other substances are not unaltered and that comparisons of blood and urine concentrations (clearances) have similar significance in the normal and nephritic kidney; (b) (from conclusion 4), that tubular dysfunction may play a part in the ultimate failure of the compensating kidney in all forms of chronic Bright's disease where the tubule walls are similarly affected.

MECHANISM OF UREA EXCRETION

1. Urea is present in the cells of the proximal convoluted tubule in a concentration higher than that of the blood or than that of the cells of any of the other kidney tubules. 2. Such a condition can only be reconciled to an assumption of an active secretion (excretion) on the part of these cells. 3. Urea also passes through the glomerular filter with the other crystalloids of the blood plasma. 4. The final concentration of urea is due to the above mentioned secretion by the proximal convoluted tubule, and to the absorption of water in other parts of the tubule.

The renal lesions of electrolyte imbalance. IV. The intranephronic calculosis of experimental magnesium depletion

A dietary depletion of magnesium in rats leads to the production in the thin limb of Henle's loop of the nephrons of spherical microliths composed of a matrix of PAS-positive substances and calcium phosphate (3). These microliths grow by accretion to form intranephronic calculi. The classical pathological syndrome of clinical nephrolithiasis is thus reproduced within the nephron; to wit, the origin of the calculus at a certain level, local traumatic damage at the site of its origin, passage with the fluid flow down the urinary passages, lodgment of the calculus at some restricting point, obstruction of fluid flow and the usual consequent localized intrarenal "hydronephrotic" alterations of regressive atrophic cellular dysplasias within the nephron. To the classical description of the two forms of urinary lithiases occurring in the bladder and in the renal pelvis must therefore be added a third form, intranephronic calculosis. From the first origin of a microlith to its ultimate form as a calculus its organized structure is characterized by its matrix (PAS-positive materials) in which the periodic precipitation of crystalline mineral (Ca(++), PO(3) (---)) occurs in a pattern simulating Liesegang rings.

CELLULAR MECHANISMS OF PROTEIN METABOLISM IN THE NEPHRON

1. The exaggeration of "hyaline droplet" formation observed in the renal lesion of epidemic hemorrhagic fever when treated with the infusion of large amounts of human serum albumin and the histochemical characteristics of the droplets so formed afford evidence towards their identification with the protein absorption droplets of experimental procedures and with those that occur in other renal diseases. 2. Protein absorption droplets (hyaline droplets) are the visible aspect of pathological modifications of a physiological process; i.e., the continuing reabsorption of plasma proteins by the proximal convolutions. 3. The mitochondria of the renal cells are directly involved in both the physiological and the abnormal reabsorption and disposal of the plasma proteins; the absorption droplets are a complex of reabsorbed proteins and mitochondrial substances and enzymes; they result whenever disposal is at a rate insufficient to prevent accumulation. 4. Failure of intracellular disposal of reabsorbed protein is determined by (a) the quantitative and qualitative characteristics of the protein and (b) by the functional state of renal cell. 5. Various factors in renal disease that result in disturbances of reabsorption and of intracellular disposal, both with and without droplet formation, are described.