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

Renal pathophysiology: lessons learned from the canine remnant kidney model

OBJECTIVE

To review the pathophysiology of chronic kidney disease (CKD) in dogs and the contributions of the canine remnant kidney model to our understanding of this disease.

DATA SOURCES

Original studies in the human and veterinary medical fields.

DATA SYNTHESIS

Three of the fundamental principles of modern nephrology-the intact nephron hypothesis, the trade-off hypothesis, and the hyperfiltration theory were developed directly as a result of studies of the remnant kidney model. Most of the pivotal early studies were conducted in dogs. As a result, our understanding of CKD, and of the renal and systemic adaptations to CKD, is largely based on studies of this model.

CONCLUSIONS

Studies of the remnant kidney model have advanced our understanding of the pathophysiology of CKD. Nearly every therapeutic intervention used in CKD, by veterinarians and physicians alike, has its basis in studies of the remnant kidney model or in knowledge that was derived from studies of this model. A great debt is owed to the canine participants in these studies and to a small number of key scientists who conducted this important and insightful research.

Atubular glomeruli in chronic renal disease

The pathological changes in chronic renal failure are heterogeneous and may depend on the primary disease process. Renal function is better correlated with tubular and interstitial changes than with glomerular changes detectable in simple two-dimensional sections. Atubular glomeruli have been demonstrated in many tubulointerstitial disorders. They constitute a significant portion of the glomerular population in some chronic renal diseases. The atubular glomeruli are generally small, but they have open capillaries and minor ultrastructural changes. The number of capillaries is decreased. Glomeruli connected to normal proximal tubules have volumes at the normal level or above. They have not been shown to be eliminated. The presence of atubular glomeruli may explain the correlation between the volume of proximal tubules and the volume of interstitium, on the one hand, and altered renal function on the other. The presence of atubular glomeruli could explain the irreversibility of chronic renal diseases. It is likely that interstitial fibrosis and tubular atrophy in themselves contribute to the decrease in renal function of both glomerular and nonglomerular renal diseases. In glomerular diseases, the glomerular lesion and hyperfiltration may play the major part in the pathogenesis of the deterioration of renal function. The available evidence points toward glomerulo-tubular disconnection as an important and common cause of progression and irreversibility of chronic renal diseases. It provides a simple explanation for the common observation of severely reduced kidney function and mostly normal-looking glomeruli--at least in two dimensions.

The application of renal microdissection to the study of kidney disease in infancy and childhood

The methods of renal microdissection are of essential value in the study of kid ney problems in infancy and childhood. Characteristics of nephrons in normal kidneys in the pediatric age group are presented, as well as examples of some of the proximal tubular abnormalities which have been demonstrated in renal disease in infancy and childhood.

These illustrations were shown in an Exhibit at the American Association of Urology Meeting and won an Honorable Mention; and at the College of American Pathologists ASCP Meeting where it re ceived the Gold Award in the Educational Division.

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.

INFLUENCE OF EXPERIMENTAL KIDNEY DAMAGE ON HISTOCHEMICALLY DEMONSTRABLE LIPASE ACTIVITY IN THE RAT. COMPARISON WITH ALKALINE PHOSPHATASE ACTIVITY

Lipase activity was found in the cytoplasm of the proximal convoluted tubules in tissue sections of rat, rabbit, dog, mouse, hamster, and guinea pig, stained according to Gomori's method. Uranium and mercury poisoning do not inactivate the enzyme in necrotic cells of the proximal convoluted tubules. Its activity diminished in the atrophic and regenerating cells of the kidneys of rats, surviving the acute phase of the intoxication. In the acute stage of choline deficiency marked reduction in enzymatic activity was seen in the necrotic tubules, and in the atrophied and regenerating tubules in the subacute stage. Lipase activity was markedly diminished in hydronephrotic kidneys 10 to 12 days after ligation of the ureter. In sections stained for alkaline phosphatase activity nearly identical alterations were found. Experimental damage influences both histochemically demonstrable enzymes in a similar manner.