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At least 19 recordsLinked to original sources

PubMed1977

Homogeneous cell populations from rabbit kidney cortex. Proximal, distal tubule, and renin-active cell isolated by free-flow electrophoresis.

A single-cell suspension has been prepared from rabbit kidney cortex by using a Ca-binding medium and gentle mechanical forces. The suspension was subjected to carrier-free electrophoresis, and several cell fractions were obtained. Proximal and distal tubule cell populations could be identified by their morphology. Renin-containing cells were located by means of radioimmunoassay. The morphology of the cells and their vitality (uridine incorporation) are discussed.

Animals↗

PubMed1979

The occurrence of lipid droplets in the proximal and distal tubules of the rat kidney after folic acid treatment.

Folic acid in high doses gives rise to an accumulation of lipid droplets in the kidney in addition to other changes in the epithelial of both proximal and distal tubules. With the administration of methionine a decrease of lipid droplets and an improvement of the structures of most of the membranes and mitochrondria are observed. These findings have been discussed in regard to the theory of the "chemically induced hyperplasia of the kidneys" related to folic acid.

Animals↗

PubMed1977

Micropuncture study of fluid handling in the cat kidney.

Superficial proximal and distal tubules of both kidneys of pentobarbital-anesthetized cats, infused with 2.5% (w/v) polyfructosan in Ringer solution at 0.45 ml/min, were micropunctured. Whole one-kidney GFR average 4.1 ml/min. SNGFR averaged 15 nl/min in 51 determinations and was proportional to whole-kidney GFR in individual cats. Absolute fluid reabsorption along the length of the accessible portion of the proximal tubule was 1.6 nl/min.mm. The length of the whole proximal tubule was 6 mm as measured from the glomerulum to the descending thin limb of Henle's loop. The length of the distal tubule was 3.5 mm from the macula densa to the first branching of the collecting duct. Proximal fluid was isoosmolar with plasma whereas fluid entering the distal tubule was markedly hyposmolar. Late distal tubular fluid samples were also isosmolar. The cat appears to be well suited for micropuncture experiments in terms of freedom from respiratory movements and the presence of surface distal tubules.

Animals↗

PubMed1977

Is the diverticulum of the distal and collecting tubules a preliminary stage of the simple cyst in the adult?

Whereas the outlines of nephrons and collecting ducts in kidneys from subjects less than 20 years old age regular, the number of diverticula on the distal tubule in kidneys from adults increase with age. An embryogenic progression from diverticula to microscopic and macroscopic cysts to radiologically detectable cysts can be established from morphological anomalies found in kidneys from adults. Therefore, a diverticulum on distal and collecting tubules and collecting tubules is postulated as the precursor of a simple cyst.

Adult↗

PubMed1978

[Subcellular morphology of the tubules in the rat compensatory-hypertrophic kidney according to the morphometric data].

Ultrastructure of sinuous proximal and straight distal tubules, as well as collecting tubules of the cortical layer in the rat kidney fixed with perfusion has been studied with electron microscopic morphometry 7--8 weeks after contralateral nephrectomy. The volume of mitochondria, the area of their crisis, the area of the membranes in intracellular labyrinth and other morphometrical parameters have been calculated. Relative volume of mitochondria in the nephron areas studied does not change, while in the collecting tubules it is elevated. The area of crisis in mitochondria and "coefficient of morphological organization level" of these organells in the proximal tubules are increased, in the distal do not change, in the collecting tubules increase again. Subcellular changes described are discussed mainly in terms of enhancement of concentrating function of the compensatory-hypertrophic kidney.

Adaptation, Physiological↗

PubMed1976

[Quantitative morphological investigation of the effect of ether anaesthesia on the kidney of the rat (author's transl)].

In the proximal and distal convoluted segments and the collecting tubule of the kidneys of 24 male albino rats, type Wistar TNO W 70 SPF, the nuclear volume was measured after the animals had been anaesthetized with ether for 15, 40 and 80 min. In contrast to nontreated controls there was a decrease in average nuclear size of 12.6% and 11.1% after 15 and 40 min in the proximal convoluted segment. Changes in nuclear size could not be detected in the distal convoluted segment and in the collecting tubules. While the decrease in the nuclear volume in the proximal convolution is considered to be a direct effect of ether, the enhanced reabsorption of sodium mentioned in other studies could be explained by an alpha-receptor mediated transport effect of the narcotic agent.

Anesthesia, Inhalation↗

PubMed1975

Scanning electron microscopy of the nephrotic kidney.

Scanning electron microscopy (SEMy), supplemented with light microscopy and transmission electron microscopy, was used to study aminonucleoside nephrosis in rats. The visceral epithelium undergoes dramatic restructing in response to aminonucleoside nephrosis. Due in part to an accumulation of intracellular vacuoles, kidney podocytes swell in size. Podocyte major processes lose their many pedicles and slit pores and form close junctions (80 A) with adjacent podocytes. Although no prominant pores opening into the urinary space are found in the visceral epithelium, there is evidence that podocyte vacuoles may rupture and thereby release protein into the urinary space. Many parietal cells also increase in size, accumulate intracellular vacuoles and come into very cose proximity to the visceral epithelium. Casts of PAS-positive, electron-dense material fill the lumina of many uriniferous tubules. Although most proximal tubules exhibit an extensive loss of brush border, no significant changes in other kidney microprojections or cilia were noted. Transmission electron and light microscopy of nephrotic kidneys reveal considerable changes in proximal and distal tubules including a reduction in mitochondria, in cell height, in electron density of the cytoplasmic matrix, in lateral and basal plasmalemma infolds, enlarged euchromatic nuclei, dilated lumens, and accumulation of PAS-positive cytoplasmic granules. SEMy of kidney needle biopsies from patients with proteinuria reveal that SEMy is useful for evaluating glomerular changes in man.

Animals↗

PubMed1979

Effect of volume expansion on renal glucose transport in normal and uremic dogs.

Proximal and distal tubule micropuncture studies were performed in normal and uremic remnant-kidney dogs to examine the tubule mechanism of glucose reabsorption before and after 10% extracellular volume expansion. In normal dogs volume expansion markedly inhibited glucose reabsorption in the proximal convoluted tubule, but the ensuing increase in further distal glucose delivery was nearly completely reabsorbed in the intermediate segment (between late proximal tubule and distal tubule). In the uremic, remnant-kidney dogs, glomerulotubular balance for glucose was well maintained in the proximal convoluted tubule despite an adaptive increase in nephron filtration rate. Volume expansion markedly increased glucose delivery out of the proximal convoluted tubule and an incomplete glucose reabsorption in the intermediate segment led to glycosuria. When glucose delivery to the intermediate segment was increased to a comparable degree by subthreshold glucose loading in hydropenic normal dogs, glucose reabsorption in this segment was virtually complete, suggesting that in the volume-expanded uremic dogs glucose reabsorptive capacity in the intermediate segment was reduced. Thus, the intermediate segment appears to play a significant role in the fine regulation of urinary glucose excretion.

Animals↗

PubMed1975

Transport ATPase cytochemistry: ultrastructural localization of potassium-dependent and potassium-independent phosphatase activities in rat kidney cortex.

A cytochemical method for the light and electron microscope localization of the K- and Mg-dependent phosphatase component of the Na-K-ATPase complex was applied to rat kidney cortex, utilizing p-nitrophenylphosphate (NPP) as substrate. Localization of K-N-ATPase activity in kidneys fixed by perfusion with 1% paraformaldehyde -0.25% glutaraldehyde demonstrated that distal tubules are the major cortical site for this sodium transport enzyme. Cortical collecting tubules were moderately reactive, whereas activity in proximal tubules was resolved only after short fixation times and long incubations. In all cases, K-NPPase activity was restricted to the cytoplasmic side of the basolateral plasma membranes, which are characterized in these neplron segments by elaborate folding of the cell surface. Although the rat K-NPPase appeared almost completely insensitive to ouabain with this cytochemical medium, parallel studies with the more glycoside-sensitive rabbit kidney indicated that K-NPPase activity in these nephron segments is sensitive to this inhibitor. In addition to K-NPPase, nonspecific alkaline phosphatase also hydrolyzed NPP. The latter could be differentiated cytochemically from the specific phosphatase, since alkaline phosphatase was K-independent, insensitive to ouabain, and specifically inhibited by cysteine. Unlike K-NPPPase, alkaline phosphatase was localized primarily to the extracellular side of the microvillar border of proximal tubules. A small amount of cysteine-sensitive activity was resolved along peritubular surfaces of proximal tubules. Distal tubules were unreactive. In comparative studies, Mg-ATPase activity was localized along the extracellular side of the luminal and basolateral surfaces of proximal and distal tubules and the basolateral membranes of collecting tubules.

Adenosine Triphosphatases↗

PubMed1975

Histological examination of the aldolase monomer composition of cells from human kidney and hypernephroid carcinoma.

Aldolase was specifically fixed in tissue sections by the use of antibody prepared either against aldolase A or against aldolase B. The localization of the antigen was demonstrated with the immuno-histochemical method. Aldolase A was found to be the predominant constituent in the cytoplasm of the distal tubules, the large vessels and the glomerula of normal kidney, and aldolase B in the proximal tubules. The collecting tubules and the capillaries contained a mixture of the two types. In the hypernephroid carcinoma cells only aldolase A could be found, but the capillaries within the tumor tissue did contain some aldolase B. Confirmation of these results was obtained by analysis of homogenate prepared with carefully selected tissue parts.

Adenocarcinoma↗

PubMed1976

The differentiation of proximal and distal tubules in the male rat kidney: the appearance of aldolase isozymes, aminopeptidase and alkaline phosphatase during ontogeny.

1. The specific activities of aminopeptidase, alkaline phosphatase and aldolase isozymes were measured in homogenates of kidneys taken at different stages of ontogeny. The cellular localization of these enzymes was studied in cryostat tissue sections using substrate linked assays for aminopeptidase and alkaline phosphatase and the mixed aggregation immuno-cytochemical technique for aldolase isozymes; local enzyme concentrations were estimated photometrically. 2. The presence of both aldolase-A and aldolase-B was demonstrated in all metanephrogenic cells (and at still higher concentrations in collecting tubule cells) of the rat fetus 16 days after conception and in the undifferentiated cells of the neogenetic zone of kidney up to 8 days after birth; no aminopeptidase or alkaline phosphatase could be found in these cells. 3. Measurements made on stained tissue sections show that the shift towards aldolase-B, seen in homogenate analyses, is due to a change in the relative amounts of proximal tubules. No evidence was seen for repression in the synthesis of aldolase-A or aldolase-B monomers in the different kidney cells during ontogeny. 4. Two transitions in the mode of nephron differentiation were observed: one was shortly after birth, the other followed weaning. Before the first transition the concentrations of the enzymes increased to different degrees, such that the enzymes reached concentrations comparable with those as in the cells of adult rats by 2 to 4 days post partum. After the second transition proximal tubule size and specific activity of brush border membrane enzymes increased 3 fold. In contrast, the distal tubules did not increase significantly in size, but their aldolase-A concentration increased 3 fold. 5. Evidence based on enzyme quantification and morphometry in kidney sections is presented to demonstrate that the proximal tubule cells show functional adaptation by two independent mechanisms: specific amplification of gene expression and hypertrophy. In contrast, the distal tubule shows functional adaptation only by specific amplification of gene expression.

Alkaline Phosphatase↗

PubMed1977

Kidney in the aging cat: neutral lipid and adenyl cyclase histochemistry.

Neutral lipid and adenyl cyclase were evaluated to determine their concentrations in the kidney of the aging cat. Kidneys from 24 domestic cats 2 months to 7.5 years old in 6 age groups were examined by light microscopic and histochemical methods. Activity in anatomic components of the kidney was assessed on a quantitative basis for evaluation of mean activity between the age groups. Renal components generally were stable in activity in the cats with advancing age. A significant increase in lipid concentration occurred in the convoluted segments of the proximal tubules with advancing age. In contrast, the straight segments of the proximal tubules displayed a significant decrease in lipid concentration with aging. Significant increases in adenyl cyclase activity were evident with aging in the ascending thick limb of Henle's loop and distal tubules.

Adenylyl Cyclases↗

PubMed1978

Hereditary polycystic kidney disease (adult form): a microdissection study of two cases at an early stage of the disease.

Kidney fragments from two cases of hereditary polycystic kidney disease (adult form) at an early stage were examined by microdissection. Localized cystic cystic dilatations were found in proximal and distal tubules, loops of Henle, and collecting tubules. Entirely normal nephrons and collecting tubules were also observed. Abnormal branching of collecting tubules or the abnormal attachment of nephrons, as described in other microdissection studies, were not found. Our observations do not confirm the hypothesis that the adult form of hereditary polycystic kidney disease is the consequence of ampullary dysfunction during early development.

Adult↗

PubMed1976

Distribution of calcitonin-sensitive adenylate cyclase activity along the rabbit kidney tubule.

The adenylate cyclase [ATP pyrophosphatelyase (cyclizing), EC 4.6.1.1] sensitivity to salmon calcitonin in 11 different segments of the rabbit nephron was investigated using a micromethod for enzyme activity measurements in samples, each containing a single piece of tubule. The required segments were isolated by microdissection from collagenase-treated rabbit kidneys. The results were expressed as femtomoles of adenosine 3':5'-cyclic monophosphate formed per mm of tubular length per 30 min of incubation time. In the presence of 0.1 mug/ml of synthetic salmon calcitonin, it was found that eight segments exhibited no hormonal sensitivity whereas maximal responses were induced in three segments, the "bright" portion of the distal convoluted tubule, the cortical and the medullary portions of the thick ascending limb of the loop of Henle (stimulated over control activity ratios were 32, 11, and27). The very high sensitivity to calcitonin of the adenylate cyclase contained in these three segments (0.01 ng/ml of salmon calcitonin inducing a 2-fold stimulation; half-miximal stimulation corresponding to about 0.3 ng/ml of salmon calcitonin) suggests that the distal convoluted tubule, as well as th cortical and medullary portions of the thick ascending limb of the loop of Henle represent physiological target structures of calcitonin action within the kidney.

Adenylyl Cyclases↗

PubMed1975

Metabolic patterns in various structures of the rat nephron. The distribution of enzymes of carbohydrate metabolism.

By means of the microdissection technique applied on kidney tissue, the following results were obtained: Hexokinase, an enzyme of glycolysis, revealed a low activity in the proximal and a high activity in the distal tubule. This distribution pattern is consistent with the finding that glucose is the main fuel for the distal tubule. Glucose-6-phosphatase, an enzyme of gluconeogenesis, demonstrates a significant activity in the distal tubule and in the glomerulus. Both structures are, however, no glucose producers. Phosphoenolpyruvate carboxykinase, the key enzyme of gluconeogenesis, is found only in the segments of the proximal tubule. The distal tubule lacks any activity. This is also the case during starvation and metabolic acidosis when gluconeogenesis is stimulated. Glutamic dehydrogenase, -an enzyme possibly connected with ammoniagenesis-, malate- and lactate dehydrogenase-, enzymes involved with hydrogen transfer through the mitochondrial membrane-, showed a close parallelism to phosphoenolpyruvate carboxykinase in their distribution along the proximal tubule. The bidirectional function of glyceraldehyde-P dehydrogenase is well documented by the close correlation to phosphoenolpyruvate carboxykinase (gluconeogenesis) in the proximal tubule and to pyruvic kinase (glycolysis) in the distal tubule.

Ammonia↗

PubMed1976

Effects of parathyroid hormone on sodium and calcium transport in the dog nephron.

1. The effect of purified bovine parathyroid hormone on renal tubular reabsorption of sodium and calcium has been studied by micropuncture in intact and recently thyroparathyroidectomized dogs. 2. Parathyroid hormone increased the rejection of sodium and calcium proportionately at the late proximal tubule in both intact and operated dogs. 3. In both groups of dogs, there was increased delivery of sodium and calcium to the distal tubule after the hormone. However, the Ca/Na ratio decreased, suggesting some selective enhancement of calcium reabsorption before the superficial distal puncture site. 4. In the final urine, the Ca/Na ratio decreased highly significantly in both groups of dogs, indicating a further selective effect of parathyroid hormone on calcium reabsorption in or beyond the distal convoluted tubule.

Absorption↗

PubMed1978

Magnesium handling in the dog kidney: a micropuncture study.

Micropuncture and clearance experiments were done on normal dogs to investigate magnesium handling by proximal and distal nephron segments. Tubular fluid electrolytes were analyzed with the electron microprobe. Tubular fluid to ultrafilterable magnesium ratio (TF/UF magnesium) was observed to rise above unity but less than the TF/P insulin ratio generated along the proximal tubule. This is in contrast to the other major cations, the ratios of which remain close to unity as water is abstracted. Tubular fluid obtained from the distal tubule contained less magnesium than the glomerular filtrate (mean TF/UF magnesium of 0.6) indicating the loop of Henle is the major nephron segment reclaiming a significant portion of the filtered load. The faction of filtered load remaining at the distal sampling site was similar to the fraction appearing in the urine (8% vs 7%) indicating very little reabsorption beyond the distal tubule in these normal states.

Animals↗

PubMedDate not supplied

Chronic reduction in renal mass: micropuncture studies of response to volume expansion and furosemide.

Chronic nephron loss is compensated by functional adaptations which preserve electrolyte homeostasis. The response to volume expansion and diuretics was tested in dogs. Three phase recollection micropuncture studies were performed to assess the response of the remnant kidney in various stages of renal failure to furosemide administration (10 mg/Kg) and graded volume expansion (3 percent and 10 percent body weight). After the diuretic maneuvers, mean fractional excretion of sodium, potassium and water rose progressively in normal dogs (Stage I), with a greater increase in the remnant kidneys in the presence (Stage II) and absence (Stage III) of the contralateral kidney. Proximal and distal TF/P (Inulin) ratios were depressed after 3 percent volume expansion. However, proximal TF/P (Inulin) was not further lowered after 10 percent volume expansion and furosemide administration, while distal TF/P (Inulin) ratios were progressively depressed. The distal TF/P (Inulin) ratios in Stage III were significantly lower than in Stage II under analogous conditions. Our results suggest that the adaptive increase in the response of sodium transport by the remnant kidney to the diuretic maneuvers occurs in the loop of Henle, both in the azotemic and the non-azotemic stage. Adaptation of potassium excretion, as revealed by distal micropuncture, took place in the azotemic Stage III. Chronic functional adaptation for electrolyte transport occurs even before azotemia in the distal nephron and includes the proximal tubule with azotemia.

Adaptation, Physiological↗