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At least 19 recordsLinked to original sources
PubMed1979

Primary culture of mammalian nephron epithelia: requirements for cell outgrowth and proliferation from defined explanted nephron segments.

Nephron segments were dissected from fetal or from early postnatal rabbit kidneys (n = 86) and explanted individually into primary tissue culture. Outgrowth of epithelioid cells and proliferation in monolayers from the collecting tubule and the thick ascending limb of Henle's loop occurred regularly if a special substratum and matrix were used. Media were either supplemented with non-proteins (defined media) or with embryo extract and fetal sera (undefined media). Outgrowth and monolayer spreading were recorded by Differential Interference Contrast Microscopy. Monolayer cells resemble those seen with the same recording technique during tubule in vitro perfusion. Undefined media were essential for growth of convoluted tubule segments from embryonic Nephron Anlagen and outgrowth of cells from proximal straight tubules, in contrast to the distal nephron segments. The specific functional and morphological properties of cells derived from primary culture of nephron segments are under study.

Animals↗
PubMed1976

Effect of diuresis and nephron dimensional heterogeneity on the distribution of nephron filtration rates.

Conflicting data in studies of the effect of natriuresis on intrarenal single nephron glomerular filtration rate (SNGFR) redistribution may arise from the interplay of hitherto largely overlooked factors. In the present work, the effect of diuresis induced by saline, glucose or mannitol, as well as the effect of anatomical nephron heterogeneity, were studied. A highly significant positive correlation was found between the logarithm of the urine flow per gram of kidney weight (log V) and the mean superficial (S) to mean juxtamedullary (JM) SNGFR ratio. The rise in S/JM SNGFR with diuresis was primarily a function of decreased JM SNGFR. Total proximal tubular length (TPL) was used as a measure of nephron size. The distribution of nephron sizes was evaluated as S/JM TPL. The effects of urine flow and anatomical heterogeneity on S/JM SNGFR were spearated by means of multiple regression analysis, which yielded the following equation: S/JM SNGFR = -0.049 + 0.179 log V + 0.818 S/JM TPL. Both slopes were highly significant (P less than 0.001). These findings indicate that S/JM SNGFR increases with urine flow, independently of sodium homeostasis, and that anatomical heterogeneity has a marked effect and must, therefore, be controlled. Conflicting data in the literature are harmonized with the present data when appropriate correction can be made for the dimensional factor. There is no evidence that SNGFR redistributions play a role in sodium homeostasis.

Animals↗
PubMed1977

Developmental changes in nephron number, proximal tubular length and superficial nephron glomerular filtration rate of rats.

1. Post-natal development of single nephron glomerular filtration rate, superficial proximal tubular length, nephron number and kidney weight have been studied in Sprague Dawley and in Wistar rats. 2. Superficial tubular length is a non-linear function of body weight or age. There seems to be a rapid growth until animals weigh about 150 g in Wistar rats. In this strain, growth is slower thereafter. This difference is not as evident in Sprague Dawley rats. 3. Nephron numbers increase over the same period at which rapid tubular growth occurs. 4. Sprague Dawley rats have somewhat fewer, but longer, proximal tubules than do Wistar rats. 5. In all animals weighing more than 100 g, SNGFR is linearly related to weight. For younger, smaller Sprague Dawley rats, the same linearity holds over the age range studied--older than 20 days of age. In Wistar rats, SNGFR relative to weight is less in young animals. 6. By relating SNGFR to total kidney GFR, evidence is obtained that maturation of renal function also involves a greater increase in filtration by superficial than by juxtamedullary nephrons.

Age Factors↗
PubMed1976

Single nephron glomerular filtration rate ratios of superficial, intercortical and juxtamedullary nephrons in rats during development.

In 20, 40 and 60-day-old rats the filtration rate was studied using Baines modification of Hanssen's Na4Fe (14CN)6 method enabeling the determination of single nephron glomerular filtration rate (SNGFR) ratio between superficial (S), intercortical (I) and juxtamedullary (J) nephrons. The proximal tubule lengths were determined as well. A close correlation was obtained between age and S/I, I/J and S/J of proximal tubule lengths and between age and I/J, S/J 14C-activities of ferro-cyanide. Presented findings confirm the data on the increasing role of superficial nephrons in the course of postnatal development of rat.

Age Factors↗
PubMed1978

Deep nephron function after release of acute unilateral ureteral obstruction in the young rat.

The effects of acute unilateral ureteral obstruction (UUO) of 18 h duration on deep nephron function was evaluated in 14 weanling rats with the technique of micropuncture. After release of UUO, 3.4 +/- 0.66% (SE) of the filtered water remained at the tip of the collecting duct nearly fivefold greater than in controls (0.75 +/- 0.10%). Similar differences were seen in fractional sodium that remained at this site. The ratio of tubular fluid osmolality to that of plasma was also reduced in the UUO group (1.53 +/- 0.06 vs. 4.60 +/- 0.26 in controls, P less than 0.001). Single nephron glomerular filtration rate of cortical and deep nephrons was significantly less (P less than 0.001) after release of UUO. Although the percentage of filtering nephrons was significantly reduced in both nephron populations, the decline in glomerular filtration rate was greater in cortical than in juxtamedullary nephrons (cortical:juxtamedullary nephrons = 27.6 +/- 4.5% vs. 53.3 +/- 5.2% in controls, P less than 0.005) which suggests that single nephron glomerular filtration rate is redistributed to deep nephrons after release of UUO. In contrast to cortical nephrons, the amount of tubular fluid which remains near the bend of the loop of Henle of deep nephrons was greater after release of UUO. This appeared to be the result of a decrease in the reabsorption of both water (tubular fluid:plasma inulin = 2.41 +/- 0.16 vs. 7.94 +/- 0.69 in controls, P less than 0.001) and sodium (52.3 +/- 4% vs. 40.7 +/- 2.9% of the filtered sodium in controls, P less than 0.02). It is suggested that this altered reabsorption occurs along both the proximal tubule and descending limb of the loop of Henle of juxtamedullary nephrons. Inner medullary plasma flow (IMPF), as measured with the [125I]albumin-accumulation technique, was significantly depressed before release of UUO, but exceeded control values 90 min postrelease. Such changes imply that the filtration fraction of deep nephrons is decreased and that physical factors in the proximal tubular reabsorption of sodium have been altered. When papillary solute content was measured before release of UUO it was low (428 +/- 23 vs. 1,205 +/- 106 mosmol/kg in controls, P less than 0.001) which indicates that the decline in papillary osmolality is not a consequence of the increased IMPF seen after ureteral release, but rather precedes it. In fact, the decline in papillary osmolality may contribute to the increase in IMPF after release of UUO and to the decreased reabsorption of fluid along the descending limb of the loop of Henle.

Animals↗
PubMed1976

A basic study of the Hanssen technique for evaluation of single nephron glomerular filtration rate.

The purpose of this study was mainly to examine some basic problems of the Hanssen technique for the evaluation of single nephron glomerular filtration rate (SNGFR). Firstly, experiments were performed using Wistar rats to determine the amount of C14-ferrocyanide necessary to give sufficient C14 radioactivity in dissected nephrons. Using 200 muCi of C14-ferrocyanide, the samples of dissected nephrons provided only twice as much as background. Hence, we chose the amount of 600 to 700 muCi of C14-ferrocyanide for each rat in the later experiments, which yielded the radioactivity 5 to 6 times as much as background. Secondly, the homogeneity of intrarenal C14-ferrocyanide distribution was tested. Five superficial (SUP) and juxtamedullary (JM) proximal tubules four different regions were dissected and the radioactivity of those nephrons was counted. The distribution of C14-ferrocyanide in each piece was representative of the overal distribution. The summary of morphologic and clearance studies were as follows. The mean lengths of proximal tubules of 40 SUP nephrons, 5.3 +/- 0.2 mm, and 39 JM nephrons, 6.3 +/- 0.1 mm, were significantly different (P less than 0.01). The mean glomerular diameter of the JM nephrons, 110 +/- 2.7 mu, was significantly greater than that of the SUP nephrons, 95 +/- 3.1 mu (P less than 0.01). The mean SNGFR of 129 SUP nephrons, 23.4 +/- 4.2 nl/min/100g Body Weight (BW), and that of 130 JM nephrons, 34.5 +/- 5.1 nl/min/100g BW, were significantly different (P less than 0.01). The ratio of superficial/juxtamedullary nephron glomerular filtration rate (S/JM Ratio) was 0.85 +/- 0.02. We conclude that C14-ferrocyanide is regularly distributed to the kidney and that it is necessary to infuse sufficient amount of C14-ferrocyanide in this technique.

Animals↗
PubMed1975

Nephron functional heterogeneity in the postobstructive kidney.

The purpose of this study was to determine the distribution of nephron filtration rates between superficial and juxtamedullary nephrons (S/J ratio) in kidneys studied immediately after relief of 24 hr total obstruction (acute) and after relief of prolonged partial obstruction (chronic). Injection of 14C-ferrocyanide and microdissection (modified Hanssen's technique) was used to provide an index of superficial and deep nephron glomerular filtration rate (GFR), and standard clearance determinations were done. In normal kidneys S/J ratio of 14C content (nephron GFR) was 0.73 plus or minus 0.03, a value similar to those obtained by other workers. After relief of acute obstruction, nephron GFR was too low for accurate measurement in 22% of superficial and 13% of deep nephrons. The mean S/J ratio of 14C content was similar to control, being 0.67 plus or minus 0.07, with only three of seven kidney showing loss of the normal S/J ratio. Since redistribution of nephron GFR was an inconsistent finding, while marked diuresis and natriuresis occurred in all rats, it appears that redistribution of nephron GFR is not an important factor in the phenomenon of postobstructive diuresis. After relief of chronic obstruction, diuresis and natriuresis were less marked but the mean S/J ratio of 14C content was 0.95 plus or minus 0.11, and in the majority of kidneys (six of eight), there was loss of distinction between superficial and deep nephron GFR. This redistribution of nephron function after relief of chronic, rather than acute, obstruction may be due to the more severe structural damage to the renal medulla of such kidneys and, although not responsible for postobstructive diuresis, it may be important in the diminished capacity of the chronically hydronephrotic kidney to conserve salt and water.

Acute Disease↗
PubMed1978

Renal potassium transport: contributions of individual nephron segments and populations.

General features of the processes that contribute to renal potassium excretion are understood from clearance, stop-flow, micropuncture, and in vitro microperfusion experiments. However, the complex architecture of the kidney has made it difficult to examine individual nephron segments in all parts of the kidney. Accordingly, the extent to which distinguishable nephron populations, such as superficial and deep, may differ in their contributions to overall potassium excretion are not known. Also, the nature of transport processes across the successive segments of the nephrons (including not only the underlying cellular mechanisms, but even the direction of transport) is not known for all segments in any one nephron population. Excreted potassium is derived both from filtered potassium that escapes reabsorption and from secreted potassium. The filtered portion is large in amphibians and may be larger than generally recognized in mammals. The remainder is secreted primarily by distal nephron segments (distal tubule and cortical collecting duct). Potassium is also secreted into descending limbs of Henle loops; apparently this fraction is recycled from collecting ducts, and so does not represent an additional quantity of potassium transferred from blood to tubule fluid. Systemic factors that affect potassium excretion (potassium intake, sodium chloride intake, mineralocorticoid hormone levels, acid-base balance, and diuretic treatments) do so by modifying the net uptake of potassium from blood to cell and by altering the rate of fluid flow through the distal nephron. Under most circumstances, the distal nephron in the cortex appears to secrete potassium and the medullary collecting duct reabsorbs potassium. Although it is clear that successive nephron segments transport potassium in different ways, evidence to date does not indicate that potassium is handled differently by superficial nephrons compared to nephrons whose glomeruli lie in the deeper levels of the cortex.

Acid-Base Equilibrium↗
PubMed1977

Phosphate transport in superficial and deep nephrons in phosphate-loaded rats.

We tested the hypothesis that greater phosphate delivery from deep nephrons than from superficial nephrons contributes to the addition of phosphate to the collecting system during phosphate loading. In the first group of eight anesthetized Munich-Wistar rats infused with phosphate and parathyroid hormone (PTH), fractional delivery of phosphate (FDP%) from superficial distal tubules was 56 +/- 6%, significantly less than the amount appearing in the urine, 67 +/- 6% (P less than 0.01). In the second group of six rats, we determined whether this addition of phosphate could be accounted for by a higher FDP% from the deep nephrons. Free-flow micropuncture collections were taken from deep nephrons (ascending limb of the loop of Henle in the papilla), superficial nephrons (distal tubules in the cortex), and urine (duct of Bellini). The FDP% to the ascending limb of the loop of Henle in deep nephrons was 78 +/- 10%, significantly greater than to the distal convoluted tubules in superficial nephrons, 51 +/- 6% (P less than 0.005), and the fractional excretion of phosphate in urine, 72 +/- 10% (P less than 0.05). Although a difference between FDP% in superficial and deep nephrons due to reabsorption in the ascending limb of the loop of Henle cannot be ruled out from the present data, other studies indicate that this interpretation is unlikely. We conclude that greater phosphate delivery by deep nephrons contributes to the addition of phosphate to the collecting system of phosphate-loaded rats.

Animals↗
PubMed1979

Nephron obstruction in nordihydroguaiaretic acid-induced renal cystic disease.

Studies were performed to characterize conditions in rat kidneys whose nephrons were made cystic by feeding 2% nordihydroguaiaretic acid (NDGA) to the animals. Using two micropipettes, we monitored intratubular hydrostatic pressures while perfusing single surface nephrons in NDGA-exposed (5 to 7 weeks) and normal rat kidneys. The introduction of 50 nl of Ringers solution labeled with 3H-inulin at a flow rate of 25 nl/min was associated with a significant mean (+/- SEM) increase (167 +/- 61%; P less than 0.02) in pressure in cystic but not in nondilated (-0.5 +/- 27.2%) or normal (31 +/- 23%) nephrons, respectively. The relative amount of 3H-inulin excreted in 40 min from cystic (4.0 +/- 2.0%) was less than that excreted from either nondilated (19 +/- 7%; P less than 0.05) or normal (105 +/- 26%; P less than 0.01) nephrons. Intralumenal pressures in nondilated but not other nephron groups correlated with urinary flow rates (r = 0.51; P less than 0.02). Single nephron filtration rates and tubular-fluid-to-plasma 3H-inulin rations in additional rats were similar among all groups of tubules. Concluding that these data reflected increased resistance to outflow from cystic nephrons, we examined these and additional NDGA-exposed (1 to 24 weeks) kidneys. 3H-thymidine radioautography demonstrated maximum collecting tubular cell hyperplasia (13% labeling) at 2 to 3 weeks of NDGA-exposure. Microscopy and microdissection demonstrated tiny mural polyps along outer medullary segments of collecting tubules. Thirteen tubules were traced to their outlets; polyps impinging on outflow lumens were found in all 13 instances. We conclude that partial nephron obstruction exists in NDGA-exposed kidneys and that obstruction is a likely contributor to cyst formation in this model.

Animals↗
PubMed1977

Structural and functional heterogeneity of mammalian nephrons.

Since the anatomical descriptions of Bowman showing differences between nephrons originating in the superficial and deep cortex, the concept of heterogeneity has been extended from identification of dissimilarities between nephrons to recognition of inhomogeneity within major portions of individual nephrons. We are now aware of functional correlates for the anatomical differences between nephrons, between analogous parts of different nephrons, and between the three portions of the proximal tubule and the three or more parts of the distal tubule. The implications of all of these differences for major renal processes, such as isosmotic fluid transport, salt balance, hypertension, urinary acidification, and the concentration or urine are now being defined. It seems likely that new conceptual and technical approaches, especially electron probe microanalysis, will add appreciably to defining the role of heterogeneity in these and other processes. Despite the increasing complexity of nephron heterogeneity, it is recommended that our basic nomenclature be retained and that new findings be incorporated into the schema set forth by Karl Peter. It would be very helpful if reports of investigations on single nephrons or segments of nephrons were to include diagrams delineating the structures on which the work was performed.

Animals↗
PubMed1976

Functional and morphologic maturation of superficial and juxtamedullary nephrons in the rat.

The development of single nephron glomerular filtration rate (SNGFER) was studied in both superficial and juxtamedullary nephrons in rats in relation to concomitant morphologic maturation. These experiments were carried out in rats between 23 and 91 days of age (between 36 nad 275 g body weight) with the [14C]ferrocyanide infusion technique. 2. SNGFR of the superficial and juxtamedullary nephrons increased with body weight, glomerular volume and proximal tubular length. 3. The ratio SNGFR of the superficial (S) nephrons/SNGFR of the juxtamedullary (JM) nephrons rose from 0-60 in the 40-60 g rats to 0-84 in the adult rats, demonstrating the centrifugal functional maturation of the nephrons. 4. The S/JM ratio for both glomerular volume and tubular length was constant and averaged 0-72+/--0-12 and 0-81+/-0-05, respectively, indicating that while the increase in SNGFR was greater for S than for JM nephrons, this was not accompanied by concomitant disproportionate increases of glomerular volume and/or proximal tubular length between these nephron categories during development in the rat.

Age Factors↗
PubMed1976

[Comparative cytologic study of nephron structure in higher vertebrates].

A comparative study of the cytological characteristics of the epithelial lining of the nephron and collecting tubules was performed in 9 species of reptiles, 19 species of birds and 12 species of mammals. Representatives of each class of higher vertebrates were shown to have certain specific features of the epithelial lining of different parts of the nephron. Differentiation of various areas of the proximal part of the nephron proceded in phylogeny with different intensity and the maximum specialization was characteristic of the most proximal portion of this part of the nephron. In the cells of the proximal parts of nephrons of some reptiles there were phenomena of apocrine secretion. Evolution of the distal part of the nephron developed to form a loop and differentiation of the distal convoluted segment. The higher differentiation of the epithelial lining of the nephron distal part in birds and mammals, unlike in reptiles, seems to be associated with a more considerable functional specilization of this part. In the cytochemical characteristics of the epithelium of the uriniferous and collecting tubules of kidneys of higher vertebrate animals there are common regularities in the distribution of RNA, proteins and some enzymes. The polysaccharide content is maximum in the epithelial cells of kidneys of reptiles.

Alkaline Phosphatase↗
PubMed1978

Nephron heterogeneity of phosphate reabsorption.

Previous micropuncture studies in rats have demonstrated that fractional phosphate delivery (FDP%) from superficial distal nephrons is higher than in urine. To determine whether this apparent reabsorption could be accounted for by a lower FDP% from the deep nephrons, FDP% was determined in free-low micropuncture from deep nephrons (DN) (ascending limb of the loop of Henle in the papilla), superficial nephrons (SN) (distal tubules in the cortex), and urine (duct of Bellini). In six acute thyroparathyroidectomized (TPTX) rats, FDP% in DN was significantly less than SN. The urinary fractional phosphate excretion (FEP%) was significantly less than in the SN, but not significantly different from the DN. In six chronic TPTX rats, FDP% in DN was significantly less than in SN. The urinary FEP% was significantly less than the FDP% in the SN, and significantly less than the FDP% in the DN, evidence which favors phosphate reabsorption in the terminal nephron. We conclude that in TPTX rats, which are conserving phosphate, deep nephrons reabsorb phosphate more avidly than superficial nephrons.

Animals↗
PubMed1979

Response of deep nephrons and the terminal collecting duct to a reduction in renal mass.

Juxtamedullary (JM) nephron and collecting duct function was studied after a two-thirds reduction in renal mass in the young rat. The glomerular filtration rate of JM nephrons was twofold greater in the remnant kidney (RK) group than in controls, but this increase was proportional to the increase measured in surface nephrons. Despite an increase in absolute reabsorption, delivery of sodium and water to the end of the proximal tubule of superficial nephrons and to the bend of Henle's loop of JM nephrons was increased. This was a consequence of an increase in filtered load and a decrease in fractional reabsorption. Potassium handling in surface nephrons was similar to that of sodium and water. In deep nephrons of the RK group, potassium delivery to the bend was increased as a consequence of increased filtered load. The terminal portion of the collecting duct has a role in this adaptive response to a reduction in renal mass. In rats with a RK, reabsorption of water occurred along this segment; however, when the amount reabsorbed was related to delivery, fractional water reabsorption was only 30% of controls. Changes in sodium handling were more profound. In the group with the RK, sodium reabsorption was not detectable along this segment. Thus, while 40% of delivered sodium was reabsorbed in controls, in the remnant kidney group the mean was not different from zero (-1.7%).

Animals↗
PubMed1979

Architecture of the mesonephric nephron in pig and rabbit.

As a precondition for determining nephron profiles in sections, mature mesonephric nephrons from pig and rabbit embryos were isolated by a maceration technique in order to demonstrate nephron architecture, length, and diameter. In the pig the proximal tubule is largely constant. In the distal tubule the pre-attachment zone shows the greatest variation. The zone of attachment ot the corpuscle and the ventrolaterally directed post-attachment coil has a predictable course as does the collecting tubule. In contrast to earlier reports, the nephron shows no drastic differences in tubule diameter and is up to 33 mm long. The proportional length of the three major nephron segments is surprisingly constant. The rabbit nephron, although much shorter (4 mm) and simpler, with an alomst S-shaped pattern, is less easily understood in sections. Marked irregularities in its course are caused by the different behaviour of the terminal proximal segments. The distal tubule shows an ampullary dilatation in the attachment zone but can be very narrow in the pre-attachment part.

Animals↗