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W Kriz

Publications and source records attributed to W Kriz.

At least 109 records · Page 6Linked to original sources
PubMed1987

Cycles and separations: the histotopography of the urinary concentrating process.

We have analyzed the histotopography of the renal medulla of the rat in terms of cycles and separations. Cycles are pathways by which solute leaving the medulla in an ascending structure (AVR, AHL) is returned to a deeper medullary level. Separations are based on spatial incontiguity and special characteristics of the interstitium and blood supply. The two concepts are complementary: the compartmentalization resulting from separations imparts specificity to the cycles. Structural lateral heterogeneity, consisting in distinct domains organized around vascular bundles, is present in one form or another in all three medullary zones. Such compartmentalization probably leads to heterogeneity in interstitial solute concentrations, a state of affairs inconsistent with the requirements of a "central core". In all such considerations of exchanges between compartments, the lack of a unitary interstitium must be borne in mind. Instead, three general types of interstitium may be distinguished: corresponding roughly to those of the OS and VB, the interbundle region of the IS, and the IM. Among the histotopographic features of the renal medulla not usually included in models of the urinary concentrating mechanism but likely to have functional significance are the association of CD with completely distinct populations of AVR and AHL in the OM and IM; a clear-cut separation throughout the medulla between cycles involving long loops and those involving short loops; the lack of an effective countercurrent association between ascending and descending limbs of short loops in the IS; and a pronounced separation of the venous drainage of the IM from that of the OM.

Animals↗
PubMed1987

Possible role of the thick ascending limb and of the urine concentrating mechanism in the protein-induced increase in GFR and kidney mass.

The mechanisms by which high protein intake increases filtration rate and kidney hypertrophy in health and may be detrimental to the kidney in chronic renal failure are not well understood. We studied the kidneys of Sprague Dawley rats fed high (HP) and low (LP) isocaloric protein diets (32% and 10% casein, respectively) for 4 weeks. HP induced significant increases in kidney mass, GFR, and maximum urine concentrating ability (UMax). Kidney hypertrophy was characterized by (1) a selective increase in thickness of the inner stripe of the outer medulla (IS, +54%, P less than 0.001) while total kidney height (from cortex to papillary tip) increased only by 18%; (2) a considerable hypertrophy of the thick ascending limbs (TAL) in the IS (+43% epithelium volume/unit tubular length) but not in the outer stripe nor in the cortex; and (3), an increase in heterogeneity of glomerular volume between superficial and deep nephrons (P less than 0.05). these morphologic changes parallel those we previously reported in rats fed a normal protein diet (25% casein) but in which the operation of the urine concentrating mechanism was chronically stimulated by ADH infusion or by reduction in water intake. In contrast, normal kidney growth with age or kidney hypertrophy induced by uninephrectomy were not accompanied by preferential enlargement of IS structures.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Heterogeneity of the podocyte membrane in rat kidney as revealed by ethanol dehydration of unosmicated specimens.

The ultrastructure of the podocyte membrane was studied by means of transmission electron microscopy of unosmicated tissue samples after acetone or ethanol dehydration and subsequent embedding in a polyester resin. The podocyte membrane in glutaraldehyde (GA)-fixed, acetone-dehydrated samples consisted of a relatively thick, clear layer (about 6 nm) abutted by the dark staining cytoplasm and a dark surface layer. In GA-fixed, ethanol-dehydrated samples a striking intramembranous pattern was observed in the podocyte cell membrane. The luminal podocyte membrane was regularly perforated by gaps about 25 nm wide. In grazing sections these gaps appeared round and were separated by a honeycomb pattern of intact membrane. The abluminal membrane, in contrast, generally maintained its continuity. The clear layer of the podocyte membrane was thinner in ethanol-dehydrated samples than in acetone-dehydrated ones. In tissue samples fixed with GA supplemented by ruthenium red, ethanol dehydration was not associated with cell-membrane perforations. Based on these observations as well as on biochemical data from the literature we suggest that in GA-fixed, unosmicated, acetone-dehydrated samples the structural integrity of the podocyte membrane is well preserved, while ethanol dehydration extracts some specific material from regularly distributed domains in the podocyte cell membrane.

Animals↗
PubMed1986

Long-term culture of renin containing tissue.

Thin cortical tissue explants from kidneys of hydronephrotic mice were excised and incubated in different culture media containing growth and proliferation factors. Over a period of several months the content of renin in the explants and in the culture medium was repeatedly measured, to define the conditions necessary for the maintenance of renin production in a long-term culture. The best results were obtained when culturing the renal tissue in Dulbecco's medium (DMEM) with 10% fetal calf serum, 6 units/100 ml platelet-derived growth factor and 200 ng/ml glycylhistidyllysine. Renin was still present within the cells and in the culture medium after more than six months. Prevention of dedifferentiation, as evidenced in this case by the maintenance of renin production, seemed to be dependent on specific extracellular matrix proteins of renal origin. If the explants were dissociated from their matrix components by collagenase, a gradual loss of renin production was observed within 5 days. Complementation of the collagenase-digested cell suspension with different nonrenal extracellular matrix materials did not afford the stabilizing effect of the original pericellular matrix.

Animals↗
PubMed1986

Electrical properties of renal collecting duct principal cell epithelium in tissue culture.

Whereas collecting duct epithelium in vivo is composed of principal and intercalated cells, we grew a pure principal cell epithelium using a new technique involving tissue culture. These principal cells were derived from collecting duct anlagen of newborn rabbits. We investigated the electrical properties of such epithelia in a newly designed lucite double-chamber with an inner opening of 0.08 cm2. Our observations were: mean transepithelial resistance Rte was 0.83 +/- 0.2 k omega cm2 at 37 degrees C and after preincubation in aldosterone; mean transepithelial potential difference Vte was low and variable under standard conditions and at room temperature but increased to -59.5 +/- 4.4 mV (sign referring to polarity of apical surface) after preincubation in 10(-6) mol/l aldosterone and at 37 degrees C; 10(-6) mol/l amiloride added to the apical perfusion fluid largely abolished this Vte while increasing Rte by 120%; experiments with 5 X 10(-3) mol/l BaCl2 in the apical perfusion fluid failed to change Rte and Vte significantly. This principal cell epithelium therefore has characteristics of a "tight" epithelium with active sodium transport; however, its electrical properties differ from those of the isolated perfused collecting duct segment.

Aldosterone↗
PubMed1986

The structural organization of the kidney of Typhlonectes compressicaudus (Amphibia, Gymnophiona).

The structural organization of the kidney of Typhlonectes compressicaudus (Amphibia, Gymnophiona) was studied by light microscopic (LM) examination of serial paraffin and semithin Epon sections. The kidney is slender and quite long and has a mesonephric segmental construction; the excretory duct (Wolffian duct), running along the lateral side of the kidney, segmentally receives the terminal trunks of the collecting duct system. The nephron has the following parts: renal corpuscle, neck segment, proximal tubule, intermediate segment, distal tubule and connecting tubule. The distal tubule is located in a ventromedial (central) zone of the kidney; all other tubular segments lie in a dorsolateral (peripheral) zone. The renal corpuscles are found at the border between these two zones. The renal corpuscle is very large; its urinary pole faces the peripheral zone. A small proportion of neck segments receive either a nephrostomal duct or a blind branch. The proximal tubule is a thick, highly convoluted tubule. The intermediate segment is ciliated and makes a few coils. The distal tubule is composed of three portions: a highly convoluted part in the central zone, subsequently an attachment site with the renal corpuscle and a short postattachment-part. The connecting tubule and the collecting duct have a heterogeneous epithelium consisting of light and dark cells. The collecting duct is distinguished by dilated intercellular spaces. The Wolffian duct has a pseudostratified epithelium. The present study correlates the course and segmentation of the renal tubule of Typhlonectes. The tubule has three major convolutions. The first occurs in the proximal tubule in the peripheral zone; the second is established by the distal tubule and occurs in the central zone; the third is formed by the connecting tubule and is found in the peripheral zone.

Amphibians↗
PubMed1986

The shape of renal vasa recta capillaries and its effect on calculation of single capillary blood flow.

Previous studies of the renal papilla of the rat have suggested that the vasa recta capillaries can be well approximated by elliptical cylinders (C. Holliger, K. V. Lemley, S. L. Schmitt, F. C. Thomas, C. R. Robertson, and R. L. Jamison, 1983, Circ. Res., 53, 401-413). This hypothesis was validated in a morphological study employing several methods of specimen fixation and preparation. Papillas of young (body wt = 90 g) Wistar rats were fixed and subsequently examined by light and electron microscopy. Cross-sectional shapes and orientations were determined for 300 superficial vasa recta. The ratio, beta, of vessel cross-sectional major-axis-to-minor-axis lengths was 1.39 +/- 0.24 (SD). Values of beta greater than 1.0 (the value expected for circular vessels) could not be accounted for by either fixation artifact or the angle of histologic sectioning of the papillas. A quantitative estimate of the relationship between the apparent capillary diameter measured in vivo and the capillary cross-sectional area was made using a mathematical model which accounts for cross-sectional shapes and orientations of the vasa recta. This estimate implies that current methods of calculating single vas rectum blood flow using apparent diameters and blood velocities determined in vivo probably overestimate actual blood flow by about 25%.

Animals↗
PubMed1985

Ultrastructural localization of Tamm-Horsfall glycoprotein (THP) in rat kidney as revealed by protein A-gold immunocytochemistry.

The present study describes the intracellular distribution of Tamm-Horsfall protein (THP) in rat kidney. The localization was determined by immunoelectron microscopy using the protein A-gold technique. Various fixation and embedding protocols were evaluated for this purpose. Brief perfusion fixation (3 min) with 1% glutaraldehyde and embedding in a highly hydrophilic glycol methacrylate-polyester mixture were most appropriate for antigen-antibody recognition and structural preservation. The overall tissue distribution of THP was evaluated by indirect immunofluorescence microscopy; reaction was strong along the entire thick ascending limb of the loop of Henle (TAL) with enhanced fluorescence in the apical cytoplasm. On the electron microscopic level immunogold labelling was concentrated over numerous membrane-bound vesicles which form a compartment in the apical cytoplasm. The Golgi region was consistently labelled, whereas the plasma membranes revealed only sporadic labelling at the luminal side, and basolateral membranes were mostly unlabelled. Quantitative evaluation of the gold labelling, which was separately done for the inner stripe, outer stripe and cortical TAL, consistently showed the highest particle density in the apical cytoplasm. Middle and basal levels in the TAL cells were only moderately labelled. The results are discussed with respect to the current opinion which describes THP as a membrane glycoprotein. We speculate that the accumulation of THP in the apical vesicular compartment of TAL cells indicates a storage site of the protein, possibly prior to extrusion via exocytosis of the vesicle contents.

Animals↗
PubMed1985

Selective ADH-induced hypertrophy of the medullary thick ascending limb in Brattleboro rats.

A morphometric study was undertaken to quantitate the morphologic changes induced by ADH availability in the rat kidney. Homozygous Brattleboro rats with hereditary diabetes insipidus (DI) (no ADH) were compared to heterozygous Brattleboro control rats (HZ) and to DI rats after 5 to 6 weeks of continuous ADH infusion by implantable Alzet osmotic minipumps (TDI). ADH resulted in a 37% increase in mass of kidney per unit body wt. All kidney zones and all nephron segments were not increased uniformly. The inner stripe was enlarged more than other renal zones. It represented 15.5 +/- 0.7% of the total kidney height along the cortico-papillary axis in DI and 22.2 +/- 1.5% in TDI (P less than 0.025). The volume of the inner stripe in DI and TDI amounted to 10.9 +/- 0.9 and 18.0 +/- 1.0% of the total kidney volume, respectively (P less than 0.001). Selective increases in tubular diameter and cell height, due mostly to an hypertrophy of pre-existing cells, were observed in the earliest part of the thick ascending limbs (TAL) in the inner stripe, resulting in a twofold increase in epithelial volume per unit tubular length (P less than 0.001). Volume density of mitochondria and surface density of basolateral membranes were unchanged but, due to the increase in cell volume and inner stripe thickness, the amount of mitochondria and the surface area of basolateral membrane in the TAL were more than tripled in the inner stripe of treated rats. These changes provide a much greater salt transport capacity in the TAL of treated rats. They probably represent an adaptation of the early TAL to an enhanced sodium chloride transport in response to a direct ADH stimulation and/or to an increased salt delivery to this segment in the concentrating kidney.

Animals↗
PubMed1985

Pre- and postglomerular arterioles of the kidney.

Characteristics of the structural organization of the afferent and efferent glomerular arterioles of the mammalian kidney, that have so far escaped adequate functional discussion, include: presence and distribution of myoendothelial junctions in afferent and efferent arterioles and their possible functional relevance as stretch receptors; distribution of smooth-muscle cells around cortical efferent arterioles and, in particular, the presence of a contractile segment at the beginning of the efferent arterioles; elaboration of a basement membrane-like material beneath the endothelium of efferent arterioles and the continuity of this material with the mesangial and extramesangial matrix material; and structural organization of the endothelium of juxtamedullary efferent arterioles, consisting of up to 30 longitudinally arranged endothelial cells, and its possible functional significance.

Animals↗
PubMed1985

Structural adaptation of the distal convoluted tubule to prolonged furosemide treatment.

Rats were treated with furosemide, continuously applied by implanted minipumps, for 6 days. As compensation for the salt lost with the urine the animals drank large amounts of a salt solution ad libitum. This procedure resulted in an enlargement of kidney cortex. Light and electron microscopic studies revealed a proliferation of the distal convoluted tubule (DCT). The proportion of the DCT in the cortical tissue increased from 5.98 +/- 1.3% in controls to 9.54 +/- 1.7% (P less than 0.01) in treated rats. Basolateral cell membrane amplification in DCT cells increased from 17.33 +/- 2.9 to 38.24 +/- 5.8 (P less than 0.0001) in treated rats, while luminal membrane area per unit tubular length did not change. The structural changes after furosemide treatment in the DCT suggest an increase in active transcellular transport capacity of this segment. It is assumed that the chronically altered Na load of the tubular fluid (due to transport inhibition in the thick ascending limb of Henle's loop) delivered to the DCT may specifically stimulate the transport capacity of this segment by augmentation of basolateral cell membrane area. The changes occurring in the segment situated downstream to the one in which the function is impaired by furosemide emphasize the role of tubular fluid composition in the regulation of transport function.

Animals↗
PubMed1985

Morphologic and functional evidence for oxygen deficiency in the isolated perfused rat kidney.

Morphologic and functional studies were undertaken in the isolated rat kidney, perfused with an albumin-Krebs-Henseleit solution, to which 5% human erythrocytes and/or various amino acids had been added. Perfused only with the albumin-Krebs-Henseleit solution, the kidneys displayed a characteristic pattern of cell necrosis after 2 hours of perfusion, which was confined to the interbundle region of the outer medulla and was not evident in either the cortex or the inner medulla. In the outer stripe only those proximal straight tubules (P3 segments) farthest from the vascular bundles were damaged. In the inner stripe only those thick ascending loops of Henle at the periphery of the vascular bundles escaped damage; all thick ascending loops of Henle lying farthest from the bundles were severely damaged. The number of damaged tubules increased toward the border to the inner medulla. Necroses in both segments, P3 and thick ascending loops of Henle, could be prevented by perfusion with the erythrocyte-albumin-Krebs-Henseleit solution but not by the addition of glutathione, in the absence of erythrocytes. Perfusion with the erythrocyte medium also significantly improved glomerular filtration rate and sodium and glucose reabsorption. It is concluded that, in the isolated, erythrocyte-free perfused kidney, the oxygen content of the "arterial" vasa recta in the vascular bundles is only sufficient to supply the tubules in the immediate surroundings. Countercurrent exchange in the vascular bundles between arterial and "venous" vasa recta progressively lowers the arterial oxygen content as the inner stripe of the outer medulla is approached and with it the number of tubules receiving an adequate oxygen supply.

Animals↗
PubMed1984

Interendothelial junctions in kidney vessels.

The interendothelial junctions of all segments of the renal vasculature have been studied in eight species using the freeze-fracture technique. Three types of junctions have been found. Combinations of tight and gap junction elements are characteristic for interlobular arteries and proximal afferent arterioles. Continuous tight junction strands not subdivided into individual particles are typical for the glomerular arterioles close to the glomerulus and the vasa recta. The interendothelial junctions of glomerular and peritubular capillaries and cortical veins are characterized by slight elevations decorated with sparse arrays of particles on the P-face of the endothelial cell plasma membrane.

Animals↗
PubMed1984

Morphometric studies of the extraglomerular mesangial cell field in volume expanded and volume depleted rats.

The extraglomerular mesangial cell field was studied by morphometric techniques in volume expanded and volume depleted rats. The volume density of the extraglomerular mesangial interstitium was found to be significantly different between the two conditions, 16.9 +/- 3.7% in volume depletion and 29.0 +/- 4.1% in volume expansion. No difference in the volume density of the peritubular interstitium could be detected under the same conditions. These findings are interpreted as indicating a specific sensitivity of the extraglomerular mesangial interstitium to changes in body fluid content, a phenomenon which may play a role in the mechanism of resetting the tubulo-glomerular feedback control.

Animals↗
PubMed1984

Immunohistochemical localization of a protein fraction derived from rabbit renal papilla.

Studies were carried out to define antigenic characteristics of the rabbit renal collecting duct. Renal papillae of adult rabbits were homogenized, centrifuged, and the 600 X g pellet was extracted with 0.5% Triton X-100 in the presence of 1 M NaCl. The crude extract was fractionated on an anion exchange column (DEAE cellulose). A fraction enriched in acidic proteins that co-purified with a radioactive 150 kd glycoprotein from cultured collecting duct cells (Minuth 1982), was used for immunization of guinea pigs. The antiserum shows the following characteristics as revealed by indirect immunofluorescence on the rabbit kidney: 1) Among all tubular epithelial cells only principal cells of the collecting duct and the connecting tubule cell show immunoreactivity. 2) The antiserum decorates the epithelial-interstitial interface of the whole collecting duct as well as of connecting tubule and thick ascending limb of Henle's loop. 3) There is immunoreactivity of interstitial fibers throughout the kidney. 4) Epithelial cells in a variety of other organs in rabbit did not react with the antiserum. Our data demonstrate an antigenic distinction of both, the connecting tubule cell and the principal cell, discriminating these cells from other tubular epithelial cells including the intercalated cells of the collecting duct system. Furthermore, our findings point to a heterogeneity along the distal nephron with respect to the constituents of the epithelial-interstitial interface.

Animals↗
PubMed1984

Immunocytochemical localization of a renal glycoprotein (gpCDI) synthesized by cultured collecting duct cells.

A sulfated, proline-rich glycoprotein (gpCDI, apparent molecular weight 200,000 in column chromatography and 150,000 in SDS-PAGE) was isolated from cultured renal collecting duct epithelium by centrifugation. Triton X100 extraction and DEAE-cellulose ion exchange chromatography. A DEAE-cellulose ion exchange chromatography fraction with the enriched gpCDI was used for immunization of guinea pigs. The antiserum was prepared for antigen localization by indirect immunofluorescence in collecting duct cell cultures and in tissue sections of neonatal and adult rabbit kidneys. In the cultured collecting duct epithelium, antibody staining of the epithelium and structures of the extracellular matrix was age dependent. Cultures of dedifferentiated collecting duct monolayers revealed positive reaction in the cytoplasm. In neonatal and adult rabbit kidneys, the antibody was localized in the entire collecting duct system but not in the collecting duct ampullae of the newborn kidney. Staining of the cytoplasm was found only in medullary collecting ducts of the neonatal kidney; other portions revealed staining mostly at the basal circumference of the tubule and at the luminal cell borders. Apart from collecting ducts, no other tubular segments were reactive. The cortical and the medullary interstitium contained fluorescent fibres which were concentrated around vascular structures. A possible relation between gpCDI and collagenous compounds is discussed. Bowman's capsule reacted positively, whereas staining of the mesangial matrix was weak. The localization of the antigen, as revealed by indirect immunofluorescence, suggests that gpCDI occurs both in intracellular and extracellular (interstitial) location. Two main points are emphasized: Firstly gpCDI is considered an important constituent in different stages of collecting duct development, and secondly, the staining pattern of the antibody varies with the different portions of both young and adult kidney collecting ducts; this staining heterogeneity may correspond with the known regional differences of collecting duct functions.

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