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D R Abrahamson

Publications and source records attributed to D R Abrahamson.

At least 55 records · Page 3Linked to original sources
PubMed1993

Extracellular matrix (mesoglea) of Hydra vulgaris III. Formation and function during morphogenesis of hydra cell aggregates.

Hydra, as a member of the phylum Cnidaria, is characterized by a body lining organized as an epithelial bilayer with an intervening extracellular matrix (ECM) termed the mesoglea. Previous studies have established that the mesoglea has components indicative of mammalian ECM such as type IV collagen, laminin, fibronectin, and heparan sulfate proteoglycan, and these components appear to play a critical role in hydra head regeneration. A remarkable feature of hydra is its ability to reorganize into its adult structure within 96 hr to 7 days from pellets formed from dissociated hydra cells. This regenerative model has been termed the hydra cell aggregate system. The present study has been designed to characterize the biogenesis of mesoglea in hydra cell aggregates and to determine its role in morphogenesis of aggregates. We find that hydra cell aggregates first form an epithelial bilayer by 12 hr of development and then subsequently develop a mesoglea. Morphogenesis of hydra structure then follows formation of the mesoglea. Immunofluorescence studies indicate that mesoglea components are first deposited between the epithelial bilayer by about 12-17 hr of pellet formation, and pulse-labeling studies indicate that the translation rate of matrix components peaks by 48-72 hr of development. Ultrastructural studies indicate that a mature mesoglea is formed by 48-96 hr of pellet formation. Drugs such as beta-aminoproprionitrile and 2,2'-dipydridyl, which interfere with the cross-linking of collagens, and p-nitrophenyl-beta-D-xylopyranoside, which interferes with the addition of GAG moieties to proteoglycan core molecules, were found to reversibly block development of hydra cell aggregates. Transmission electron microscopy studies indicate that these drugs affect the ultrastructure of the mesoglea. In addition, both polyclonal and monoclonal antibodies raised to isolated mesoglea were found to block development of hydra cell aggregates. These studies indicate that (1) mesoglea formation is rapid and precedes morphogenetic processes during aggregate development, and (2) formation of mesoglea is essential for normal morphogenesis of hydra cell aggregates.

2,2'-Dipyridyl↗
PubMed1993

Laminin distribution in developing glomerular basement membranes.

The renal glomerular basement membrane (GMB) separates two distinctly different cell layers: the vascular endothelium, and visceral epithelial podocytes. When initial vascularization of the forming glomerulus takes place during nephrogenesis, the early GBM forms by fusion of a dual basement membrane between endothelial cells and podocytes. As glomerular capillary loops blossom, newly synthesized basement membrane segments derived from podocytes are then inserted or spliced into the fused GBM. The molecular processes accounting for either basement membrane fusion or splicing are unresolved. Using monoclonal anti-mouse laminin antibodies (mAbs) against the end of the laminin long arm (5D3), we have shown in adult mice that peripheral loop GBM is only weakly immunoreactive but the mesangial matrix and tubular basement membrane (TBM) is intensely positive. In contrast, mAbs against domains in the center of the laminin cross only label TBMs and mesangial matrices of mature mice and GBMs are negative. Immunofluorescence microscopy of neonatal mouse kidneys showed, however, that anti-laminin mAbs brightly labeled developing GBMs of glomeruli undergoing initial vascularization and capillary loop formation. Post-fusion GBMs of maturing stage glomeruli became unreactive for most anti-laminin mAbs but remained positive for 5D3. Our results therefore show that some GBM laminin epitopes are transiently expressed during glomerular development. These changes in GBM immunoreactivities may reflect proteolytic processing during basement membrane fusion and splicing, or temporally controlled synthesis of different laminin isoforms.

Animals↗
PubMed1993

Basement membrane proteoglycans and development.

Basement membranes contain distinct collagen, glycoprotein and proteoglycan species, and these exhibit considerable heterogeneity in isoform or type when different tissue types are compared. Additionally, many components are differentially expressed in organogenesis. We have considered the distributions in glomerulogenesis of two distinct basement membrane proteoglycans, a small heparan sulfate proteoglycan and a chondroitin sulfate proteoglycan (BM-CSPG). While the former was present in all kidney basement membranes through development, the latter was apparently regulated in distribution. BM-CSPG was only strongly expressed in the vasculature invading late comma stage glomeruli, and later in presumptive and mature Bowman's capsule. Over the first six to eight weeks, the capillary basement membranes contained BM-CSPG, but in gradually decreasing amounts until it became completely undetectable. The basement membrane of the adult rat glomerulus is unique in its lack of BM-CSPG. However, in diabetic rats, BM-CSPG is apparently re-expressed in the glomerular basement membrane, a potential marker for pathological changes in glomerular structure. While its function awaits elucidation, BM-CSPG may be essential for basement membrane integrity or stability and have important roles in kidney development.

Animals↗
PubMed1993

Expression of type I collagen mRNA in glomeruli of rats with passive Heymann nephritis.

In passive Heymann nephritis (PHN) glomeruli exhibit marked basement membrane expansion around subepithelial immune deposits but they fail to show any change in mRNA levels of type IV collagen, laminin or fibronectin by Northern and slot-blot analysis, or in the amount or distribution of type IV collagen or laminin by immunohistology for up to 12 weeks after disease onset. On the other hand, in situ hybridization (ISH) revealed the appearance of positive cells exhibiting mRNA for the alpha 1 chain of rat type I collagen two to three weeks after the onset of PHN in all glomeruli of all rats. Positive cells persisted for at least eight weeks. In many glomeruli, the location of the clusters of silver grains suggested that they were in visceral epithelial cells. In controls injected with normal sheep IgG, and in early PHN (< 11 days after sheep anti-Fx1A), glomeruli were negative but cells in the renal capsule and adventitia of vessels showed strong ISH and served as positive controls. RNAse pre-treatment and the "sense" probe gave appropriately negative results. RNA from PHN glomeruli contained an alpha 1 type I collagen transcript of the same size as that from rat fibroblasts. These results show that the evolution of glomerular basement membrane expansion in rat membranous nephropathy coincides with the induction of a matrix gene that is not normally expressed in glomerular cells. Further, they suggest that the intercalation of ectopically-expressed matrix molecules may contribute to the production of a disorganized basement membrane.

Animals↗
PubMed1993

Fish oil has protective and therapeutic effects on proteinuria in passive Heymann nephritis.

Passive Heymann nephritis (PHN) is a rat model of membranous nephropathy induced by injecting anti-Fx1A. The onset of proteinuria in PHN is caused by complement-mediated injury to glomerular epithelial cells (GEC) accompanied by enhanced glomerular eicosanoid production. In addition, sublethal injury by complement of rat GECs in culture leads to phospholipase activation, phospholipid hydrolysis and release of arachidonic acid and dienoic prostanoids. Based on these findings, we undertook to determine if substituting arachidonic acid (omega-6) in GEC membrane phospholipids with omega-3 fatty acids derived from fish oil would alter the development and course of proteinuria in PHN. We found that rats fed a diet containing 10% fish oil for four weeks prior to antibody injection developed 50 to 60% less proteinuria between two and six weeks after anti-Fx1A than rats fed an equivalent diet containing 10% safflower oil, and had substantial enrichment of glomerular phospholipids with omega-3 fatty acids and displacement of arachidonic acid. This outcome was associated with a 50% reduction in release of glomerular thromboxane B2 (stable metabolite of thromboxane A2) in the fish oil group. More importantly, when PHN rats with well established proteinuria while on regular chow were randomized to three dietary groups, those fed fish oil had a 25 to 50% decline in proteinuria as compared to those fed lard or safflower oil. This difference was evident within two weeks of randomization and persisted until the end of the study after eight weeks. In neither study could the differences in urine protein excretion be accounted for by protein or calorie deprivation, or by differences in blood pressure, renal function, immune response to sheep IgG, or glomerular deposition of IgG or complement. Thus, our results indicate that dietary fish oil has protective and therapeutic effects with regard to proteinuria in PHN. These benefits may relate to alterations in membrane phospholipid composition in favor of omega-3 fatty acids and release of less reactive trienoic eicosanoids.

Animals↗
PubMed1993

Quantitation and localization of laminin A, B1, and B2 chain RNA transcripts in developing kidney.

To quantitate expression of laminin A, B1, and B2 chains during kidney development, we prepared riboprobes of similar size (318-365 nucleotides) and carried out scanning densitometry of Northern blots from newborn mouse and rat kidneys. Much higher expression of B1 than A or B2 mRNAs was observed with an A-to-B1-to-B2 ratio of approximately 1:8:4 in mice and approximately 1:12:1 in rats. In addition to the 9.5-kb laminin A chain transcript, we also observed specific hybridization of the A chain probe to approximately 6-kb band in both newborn mice and rats. To localize these mRNAs, newborn rat kidneys were sieved to obtain separate glomerular and tubule fractions. Northern blots from these samples showed that most of the B1, B2, and 9.5-kb laminin A chain mRNAs were in glomerular fractions, whereas tubules contained more of the 6-kb A chain band. Analyses of poly(A)+ mRNA from newborn and adult kidneys showed severalfold decreases in adult RNA encoding the three laminin chains and the alpha 1-chain type IV collagen. However, only a 20% decline from newborn levels was seen for heparan sulfate proteoglycan (HSPG) core protein message. These quantitative results provide additional evidence that different laminin isoforms are present in separate kidney basement membranes and that HSPG core protein synthesis remains at relatively high levels in adult kidneys.

Animals↗
PubMed1993

Basement membrane proteoglycans in glomerular morphogenesis: chondroitin sulfate proteoglycan is temporally and spatially restricted during development.

We previously reported the presence of a basement membrane-specific chondroitin sulfate proteoglycan (BM-CSPG) in basement membranes of almost all adult tissues. However, an exception to this ubiquitous distribution was found in the kidney, where BM-CSPG was absent from the glomerular capillary basement membrane (GBM) but present in other basement membranes of the nephron, including collecting ducts, tubules, Bowman's capsule, and the glomerular mesangium. In light of this unique pattern of distribution and of the complex histoarchitectural reorganization occurring during nephrogenesis, the present study used light and electron microscopic immunohistochemistry to examine the distribution of BM-CSPG and basement membrane heparan sulfate proteoglycan (BM-HSPG) during prenatal and postnatal renal development in the rat. Our results show that the temporal and spatial pattern of expression of BM-CSPG during nephrogenesis is unlike that reported for other basement membrane components such as laminin, fibronectin, and BM-HSPG, all of which can be found in the earliest formed basement membranes of the vesicle-stage nephron. Although BM-CSPG is present in the basement membranes of the invading vasculature and ureteric buds, its first appearance in nephron basement membrane occurs during the late comma stage. In capillary loop-stage glomeruli of prenatal animals, BM-CSPG is present in the presumptive mesangial matrix but undetectable in the GBM. However, as postnatal glomerular maturation progresses BM-CSPG is also found in both the lamina rara interna and lamina densa of the GBM in progressively increasing amounts, being most evident in the GBM of 21-day-old animals. Micrographs of glomeruli from 42-day-old animals show that BM-CSPG gradually disappears from the GBM and, by 56 days after birth, appears to be completely absent from the GBM, its pattern of distribution resembling that of the adult animal. Our results show that BM-CSPG is not required for the initial assembly of basement membranes but may in fact serve to stabilize basement membrane structure after histoarchitectural reorganization is completed.

Animals↗
PubMed1993

Regulation of kidney organogenesis: homeobox genes, growth factors, and Wilms tumor.

Factors regulating the temporal and spatial expression of kidney developmental programs are beginning to be identified. Evidence accumulated in the past few years indicates that the Hox and Pax genes, in particular, are important for early kidney development. A number of soluble growth factors were also shown to be essential for nephrogenesis to proceed in vitro. Errors in kidney development include Wilms tumor, a common childhood malignancy, which in many cases seems to be caused by faulty transcriptional regulation.

Genes, Homeobox↗
PubMed1993

Cyclosporine-induced nephrotoxicity in deoxycorticosterone-NaCl treated rats.

This study tested the hypothesis that the adverse effects of cyclosporine (Cy) are accelerated in animals with induced hypertension. Four groups of rats were unilaterally nephrectomized at 5 weeks of age. Two weeks later, two of these groups received implantations of Silastic strips impregnated with deoxycorticosterone acetate (DOCA) and were maintained on 1% saline (DOCA-NaCl); the other two groups served as sham controls. Daily injections of Cy (20 mg/kg) were given to one DOCA-NaCl and one control group. During the initial 3 days, the Cy/DOCA-NaCl treated rats displayed a significant increase in systolic arterial pressure (SAP), but their SAP did not increase significantly thereafter. Cy/DOCA-NaCl treatment caused severe nephrotoxicity 18 days after initiation of treatment, but neither cyclosporine nor DOCA-NaCl treatment alone resulted in morphological renal damage. In Cy/DOCA-NaCl rats, the interstitial spaces between renal tubules were dramatically increased in size and contained abundant bundles of collagenous fibres, deposits of immunoreactive laminin, and infiltrates of mononuclear cells. In a second experiment, bilateral renal denervation prior to treatment did not lessen the Cy-induced renal damage. These results indicate that in the DOCA-NaCl rat, Cy treatment damages the renal cortex in a pattern similar to that observed in humans treated chronically with Cy. Further, the results indicate that an absence of renal innervation does not decrease the nephrotoxic effects of Cy in this rapid onset model.

Animals↗
PubMed1993

Hypertensive nephrosclerosis in the Dahl/Rapp rat. Initial sites of injury and effect of dietary L-arginine supplementation.

BACKGROUND: The Dahl/Rapp strains of salt-sensitive (SS/Jr) and salt-resistant (SR/Jr) rat were developed to examine pathogenetic mechanisms that produce hypertension in response to an increase in dietary salt. We have shown that providing SS/Jr rats with L-arginine, the metabolic precursor of nitric oxide, acutely prevented salt-sensitive hypertension, suggesting that SS/Jr rats developed hypertension because of inadequate nitric oxide production while on a high-salt diet. EXPERIMENTAL DESIGN: Male 23-day SS/Jr and SR/Jr rats were placed on chow that contained 8% sodium chloride. One group of SS/Jr rats also received L-arginine, 1.25 g/liter, in their drinking water. These three groups were examined at weekly intervals for 4 weeks. RESULTS: SS/Jr rats rapidly developed hypertension when placed on the high-salt chow. After 2 weeks on this diet, inulin clearance dramatically decreased, and albumin excretion rate increased. By the fourth week of study, SS/Jr rats on the high-salt diet had died or were dying. Coincident with the progressive decline in inulin clearance, renal morphologic analysis confirmed development of myointimal thickening, fibrinoid necrosis, and glomerulosclerosis. In contrast, over the 4 weeks of study, SS/Jr rats supplemented with oral L-arginine did not develop hypertension and any of the associated renal complications seen in age-matched SS/Jr rats on the high-salt diet. L-Arginine also corrected hypertension in SS/Jr rats exposed to the high-salt chow for 2 weeks before the inception of L-arginine. L-Arginine administration after 3 weeks on this chow, however, failed to reverse hypertension and the depressed inulin clearance and morphologic renal damage. CONCLUSIONS: Along with previous work (Chen PY, Sanders PW, J Clin Invest 88:1559-67), these studies were consistent with the hypothesis that hypertension and hypertensive nephrosclerosis developed in SS/Jr rats because, while on a high-salt diet, substrate (L-arginine) became a rate-limiting factor in the synthesis of nitric oxide.

Animals↗
PubMed1992

Immunoelectron microscopic localization of laminin in rat ovarian follicles.

We studied the immunohistochemical and ultrastructural distribution of laminin in ovaries of immature and mature rats. When sections from 1-8-week-old rat ovaries were labeled directly with conjugates of affinity purified anti-laminin IgG-horseradish peroxidase (HRP), the antibodies bound to all ovarian basement membranes including those surrounding follicles in different stages of maturation. In addition, intracellular labeling was seen in granulosa and theca cells of follicles undergoing rapid development (preantral and antral stages) and in basement membrane-like structures of the Call-Exner bodies. Intracellular laminin was generally not detected, however, in any cells of primordial or atretic follicles. Tissue processed for immunoelectron microscopy 1 hour after the intravenous injection of anti-laminin IgG-HRP showed binding of antibody in linear patterns along endothelial and follicular epithelial basement membranes. Discontinuous strands of laminin-positive, extracellular matrices were also seen between theca cells of all follicles. In addition, injected anti-laminin IgG labeled perisinusoidal basement membranes located within corpora luteae and patches of basement membrane material between granulosa lutein cells. When ovaries were examined 5 d after the intravenous injections of anti-laminin IgG-HRP, uneven or segmented labeling was found in subepithelial basement membranes surrounding developing follicles. Our results therefore indicate that granulosa and theca cells participate directly in basement membrane laminin biosynthesis and suggest that this new laminin is spliced into existing basement membranes during follicular growth.

Animals↗
PubMed1992

Loss of laminin epitopes during glomerular basement membrane assembly in developing mouse kidneys.

Kidney glomerular basement membranes (GMBs) originate in development from fusion of a dual basement membrane between endothelial cells and primitive epithelial podocytes. After fusion, segments of newly synthesized matrix, derived primarily from podocytes, appear as subepithelial outpockets and are spliced into GBMs during glomerular capillary loop expansion. To investigate GBM assembly further, we examined newborn mouse kidneys with monoclonal rat anti-mouse laminin IgGs (MAb) conjugated to horseradish peroxidase (HRP). In adults, these MAb strongly label glomerular mesangial matrices but bind only weakly or not at all to mature GBMs. In contrast, anti-laminin MAb intensely bound newborn mouse GBMs undergoing initial assembly. After intraperitoneal injection of MAb-HRP into neonates, dense binding occurred across both subendothelial and subepithelial pre-fusion GMBs as well as forming mesangial matrices. Considerably less MAb binding was seen, however, in post-fusion GBMs from more mature glomeruli in the same section, although mesangial matrices remained positive. In addition, new subepithelial segments in areas of splicing were negative. These results conflict with those obtained previously with injections of polyclonal anti-laminin IgGs into newborns or adults, which result in complete labeling of all GBMs. Although epitope masking cannot be completely excluded, we believe that decreased MAb binding to developing GBM reflects actual epitope loss. This loss could occur by laminin isoform substitution, conformational change, and/or proteolytic processing during GBM assembly.

Aging↗
PubMed1991

Development of kidney tubular basement membranes.

Although some progress has been made in recent years, there are truly large gaps in our basic knowledge on how the TBM is assembled during development. Some of the new evidence presented here indicates that both the tubular epithelium and interstitial fibroblasts participate in TBM protein biosynthesis during nephrogenesis. In addition, newly assembled segments of TBM are spliced or inserted into existing TBM during tubule expansion and elongation. A similar splicing mechanism has been described previously in the GBM, endocrine organs, and intestinal villi, and this mechanism therefore probably represents a fundamental process of basement membrane formation. A major unresolved question at present, however, is how this mechanism operates at the molecular level. Does the newly formed basement membrane contain identical components as that already present? Since an enzymatic process is likely occurring in the insertion of new matrix into old, which enzymes are involved? What is the cellular origin of these enzymes and which matrix component(s) is their substrate? Even more fundamental yet unanswered questions have to do with the mechanisms of epithelial induction, basement membrane gene activation, and tubular morphogenesis. Once the basement membrane is fully formed at the completion of nephrogenesis, what controls basement membrane turnover and how does this operate? Clearly, much additional research is necessary to address these questions. This work is needed, however, before we can fully understand the important roles basement membranes play in normal development as well as in disease.

Animals↗
PubMed1991

Structural changes induced by osmotic water flow in rabbit proximal tubule.

When a transepithelial osmotic difference was imposed in perfused proximal straight tubules (270 mOsm/kg H2O in the lumen and 290 in the bath) in the absence of bath colloid, a severe vacuolation (appearance of lucent spaces) developed within the epithelium such that view of the lumen border was obscured within 5 +/- 1 min (N = 13 tubules at 23 degrees C). This vacuolation was less severe if the bath was hypotonic to the lumen or if the magnitude of the osmotic difference was reduced. If colloid (6% wt/vol of either bovine serum albumin or 70,000 molecular wt dextran) was included in the bathing medium, vacuolation was either not observed or was minimal, but became severe upon removal of the colloid and obscured the lumen within 6 +/- 1 min (N = 8 for albumin and N = 4 for dextran at 23 degrees C). At 38 degrees C, vacuolation obscured the lumen within 4 +/- 1 min following the removal of albumin (N = 5). ANOVA suggests that none of the times for vacuolation to occur differed. The rate of passive volume flow due to the osmotic difference was unaffected by vacuolation (0.9 +/- 0.1 nl.min-1.mm-1 with albumin to 0.8 +/- 0.1 without albumin and vacuolated, N = 8 at 23 degrees C, P greater than 0.2 using a paired t-test). Electron microscopic examination of tubules fixed after vacuolation showed lucent spaces within the cytoplasm. These results suggest that the presence of serosal colloid protected the epithelial cells from injury during rapid transepithelial water flow. The mechanism for this protective effect is not apparent, but may be related to effects of colloid in maintaining normal volume absorption in the proximal nephron.

Animals↗
PubMed1991

Epitope mapping of the laminin molecule in murine skin basement membrane zone: demonstration of spatial differences in ultrastructural localization.

Results of studies performed to date with polyclonal antilaminin antibodies have been conflicting as to the ultrastructural localization of this glycoprotein in skin basement membrane zone (BMZ). Whereas initial reports suggested its presence solely within the lamina lucida (LL), others have suggested that laminin is instead an exclusive component of the lamina densa (LD). In an attempt to more critically address this issue, we have examined both intact and partially separated (via 1 M NaCl) murine skin BMZ by indirect immunoelectron microscopy via a two-step immunoperoxidase technique on unfixed cryopreserved tissue, utilizing nine well-characterized monoclonal antibodies with binding specificity for laminin. Localization of the sites of the epitopes recognized by these antibodies on isolated laminin molecules was previously determined by rotary shadowing and by biochemical analyses on enzymatic fragments of laminin. Whereas at least faint immunoreactants were detected in both regions with eight of nine antibodies, predominant staining was noted within the LL with three of eight and within (and even sparsely below) the LD in three of eight. One antibody bound solely to the LL; another bound equally within both regions. Although some overlap was noted, it appears that the epitope on the distal portion of the long arm of the laminin molecule resides primarily within the skin LD, whereas epitopes on more central portions of the short arms are present within the LL or within both LL and LD. The findings of stratification of laminin epitopes within skin BMZ supports a similar recent observation in mouse kidney and suggests that portions of the laminin molecule span both LD and LL, and that there may be a non-random spatial orientation for the laminin molecule within murine skin BMZ.

Animals↗
PubMed1991

Glomerular basement membrane expansion in passive Heymann nephritis. Absence of increased synthesis of type IV collagen, laminin, or fibronectin.

The distribution and synthetic rate of glomerular basement membrane components was examined in the Passive Heymann Nephritis model of experimental membranous nephropathy. The extensive tissue injury that developed included subepithelial electron-dense deposits, podocyte foot process effacement, and expansion of the glomerular basement membrane. Levels of mRNA for type IV collagen, laminin, and fibronectin from isolated glomeruli was quantitated by slot-blot analysis and showed no change in experimental animals as compared to controls at either 1 week, 3 weeks, or 3 months after disease induction. Immunoelectron microscopy with gold-labeled anti-laminin IgG revealed no difference in the number of particles bound to the glomerular basement membrane of experimental animals and controls. Immunofluorescence with both type IV collagen antisera and anti-laminin antibody showed no difference in the intensity or pattern of staining. Despite extensive glomerular damage and glomerular basement membrane thickening, no evidence was found for either an increase in the synthetic rate of type IV collagen, laminin, or fibronectin or for an accumulation of basement membrane laminin within the damaged glomeruli. Alternate processes, such as diminished density of matrix components or accumulation of other unmeasured matrix constituents, presumably account for the expansion of the glomerular basement membrane seen in experimental membranous nephropathy.

Animals↗
PubMed1991

Glomerular development in intraocular and intrarenal grafts of fetal kidneys.

To examine nephrogenesis in allogeneic grafts, we implanted fetal (day 14 postconception) rat kidneys, which contained only immature tubules, and day 15 to 17 postconception kidneys (with immature tubules and developing glomeruli) into the anterior eye chamber or under the renal capsule of mature rat hosts. Within 9 to 10 days, every graft became richly vascularized, new nephrons were induced to form, and extensive glomerular and tubular cytodifferentiation occurred in all implants. Electron microscopy showed well-formed maturing-stage glomeruli containing erythrocytes, fenestrated endothelial cells, mesangial cells, and fully developed podocytes with foot processes and slit diaphragms. Tubules morphologically corresponding to proximal tubules and containing epithelial cells with tall apical microvilli, as well as distal tubular segments, were also observed. Intravenous injections of antilaminin IgG into hosts resulted in labeling of glomerular basement membranes in grafted kidneys, confirming perfusion of the grafts by host vasculature. Some ultrastructural abnormalities were observed in the grafted kidneys, including the persistence of unfused basement membranes in capillary walls of some maturing-stage glomeruli, and signs of graft rejection were obvious in most samples by 16 days after implantation. Despite these irregularities, however, the ability to establish allogeneic grafts of developing kidneys presents an opportunity to explore glomerular development in a variety of genetic and physiological backgrounds.

Animals↗