Biomedical subjects

G B Ryan

Publications and source records attributed to G B Ryan.

At least 37 records · Page 2Linked to original sources

PubMed1989

Protamine sulphate-induced proteinuria: the roles of glomerular injury and depletion of polyanion.

It has been claimed that intrarenal injection of polycations results in proteinuria due to neutralization of glomerular basement membrane polyanionic charge without any glomerular morphological changes. To study the effects of polycation infusion on the renal glomerulus, the left kidney of rats was directly injected with protamine sulphate through the renal artery. Urine was collected from each kidney before and after injection, and protein excretion rates were determined. Ninety minutes after completion of the injection both kidneys were perfusion-fixed and the morphology and colloidal iron staining of the kidneys were studied by light and electron microscopy. Intrarenal injection of 0.5, 1, and 2 mg of protamine sulphate produced minimal or mild proteinuria in the majority of animals. Higher doses (5 mg) commonly resulted in decreased protein excretion associated with oliguria. Colloidal iron staining of glomerular polyanionic sites was undiminished when compared with control kidneys. Injection of protamine sulphate resulted in capillary thrombosis and severe damage to both glomerular and tubular epithelium in 6 of 16 kidneys. In the remaining kidneys, milder focal changes were apparent. Although its mechanism of action is unclear, it is apparent that protamine sulphate, even in small doses, is toxic to the cellular components of the glomerulus and tubules, thus accounting for the range of changes observed in renal function.

Animals↗

PubMed1989

Glomerular podocytes in cultured rat kidney slices. A qualitative and quantitative electron-microscopic study.

The ultrastructure of rat glomerular epithelial cells (podocytes) in kidney slices in vitro was examined using qualitative and quantitative electron microscopy. The kidney slices were cultured in Medium 199 with Hanks' salts in a 5% CO2/95% O2 environment for up to 14 days. Few changes in podocyte ultrastructure occurred in the first 12 h of culture, but by 24 h cell bodies were rounded, microvilli were present on all podocyte surfaces, and some foot processes had been replaced by flattened expanses of cytoplasm. These changes were more pronounced by 3 days, when some podocytes had developed pseudopodal extensions and appeared to be migrating from glomeruli onto the slice surface. Podocytes could still be identified after 8, 10 and 14 days of culture, although relatively few glomeruli remained at 14 days. Morphometric methods were used to analyse podocyte shape, volume and surface area during the first 4 days of culture. The most significant change involved loss of foot processes: the number of filtration slits per 100 microns of basement membrane decreased from 211.8 +/- 15.0 (mean +/- SD) at the commencement of culture, to 55.3 +/- 22.6 after 2 days (p less than 0.001). These data provide baseline information for in vitro studies on the effects of nephrotoxins on podocytes.

Animals↗

PubMed1989

Evidence that dopaminergic sympathetic axons supply the medullary arterioles of human kidney.

The ability of the kidney to excrete sodium appears to depend on release of dopamine from intrarenal sources. In the present study, we have used immunohistochemistry to examine the possibility that renal dopaminergic nerves constitute one of these sources. We found that the sympathetic axons supplying cortical structures in human kidney contain tyrosine hydroxylase-like immunoreactivity but lack DOPA decarboxylase-like immunoreactivity. By contrast, the vasa recta arterioles of the renal medulla are supplied by varicose tyrosine hydroxylase-positive nerve fibres, some of which also contain DOPA decarboxylase. As DOPA decarboxylase has been demonstrated in other situations to be a selective marker for dopaminergic terminal axons, our results suggest the innervation of renal medullary blood vessels in man by both noradrenergic and dopaminergic sympathetic nerves.

Adult↗

PubMed1989

Ultrastructural changes in renal tubules associated with glomerular bleeding.

Renal biopsies from ten patients presenting with macroscopic or heavy microscopic hematuria, shown to be glomerular in origin, were examined by light and electron microscopy. All biopsies showed erythrocytes within tubules by light microscopy and, in five cases, there were morphologic features of acute tubular necrosis. In four biopsies there was clear evidence by electron microscopy of uptake of erythrocytes by renal tubular epithelial cells, associated with some blunting of epithelial microvilli, vacuolar change and increased lysosomal content. Associated with erythrophagocytosis, the subsequent pathway of erythrocyte destruction within renal tubular epithelial cells closely resembled the hemolytic pathway described in macrophages of the reticuloendothelial system.

Adult↗

PubMed1989

Glomerular actions of ANG II during reduction of renal artery pressure: a morphometric analysis.

The glomeruli of kidneys subjected to reduced perfusion pressure were examined morphometrically. The left renal artery was narrowed for 30 min in anesthetized dogs with (n = 6) or without (n = 7) converting-enzyme inhibition (captopril). The kidneys were then rapidly fixed by glutaraldehyde perfusion at high flow rate. In a comparison of glomeruli of kidneys subjected to pressure reduction in captopril-treated and untreated dogs, there was significantly greater mesangial contraction in the latter, but morphometric analysis revealed no significant differences in the glomerular surface area available for filtration as evidenced by glomerular capillary volume fractions, surface areas of the filtering basement membrane between epithelial and endothelial cells, or the length densities of the glomerular epithelial slits. In a comparison of the left (pressure reduction) and right (no pressure reduction) kidneys in the captopril-treated dogs, there was no significant effect of reduction of renal perfusion pressure per se on mesangial contraction or glomerular filtration surface area when angiotensin (ANG) II formation was blocked. Thus ANG II caused mesangial cell contraction after renal artery stenosis, but this did not significantly change glomerular ultrafiltration surface area.

Angiotensin II↗

PubMed1989

Microscopic study of cortical explants from lamb kidney in culture.

Cortical explants from lamb kidney have been maintained in organ culture for up to 12 days. Early in culture, the tissue showed limited necrosis, but most tissue elements, especially those closest to the medium, significantly recovered by day 5. Glomerular peripolar cells were present for at least the first 3 days of culture. Neotubular formation was noted by day 5, often appearing as cyst-like structures. Glomerular podocytes lost their foot processes early in culture but apparently remained viable throughout the total culture period.

Animals↗

PubMed1989

Co-localization of neuron-specific enolase-like and kallikrein-like immunoreactivity in ductal and tubular epithelium of sheep salivary gland and kidney.

Neuron-specific enolase-like and kallikrein-like immunoreactivity was found to be co-localized in the ductal elements of the submandibular gland and in the more distal portions of the nephron in the kidney of newborn lambs. Some glomerular peripolar cells in the kidney were immunopositive for neuron-specific enolase without detectable kallikrein-like immunoreactivity.

Animals↗

PubMed1989

Immunohistochemical study of peripolar cells of the sheep.

The proposal that the cytoplasmic granules of glomerular peripolar cells (PPCs) of the adult sheep and lamb contain a kallikrein-like substance has been re-examined. After extensive characterisation and purification of anti-kallikrein antibodies, it was concluded that PPCs do not contain immunohistochemically detectable amounts of urinary kallikrein; nor do such cells appear to synthesise kallikrein as shown by hybridisation histochemistry studies. They are also not renin-immunopositive. On the other hand, a proportion of them exhibit neuron-specific enolase (NSE) immunoreactivity, unlike the apparently closely related visceral and parietal epithelial cells.

Animals↗

PubMed1988

Morphologic changes in the renal glomerulus and the juxtaglomerular apparatus in human preeclampsia.

The renal biopsies of ten women with preeclampsia without other underlying renal disease were examined in detail using light and electron microscopy and immunofluorescence. Characteristic preeclamptic glomerular lesions with endocapillary cell swelling, subendothelial and mesangial deposits, and mesangial interposition were detected in each patient. Juxtaglomerular regions were not prominent and were poorly granulated on light microscopy; ultrastructurally, they showed myoepithelioid cells with sparse renin granulation and considerable heterogeneity of granule size and density in association with relatively meagre granular endoplasmic reticulum and Golgi profiles. These morphologic findings suggest that, in patients with clinical and renal biopsy evidence of preeclampsia, there is no significant stimulation of the renin-angiotensin system.

Adolescent↗

PubMed1988

The innervation of the renal cortex in the dog. An ultrastructural study.

Two cytochemical techniques were used at the ultrastructural level to study the distribution of specific axon types to different intrarenal structures in the dog. Using the chromaffin reaction to distinguish catecholaminergic fibres from other axon populations, it was found that the renal cortex of the dog is supplied only by catecholaminergic nerves. Immunostaining for tyrosine hydroxylase (TH) labelled all of the intracortical nerves, and 20% to 25% of these profiles also contained dopa decarboxylase (DDC)-immunoreactivity, indicating they were dopaminergic rather than noradrenergic. Both DDC-positive and DDC-negative axons were seen in close association (approximately 80 nm) with blood vessels and juxtaglomerular cells as well as tubular epithelial cells. The distribution of TH- and DDC-immunoreactive nerves in the renal cortex is compatible with existing functional evidence indicating that both dopaminergic and noradrenergic nerves are involved in the regulation of renal blood flow, tubular reabsorption and renin release.

Animals↗

PubMed1988

Immunohistochemical identification of plasma proteins in cytoplasmic granules of peripolar cells of the sheep.

The cytoplasmic granules of glomerular periopolar cells of the newborn lamb and sheep have been shown to contain immunoreactive albumin and immunoglobulin using immunohistochemistry and ultrastructural immunocytochemistry. It is most likely that the granule contents include material derived from filtered plasma proteins, although the basis for such uptake, localised to glomerular epithelial cells in the peripolar region, remains unexplained.

Animals↗

PubMed1987

Intercellular spaces between macula densa cells: an ultrastructural study comparing high pressure perfusion fixation with in situ drip-fixation of rat kidney.

In situ drip-fixation of superficial glomeruli and tubules in the rat kidney verified the results obtained from high pressure perfusion fixation studies indicating that distinct spaces normally exist between the cells of the macula densa. Following treatment with frusemide these intercellular spaces between the macula densa cells became closed in both drip-fixed and perfusion-fixed kidneys. These findings suggest that the variability of extracellular compartmentation found in the macula densa is unlikely to be an artifact but most likely represents changes in the in vivo status of the macula densa.

Animals↗

PubMed1987

Purification and cloning of a corpuscles of Stannius protein from Anguilla australis.

The kidneys of teleost fish are associated with tissues containing secretory granules--the corpuscles of Stannius (CS). Electron microscopy indicates that the granules are of a proteinaceous nature and may represent hormones or enzymes of unrecognized physiological and biochemical function. In the present study, two-dimensional gel electrophoresis and electroelution was used to purify the major protein to homogeneity; it is approximately 32,000 Da in the reduced form and glycosylated. From the partial NH2-terminal sequence, a 75-mer oligonucleotide probe was synthesized and used to isolate a cDNA clone from which the complete amino acid sequence of the major CS protein was deduced. Polyclonal antibodies raised against CS homogenates were specific for the CS proteins (confirmed by immunohistochemistry). Hybridization histochemistry was used to confirm the location of the mRNA encoding the isolated protein. Incubation of CS homogenate with eel plasma or ovine renin substrate did not result in any angiotensin-like peptides whereas kidney homogenate did.

Amino Acid Sequence↗

PubMed1987

Angiotensin II-induced contraction of mesangial cells in acute renal artery stenosis in dogs.

1. Renal artery stenosis was induced in anaesthetized dogs, and the kidney rapidly fixed after 30 min. 2. Electron microscopy revealed marked folding of the paramesangial basement membrane in stenotic kidneys (n = 7). The extent of this folding was significantly less in dogs treated with captopril (n = 6). 3. It is suggested that this folding reflects angiotensin II-induced contraction of the mesangial cells, which may help maintain glomerular filtration rate following stenosis.

Angiotensin II↗

PubMed1987

Glomerular epithelial abnormalities associated with the onset of proteinuria in aminonucleoside nephrosis.

A sequential ultrastructural study has been made of glomerular podocytic epithelium before and after the onset of proteinuria induced by daily subcutaneous injections of low doses of puromycin aminonucleoside (PAN). At 4 days, before the onset of proteinuria, the principal change was extensive replacement of podocytic foot processes by broad expanses of epithelial cytoplasm. At 5 days, when proteinuria had developed, the epithelial cells showed in addition multiple cytoplasmic droplets, many large balloon like vacuoles, some of which were ruptured, and many foci of epithelial detachment from the glomerular basement membrane (GBM). Of particular significance, the onset of proteinuria coincided precisely with the development of areas of epithelial detachment that led to direct continuity between externally denuded GBM and the urinary space. It seems likely that these areas are the primary sites of protein leakage across the GBM in this experimental model.

Animals↗

PubMed1986

Distribution of glomerular peripolar cells in different mammalian species.

Peripolar cells are granulated glomerular epithelial cells that form a cuff around the vascular pole of the glomerulus. Quantitation of these cells in 17 species of mammals (including man, several laboratory animals and a variety of other species) indicated that they were detectable by light microscopy in all but one of the mammals that were examined (the Australian hopping mouse). In adult mammals with detectable peripolar cells, the "peripolar cell index" (the percentage of randomly sectioned glomeruli that displayed peripolar cells in histological sections of kidney) ranged from 0.15 (for echidna) to 11.86 (for sheep). Newborn lambs and rats showed strikingly high values (23.30 and 10.76, respectively) compared with their adult counterparts. Using electron microscopy, peripolar cells were observed in all species that were examined, including the Australian hopping mouse. Morphologically, peripolar cells were similar in all species although their size and granule population varied. They showed a predominantly outer cortical glomerular distribution and a close anatomical relationship with the renin-containing myo-epithelioid cells. These findings indicate that peripolar cells are present in a wide variety of species and support the view that such cells may play a significant role in the regulation of normal renal function.

Aging↗

PubMed1986

Localization of sympathetic and sensory neurons innervating the rat kidney.

Following injection of horseradish peroxidase (HRP) into the hilar region of the left kidney of the rat, 66% of labeled sympathetic neurons were located in the ipsilateral paravertebral ganglia, with most cells in T13 and L1, and 14% were located in equivalent segments of the contralateral chain. A similar distribution of sympathetic neurons projected to the right kidney, with most cells in T12 and T13 paravertebral ganglia. Only 20% of the total sympathetic supply to either kidney arose from the prevertebral ganglia. The renal sensory innervation was also bilateral in origin, with about 80% of the neurons arising from ipsilateral dorsal root ganglia. Injection of HRP into the caudal and rostral poles of the left kidney labeled paravertebral neurons which were concentrated in ganglia L1 and T13, respectively, but did not label any sensory neurons. We conclude that most of the renal sympathetic innervation is paravertebral in origin, and that a substantial bilateral component exists for both sympathetic and sensory supplies. Neurons arising from the contralateral side have their cell bodies in segments that provide the main ipsilateral innervation to the same kidney. The majority of sensory axons appear to be restricted to subcortical areas.

Adrenergic Fibers↗

PubMed1986

Effect of sodium intake and sodium delivery to the macula densa on renal renin content and juxtaglomerular apparatus morphology.

Active and inactive renin were measured in individual juxtaglomerular apparatus (JGA) and in whole kidney homogenates. The morphology of the JGA was examined in microbiopsy glomerular specimens and in kidneys fixed by arterial perfusion. In rats on high and normal salt intake the total renin content of a single JGA was 14 (s.e.m. = 3) and 29 (s.e.m. = 4) ng AI/h, respectively. The amount of cystoplasm occupied by renin granules was 20% and 27%. Crystalline cores were seen in 1.5% and 7% of the granules, respectively. Increased delivery of NaCl to the macula densa did not alter total renin, but decreased inactive renin from 30% to 0, crystalline core-containing cells from 33% to 14% and decreased the percentage of granules with crystalline cores from 12% to 2.2%. Increased sodium in the diet and increased delivery of NaCl to the macula densa decreased the proportion of renin present in the inactive form and decreased the proportion of crystalline cores. These coincidental alterations suggest that crystalline cores contain inactive renin and suggest that the delivery of sodium to the macula densa activates renin.

Animals↗