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D G Oreopoulos

Publications and source records attributed to D G Oreopoulos.

At least 199 records · Page 11Linked to original sources
PubMed1984

Electron microscopic study of the peritoneal kinetics of iron dextran during peritoneal dialysis in the rabbit.

Iron dextran, an electron-dense tracer, was given intravenously (100 mg of iron/100 g of body weight) to 8 normal rabbits to study its movement from the plasma to the peritoneal cavity during peritoneal dialysis. The dialysate infused at 75 ml/kg contained 1.5 g/dl of glucose in 4 animals and 4.25 g/dl in the remainder. Peritoneal dialysis was discontinued and the peritoneum was fixed in vivo at various times (20-120 min) after the injection of the iron dextran. Large amounts of tracer were detected in the effluent after draining the peritoneal cavity. Electron microscopic examination of the mesentery showed particles of iron dextran in the endothelial cells of small vessels (capillaries and venules) the interstitium and the mesothelial cells adjacent to vessels irrespective of the dialysate concentration or duration of dialysis. Tracer was not clearly demonstrated in the interendothelial or intermesothelial spaces. In the mesothelial cells, the particles were found exclusively in (small, elongated or large) vesicles, while in the endothelial cells they were both in vesicles and free in the cytoplasm. Our findings suggest that during the 20- to 120-min period after intravenous administration, the intracellular transport of iron dextran, depends on either moving vesicles or the presence of pre-existing tunnels in the mesothelial cells of rabbit mesentery.

Animals↗
PubMed1983

Humane medicine.

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Humanism↗
PubMed1983

The mode of progression of subperiosteal resorption in the hyperparathyroidism of chronic renal failure.

Subperiosteal resorption in finger phalanges is usually thought to be the result of osteoclastic bone resorption on the periosteal surface of bone, progressive centripetally, with creation of the serrated appearances and "lace-like" patterns in periosteal cortical bone. Our longitudinal microradioscopic observations in patients with secondary hyperparathyroidism of chronic renal failure have revealed evidence of another pathogenetic mechanism: by the enlargement of intracortical juxtaperiosteal resorption spaces, the remaining thin layer of bone is broken down from inside the bone, i.e., a centrifugal rather than centripetal process.

Adult↗
PubMed1983

Ultrastructure of normal rabbit mesentery.

The ultrastructure of the mesentery was examined by electron microscope (EM) after in vivo fixation in 7 normal rabbits. In 1, the fixation was performed after intravenous injection of an electron-dense tracer (iron dextran) and intraperitoneal infusion of dialysate 4.25% for 1 h. We studied morphometric data of what is considered to be the active peritoneal dialysis membrane, i.e. capillary endothelial cells, interstitium and mesothelial cells. The mesothelial cells are flattened and overlapping with tight junctions between them. They lie on a continuous basement membrane and they contain numerous intracytoplasmic vesicles, separated or in clusters. The mesenteric microvessels were mainly true capillaries of continuous type and postcapillary venules. Capillary lymphatics and larger lymphatic channels (lacunae) seem to be more extensive than the blood capillaries and venules. The endothelial cells contain many vesicles. The interstitium consists of bundles of collagen, fibroblasts and occasional macrophages. The electron-dense tracer was found in the vesicles of the mesothelial cells suggesting that vesicular transport may play an important part in the transportation of at least molecules of a certain size.

Animals↗
PubMed1983

Ultrastructural studies of renal stones from patients on continuous ambulatory peritoneal dialysis.

Patients on haemodialysis or peritoneal dialysis due to renal failure have an unusually high incidence of kidney stones (from 5 to 51% depending on methodology). However, there is a controversy on the composition of these stones - whether they are calcium oxalate stones or matrix stones. This paper presents ultrastructural evidence that these stones are in fact heterogeneous, ranging from calcium oxalate stones with little organic matrix component, through calcium oxalate and calcium apatite stones with substantial organic matrix component, to matrix stones with little inorganic material component. The correlative analytical methodology developed in this laboratory employing analytical scanning and transmission electron microscopy, electron and x-ray diffraction, as well as biochemistry, was reported previously. For the calcium oxalate stones, scanning electron microscopy showed that numerous small crystals of 1-3 micron in size were exposed to stone surfaces, apparently in an unorganized manner. However, transmission electron microscopy sections showed orderly stacking of crystals held together by organic matrix, just like bricks held together by mortar. For the matrix stones, scanning electron microscopy showed smooth stone surfaces while transmission electron microscopy sections showed focal areas of calcium oxalate or apatite deposits as identified by selected area electron diffraction.

Apatites↗
PubMed1982

Experimental model for studies of continuous peritoneal'dialysis in uremic rabbits.

In this paper we describe an experimental model designed for studies of continuous ambulatory peritoneal dialysis (CAPD) in uremic rabbits. We preferred the study of uremic animals because it is not known whether peritoneal membrane differs between normal and uremic animals. Animals made uremic after bilateral nephrectomy could not survive on dialysis. Instead, partial nephrectomy of one kidney and partial (5/6) destruction of the cortex of the remaining kidney by electrocauterization provided a simple and reproducible model. CAPD resulted in adequate control of uremia but the animals showed significant decreases in total plasma proteins and weight. This model is suitable for studies of the metabolic complications of CAPD.

Animals↗
PubMed1981

Treatment of renal osteodystrophy with 1,25-dihydroxycholecalciferol.

Nine patients with renal osteodystrophy were tested for 6.5 to 35 months with 1,25-dihydroxycholecalciferol (1,25-DHCC). A close biochemical follow-up was performed during the first 6 months of treatment, including biweekly determinations of serum calcium, phosphorus, magnesium, alkaline phosphatase and creatinine levels. A bone biopsy, radiologic investigations and determinations of plasma levels of immunoreactive parathyroid hormone (IPTH) and intestinal absorption of calcium 47 were performed before and after the 6 months. Although the five patients with osteitis fibrosa showed a significant improvement, the four with predominantly osteomalacic lesions showed no response to treatment. These four had a normal initial plasma iPTH level, higher serum calcium levels than the other five patients, extreme sensitivity to 1,25-DHCC, with frequent episodes of hypercalcemia, and only a slightly increased serum alkaline phosphatase level, which remained unchanged during treatment. All but one of the patients, irrespective of the histologic abnormality, showed a decrease in the uptake of radionuclide by bone after treatment. The renal function of one patient, a man with long-standing stable renal failure who had not undergone dialysis, deteriorated during treatment.

Calcitriol↗