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Biomedical subjects

A Velasco

Publications and source records attributed to A Velasco.

At least 19 recordsLinked to original sources
PubMed1992

Presence of Golgi remnant membranes in the cytoplasm of brefeldin A-treated cells.

Brefeldin A (BFA) rapidly blocks secretion, induces disassembly of the Golgi complex and causes a redistribution of Golgi components into the endoplasmic reticulum (ER). In addition to these effects on the exocytotic pathway, BFA has been shown to induce fusion of endosomal membranes with the trans-Golgi network in some cell types. To better understand the mechanism through which BFA disrupts the exocytotic traffic, we have examined its effects on the ultrastructural organization of the Golgi complex. Within minutes of exposure to BFA, the Golgi cisternae were fragmented into a number of small tubules and vesicles, many of which had a non-clathrin coat on their cytosolic surface. In addition, a complex structure consisting of anastomosing tubules and associated vesicles appeared in the cytoplasm of cells incubated with BFA for 10 min or longer. These tubular networks were permanent, distinct structures separated from the ER cisternae. They contained cis, middle, and trans Golgi proteins as well as the lipid analogue C5-DMB-ceramide. Furthermore, secretory proteoglycans en route through the Golgi were retained in the lumen of the tubular networks. As judged by the endocytosis of cationized ferritin, endosomes do not contribute to the formation of these tubular networks. Reassembly of the Golgi complex after BFA incubation involved fragmentation and reorganization of the tubular networks as well as fusion with vesicles budded from the ER. We conclude that although in the presence of BFA the bulk of Golgi membranes are induced to fuse with the ER, as indicated by the detection of Golgi markers in this organelle, a fraction of these membranes remain in the cytoplasm organized as Golgi remnants.

Animals↗
PubMed1992

Retroperitoneal Castleman's disease.

A case of Castleman's disease localized in the retroperitoneal space is reported. A 29-year-old patient had a mass 15 cm in diameter with radial calcification. After surgical resection, both the patient's anemia and hypergammaglobulinemia disappeared. Castleman's disease should be considered when facing a solid retroperitoneal or mesenteric mass, mainly if anemia and hypergammaglobulinemia are present. Previous reports about this unusual condition are reviewed.

Adult↗
PubMed1992

An atlas of the brain of the tench (Tinca tinca L., 1758; Cyprinidae, Teleostei).

This report provides an atlas of the tench brain in the transverse plane. The brain atlas is based on paraffin-embedded brains which are serially sectioned and stained with cresyl violet. It consists of drawings and photographs at several levels throughout the main divisions of the tench brain. The brain of the tench shows important variations in the shape, extension and boundaries of different brain areas and nuclei in comparison with those previously described in the brain of other teleosts.

Anatomy, Artistic↗
PubMed1992

[Inflammatory pseudotumor of the liver].

Inflammatory pseudotumor is a pathological process whose cause is unknown, and whose macroscopic appearance is that of a malignant tumor, but it is in fact of inflammatory nature. Inflammatory pseudotumor of the liver is infrequent, but must be taken into account in the differential diagnosis of liver masses. A case report is presented, with review of the literature. Because of its benign nature, an aggressive approach is not recommended.

Adult↗
PubMed1991

Presence of terminal N-acetylgalactosamine residues in subregions of the endoplasmic reticulum is influenced by cell differentiation in culture.

Using Helix pomatia lectin as a specific probe for terminal, nonreducing N-acetylgalactosamine residues, glycoprotein precursors bearing newly initiated O-linked oligosaccharides have been localized in the lumen of the endoplasmic reticulum and cis-Golgi cisternae. This pattern contrasts with the detection of the terminal disaccharide galactose beta-1,3-N-acetylgalactosamine by Arachis hypogaea lectin in middle and trans-Golgi compartments, which are considered elongation sites for O-glycosylation. Distribution of H. pomatia ligands in the endoplasmic reticulum is confined to specialized regions or subcompartments in both human colonic adenocarcinoma cells and cultured chicken chondrocytes. Since in cartilage, chondrocytes contain H. pomatia-binding sites exclusively concentrated in cis-Golgi cisternae, primary cultures of this cell type have been used to study those conditions that promote initiation of O-glycosylation in the endoplasmic reticulum. A correlation has been found between the age of the culture and the extent of reactivity of the endoplasmic reticulum with either H. pomatia lectin or antibody against the sequence GalNAc alpha-serine/threonine (Tn antigen). Cells showing an extensive reaction are not hindered in their secretory activity and still maintain the chondrocyte phenotype. Taken together the results suggest that the intracellular distribution of the glycosylation enzymes is not only cell type-specific as previously shown (Roth, J., Taatjes, D. J., Weinstein, J., Paulson, J. C., Greenwell, P., and Watkins, W. M. (1986) J. Biol. Chem. 261, 14307-14312) but it might also vary depending on the stage of cell differentiation.

Acetylgalactosamine↗
PubMed1991

Effects of dimethylsulfoxide on the oxidative metabolism of certain tissues in rats in vitro.

Administration of 10 mM dimethylsulfoxide inhibits oxygen uptake in in vitro rat brain slices incubated in a Krebs-Ringer phosphate pH 7.4 solution containing 10 mM glucose. The effect is inverted when excessive potassium is added to the solution and the amount of sodium chloride is substituted by choline chloride. Using 10 mM, we observed a decrease in oxygen uptake in rat heart slices incubated in a Krebs-Ringer phosphate solution containing 131.8 mM Na+, 105.4 mM K+ and no calcium. Dimethylsulfoxide 10 mM, 1 mM and 0.1 mM does not alter the Na+/K+ ATPase activity nor the ouabain insensitive ATPase activity in in vitro preparations of rat brain, kidney and heart.

Adenosine Triphosphatases↗
PubMed1991

[Benign common bile duct stenosis: percutaneous dilatation in a case].

A 41 year old woman developed obstructive biliary tract disease 3 years after cholecystectomy. A surgical attempt to relieve the obstruction failed and a benign stricture of the common duct was shown at cholangiography. Percutaneous dilatation of the stricture was performed through the draining tube with excellent clinical and laboratory results.

Adult↗
PubMed1991

[Gastroesophageal reflux and esophagitis (II). Treatment guidelines].

The current therapeutic approach to gastroesophageal reflux disease is reviewed. Dietary measures, postural measures and drug therapy can be used to alleviate symptoms and for improving healing of esophageal lesions. Surgery can be used only in a few cases. Antacids, alginic acid, and motor-stimulating drugs i.e. metoclopramide and bethanecol, may be sufficient to treat pathologic reflux without esophagitis. When erosive or ulcerative lesions, a more vigorous treatment including H2 receptor blockers and omeprazole can be used.

Esophagitis↗
PubMed1991

[Pseudothrombocytopenia: incidence, causes and methods of detection].

A prospective study of 20,761 routine clinical blood specimens was conducted in order to evaluate incidence and causes of pseudothrombocytopenia. All specimens were drawn in outpatient regimen and were analyzed by using the Coulter STKR autoanalyzer. The incidence of pseudothrombocytopenia was 0.15%, values clearly lower than others previously reported in hospitalized patients (1.9%). Of these patients, 72% had EDTA-induced platelet clumping sometimes associated to sodium citrate and 28% had spurious low platelet counts due to large platelets. No other causes of pseudothrombocytopenia were appreciated. It is important to remark that 49% of low platelet counts detected by the Coulter STKR have been due to pseudothrombocytopenia, and this instrument showed normal platelet and leukocyte histogram in 10% of these cases. Although time consuming these results confirm the necessity of preparation and examination of all blood smears presenting thrombocytopenia by automated cell-counting despite normal histograms. This approach would avoid erroneous diagnosis and dangerous medical or surgical therapy. A correlation of pseudothrombocytopenia with age, sex or clinical diagnosis were not found.

Adolescent↗
PubMed1990

[Complicated primary splenic cyst: a clinical case].

A 16 year old man developed progressive swelling at the left hypochondrium over a 3 month period. Non painful splenomegaly was shown by physical examination and confirmed by ultrasonography and scintigraphy. Successful splenectomy disclosed a primary splenic cyst. The patient recovered uneventfully.

Adolescent↗
PubMed1989

Precursors of chondroitin sulfate proteoglycan are segregated within a subcompartment of the chondrocyte endoplasmic reticulum.

Immunocytochemical methods were used at the levels of light and electron microscopy to examine the intracellular compartments of chondrocytes involved in extracellular matrix biosynthesis. The results of our studies provide morphological evidence for the compartmentalization of secretory proteins in the ER. Precursors of the large chondroitin sulfate proteoglycan (CSPG), the major proteoglycan species produced by chondrocytes, were present in the Golgi complex. In addition, CSPG precursors were localized in specialized regions of the ER. Link protein, a separate gene product which functions to stabilize extracellular aggregates of CSPG monomers with hyaluronic acid, was segregated similarly. In contrast, type II procollagen, another major secretory molecule produced by chondrocytes, was found homogeneously distributed throughout the ER. The CSPG precursor-containing ER compartment exhibits a variable tubulo-vesicular morphology but is invariably recognized as an electronlucent, smooth membrane-bounded region continuous with typical ribosome-studded elements of the rough ER. The observation that this ER structure does not stain with antibodies against resident ER proteins also suggests that the compartment is a specialized region distinct from the main part of the ER. These results support recent studies that consider the ER as a compartmentalized organelle and are discussed in light of the possible implications for proteoglycan biosynthesis and processing.

Animals↗