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Biomedical subjects

N Savion

Publications and source records attributed to N Savion.

At least 73 records · Page 4Linked to original sources
PubMed1992

Ultrastructural damage in photosensitized endothelial cells: dependence on hematoporphyrin delivery pathways.

The subcellular photodamage to endothelial cells in culture, revealed by transmission electron microscopy, was correlated with discrete delivery pathways of hematoporphyrin (HP). Cell detachment from the extracellular matrix, prominent water influx starting at the outer membrane and formation of blebs followed by cell death were the result of photodynamic damage induced by aqueous HP. Serum-bound HP was internalized by endocytosis and accumulated in lysosomal compartments as located after photosensitization. Obstructed lysosomal membranes, degradation of chromatin and swelling of endoplasmic reticulum were revealed in these cells. Red blood cells (RBCs), preincubated with HP, delivered low amounts of the drug to endothelial cells. The photodamage was limited to the nucleus and nucleolus. The role of photosensitizer delivery pathways in cancer cell damage is discussed.

Animals↗
PubMed1992

Platelet protection by aprotinin in cardiopulmonary bypass: electron microscopic study.

To evaluate the functional integrity of platelets in patients administered the proteinase inhibitor aprotinin during cardiopulmonary bypass, 20 patients undergoing a complicated and prolonged open heart operation were studied. They were randomized to receive either a high dose of aprotinin (total dose, 6 to 7 x 10(6) KIU) before and during cardiopulmonary bypass (10 patients) or a placebo (10 patients). Blood samples were collected preoperatively, at the termination of bypass, and 90 minutes thereafter to assess platelet count and aggregation on extracellular matrix, which was studied by scanning electron microscopy. On a scale of 1 to 4, mean preoperative platelet aggregation grades were similar in both groups (3.5 +/- 0.5). Postoperatively, at the termination of cardiopulmonary bypass and 90 minutes thereafter, all 10 patients treated with aprotinin revealed normal, unchanged platelet aggregation (grade, 3.5 +/- 0.5), whereas all placebo-treated patients showed severely disturbed aggregation (grade, 1.4 +/- 0.5) (p less than 0.001). The platelet count was similar in both groups before and after operation (preoperatively, 182 +/- 75 x 10(9)/L and 146 +/- 30 x 10(9)/L, and postoperatively, 87 +/- 13 x 10(9)/L and 80 +/- 27 x 10(9)/L for the aprotinin and placebo groups, respectively). Total 24-hour postoperative bleeding and blood requirement were significantly lower in the aprotinin group (371 +/- 84 mL and 2 +/- 0.7 units, respectively) compared with the placebo group (608 +/- 28 mL and 3.4 +/- 1.3 units, respectively) (p less than 0.01). These results demonstrate that improved postoperative hemostasis is directly related to the complete preservation of platelet function achieved by the protective properties of aprotinin.

Adult↗
PubMed1992

Alpha melanocyte stimulating hormone (alpha-MSH) enhances eicosanoid production by bovine retinal pigment epithelium.

Explants of bovine eyes consisting of retina, with its underlying choroid and sclera (termed retinal explants) were maintained in organ culture in the absence or presence of alpha-melanocyte stimulating hormone (alpha-MSH) for up to 19 days. The conditioned media was collected twice a week and assayed for the following eicosanoids, prostaglandin E2 (PGE2) and prostacyclin. The addition of alpha-MSH to the incubation media resulted in a 1.5 fold enhancement in the production of both PGE2 and prostacyclin. This stimulatory effect diminished after 11 days. Additionally, the three tissue components comprising the retinal explants i.e. 1. neural retina 2. retinal pigment epithelium (RPE) with its underlying vascular layer (choroid) and 3. scleral tissue were separated and incubated in the presence or absence of alpha-MSH. Hormone treatment caused an enhanced eicosanoid production by RPE tissue alone, while its production by the neuronal retina and sclera was reduced or unaffected respectively. This demonstrates that the RPE layer is the source for the alpha-MSH induced eicosanoid production observed in the whole retinal explant. Our findings demonstrate, for the first time that alpha-MSH can stimulate prostaglandin production by RPE maintained in organ culture.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

A quantitative in vitro model for silicone oil emulsification. Role of blood constituents.

To understand why some patients seem to be protected from emulsification and others are not, the authors developed an in vitro model for quantitative analysis of silicone oil emulsification. The pro-emulsifying potential of substances and blood components that may have access to the vitreous cavity in a patient's eye was analyzed. In this model, red blood cell ghosts had the highest emulsifying effect; plasma and lymphocytes also had a significant emulsifying effect. Phospholipids in membranes and other soluble blood components may play important roles in this process. These results suggest the importance of avoiding and removing hemorrhage and avoiding inflammation when silicone oil is used in vitreoretinal surgery.

Blood Cells↗
PubMed1992

Binding of a cementum attachment protein to extracellular matrix components and to dental surfaces.

Cementum proteins (CP) have been shown to mediate cell attachment. Among these, a 55 kDa protein was isolated. The purpose of the present study was to assess the capacity of CP to bind to non-demineralized and demineralized root surfaces and to support cell attachment to dentin. CP were prepared by sequential extraction of bovine cementum with 25 mM EDTA, 0.5 M acetic acid followed by 4 M guanidine HCl. The latter was subjected to ion exchange chromatography on a DEAE-3SW column and eluted stepwise with a 0-0.5 M NaCl gradient. CP were labelled with 125I and the capacity of 125I-CP to bind to mineralized and partially demineralized dentin, synthetic hydroxyapatite, collagen, fibronectin and fibrillar collagen-fibronectin complex was assessed. It was found that CP bind specifically to mineralized dentin and synthetic hydroxyapatite but not to demineralized dentin. The specific binding was 60% of the total binding. SDS-PAGE analysis of the proteins bound to dentin indicated that the main bound protein had a molecular weight of 55 kDa. CP exhibited high affinity for fibronectin (kD = 1.56 x 10(-10) M) and fibronectin-collagen complex, but their binding to either molecular or fibrillar collagen was negligible. It is suggested that CP may play an important role in the attachment of cells of the periodontium to cementum extracellular matrix during homeostasis and regeneration.

Animals↗
PubMed1992

Cellular functions related to metastasis differing between low- and high-malignancy variants of AKR lymphoma.

Two AKR lymphoma variants of low (LM) and high (HM) malignancy were characterized for cell properties important for metastatic capacity. Previous data suggested that these murine lymphoma variants differed in the late phase of metastasis. In the present study we attempted to determine more accurately the stage in which they differ. The HM cells attached less efficiently than the LM ones to both endothelial cells (5 times) and extracellular matrix (twice), possibly indicating a more efficient extravasation capacity of the HM cells. The level of heparinase was low in the two variant cells. Attachment to liver sections was, however, more efficient with the HM than with the LM cells.

AKR murine leukemia virus↗
PubMed1991

Release of a small two-chain form of antithrombin III from a conformationally changed antithrombin III-thrombin complex.

Reaction of antithrombin III (AT) with thrombin results in the formation of stable antithrombin III-thrombin (AT-T) complex with a Mr of 92.5-kDa, accompanied by the appearance of a proteolytically modified form of the inhibitor (ATM). Under these conditions AT-T is also transformed to a smaller complex (AT-TS). This smaller complex (81-kDa), a product of a conformational change at the AT moiety of the AT-T complex, is further transformed to a very small complex (AT-TVS) with a Mr of 71-kDa. Along with this process, AT-TS slowly dissociates to a free enzyme and a small, presumably two-chain product of AT (ATMS) with a Mr of 49-kDa. The newly described component, ATMS, naturally occurs in plasma and serum and accumulates significantly in plasma of patients suffering from cardiovascular disease.

Amino Acid Sequence↗
PubMed1991

Changes in plasmatic tissue-type plasminogen activator and plasminogen activator inhibitor activity during acute arterial occlusion associated with severe ischemia.

Severe lower limb ischemia in patients with acute arterial occlusion was associated with a significant increase in systemic fibrinolytic activity. Plasmatic level of t-PA activity was twice the normal value at the peak of ischemia. This level declined gradually within no less than 40 hours after reperfusion procedure or limb amputation had reverted the ischemic state. In spite of major tissue damage and surgical trauma, plasmatic PAI activity stayed within normal range, and did not increase within the first 24 hours postoperatively. These findings strongly suggest that acute ischemia initiates systemic induction of excessive and continuous release of t-PA, which outweighs any anticipated increase in PAI activity.

Arterial Occlusive Diseases↗
PubMed1991

Characterization of the cellular binding domain and the effects of monoclonal antibodies and thrombin inhibitors on the binding and internalization of the antithrombin-III--thrombin complex by cultured cells.

Antithrombin III (AT) binds to cultured cells mainly as a complex with thrombin or other serine proteases rather than in its free form. This implies that, upon complex formation, a new determinant appears on the AT molecule which is recognized by the cells. Fragmentation of AT by cyanogen bromide exposes this determinant and an 8-kDa fragment is recognized by cultured cells. The binding of this fragment to cultured cells is inhibited by antithrombin-III-thrombin (AT-T) complex, but not by free AT. The putative cellular binding domain of AT-T is located over amino acid residues 253-314 of AT, in the large loop close to the carboxy-terminus of the molecule. The cell-associated AT-T is internalized and degraded, forming the thrombin-modified AT (ATM). This process is inhibited by lysosomal degradation inhibitors, such as chloroquine or benzamidine. Thus, the appearance of ATM in cells is not a result of its binding to the cell surface, but probably a result of lysosomal degradation of cell-associated AT-T. Another degradation product, with a molecular mass of 43 kDa, appears in cells along with the appearance of ATM. Hirudin, a specific inhibitor of thrombin, inhibits the cellular internalization of AT-T complexes, indicating a possible role for thrombin activity in the internalization process of complexes. Monoclonal antibodies (mAb) against AT, whose epitopes on the AT molecule have been located, affect the binding of AT-T to cultured cells. Two mAb, A10 whose epitope is found outside of the cellular binding site, and B108 whose epitope may overlap this sequence, totally inhibit the binding of the complex to cells. Inhibition of binding results either from steric hindrance or induced changes in the binding site.

Animals↗
PubMed1991

Epithelial-connective tissue interaction on the tooth surface: an in vitro model.

In the present study, and in vitro system was developed and designed to examine the interaction between gingival fibroblasts (GF) and epithelial cells (EC) on the tooth surface. Porcine roots were cut transversely into 300 microns-thick root slices (RS). Gingival explants were placed on the upper RS surface and cultured in a defined medium permissive for the growth of EC. After 4 or 6 days, RS yielding EC were transferred onto confluent cultures of GF and further co-cultured for either 4 or 8 d. Cultures were then fixed and examined by SEM. The upper RS surfaces and the upper half of their peripheral aspect were covered by EC. The lower half of the peripheral RS surfaces were populated by GF originating from the confluent culture of GF. EC and GF made contact at approximately the middle of the side of the root slice. In cultures of epithelial components grown in defined medium for either 4 or 6 d and harvested 4 d after assembling the system, the EC-GF junction was located 117 +/- 45 and 271 +/- 82 microns, respectively from the upper RS aspect. Extending the co-culture period did not affect the EC-GF junction location. These results indicate that GF-EC contact stops the migration of these cells on root surfaces in vitro. The described system should be valuable for studying cellular events that may affect the formation of a new dentogingival junction following surgical periodontal therapy.

Animals↗
PubMed1991

Heparan sulfate and fibronectin improve the capacity of collagen barriers to prevent apical migration of the junctional epithelium.

The objective of the present study was to assess the effect of bilayered/collagen barriers enriched with fibronectin and heparan sulfate on the prevention of apical migration of the epithelium during the initial stage of periodontal wound healing. Experimental osseous defects were produced on the labial aspect of maxillary canines in dogs. Experimental sites were treated with either bilayered enriched collagen barriers or with non-enriched bilayered collagen barriers, using the guided tissue regeneration technique. Control sites were treated with monolayered collagen barriers that were not enriched with fibronectin and heparan sulfate. Histologic and histomorphometric examinations performed on specimens obtained 20 days post-operative indicate the formation of a short junctional epithelium in the experimental sites treated with enriched collagen barriers. In this group, 95% of the occlusal-apical length of the defects was repopulated by connective tissue cells. In the other 2 groups, a long junctional epithelium developed with only 65% of the occlusal-apical length of the defects being repopulated by connective tissue cells. These findings suggest that the enrichment of collagen barriers with fibronectin and heparan sulfate may be important to enhance the repopulation of exposed root surfaces by connective tissue cells and prevent the apical migration of the epithelium during the initial stages of periodontal wound healing.

Alveolar Process↗
PubMed1991

Metabolism of cholesterol and phospholipids in cultured human vascular smooth muscle cells: differences between artery and vein-derived cells and the effect of oxygen partial pressure.

Human smooth muscle (SM) cells derived from vena saphena magna, aorta abdominalis and arteria mamaria were grown in culture under 40 or 145 mmHg oxygen partial pressure (pO2) and their lipid metabolism studied. Esterification of the cellular [3H]cholesterol was higher by 2.5-fold in artery derived than in vein-derived cells and was slightly higher in cultures exposed to 145 mmHg than to 40 mmHg pO2. Cholesterol efflux in the presence of high density lipoprotein (HDL) in the incubation medium was higher in artery-derived than vein-derived cells. Apolipoprotein (apo) AI also supported cholesterol efflux to a higher extent in artery than in vein-derived cells. Cholesterol efflux in the presence of apo AI was accompanied by a decrease of 50% in cellular [3H]cholesteryl ester in both cell types. SM cultures exposed to [3H]choline incorporated about 90% of the radioactivity to phosphatidylcholine (PC) and 10% to sphingomyelin (SPM). During 5 days exposure to [3H]choline, 10 to 15% and 20 to 30% of the newly synthesized PC and SPM, respectively, were released by vein-derived cells into the incubation medium. The relative amount of SPM of the total radioactive phospholipids released by vein-derived cultures was significantly higher in cultures growing under 40 mmHg than 145 mmHg pO2 reaching a value of up to 33% of the radioactive phospholipids in the incubation medium. HDL was shown to serve as an acceptor for phospholipids released by both vein and artery-derived SM cells, while free apo AI supported phospholipid efflux in artery but not in vein-derived SM cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteries↗
PubMed1991

Biochemical analysis of a human humoral fibroblast inhibitory factor associated with impaired vascular prosthetic graft incorporation.

A specific inhibitory factor was isolated from human serum of a patient who manifested impaired prosthetic graft tissue incorporation. The latter reaction was hypothesized to be related to inhibiting fibroblast proliferation by a specific humoral factor. The crude inhibitory serum was tested against a pool of normal human sera with different cell types in culture. Proliferation of human skin fibroblast and human smooth muscle cell cultures incubated in the presence of 50% inhibitory serum were inhibited up to 58% and 37%, respectively. Proliferation of bovine capillary endothelial cell cultures was stimulated under similar conditions. Isolation and purification of the inhibitory factor from crude serum were initiated by ammonium sulfate precipitation. The pellet was further fractionated by sepharose 6B gel filtration. The inhibitory activity was eluted from the column in a relatively purified form as indicated by gel electrophoresis of the inhibitory fractions, which demonstrated a specific band corresponding to the inhibitory protein, with an apparent relative molecular mass of 230 kDa. The inhibitory factor showed a high affinity to concanavalin A, indicating its nature as a glycoprotein not associated with albumin or immunoglobulin fractions of the serum.

Aged↗
PubMed1990

Granulocyte-macrophage colony-stimulating factor enhances cationic antimicrobial protein synthesis by human neutrophils.

We analyzed the effect of recombinant human granulocyte macrophage CSF (GM-CSF) on protein synthesis in peripheral blood polymorphonuclear leukocytes. GM-CSF enhanced PMN 35S-methionine incorporation 1.5-fold over a 2-h incubation period. The effect of GM-CSF on the synthesis of specific proteins was investigated by separating the radiolabeled proteins on SDS-PAGE followed by autoradiography. Stimulation of protein synthesis by GM-CSF was rapid (2 h), dose dependent, and affected at least 10 separate polypeptides. Using ion exchange chromatography some of the GM-CSF-enhanced proteins were identified to have a cationic nature, including the 37- and the 57-kDA proteins whose synthesis was increased by GM-CSF 2.4-fold and 1.6-fold, respectively. The cationic protein fractions from GM-CSF-primed and control cells were eluted from an ion exchange column and tested for their antimicrobial activity. An overall twofold increase in the amount of cationic proteins was recovered from GM-CSF-treated cells as compared to control cells, and these proteins showed a proportional enhanced killing of S. typhimurium. These results suggest that enhanced cationic protein synthesis is an important mechanism whereby GM-CSF can increase neutrophil microbicidal activity via nonoxidative pathways.

Antimicrobial Cationic Peptides↗
PubMed1990

Analysis of thymic stromal cell subpopulations grown in vitro on extracellular matrix in defined medium. I. Growth conditions and morphology of murine thymic epithelial and mesenchymal cells.

We report here the successful selective cultivation of murine thymic mesenchymal reticular cells (MTMC) and murine thymic epithelial cells (MTEC) grown on extracellular matrix in the presence of defined medium. The selective growth of these two cell types was based on 1) conditions of tissue disruption and 2) differential growth requirements. Both cell types were dependent on transferrin, high density lipoproteins, insulin, hydrocortisone, and epidermal growth factor, whereas MTMC was dependent also on selenium and 3,5,3'-triiodothyronine. The elimination of single factors or extracellular matrix resulted in specific and different changes in the growth pattern of each cell subpopulation. Cells of both types exhibited the ultrastructural features of high metabolic activity. The epithelial nature of MTEC cultures was defined by bundles of tonofilaments and desmosomes and by positive staining to keratins and negative to vimentin. In addition MTEC were positively stained with mAb to thymic medullary epithelial cells and by Ulex europeus agglutinin, and were able to form Hassall's corpuscles, suggesting their medullary origin. MTEC were also H-2 and Ia positive. In contrast MTMC were positive for vimentin and periodic acid-Schiff, low positive for H-2, and negative for keratin and Ia. Both cells did not contain nonspecific esterase, nor did they phagocytize latex beads. With the use of all these criteria we classified MTEC as epithelial cells from the medullary compartment of the thymus and MTMC as reticular cells of mesenchymal origin.

Animals↗
PubMed1990

Analysis of thymic stromal cell subpopulations grown in vitro on extracellular matrix in defined medium. II. Cytokine activities in murine thymic epithelial and mesenchymal cell culture supernatants.

Two morphologically distinct primary cultures of murine thymic stroma were established and found to be of epithelial (MTEC) and mesenchymal (MTMC) origin. These cultures were generated by selective conditions of tissue disruption and were maintained on extracellular matrix in defined medium. Culture supernatants (CS) from these cultures (EC-CS and MC-CS respectively), were tested for cytokine production and for effects on thymocyte maturation. Both supernatants displayed the activities of IL-3 and of granulocyte/macrophage-CSF and not of IL-1, -2, -4, or IFN. In addition they were found to be mitogenic to murine thymocytes in a "spontaneous" [3H]TdR incorporation assay. The two supernatants differed, however, in their effect on Con A stimulation. EC-CS had a strong enhancing effect, both when used for preincubation (18 h) before Con A stimulation or when present simultaneously with it. MC-CS had a small inconsistent effect under these conditions. Also EC-CS enhanced IL-2 and IL-3 production by thymocytes. The responsive thymocyte subpopulation was the one that does not bind peanut agglutinin. CS of an established thymic epithelial cell line displayed only part of these activities at a considerably lower level. CS from primary kidney cell culture was completely devoid of activity. The results suggest that primary thymic stromal cell cultures, cultivated under the defined conditions described here, may better preserve physiologic secretory activities, and probably also other cell functions, compared with established cell lines. Furthermore, the results are compatible with the hypothesis that the soluble factors, secreted by thymic stromal cells, are active on either very early or late stages of thymic differentiation, whereas the main intrathymic stages of differentiation are conceivable dependent primarily on direct contact with stromal cells.

Animals↗
PubMed1990

Transfusion of fresh whole blood stored (4 degrees C) for short period fails to improve platelet aggregation on extracellular matrix and clinical hemostasis after cardiopulmonary bypass.

It has recently been shown that the hemostatic effect of 1 unit of fresh whole blood is equivalent to the effect of 8 to 10 platelet units. This study was designed to evaluate the effect of short periods of cold (4 degrees C) storage on the hemostatic effect of fresh whole blood transfusion in 36 patients immediately after cardiopulmonary bypass. Twelve patients (group A) received unrefrigerated fresh whole blood, 12 (group B) received fresh whole blood after 5 hours' storage at 4 degrees C, and 12 (group C) after 24 hours' storage at 4 degrees C. For evaluation of platelet function, a method with an extracellular matrix and an electron microscope was used. The platelet function was graded from 1 to 4, with grade 4 being normal aggregation. Postoperatively, group A patients bled less than groups B and C (267 +/- 42 versus 397 +/- 72 and 601 +/- 172 ml/24 hr, respectively, p less than 0.001) and therefore received fewer blood units (1.4 +/- 0.5 versus 2 +/- 0.9 and 3 +/- 1.4, respectively, p less than 0.01). Five patients of group A (42%) reached grade A aggregation after transfusion of unstored fresh whole blood, compared with two (17%) of group B and none (0%) of group C (p less than 0.01). Posttransfusion platelet count and mean platelet volume were not significantly different in the three groups. We conclude that storage at 4 degrees C, even for a short period of 5 hours, diminishes the hemostatic effect of fresh whole blood by decreasing platelet aggregability.

Blood Physiological Phenomena↗