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Biomedical subjects

S David

Publications and source records attributed to S David.

At least 91 records · Page 5Linked to original sources
PubMed1994

Acute myocardial infarction in angiographically normal coronary arteries following induction of general anesthesia.

Coronary spasm may occur with angiographically normal and diseased coronary arteries. General anesthesia has been described only rarely as a triggering event for coronary artery spasm, and only once before in the presence of angiographically normal coronary arteries. We have now seen three patients presenting with acute ST-segment elevation following induction of general anesthesia with enzyme evidence of myocardial necrosis in two patients. Cardiac catheterization was performed in all three patients with one of the procedures performed on an emergency basis owing to hemodynamic compromise. All three patients demonstrated angiographically normal coronary arteries. The electrocardiograms and coronary arteriograms are presented, and possible mechanisms for the injury pattern seen on the electrocardiogram are discussed. Coronary vasospasm causing an acute injury pattern on the electrocardiogram can be caused by general anesthesia and has to be recognized promptly and treated appropriately to prevent more serious complications.

Anesthesia, General↗
PubMed1994

Dibutyryl cAMP, interleukin-1 beta, and macrophage conditioned medium enhance the ability of astrocytes to promote neurite growth.

Astrocytes purified from the neonatal rat brain were cultured for up to 3 weeks prior to being treated with agents that can induce reactive changes in astrocytes. These agents included dibutyryl cAMP, interleukin-1 beta, and macrophage conditioned media. After treating astrocytes for 3 days, the agents were removed and the ability of the astrocytes to support neurite growth was assessed by plating neonatal rat cerebellar cortical neurons. All the agents increased the ability of astrocytes to support the growth of long neurites. This was particularly evident with astrocytes treated with dibutyryl cAMP and LPS macrophage-conditioned medium. These results provide direct evidence that the reactive changes induced in astrocytes in this in vitro model might aid the growth of neurites. Similar changes may underlie the injury-induced axonal sprouting that occurs in vivo.

Animals↗
PubMed1994

Immunocytochemical and functional characterization of an immortalized type 1 astrocytic cell line.

The DI TNC1 cell line has been derived from cultures of rat brain astrocytes by targeted oncogenesis. Cultured astrocytes are known to promote neurite outgrowth via the production of adhesion molecules found either on the cell surface or in the extracellular matrix. We sought to investigate whether DI TNC1 cells retained the ability to produce such neurite-inducing molecules, and promote neurite growth. We found by immunofluorescence that DI TNC1 cells expressed laminin, N-CAM and 1A1. The latter is a cell adhesion molecule that is expressed exclusively on astrocytes of the type 1 lineage. In vitro neurite outgrowth assays were also used to assess the functional properties of these cells. Monolayers of DI TNC1 cells were almost as effective a substrate as monolayers of astrocytes purified from the neonatal rat brain in their ability to support neurite outgrowth. In addition, PC12 cells grown on extracellular matrix derived from either DI TNC1 cells or neonatal astrocytes displayed significantly more neurite growth than cells plated on plastic. This effect was partially inhibited by preincubation of the extracellular matrix with anti-laminin antibodies. Taken together, these results suggest that the immortalized DI TNC1 cells show many similarities to neonatal astrocytes. Given the heterogeneity of cultured astrocytes, this homogeneous cell line may prove to be particularly useful for future investigations on interactions between glia and neurons.

Animals↗
PubMed1994

Tenascin in the injured rat optic nerve and in non-neuronal cells in vitro: potential role in neural repair.

The distribution of tenascin was examined in the lesioned adult rat optic nerve and central nervous system (CNS) non-neuronal cells in vitro, by means of a double immunofluorescence technique. Tenascin-like immunoreactivity is localized to the leptomeninges and astrocytes that border the site of optic nerve transection. Anti-tenascin labeling was observed as early as 24 hours after transection, when it appeared as a fine interface between leptomeninges and neural tissue. The anti-tenascin labeling increased in the cells at this border zone during the next 2 weeks, and disappeared 18-21 days after transection. In vitro studies further confirmed that both astrocytes and leptomeningeal cells express tenascin as detected by immunofluorescence labeling with anti-tenascin antibodies. However, the pattern of immunolabeling associated with the two cell types differed. Astrocytes showed exclusively punctate labeling of the cell surface, while leptomeningeal cells showed mainly coarse, fibrillary, matrix-like deposits. Astrocytes and leptomeningeal cells remained segregated when cocultured. In these cultures, an increased amount of the fibrillary, matrix-like deposits of tenascin was also observed in the region of the interface between astrocytes and leptomeningeal cells when these two cell types contact each other. Given the antiadhesive and antispreading properties of tenascin, these in vivo and in vitro results suggest that tenascin might play a role in the initial segregation of leptomeningeal cells from neural tissue at the site of CNS trauma during the first 2 weeks after injury, i.e., prior to the formation of a fully differentiated glia limitans. Therefore, tenascin may influence the early stages in the formation of the glia limitans, and thus prevent the indiscriminate migration of leptomeningeal cells into CNS tissue after injury.

Animals↗
PubMed1994

Distinction of weakly homologous cDNA amplificates by single-strand conformation polymorphism analysis: application to guanylyl cyclase isozymes.

By use of the polymerase chain reaction (PCR), uniform amplification products of 225 to 240 bp length were obtained from five cDNA clones representing different types of guanylyl cyclases. These short DNA double strands were differentiated by single-strand conformation polymorphism (SSCP), using polyacrylamide gel electrophoresis with the Pharmacia Phast-System. Following heat denaturation, the samples were separated on native polyacrylamide gels at different running temperatures. Nucleic acids on the gel were detected by an automated silver stain procedure. Using 7.5% homogeneous or 4-15% gradient polyacrylamide gels at a temperature of 12 degrees C, single-strand conformations of amplificates, representing three different particulate guanylyl cyclases and the two subunits of soluble guanylyl cyclase, were differentiated. The characteristic banding patterns resulting from dissimilar migration of the single-strand conformations were assigned to different guanylyl cyclase types. For the enzyme family of guanylyl cyclases, the feasibility of a combined PCR and electrophoresis approach for analyzing the expression of related genes was demonstrated. This application of the PCR-SSCP technique provided a rapid and sensitive tool for the characterization of PCR products obtained with a common primer pair and suggested its use for investigating the tissue distribution of gene expression within a class of homologous proteins.

Animals↗
PubMed1994

A monoclonal antibody that recognizes an adhesion molecule expressed by certain cells of neuroectodermal and mesenchymal origin.

A cell surface glycoprotein has been identified from detergent extracts of cultured astrocytes obtained from neonatal rat cerebral cortex using a mouse monoclonal antibody (MAb 1A1). This antibody inhibits neuron-astrocyte and astrocyte-astrocyte adhesion, as well as neurite outgrowth on astrocytes in vitro. The MAb 1A1 does not bind to tissue sections, but by indirect immunofluorescence of dissociated CNS cultures, the antibody labels subpopulations of astrocytes (flat, type 1 astrocytes and Bergmann glia) and cells derived from the mesenchyme (leptomeninges and fibroblasts). The latter cells are labeled only when grown to confluency. The 1A1 cell surface glycoprotein appears as a single band of approximately 135 kDa on both reduced and nonreduced SDS-PAGE. Based on its unique cell-type distribution, functional properties and biochemical analysis, this 135-kDa protein appears to be distinct from other known adhesion molecules expressed on astrocytes. This molecule, thus, belongs to the growing list of cell adhesion molecules that may play a role in histogenesis and axonal growth during development of the mammalian CNS.

Animals↗
PubMed1994

The role of an astrocyte surface molecule in neuronal migration in the developing rat cerebellum.

We have shown previously that the MAb 1A1 recognizes a cell surface glycoprotein with adhesive properties expressed exclusively on astrocytes in the rat central nervous system (CNS). In this study, the role of this molecule in neuronal migration in the developing rat cerebellum was investigated by antibody perturbation experiments. The MAb 1A1 binds to the surface of cultured radial Bergmann glia, a subclass of astrocytes known to guide the migration of postmitotic neurons by cell-cell contact, but does not bind to neurons in the cerebellum. The antibody does not bind to tissue sections for immunohistochemical studies. However, by immunoprecipitation the level of this antigen increases by about twofold between Postnatal Day 1 (P1) and P20 followed by a decrease to the P1 level at P35. In addition, the number of 1A1+ Bergmann glia also increases from 33 to 78% between P1 and P7 in dissociated cell cultures. Monovalent fragments of the MAb 1A1 inhibit the adhesion of neurons to Bergmann glia by about 50% in dissociated cultures of the P7 cerebellum. In addition, the migration of neurons on Bergmann glia was assessed in microexplant cultures of the P7 cerebellar cortex after 3 days in vitro. In these experiments the MAb 1A1 blocks the migration of neurons by 60%. These findings suggest that the 1A1 molecule might play a role in glial-guided neuronal migration in the developing cerebellum.

Animals↗
PubMed1994

Production of a monoclonal antibody against human amelogenin.

The extracellular organic matrix of developing human enamel is composed of two major classes of proteins, the hydrophobic amelogenins and the acidic enamelins. In order to identify, purify, and characterize the amelogenins from this complex mixture of proteins, and to study their ultrastructural localization and their pathways of synthesis, secretion, and degradation, specific and sensitive probes are needed. In the present paper the production of a monoclonal antibody against human amelogenin employing an intrasplenic primary immunization protocol is described. The monoclonal antibody produced is IgM and recognizes major human amelogenin protein bands in Western immunoblot assays. It also recognizes amelogenin protein bands from other species, specifically bovine and porcine. Indirect immunohistochemical studies showed the monoclonal antibody to react specifically with the extracellular matrix of human developing enamel. It did not react with the underlying dentin layer.

Amelogenin↗
PubMed1994

Identification of myelin-associated glycoprotein as a major myelin-derived inhibitor of neurite growth.

Contact-dependent axon growth inhibitory activity is present in CNS myelin, but the inhibitory proteins have not been fully characterized. We report here that at least two peaks of inhibitory activity can be separated by fractionating solubilized CNS myelin proteins by DEAE chromatography. A major peak of inhibitory activity corresponded to the elution profile of myelin-associated glycoprotein (MAG). Immunodepletion of MAG from these inhibitory fractions removed neurite growth inhibition, whereas recombinant MAG (ectodomain) was a potent inhibitor of neurite outgrowth. Immunodepletion of MAG from total extracts of CNS myelin restored neurite growth up to 63% of control levels. These results establish that MAG is a significant, and possibly the major, inhibitor in CNS myelin; this has broad implications for axonal regeneration in the injured mammalian CNS.

Animals↗
PubMed1994

Alternative pathway activation of complement by cultured human proximal tubular epithelial cells.

Human proximal tubular epithelial cells (PTEC) incubated with normal human serum (NHS) were found to fix on their surface C3, properdin, terminal complement components and C5b-9 MAC neoantigen, but not C1q and C4, by immunofluorescence. Complement fixation was abrogated if PTEC were incubated with EDTA-treated NHS or C3-deficient human serum, but not with Mg EGTA-treated NHS or C1q-deficient human serum, showing the prevalent activation of the alternative pathway of complement. This event was followed by marked cytoskeleton alterations with disruption of the actin cortical network, redistribution of actin throughout the cytoplasm and formation of blebs, and by cell cytolysis. In addition, superoxide anion and hydrogen peroxide production and chemiluminescence response were detected in consequence of MAC insertion on PTEC plasma membrane. The dependency on MAC of the observed biological effects of complement fixation on PTEC surface was shown by using sera selectively deficient of terminal components of complement (C6 or C8), and therefore unable to form the C5b-9 MAC, and by restoring the ability to form MAC after addition of purified C6 or C8. The possible pathogenetic relevance of these observations in tubulointerstitial injury occurring in patients with complementuria due to non-selective proteinuria, is discussed.

Blood↗
PubMed1994

Hemoglobin is a late event in the differentiation of Friend erythroleukemic cells in-vitro. I. The role of interferon-induced proteins.

Here we report that the interferon (IFN)-induced proteins, 2'-5'-oligoadenylate synthetase (OAS) and IFN-induced protein kinase (PKI), appearance and activity precede that of hemoglobin (Hb) in the differentiation process of Friend erythroleukemic cells (FLC). Since our results are correlative, we assume that OAS and PKI are activated, and act at an early stage in the differentiation process, enabling the late onset of Hb synthesis. It is, thus, suggested that red blood cells harboring specific differentiating genes may be used as more efficient carriers of oxygen-binding molecules.

2',5'-Oligoadenylate Synthetase↗
PubMed1994

Basic therapeutic requirements in the treatment of sepsis in acute renal failure.

Acute renal failure (ARF) is a common manifestation of a septic condition which very often complicates surgical and traumatic events. The release of endotoxin, a lipopolysaccharide (LPS) from the cell wall of Gram-negative bacteria, and subsequently of numerous host mediators, is the initiating event of sepsis syndrome and eventually of septic shock. Particularly interesting is the observation that not only endotoxins but also Staphylococcus aureus which does not produce endotoxins induce the same cardiovascular changes of septic shock. The main aspect of septic shock is the inadequate oxygen supply to the body tissues. However, despite the documented myocardial depression in the course of septic shock, myocardial ischaemia is not to be considered a contributing factor, and the coronary blood flow is normal or even increased. Protein hypercatabolism can be at best only limited; in any case the optimal protein-sparing effect was observed with 1.5 g/kg proteins. Recently monoclonal antibodies to endotoxin core glycolipid have been developed; they are: (a) E5, a murine IgM anti-lipid A monoclonal antibody; (b) HA-1A, a human monoclonal antibody to endotoxin core glycolipid. In conclusion, hypercatabolic septic patients should be managed in an intensive care environment where a continuous monitoring of fluids, electrolytes, and acid-base disorders can be achieved. Surgical search of septic foci, and wide-spectrum antibiotic therapy are fundamental measures to combat cytokine and vasodilator production which impair tissue perfusion and create the premise of a shock status complicated by lactic acidosis. Dialysis treatment is a further complementary but fundamental approach that allows a large fluid and nutritional intake and a continuous correction of electrolyte and acid-base disorders.

Acute Kidney Injury↗
PubMed1993

Antisense inhibition of AMEL translation demonstrates supramolecular controls for enamel HAP crystal growth during embryonic mouse molar development.

During tooth development, enamel organ epithelial cells express a tissue-specific gene product (amelogenin) which presumably functions to control calcium hydroxyapatite crystal growth patterns during enamel biomineralization. The present studies were designed to test the hypothesis that amelogenin as a supramolecular aggregate regulates crystal growth during enamel biomineralization. Antisense oligodeoxynucleotide strategy was used in a simple organ culture system to inhibit amelogenin translation. Under these experimental conditions, antisense treatment prior to and during amelogenin expression resulted in inhibition of amelogenin translation products within immunoprecipitated [35S]methionine metabolically labeled proteins. To determine the efficiency of antisense treatment in this model system, digoxigenin-labeled oligodeoxynucleotides were observed to diffuse throughout the tooth explants including the target ameloblast cells within 24 hours. Ultrastructural analyses of amelogenin supramolecular assembly as electron-dense stippled materials in antisense treated cultures demonstrated dysmorphology of the extracellular enamel matrix with a significant reduction in crystal length and width. We conclude that secreted extracellular proteins form a supramolecular aggregate, which controls both the orientation and dimensions of enamel crystal formation during tooth development.

Amelogenesis↗