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Biomedical subjects

A Cattaneo

Publications and source records attributed to A Cattaneo.

At least 163 records · Page 9Linked to original sources
PubMed1987

Polymeric immunoglobulin M is secreted by transfectants of non-lymphoid cells in the absence of immunoglobulin J chain.

Plasmids were constructed in which expression of genes encoding the heavy and light chains of a hapten-specific IgM antibody is under control of a heat shock promoter. Glioma, phaeochromocytoma and other non-lymphoid cell lines transfected with the plasmids were able to process and secrete immunoglobulin following heat induction. The glioma transfectants were studied in detail and were shown to secrete polymeric IgM in a yield similar to that obtained with a plasmacytoma. However, the glioma IgM was not associated with J chain and was largely composed of pentamers and hexamers. Thus, neither J chain nor other lymphoid-specific proteins are required for assembly and secretion of polymeric IgM although the absence of J chain may encourage hexamer formation.

Animals↗
PubMed1986

A functional domain on the alpha-latrotoxin molecule, distinct from the binding site, involved in catecholamine secretion from PC12 cells: identification with monoclonal antibodies.

Seven monoclonal antibodies (mAbs) have been produced against alpha-latrotoxin (alpha-Latx), the toxin component of black widow spider venom that stimulates release of neurotransmitters from PC12 cells. These mAbs were characterized by an enzyme-linked immunosorbent assay and by neutralization analysis of the secretagogue properties of the toxin. The production of a panel of mAbs, possibly directed against different epitopes of alpha-Latx, provides a useful set of reagents to dissect the molecular regions of the toxin having different functions and to describe steps of its mode of action in responsive cells. Attention was focused on one of these mAbs (4C4.1), which inhibits in a dose-dependent fashion both toxin-stimulated and crude venom stimulated dopamine release from PC12 cells, prevents toxin-induced 45Ca2+ accumulation in PC12, alters toxin-dependent phosphoinositide breakdown, and prevents toxin-induced channel formation in artificial lipid bilayers. Since, within certain experimental conditions, mAb 4C4.1 is able to recognize the toxin bound to cells, we conclude that its effects were not a consequence of a direct interference with binding. On the basis of kinetic analysis of mAb interference on toxin action, expressed as accumulation of inositol phosphates and transmitter secretion, we suggest that the described effects result primarily from the blockade of an event immediately successive to binding and central for the full expression of toxin action. The availability of mAb 4C4.1 now makes possible the molecular characterization of the toxin moiety responsible for such an event.

Adrenal Gland Neoplasms↗
PubMed1986

The toxicity of 2,4-dichlorophenoxyacetic acid to the adult crested newt.

The toxicity of the herbicide Agroxone 5, a commercial formulation of the iso-octyl ester of 2,4-dichlorophenoxyacetic acid (2,4-D), in the adult crested newt (Triturus cristatus carnifex) was tested after percutaneous exposure. The compound was lethal to all the animals within 72 hr at concentrations of 100, 125, and 150 ppm. Males appeared to be more susceptible than females to the toxic effects of 2,4-D, since the LT50 values at 75 ppm were 102 and 132 hr for male and female newts, respectively. At 50 ppm, all the males died within 31 days of exposure, whereas the females were still alive at the end of the 3-month experiment. Only one male died at 25 ppm after 21 days. Vacuolar degeneration of liver parenchyma and necrosis of kidney tubules were found at lethal concentrations of 2,4-D. The severity of the lesions was related to the duration of exposure more than to the concentration of the herbicide.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1985

Synthesis and content of a DNA-binding protein with lactic dehydrogenase activity are reduced by nerve growth factor in the neoplastic cell line PC12.

We have previously demonstrated that synthesis of a 34 kD protein having specific, high affinity for single-stranded DNA (34kD-ssb protein), is markedly inhibited by nerve growth factor (NGF) in the neoplastic clonal cell line PC12. We report here that total content as well as mRNA for this protein are progressively reduced in PC12 cells undergoing mitotic arrest and morphological differentiation induced by NGF. It is also shown that binding of the 34K-ssb protein to ssDNA is fully inhibited by NADH but not by NAD+ or by several other nucleotides. Enzymatic tests on the possible NADH/NAD+-dependent dehydrogenase activity of the 34K-ssb protein have demonstrated that it has lactic dehydrogenase activity (LDH) with a specific activity comparable to that of rabbit muscle. Furthermore, the 34K-ssb protein has the same peptide mapping as LDH purified from rat muscle. Antibodies directed against the 34K-ssb protein cross-react with the rabbit muscle enzyme and, vice versa, antibodies raised against rabbit LDH cross-react with the 34K-ssb protein. It is concluded that the 34K-ssb protein is identifiable with the type M of LDH, although possible differences in primary structure of the two proteins may have escaped the present studies. We hypothesize that interaction of the PC12 lactic dehydrogenase with ssDNA occurs also in vivo, as indicated by the findings reported in the accompanying paper, and may be modulated by the cellular content of NADH which, in turn, is related to energy metabolism.

Animals↗
PubMed1985

Nuclear localization of a lactic dehydrogenase with single-stranded DNA-binding properties.

In the preceding article [1] we identified the 34 kD single-stranded DNA-binding (ssb) protein, whose synthesis is inhibited in PC12 cells concomitantly with nerve growth factor (NGF)-induced mitotic arrest, with the enzyme lactic dehydrogenase (LDH-ssb protein). Localization studies performed with antibodies raised against the LDH-ssb protein demonstrate the presence of a pool of this protein in the nucleus of several cell types. The nuclear association of this protein is sensitive to DNase treatment of the cells and quantitative electron microscopy confirms that the LDH-ssb protein is located close to chromatin structures. These results point to a possible involvement of the LDH-ssb protein in some nuclear function(s).

Animals↗
PubMed1984

Nerve growth factor inhibits the synthesis of a single-stranded DNA binding protein in pheochromocytoma cells (clone PC12).

Arrest of mitosis and neurite outgrowth induced by nerve growth factor (NGF) in rat pheochromocytoma cells (clone PC12) is accompanied by a progressive inhibition of the synthesis of a protein that binds to single-stranded but not to double-stranded DNA. Time course experiments show that this inhibition is already apparent after a 2-day incubation with NGF and is maximum (85-95%) upon achievement of complete PC12 cell differentiation. Inhibition of the synthesis of this single-stranded DNA binding protein after 48 hr of incubation with NGF is potentiated by concomitant treatment of PC12 cells with antimitotic drugs acting at different levels of DNA replication. Purification on a preparative scale of this protein and analysis of its major physicochemical properties show that: (i) it constitutes 0.5% of total soluble proteins of naive PC12 cells; (ii) its molecular weight measured by NaDodSO4/PAGE is Mr 34,000 (sucrose gradient centrifugation under nondenaturing conditions yields a sedimentation coefficient s20,w of 8.1 S, indicating that the native protein is an oligomer); (iii) amino acid analysis demonstrates a preponderance of acidic over basic residues, while electrofocusing experiments show that it has an isoelectric point around 8.0; (iv) approximately 15% of the protein is phosphorylated in vivo. It is postulated that control of the synthesis of this protein is connected with activation of a differentiative program triggered by NGF in the PC12 neoplastic cell line at some step(s) of DNA activity.

Adrenal Gland Neoplasms↗
PubMed1983

Hidden receptors for nerve growth factor in PC12 cells.

The binding of nerve growth factor (NGF) to its receptors in PC12 cells was studied in two experimental conditions: (a) cell fixation with paraformaldehyde followed by permeabilization of the plasma membrane with methanol and (b) metabolic poisoning of living cells with sodium azide. Paraformaldehyde fixation of PC12 cells causes a 60-70% reduction of NGF binding capacity; the original binding capacity is restored following permeabilization with methanol. A kinetic analysis of NGF binding under these conditions reveals a single homogeneous population of receptors at variance with experiments performed in living cells where two kinetically distinct types of NGF receptors were demonstrated [Landreth, G. E. and Shooter, E. M. (1980) Proc. Natl Acad. Sci. USA, 77, 4751-4755; Schechter, A. L. and Bothwell, M. A. (1981) Cell, 24, 867-874]. Our results suggest that a proportion of the NGF receptors in PC12 cells is hidden, i.e. not available for binding to the ligand, and in a dynamic equilibrium with exposed receptors. The existence of hidden receptors is confirmed by treatment of PC12 cells with sodium azide, which causes a 50% reduction in NGF binding capacity and protection from trypsin digestion of the remaining pool of hidden receptors. The latter become exposed at the cell surface following removal of sodium azide. Our data provide an interpretation for the as yet unsatisfactorily explained data on NGF receptors.

Cell Line↗
PubMed1983

A macromolecular structure favouring microtubule assembly in NGF-differentiated pheochromocytoma cells (PC12).

Cellular extracts derived from pheochromocytoma cells (PC12-) inhibit the assembly of calf brain tubulin, while those derived from nerve growth factor-differentiated cells (PC12+) do not display this effect. Incubation with RNase abolishes the inhibition by PC12- extracts and reveals the presence of an activating effect exerted by PC12+ extracts. Activation of microtubule assembly is enhanced when extracts are prepared from PC12+ cells exposed for 1 day to 1.0 microM taxol and is abolished when PC12+ extracts are: (a) prepared from cells incubated for 1 day with 1 microM colchicine, (b) treated with the non-ionic detergent Nonidet P-40 or (c) centrifuged at 100 000 g instead of 80 000 g. 2D gel electrophoresis of the proteins of the 100 000 g pellet responsible for the activating effect (referred to as 100 K g pellet) reveals the presence of 100 K, 88 K and 32 K proteins which are markedly enriched in PC12+ extracts. The 88 K protein is further enriched in taxol-treated cells and markedly reduced in the same cells incubated with colchicine. A correlation between the differential protein composition of the 100 K g pellets and their effect on microtubule formation is postulated.

Adrenal Gland Neoplasms↗
PubMed1983

[Transabdominal echotomography in the staging of tumors of the bladder].

Transabdominal wall ultrasonography in the study of the bladder tumours is a simple and athraumatic method. In this prospective study the ultrasonographic patterns considered allow the differentiation among three principal classes: I group: superficial tumours with intact bladder wall; II group: invading tumours with the disappearance of the bladder wall behind the tumour (it is not possible to differentiate a superficial muscle involvement to a deeper invasion); III group: tumours with extra-vesical extension. The ultrasonic stage grouping has been compared with pathological staging, in a series of 46 patients (1981-1982). The I group (superficial tumours), corresponding to Pis-P1 pathological stage, and the III group, corresponding to P4, have a good accuracy (85% and 87,5%). In the II group, corresponding to P2-P3, the accuracy is less (72%) and it is not possible to differentiate between the two pathological stages. Transabdominal wall ultrasonography should be the first investigation in the preoperatory staging of bladder tumours.

Humans↗
PubMed1982

Contrast influence on perceived orientation.

When two gratings of slightly different orientation and equal contrast are presented dichoptically the observer perceives a unique fused grating at an orientation intermediate between the two (cyclofusion). We show here that if the contrast of the two gratings is different the perceived orientation of the fused grating depends on the relative contrast of the two monocular images. The results show that the perceived orientation varies linearly with the contrast difference, provided that the contrast values of the gratings presented to each eye are such as to give rise to a fused image. In these conditions, the perceived orientation is the average of the two monocular orientations, weighted with their contrast.

Depth Perception↗