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Biomedical subjects

F Stirpe

Publications and source records attributed to F Stirpe.

At least 145 records · Page 8Linked to original sources
PubMed1981

A comparison of the accumulation of ricin by hepatic parenchymal and non-parenchymal cells and its inhibition of protein synthesis.

Rat liver non-parenchymal cells in vivo were found to accumulate 125I-labelled ricin to a much greater extent than parenchymal cells. Similarly, in monolayer cell cultures, the rate of ricin uptake by non-parenchymal Kupffer cells was several times that by parenchymal cells. Evidence is provided also to suggest that ricin is primarily recognized by Kupffer cells via terminal mannose residues in the toxin, whereas ricin uptake by parenchymal cells was consistent with a role of the previously postulated galactosyl-containing cell receptors. Protein synthesis in Kupffer cells in vitro, although observed to occur at a lower rate than in parenchymal cells, was 100--1000-times more sensitive to inhibition by ricin. The selective damage known to be caused to liver sinusoids by ricin, therefore, may reflect both the relative efficiency with which the toxin is taken up by these cells and the extreme sensitivity of protein synthesis in the cells to inhibition by ricin.

Animals↗
PubMed1981

Cytotoxicity acquired by conjugation of an anti-Thy1.1 monoclonal antibody and the ribosome-inactivating protein, gelonin.

Gelonin, a plant protein which can powerfully reduce the protein-synthetic capacity of ribosome preparations, was covalently coupled to anti-Thy1.2 antibody. The conjugate was prepared using N-succinimidyl-3-(2-pyridyldithio)propionate which generates a disulphide linkage between the component molecules. Two conjugate fractions were obtained with Mr of 180 000 and greater than 200 000. After its linkage of the antibody, gelonin suppressed those Thy1.1-bearing T lymphocytes from AKR mice which will respond to phytohaemagglutinin and concanavalin A in tissue culture. The [3H]leucine incorporation with the T-cell mitogens was inhibited by 50% with the 180 000-Mr fraction at a concentration of 0.4 nM and with the greater than 200 000-Mr fraction of pM. Unconjugated gelonin induced comparable reductions in T-cell responsiveness but at concentrations of 30 nM. The conjugates exerted little or no effect upon B lymphocytes or T lymphocytes from CBA mice (Thy1.2 + ve). Thy1.1-expressing AKR lymphoma cell lines, AKR-A and BW5147, were found to be sensitive to the conjugates, albeit much less so than the normal T lymphocytes. The conjugates injected in vivo significantly prolonged the life of CBA mice bearing in an AKR-A lymphoma allograft. It is concluded that gelonin can, by its linkage to an antibody, be rendered cytotoxic with a potency to match or exceed those of the toxins abrin and ricin.

Animals↗
PubMed1981

Dianthins, ribosome-damaging proteins with anti-viral properties from Dianthus caryophyllus L. (carnation).

1. Dianthin 30 and dianthin 32, two proteins isolated from the leaves of Diathus caryophyllus (carnation), were purified to homogeneity by chromatography on CM-cellulose. 2. The mol.wt. of dianthin 30 is 29 500 and that of dianthin 32 is 31 700. Both dianthins are glycoproteins containing mannose. 3. Dianthins inhibit protein synthesis in a lysate of rabbit reticulocytes, with an ID50 (concentration giving 50% inhibition) of 9.15 ng/ml (dianthin 30) and 3.6 ng/ml (dianthin 32). They act by damaging ribosomes in a less-than-equimolar ratio. Protein synthesis by intact cells is partially inhibited by dianthins at a concentration of 100 microgram/ml. 4. Dianthins mixed with tobacco-mosaic virus strongly decrease the number of local lesions on leaves of Nicotiana glutinosa.

Antiviral Agents↗
PubMed1980

Mitogenic and haemagglutinating properties of a lectinpurified from Hura crepitans seeds.

A lectin from the seeds of Hura crepitans has been purified to homogeneity by affinity chromatography on acid-treated Sepharose CL-6B, followed by elution with D-galactose. The lectin is a glucosamine-containing glycoprotein with a molecular weight of 120 00, as determined by sucrose density gradient centrifugation, and consists of identical subunits with molecular weights of 30 000. The amino acid composition and total neutral sugar content are given. The Hura lectin agglutinates directly erythrocytes from several species, without specificity for human blood groups. In all cases, with the exception of pig erythrocytes, agglutination was enhanced by neuraminidase. Agglutination was inhibited, in decreasing order of potency, by N-acetyl-D-galactosamine, by D-galactose and galactose-containing oligosaccharides. The lectin has mitogenic activity for purified human T lymphocytes but not for B lymphocytes, and the activity is still evident at a concentration as low as 10 ng/ml. The specific mitogenic activity increases throughout the purification process.

Acetylgalactosamine↗
PubMed1980

Inhibition of protein synthesis by a toxic lectin from Viscum album L. (mistletoe).

1. The haemagglutinating and toxic lectin from Viscum album L. (mistletoe) inhibits protein synthesis in a lysate of rabbit reticulocytes, with an ID50 (concentration giving 50% inhibition) of 2.6 microgram/ml. This effect is enhanced (ID50 0.21 microgram/ml) if the lectin is reduced with 2-mercaptoethanol. 2. The lectin inhibits protein synthesis also in BL8L cells in culture. Inhibition occurs after a lag time of 3 h. The ID50 is 7 ng/ml, and increases after reduction of the lectin. 3. This and the gross lesions observed in rats poisoned with V. album lectin indicate this is a toxin very similar to ricin.

Animals↗
PubMed1980

Seed extracts inhibiting protein synthesis in vitro.

Of 33 seed extracts examined, 12 inhibited protein synthesis in a rabbit reticulocyte lysate. This activity seems to be due to a protein, since (i) it was recovered with the (NH4)2SO4 precipitate, (ii) it was retained by dialysis membranes, and (iii) in all cases but one was destroyed by boiling. Only the extracts from the seeds of Adenia digitata and, to a lower extent, of Euonymus europaeus inhibited protein synthesis in intact cells.

Animals↗
PubMed1980

Inhibition of protein synthesis in vitro by proteins from the seeds of Momordica charantia (bitter pear melon).

1. A haemagglutinating lectin was purified from the seeds of Momordica charantia by affinity chromatography on Sepharose 4B and on acid-treated Sepharose 6B. It has mol.wt. 115 000 and consists of four subunits, of mol.wts. 30 500, 29 000, 28 500 and 27 000. 2. The lectin inhibits protein synthesis by a rabbit reticulocyte lysate with an ID50 (concentration giving 50% inhibition) of approx. 5 micrograms/ml. Protein synthesis by Yoshida ascites cells is partially inhibited by the lectin at a concentration of 100 micrograms/ml. 3. From the same seeds another protein was purified which has mol.wt. 23 000 and is a very potent inhibitor of protein synthesis in the lysate system, with an ID50 of 1.8 ng/ml. This inhibitor has no effect on protein synthesis by Yoshida cells, and has no haemagglutinating properties. 4. Artemia salina ribosomes preincubated with the lectin or with the inhibitor lose their capacity to perform protein synthesis. The proteins seem to act catalytically, since they inactivate a molar excess of ribosomes. 5. The lectin and the inhibitor are somewhat toxic to mice, the LD50 being 316 and 340 micrograms/100 g body wt. respectively.

Animals↗
PubMed1980

Purification and properties of different forms of modeccin, the toxin of Adenia digitata. Separation of subunits with inhibitory and lectin activity.

1. The subunits were isolated of modeccin (subsequently referred to as modeccin 4B), the toxin purified from the roots of Adenia digitata by affinity chromatography on Sepharose 4B [Gasperi-Campani, Barbieri, Lorenzoni, Montanaro, Sperti, Bonetti & Stirpe (1978) Biochem J. 174, 491-496]. They are an A subunit (mol.wt. 26 000), which inhibits protein synthesis, and a B subunit (mol.wt. 31 000), which binds to cells. Both sununits, as well as intact modeccin, gave single bands on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, but showed some heterogeneity on isoelectric focusing and on polyacrylamide-gel electrophoresis at pH 9.5. 2. A second form of modeccin, not retained by Sepharose 4B, was purified by affinity chromatography on acid-treated Sepharose 6B: this form is subsequently termed modeccin 6B 3. Modeccin 6B has a molecular weight indistinguishable from that of modeccin 4B, and consists of two subunits of mol.wts. 27 000 and 31 000, joined by a disulphide bond. The subunits were not isolated because of their high insolubility in the absence of sodium dodecyl sulphate. 4. As compared with modeccin 4B, modeccin 6B is slightly less toxic to animals, does not agglutinate erythrocytes, and is a more potent inhibitor of protein synthesis in a lysate of rabbit reticulocytes, giving 50% inhibition at the concentration of 0.31 microgram/ml.

Animals↗
PubMed1980

Toxicity of Momordica charantia lectin and inhibitor for human normal and leukaemic lymphocytes.

A haemagglutinin (lectin) and another protein (inhibitor) purified from the seeds of Momordica charantia inhibited protein and subsequently DNA synthesis in normal (mitogen-stimulated) and leukaemic human peripheral blood lymphocytes. The effect of the lectin was more rapid and more pronounced than that of the inhibitor, probably due to a better penetration of the lectin into cells. Both proteins acted on lymphocytes more markedly and at concentrations much lower than those required to inhibit protein synthesis in Yoshida ascites cells.

DNA↗
PubMed1979

Haemagglutinating activity of modeccin.

Modeccin, the toxin of Adenia digitata, agglutinates erythrocytes from several mammalian species. The haemagglutinating activity is enhanced by neuraminidase and is inhibited by galactose and by galactose-containing sugars.

Animals↗
PubMed1979

Inhibition of protein synthesis in vitro by a lectin from Momordica charantia and by other haemagglutinins.

Protein synthesis by a rabbit reticulocyte lysate is inhibited by the haemagglutinating lectins from Momordica charantia and Crotalaria juncea seeds and from the roe of Rutilus rutilus, and by a commercial preparation of the mitogenic lectin from Phytolacca americana. The haemagglutinins from the seeds of Ricinus communis and of Vicia cracca acquired inhibitory activity after their reduction with 2-mercaptoethanol.

Cell-Free System↗
PubMed1979

Effect of modeccin on rat liver ribosomes in vivo.

1. Rat liver microsomes isolated at 6 and 12 h of poisoning with 3 x LD50 (0.3 microgram/100 g body wt.) of modeccin, the toxin of Adenia digitata, have a decreased capacity of protein synthesis in vitro. 2. A similar decrease of protein synthesis is observed with polysomes at 6 h of poisoning. Experiments with recombined ribosomal subunits demonstrate that this is due to inactivation of the 60 S ribosomal subunit. 3. At 6 h of poisoning there is a marked vesiculation and degranulation of the hepatocyte rough endoplasmic reticulum, which is completely fragmented at 24 h of poisoning. Hepatocyte mitochondria are swollen at 6 h and shrunk at 24 h of poisoning. 4. It is concluded that modeccin penetrates inside hepatocytes in vivo, and damages ribosomes in the same manner as it does in vitro. However, mitochondrial damage indicates that ribosomes may not be the only target of modeccin in vivo.

Animals↗
PubMed1979

Selective lesions of acinar pancreatic cells in rats poisoned with abrin. A morphological and biochemical study.

Rats poisoned with abrin (2.5 micrograms/100 g body weight) died within 36 h with severe necrosis of acinar pancreatic cells. Incorporation in vivo of labelled amino acids into pancreatic protein was greatly impaired 6 h after poisoning. Microsomes isolated from the pancreas of poisoned rats at 6 h had a reduced capacity for protein synthesis in vitro. Incorporation in vivo of orotic acid into pancreatic RNA was decreased 12 h after poisoning.

Abrin↗
PubMed1979

Purification and partial characterization of a mitogenic lectin from Vicia sativa.

From the seeds of Vicia sativa a lectin has been purified by affinity chromatography on Sephadex G-100, followed by specific elution with D-glucose. The lectin is a glycoprotein with a molecular weight of 70 000. The aminoacid composition and the total sugar content have been determined. This lectin agglutinates horse, rabbit and human erythrocytes, with no specificity for human blood groups, but does not agglutinate calf and sheep erythrocytes. The agglutinating activity is inhibited by mono-, di-, and trisaccharides with a pyranosyl residue whose free hydroxyl group in position 4 has the configuration of glucose, and by fructose. The lectin has mitogenic activity on human peripheral blood lymphocytes.

Amino Acids↗
PubMed1979

Effect of intraventricularly injected ricin on protein synthesis in rat brain.

Ricin, a protein from the seeds of Ricinus communis which inhibits protein synthesis by eukaryotic ribosomes, is highly toxic when injected intraventricularly to rats, the LD50 being 0.241 micrograms/rat at 72 hr and 0.084 micrograms/rat at 7 days. Poisoned animals showed signs of central depression; they did not die before 20 hr of intoxication. Incorporation of amino acids in vivo into brain total protein and into brain ribosomes was impaired, as was protein synthesis in vitro by microsomes isolated from the brain of poisoned rats.

Animals↗