Biomedical subjects

O Cascone

Publications and source records attributed to O Cascone.

At least 37 records · Page 2Linked to original sources

PubMed1989

Antigenicity of basement membrane fractions obtained from rat seminiferous tubules.

A noncollagenous fraction of basement membrane (D-STBM) obtained from rat testes was submitted to sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis (SDS-PAGE), and eight well-defined bands were detected. A cross-reaction with an antiserum against laminin was revealed by immunoblotting in five bands, with molecular weights ranging from 54 to 64 kDa. No further resolution of these components could be obtained by size exclusion and ionic exchange chromatography. Fifty-two percent of the rats immunized with D-STBM and adjuvants developed a mild multifocal damage of the testis. The lesions were characterized by foci of seminiferous tubules with different degrees of sloughing and/or atrophy of the germinal epithelium. Giant multinucleated cells were frequently seen, and mild interstitial mononuclear cell infiltrates were also detected. By immunofluorescence, deposits of rat IgG with a faint discontinuous linear pattern were observed along the walls of the seminiferous tubules. Circulating antibodies to D-STBM were detected by ELISA in 100% of the rats, whereas in a cross-reaction with laminin antibodies were detected in only 63%. All rats studied revealed a positive delayed type of hypersensitivity (DTH) response to D-STBM. None of the control rats injected with saline and adjuvants presented circulating antibodies to D-STBM or laminin or a positive DTH reaction to D-STBM. Some control group rats (10%) revealed few isolated seminiferous tubules with some degree of sloughing of the germinal epithelium.

Animals↗

PubMed1988

An approach to the three-dimensional structure of bovine growth hormone based on chemical modification and secondary structure prediction.

Three different methods have been applied to the prediction of secondary structure. The prediction that better fitted the chemical data was chosen. Two regions of the bovine growth hormone molecule (111-117 and 166-174) appear to be exposed to the solvent, according to hydropathic analysis but have several charged residues not reactive towards their specific reagents. Two molecular domains are postulated, each one bearing a region with charged residues on its surface and interacting with the other in the molecule by means of saline bridges. The hydrophobic core of the molecule is formed by the ensemble of the hydrophobic region predicted between residues 81 and 108, and the hydrophobic faces of the amphiphilic helices 109-127 and 9-33.

Amino Acid Sequence↗

PubMed1987

Ethoxyformylation of histidine residues in equine growth hormone.

Reactivity of histidine residues in equine growth hormone to ethoxyformic anhydride was studied. The existence of two kinetically different sets was demonstrated: one of them including only the slow reacting histidine 169 (k = 0.164 min-1) and the other containing fast reacting histidines 19 and 21 (k = 0.892 min-1). A correlation between the decrease in the capacity to compete with 125I-labeled hormone for rat liver binding sites and the degree of ethoxyformylation of the fast group was found. Circular dichroism studies indicated no significant conformational changes in the protein with all three residues modified. These results fully agree with those obtained for bovine growth hormone which is further evidence supporting the vinculation of histidines 19 and/or 21 with the binding site of these hormones to their specific receptors.

Amino Acids↗

PubMed1986

Hydrophobicity modulation as a tool for the purification of histidyl peptides.

A methodology is described for purification of histidyl peptides based on the changes in hydrophobicity induced by the specific and reversible modification of histidine residues by ethoxyformic anhydride. The mixture of modified peptides is subjected to HPLC; peptides containing modified histidines are detected at 242 nm, recovered, deethoxyformylated, and rechromatographed under the same conditions, then being detected at 220 nm. This procedure allows their isolation free from contaminants.

Amino Acid Sequence↗

PubMed1986

Molecular characterization of a protein, insoluble at low temperature, produced by Clostridium botulinum type G.

A preliminary study of a low-toxicity protein, called cryoprotein, produced by Clostridium botulinum type G, led to a better characterization of this substance and to discriminate its relationship with type G botulinum toxin. This sparingly soluble protein has been characterized as an aggregated form of a soluble precursor with an Mr of 170,000. This phenomenon is temperature-dependent. The monomeric protein is usually contaminated with a lower Mr form (150,000) quite probably originated by a limited proteolytic process. The amino acid composition of this protein is relatively analogous to that of the botulinum toxins A and B, the only notable exception being the absence of cysteine. The N-terminal amino acid is alanine and the C-terminal sequence is Val-Ala-Leu-OH. The low toxicity which is usually demonstrable in samples of this protein disappears after a reductive treatment, strongly suggesting that it is not an intrinsic property. Taking into account that some of its physiochemical properties are similar to those of the known botulinal toxins, it is quite probable that this substance accompanies G toxin preparations currently obtained by routine methods, increasing its non-toxic antigenic mass. This fact could be critical to the sensitivity and specificity of G toxin immunological detection methods.

Amino Acids↗

PubMed1984

Amino acid sequences around the cystine residues in alpaca growth hormone.

Half-cystine peptides were isolated from the enzymatic digest of reduced and carbamidomethylated alpaca growth hormone. From their amino acid composition and determination of the end terminal residues we propose the amino acid sequence around the two disulphide bridges, partially based on homology with other mammalian growth hormones. The proposed sequence is identical to that of equine growth hormone and very similar to those of rat, bovine and ovine hormones.

Amino Acid Sequence↗

PubMed1984

Basic and acidic hydrophilic residues involved in the interaction between protomers of the bovine growth hormone dimer.

Reactivity of histidine and arginine residues--as well as of carboxyl-groups--in the covalently stabilized dimer of bovine growth hormone, was studied in comparison with their reactivity in the monomeric form. Results obtained by reaction of histidine and arginine residues with ethoxyformic anhydride and cyclohexanedione, respectively, were similar for both proteins. The reactivity of two carboxyl-groups towards a soluble carbodiimide becomes impaired in the dimer, thus suggesting that their location is within the protomer interaction area.

Arginine↗

PubMed1984

Hydrophobic residues involved in the interaction between protomers of the bovine growth hormone dimer. Methionine and tyrosine residues.

The bovine growth hormone dimeric form covalently stabilized by cross-linking with dimethyl suberimidate (DMS) and the hormone modified by DMS without forming covalent links with other hormone molecules (DMS-bGH) were oxidized with chloramine-T at molar-ratios of 2 and 50 with respect to methionine content. The extent of oxidation undergone by each methionine residue, estimated on the purified tryptic peptides, closely resembled that obtained for the native hormone, thus suggesting that methionine residues are not involved in the protomers interaction area. Evaluation of the reactivity of tyrosine residues toward tetranitromethane indicated that, in both the covalent dimer and DMS-bGH, tyrosine residues 35, 174 and 142 are the more susceptible to undergo reaction. Net charges can be induced in the iodotyrosine residues in the iodinated hormone, by setting the pH at 10.5. At this pH, dissociation of a fraction of uniformly iodinated hormone was observed in the derivatives containing 2 or more iodine atoms, indicating that tyrosine residues might integrate the contact area between protomers.

Chloramines↗

PubMed1983

The nicotinic acetylcholine receptor from Discopyge tschudii: purification, characterization and reconstitution into liposomes.

The nicotinic acetylcholine receptor from Discopyge tschudii electroplax was purified by affinity chromatography on Affi-Gel 401 using bromoacetylcholine as the ligand. Its specific activity was about 4000 pmol 125I-alpha-bungarotoxin/mg protein. SDS-polyacrylamide gel electrophoresis revealed four bands of apparent molecular weights: 41,200, 49,500, 60,000 and 66,300. The amino acid composition of each individual subunit was determined. Native membranes, rich in nicotinic receptor exhibited carbamylcholine-catalysed cation transport (blocked by curare and desensitized by prior incubation with the cholinergic agonist). The functional activity of the purified material could be reconstituted into soybean lecithin liposomes. Our data show that the Discopyge tschudii nicotinic receptor is similar to that from Torpedo californica.

Acetylcholinesterase↗

PubMed1983

Ethoxyformylation of bovine growth hormone.

Reactivity of histidines in bovine growth hormone towards ethoxyformic anhydride was investigated and localization in the molecule of two kinetically distinguishable classes was achieved, a slow class including only histidine residue 169 (k = 0.180 min-1) and a fast one composed of histidines 19 and 21 (k = 0.900 min-1). Total ethoxyformylation of bovine growth hormone brought about a complete loss of its capacity to compete with 125I-labelled hormone for rat-liver binding sites, but modification of approximately half of the fast histidine group was enough to produce an important decrease in this capacity. Circular dichroism studies indicated no significant changes in protein conformation with all three histidine residues modified. Practically full binding capacity was restored when these residues were regenerated by treatment with hydroxylamine. These results suggest that one or both of the fast reacting histidine residues are involved in bovine growth hormone binding to its specific receptors.

Animals↗

PubMed1981

Isolation and characterization of alpaca growth hormone.

A simple and mild procedure is described for the isolation of pituitary growth hormone from alpaca glands. It involves extractions in buffer at pH 8.7 and gel filtration in Sephadex G-75. an average yield of 1 mg purified product may be obtained from 1 g fresh alpaca pituitary glands. The alpaca hormone was examined for homogeneity by SDS-polyacrylamide gel electrophoresis, gel electro-focusing and end-group analyses. It is a protein composed of a single polypeptide chain with phenylalanine at both ends. The C-terminal sequence is -Ala-Phe. The molecular weight is approximately 21 700 and the amino acid composition very similar to that observed in equine growth hormone.

Amino Acids↗

PubMed1980

Oxidation of methionine residues in bovine growth hormone by chloramine-T.

The methionine residues in bovine growth hormone were chemically modified wih chloramine-T at pH 7.4 using different chloramine-T methionine molar ratios. Methionine 4 was shown to be the most reactive followed in decreasing order by methionines 148, 123 and 178. With a 50-fold molar excess of chloramine-T over methionine almost full oxidation of all the methionine residues was achieved. The oxidation of the four residues of methionine does not change the growth promoting activity of the hormone.

Amino Acid Sequence↗

PubMed1979

Trinitrophenylation of bovine growth hormone.

Bovine growth hormone was chemically modified with picryl sulfonic acid, at pH 8.4 during 2 and 5 min of reaction. The N-terminal residue provides the most reactive amino group followed by the epsilon-amino groups of lysine 179 and lysines 143, 69, 111, 170 and 166 in decreasing order. These results agree with those obtained previously with equine growth hormone, except that residue 156 is not modified in bovine growth hormone. An important decrease in biological activity occurs between 2 and 5 min of reaction without sensible modification in the alpha-helix content of the molecule.

Amino Acid Sequence↗

PubMed1977