Biomedical subjects
Publications and source records attributed to R Bevilacqua.
Eledoisin, administered to dogs by intra-carotid route, potently stimulated salivary secretion. The effect was not due to stimulation of cholinergic, adrenergic, histaminergic or 5-hydroxytryptaminergic receptors but was direct on salivary glands.
Eledoisin, administered to dogs by conjunctival route, potently stimulated lacrimal secretion. The effect did not depend on activation of adrenergic, histaminergic or 5-hydroxytryptaminergic receptor and was only in part due to stimulation of cholinergic receptors.
Eledoisin cured corneal lesions produced in the rabbit by cocaine but failed to heal those produced by sodium hydroxide. The effect was probably due to accelerated epithelial proliferation.
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The binding of six furocoumarins (angelicin, psoralen, 8-methoxypsoralen, 5-methoxypsoralen, 8-methylpsoralen, 4,5'8-trimethylpsoralen) to human serum and human serum albumin was studied by equilibrium dialysis using tritium labelled compounds. The results indicated that in serum all furocoumarins are bound mostly by albumin, the extent of binding being related to the structure of the furocoumarins; at any rate, high values of the bound drug, ranging from 84 to 97% were observed. The percentage of binding is strictly related to the water solubility of the compounds. A limited number of binding sites, n = 1-2.4, were detected in the albumin molecule, indicating a high specificity in the binding process. The association constants of the furocoumarins to albumin. Ka, ranged from 1.2 X 10(4) M-1 (8-methoxypsoralen) to 1.9 X 10(5) M-1 (4,5'8-trimethylpsoralen).
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The ability of 8-methoxypsoralen (8-MOP) to bind human serum albumin has been investigated in vitro through equilibrium dialysis and fluorescence quenching. By means of the first technique it was observed that, at concentrations presumably close to those obtainable in vivo following its administration in the photochemotherapy of psoriasis, over 80% of 8-MOP was bound to serum albumin. In human serum albumin fluorescence techniques revealed a preferential site of binding for 8-MOP with a high binding constant (Ka = 0.7 X 10(5) M-1) and precise steric requirements, since small conformational variations of the protein molecule were able to abolish its affinity for furocoumarin.
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The binding of some cephalosporin antibiotics, namely cephalothin, cephaloridine and cephalexin, to serum albumins was quantitized using a fluorescence probe technique. The results suggest that these drugs bind to hydrophobic sites on serum albumins. The association constants of the three drugs with bovine serum albumin showed the strongest binding for cephalothin (Ka 1.2 x 10(3) M(1)) and weaker ones for cephaloridine and cephalexin (Ka 0.59 and 0.4 x 10(3) M(-1)). Serum albumin from different species was also investigated, only minor variations in the binding properties being found.
Glutamate dehydrogenase (EC 1.4.1.2-4) has been purified and crystallized from the acetone powder of tuna liver. The enzyme has a molecular weight of 333 000 +/- 15 000 as evaluated by sedimentation equilibrium and constists of six identical subunits. Unlike the bovine enzyme the molecular weight does not increase with increasing protein concentration indicating that the tuna enzyme has no tendency to polymerize. The amino acid composition and peptide maps of the tuna and bovine liver enzyme are similar, suggesting considerable homology between the two enzymes. Furthermore, from the tryptic digest a hexadecapeptide containing a lysine residue reactive to pyridoxal 5'-phosphate exhibits the same composition and sequence as the peptide containing the reactive lysine-126 in the sequence of the bovine enzyme. The molecular activity is 25 and 510 mol of substrate per mol enzyme per s, respectively, for the glutamate oxidation and the alpha-ketoglutarate reduction with NAD or NADP as coenzymes. The enzyme is regulated by pyridine nucleotides like other vertebrate enzymes, but it also exhibits some coenzyme specificity, the activity being about fifteen times higher with NAD than with NADP.
The molecular basis of inhibition of glutamate dehydrogenase by chlorpromazine was studied by circular dichoroism, differential spectroscopy and fluorescence. Chlorpromazine appears to induce conformational changes of the enzyme at the position of aromatic amino acids, and tryptophan residues in particular are involved. On the other hand the secondary structure of the enzyme is not influenced by binding of the drug.
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