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Biomedical subjects

G Jori

Publications and source records attributed to G Jori.

At least 145 records · Page 8Linked to original sources
PubMed1983

Effect of hematoporphyrin and red light on AH-130 solid tumors in rats.

Thirty Wistar albino rats with a subcutaneous Yoshida hepatoma AH-130 were exposed to 590 to 690 nm light from a high pressure Xenon arc-lamp 24 h after intraperitoneal injection of hematoporphyrin, 5 to 10 mg/kg. In all cases, the tumor decreased rapidly in size, due to necrosis caused both by direct action of the photoactivated porphyrin on the tumor cells and by secondary effects on blood vessels. No injury of normal tissues was detected. At 2 months after phototreatment, no recurrence had occurred and the skin over the tumor area was healed. Favourable therapeutic response was obtained in preliminary experiments by irradiating the Hp-injected tumor-bearing rats with 632.8 nm-light from an He/Ne laser source.

Animals↗
PubMed1982

Chemical, photochemical and spectroscopic characterization of an alkaline proteinase from Bacillus subtilis variant DY.

Circular-dichroism and fluorescence studies indicate that the 5-dimethylaminonaphthalene-1-sulphonyl and phenylmethanesulphonyl derivatives of subtilisin DY have three-dimensional structure closely similar to that of native enzyme. The single tryptophan residue is largely accessible to the aqueous solvent, and is not directly involved in the enzyme-substrate interactions, since its photochemical modification causes only a partial inhibition of the enzyme activity. It appears very likely that the location of the single tryptophan residue in the three-dimensional structure of subtilisin DY is similar to that of the single tryptophan residue in subtilisin Carlsberg. Fluorescence-quenching experiments further indicate that the 14 tyrosine residues are also largely accessible to the aqueous solvent, and probably interact with hydrated peptide carbonyl groups. The charge environment for tryptophan and tyrosine residues in subtilisin DY, as deduced by quenching experiments with ionic species, is also discussed. In general, subtilisin DY displays strong similarities to subtilisin Carlsberg, as suggested by a comparative analysis of the amino acid composition and fluorescence properties.

Amino Acids↗
PubMed1982

Effects of pH and urea on the conformational properties of subtilisin DY.

Subtilisin DY is very resistant to the denaturing action of urea: the conformational properties are not affected up to 4.5 M-urea, and even in the presence of 8 M-urea there is only a slow loss of ordered structure and caseinolytic activity. C.d. and fluorescence-emission studies also show that this proteinase is stable in the 5.5-10.0 pH range, whereas below pH 5.5 a sharp denaturation occurs that is complete at pH 4.5. Protein denaturation leads to a change of the emission quantum yield; in particular, in the native protein, indole fluorescence is quenched by some amino groups. Moreover, subtilisin DY possesses two classes of tyrosine residues: one class of exposed residues titrates normally, with pKapp. = 10.24, whereas one class of partially buried or hydrogen-bonded residues ionizes with pKapp. = 11.58. In general, such conformational properties resemble those of other subtilisins. However, some differences occur: e.g., subtilisin DY is less stable at acidic pH values and its tyrosine residues are more accessible to the solvent. Such differences are probably due to small variations of the three-dimensional structure; e.g., subtilisin DY has a slightly lower alpha-helix content.

Bacillus subtilis↗
PubMed1981

The role of the cysteinyl and one of the tryptophyl residues in the neurotoxic action of suberitine.

The selective photooxidation of the single cysteinyl residue and one of the 3 tryptophyl residues of suberitine has been performed by irradiation using crystal violet and proflavine respectively as photosensitizers. Crystal violet and the protein form a 1:1 complex with a consequent partial inhibition of the neurotoxic activity. The latter is completely abolished by specific photooxidation of cysteine which is probably involved in the active site of the protein. The modification of the tryptophyl residue induces a large loss of the activity as a consequence of a photoinduced extensive denaturation of suberitine.

Cysteine↗
PubMed1981

Distribution of endogenous and injected porphyrins at the subcellular level in rat hepatocytes and in ascites hepatoma.

Different doses (0.5-20 mg/kg) of hematoporphyrin (HP) have been injected intraperitoneally into normal rats and rats affected by Yoshida ascites hepatoma. About 80% of HP reaching the liver was recovered in the extracellular compartment after liver perfusion, the ratio of extra- to intracellular HP being essentially independent of the administered dose. Similar data were obtained at different times after injection of 20 mg/kg HP. Intracellular HP largely accumulates in the mitochondria and in the membrane components of the nuclear fraction of isolated hepatocytes. Kinetic studies suggest that the cell receptors of highest affinity for HP are present in the external membrane. The latter result obtains for ascites hepatoma cells in an even more evident way, although the latter cells exhibit secondary HP binding sites probably constituted by cytoplasmatic proteins. Moreover, the clearance of intracellular HP from malignant cells occurs at a remarkably lower rate as compared with HP clearance from liver cells.

Animals↗
PubMed1981

Fluorescence properties of native and chemically modified mesentericopeptidase.

Studies on the fluorescence properties of native mesentericopeptidase as a function of the temperature and/or in the presence of either neutral or ionic fluorescence quenchers demonstrate that the intrinsic emission f this protein is dominated by a partially exposed tryptophyl residue, which is probably located in a site of high dielectric constant containing positively charged amino acid side chains. One largely exposed tryptophan contributes about 14% of the total emission, whereas one deeply buried tryptophan is virtually non-fluorescent. The conversion of the active site serine to cysteine and the insertion of either one phenylmethanesulfonyl or one dansyl substituent into the active site induce only subtle differences in the conformational properties with respect to the native protein; in particular, the mutual distances and orientation between the 13 tyrosyl and 3 tryptophyl residues are unaffected, as shown by singlet-singlet energy transfer experiments.

Dansyl Compounds↗
PubMed1981

Interaction of human serum albumin with hematoporphyrin and its Zn(2)+-and Fe(3)+-derivatives.

Human serum albumin at pH values above 6.8 has one strong binding site for hematoporphyrin; the stability constant of the 1:1 complex is about 10(6) M-1 as determined by Scatchard plot after estimation of the bound hematoporphyrin-induced quenching of the fluorescence emitted by the single tryptophanyl residue of the protein. Determination of the tryptophan-to-hematoporphyrin energy transfer efficiency yields a Förster parameter R0 of 6.2 - 6.9 nm, depending on the value chosen to represent the donor-acceptor mutual orientation, and a tryptophan-to-hematoporphyrin distance of about 1.7 nm. Zn2+- and Fe3+-hematoporphyrin also give a 1:1 complex with albumin, probably binding at the same site as hematoporphyrin, as shown by the identity of the energy transfer parameters; however, the metal ions do not appear to be involved in the formation of the albumin-porphyrin complex. The albumin-hematoporphyrin interaction is drastically affected by the pH of the medium; below pH 6.5 we find a large number of binding sites with weak affinity for hematoporphyrin, which disappear upon increasing the pH. The main site, below pH 6.5, has an affinity comparable with that of the secondary sites. Circular dichroism studies show that the pH effect is due to a change in the protein conformation leading to different interactions between bound porphyrin and specific amino acid side chains.

Circular Dichroism↗
PubMed1980

Photo-oxidation of L-glutamate decarboxylase from Escherichia coli, sensitized by the coenzyme pyridoxal phosphate and by proflavin.

Irradiation of L-glutamate decarboxylase (L-glutamate 1-carboxy-lyase, EC 4.1.1.15) from Escherichia coli by visible light absorbed by the intrinsic chromophore, pyridoxal phosphate, caused the selective modification of two methionines per enzyme monomer. The disulfoxide derivative exhibited modified circular dichroism, chromatographic and kinetic properties, suggesting a conformational role for the two methionine residues. Irradiation of the enzyme in the presence of proflavin revealed the presence of two distinct groups of tryptophan residues with markedly different photooxidation rate constants. No evidence of involvement of tryptophans in the catalytic mechanisms of the enzyme was obtained. The results are compared with those obtained on irradiation of L-glutamate decarboxylase from Clostridium perfringens.

Acridines↗
PubMed1980

Phototherapy-induced covalent binding of bilirubin to serum albumin.

Bilirubin displays a detectable fluorescence emission only when it is complexed with serum albumin, whereas free bilirubin has a very low fluorescence yield. Actually, nearly complete disappearance of bilirubin emission was obtained when the unirradiated human serum albumin-bilirubin complex was precipitated with acetone to extract the pigment; complete removal of protein-bound bilirubin (as monitored by fluorescence spectroscopy) was achieved by repeating the acetone extraction after incubation of the complex in the phosphate buffer, pH 7.4, containing 7 M guanidinium chloride; the latter compound causes on extensive unfolding of protein molecules. On the other hand, in the case of irradiated solutions, even after denaturation of the protein with 7 M guanidinium chloride, a detectable amount of bilirubin-type fluorescent material was found to be associated with albumin. This finding clearly shows that bilirubin and/or some photoproduct underwent in part a photoinduced covalent binding with human serum albumin. Fragmentation of the bovine albumin polypeptide chain according to the procedure detailed in the experimental section yielded only one peptide-containing material fluorescent in the 530 nm region. This fact underlines the selective nature of the photobinding reaction. The amino acid composition of the isolated peptide is shown in Table 2; the composition is closely similar with that found for peptide 187-397 of native bovine serum albumin. In the case of the jaundiced babies who were subjected to phototherapy, we were able to demonstrate that only after 7 to 9 hr of exposure to light a detectable amount of bilirubin-type fluorescent material was present even at the end of the serum treatment with acetone and guanidinium chloride (see Fig. 1; Table 1). Fractional precipitation of the serum proteins by addition of controlled amounts of ammonium sulphate showed that the fluorescent material was present only in the albumin fraction. The photoadduct disappeared about 15 to 20 days after the phototherapy had been discontinued. This period of time represents the natural turnover period of human serum albumin.

Amino Acids↗
PubMed1979

Time dependence of hematoporphyrin distribution in selected tissues of normal rats and in ascites hepatoma.

The distribution of hematoporphyrin was determined in normal rats and in rats bearing ascites hepatoma as a function of time after i.p. injection of 10-20 mg/kg of dye. In both cases, hematoporphyrin displayed a high affinity for the tumor cells. At 20 mg/kg, the maximum difference between the amount of hematoporphyrin accumulated in the tumor and in the liver was obtained at 12 h after injection (tumor/liver ratio = 28). Our results suggest that hematoporphyrin is almost exclusively metabolized in the liver and excreted via the biliary tract, whereas only minor amounts are metabolized in the tumor cells. Moreover, the binding between the porphyrin and tumor cells is competitive with serum protein binding.

Animals↗