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Biomedical subjects

E Melloni

Publications and source records attributed to E Melloni.

At least 145 records · Page 8Linked to original sources
PubMed1985

Temperature rise in biological tissue during Nd:YAG laser irradiation.

Few data are available about temperature distribution in tissue during Nd:YAG laser irradiation. To study the heat distribution that produces tissue coagulation, we used a thermographic camera aimed orthogonally to the laser beam axis to obtain thermal maps. Immediately after surgical resection, specimens of human stomach were irradiated near the resected edge, and the heat emitted sideways was detected by an infrared image system. A magnifying lens mounted on the camera enabled us to obtain 0.1 mm spatial resolution of the isothermic curves. The thermal analysis showed that the maximum depth where the increase in temperature reached 25 degrees C (corresponding to a coagulation temperature of about 60 degrees C) was never greater than 3 mm, irrespective of the power and exposure time used. Moreover, the bidimensional thermal maps showed that the temperature did not decrease in a purely exponential fashion along the beam axis, but reached a maximum at about 1 mm beneath the surface. This fact, which confirms the decrepitation theorem, could explain the explosion inside the tissues observed in surgical application of the Nd:YAG laser.

Body Temperature↗
PubMed1985

The reversible activation by Mn2+ ions of the Ca2+-requiring neutral proteinase of human erythrocytes.

Mn2+ (50 microM) satisfies the requirement for activity of the purified Ca2+-dependent neutral proteinase from human erythrocytes. Unlike the activation by Ca2+ [E. Melloni et al. (1984) Biochem. Int. 8, 477-489], the effect of Mn2+ is fully reversible and does not involve autodigestion of the native 80-kDa catalytic subunit. However, the native dimeric proenzyme (procalpain), which contains both the 80-kDa subunit and a smaller 30-kDa subunit, is not activated by Mn2+ alone but also requires the presence of micromolar concentrations of Ca2+. Under these conditions, 40% of the maximum activity is expressed without dissociation of the 80- and 30-kDa subunits. Mn2+, but not micromolar Ca2+, can also partially satisfy the metal requirement of the native 80-kDa subunit isolated after dissociation of the heterodimer. This activity is further enhanced by the addition of 5 microM Ca2+, which is ineffective in the absence of Mn2+. After procalpain is converted to active calpain by incubation with Ca2+ and substrate [S. Pontremoli et al. (1984) Biochem. Biophys. Res. Commun. 123, 331-337] full activity is observed with 5 microM Mn2+, which now substitutes completely for Ca2+. Activation of procalpain by Mn2+ represents a new mechanism for modulation of the Ca2+-dependent proteinase activity.

Calcium↗
PubMed1985

Binding of protein kinase C to neutrophil membranes in the presence of Ca2+ and its activation by a Ca2+-requiring proteinase.

In the presence of micromolar concentrations of Ca2+, both protein kinase C and a cytosolic Ca2+-requiring neutral proteinase of human neutrophils become associated with the neutrophil membrane. Binding to the membrane results in activation of the proteinase, which then catalyzes limited proteolysis of the kinase to produce a form that is fully active in the absence of Ca2+ and phospholipid. This irreversibly activated protein kinase is released from the membrane and may thus have access, in the intact cell, to intracellular protein substrates. In the absence of the proteinase, Ca2+ promotes the binding of protein kinase C, but conversion to the Ca2+/phospholipid-independent form does not occur and the kinase remains associated with the membrane fraction.

Blood Platelets↗
PubMed1985

Reversible activation of human neutrophil calpain promoted by interaction with plasma membranes.

Human neutrophil calpain is a monomer of 85 kDa molecular weight. The proteinase shows an absolute requirement for Ca2+ with maximal catalytic activity at 0.1-0.2 mM Ca2+ and negligible activity at 1-5 microM Ca2+. At this concentration of Ca2+ neutrophil calpain becomes active and reaches 65% of its maximal catalytic activity following interaction with plasma membranes. The activation is fully reversible since the enzyme returns to its native, high Ca2+ requiring form following removal of the membranes. Membrane phospholipids appear to be the physiological compounds responsible for the promotion of such reversible activation. Unlike other Ca2+ dependent proteinases, neutrophil calpain does not undergo conversion to a low Ca2+ requiring form by limited autoproteolysis.

Calcium↗
PubMed1984

Hyperthermal effects in phototherapy with hematoporphyrin derivative sensitization.

Although the photochemical reaction of hematoporphyrin derivative (HpD) appears to play a major role in cytotoxic activity, the hyperthermal contribution to tumor destruction has not yet been clarified. We investigated its role in the effectiveness of laser photoradiation therapy using MS-2 sarcoma transplanted into the hind pad of BALB/c mice as the experimental model. Mice received HpD i.v., 25 mg/kg - 24 h before exposure to light delivered from a dye laser or Nd-YAG laser, or before warming in a thermostated bath. Since our aim was not to cure the tumor, the treatment response was evaluated only as inhibition of tumor growth at different days after treatment. Our results support the view that in laser photochemotherapy the hyperthermia produced by irradiation and the photodynamic effect mediated by HpD could contribute to tumor destruction. Moreover, a synergistic interaction between the photodynamic effect and heat was observed in this experimental model.

Animals↗
PubMed1984

Laser phototherapy following HpD administration in superficial neoplastic lesions.

We report our preliminary clinical experience with hematoporphyrin derivative (HpD) injection and argon or dye laser irradiation for the treatment of 61 surface neoplastic lesions in 7 patients. Forty-three sites were multiple basal cell carcinoma in 5 patients, and the remaining 18 were cutaneous and subcutaneous recurrent breast carcinoma after mastectomy in the thoracic wall. The patients were selected on the basis of the lack of indication for conventional therapeutic modalities. The selection of irradiation procedures and laser source was based on the thickness of the lesion and extension of the disease. The photochemical reaction between HpD injected i.v. at a dose of 3 mg/kg body weight and the laser beam at a dose of 60 to 120 J/cm2 resulted in 75% favorable responses at the treated sites. Optimal therapeutic effects appeared to be critically dependent on total light dose and tumor infiltration patterns. The phototherapeutic technique proved to be effective in selected cases of neoplastic lesions, especially when conventional treatment modalities were poorly indicated or contraindicated.

Aged↗
PubMed1984

Activation by hemoglobin of the Ca2+-requiring neutral proteinase of human erythrocytes: structural requirements.

The proenzyme form of the Ca2+-requiring neutral proteinase of human erythrocytes (procalpain) is converted to the active proteinase (calpain) by low concentrations of Ca2+ in the presence of appropriate substrates such as beta-hemoglobin or heme-free beta-globin chains. Modification of these substrates by limited proteolysis with calpain abolishes their ability to promote the conversion of procalpain. A similar requirement for the presence of unmodified beta-hemoglobin or heme-free beta-globin chains is observed for the autocatalytic inactivation of calpain. The conversion of procalpain to calpain is accompanied by a small decrease in the molecular mass of the catalytic subunit, from 80 kDa to 75 kDa; however, the activation is not accelerated by the addition of a small quantity of calpain. The autocatalytic inactivation of active CANP is related to the disappearance of the 75 kDa subunit and the formation of smaller peptide fragments.

Calpain↗
PubMed1984

Binding of monoclonal antibody to cathepsin M located on the external surface of rabbit lysosomes.

A monoclonal antibody raised against rabbit liver cathepsin M binds to intact rabbit liver lysosomes. The binding is specific and is abolished by treating the lysosomes with trypsin, which has previously been shown to digest the membrane-bound cathepsin M [S. Pontremoli, E. Melloni, M. Michetti, F. Salamino, B. Sparatore, and B. L. Horecker (1982) Biochem, Biophys. Res. Commun. 106, 903-909]. Rabbit liver lysosomes are adsorbed onto Sepharose 4B coupled to anti-cathepsin M, but not to Sepharose 4B itself or to Sepharose coupled to a nonspecific antibody. The results confirm the location of membrane-bound cathepsin M on the outer surface of the lysosomal membrane.

Animals↗
PubMed1984

Two cytosolic, Ca2+-dependent, neutral proteinases from rabbit liver: purification and properties of the proenzymes.

Two Ca2+-requiring proteinases have been purified from rabbit liver cytosol and shown to be present in isolated hepatocytes. They differ in relative molecular mass, with the major and minor forms, Mr = 150,000 and Mr = 200,000, accounting for 75 and 18% of the total cytosolic neutral proteinase activity, respectively. Both are recovered as inactive proenzymes that can be converted to the active, low-Ca2+-requiring proteinases by incubation with Ca2+ and substrate [S. Pontremoli, E. Melloni, F. Salamino, B. Sparatore, M. Michetti, and B. L. Horecker (1984) Proc. Natl. Acad. Sci. USA 81, 53-56. Each proenzyme is composed of two subunits, with molecular masses of 80 and 100 kDa, respectively. Activation of the proenzymes was found to correlate with their dissociation into subunits. The optimum pH for conversion of the proenzymes to the active proteinases in the presence of 5 mM Ca2+ and 2 mg/ml of denatured globin was approximately 7.5, and the same pH optimum was observed for the digestion of denatured globin by the activated proteinases. Following activation, each proteinase was observed to undergo autolytic inactivation at rates that were dependent on the concentration of both Ca2+ and the digestible substrate. A model is proposed for the activation of the proenzymes and the subsequent inactivation of the active proteinases.

Animals↗
PubMed1984

Regulation of the Ca2+-dependent neutral proteinases from rabbit liver by an endogenous inhibitor.

An endogenous inhibitor of neutral Ca2+-dependent proteinases has been isolated from rabbit liver cytosol. The inhibitor is a heat-stable, 240-kDa, tetrameric protein. It is dissociated into its 60-kDa subunits by high concentrations of Ca2+ (0.1-1 mM), but not by lower concentrations in the physiological range. Inhibition of the 150-kDa proteinase of rabbit liver [Melloni, E., Pontremoli, S., Salamino, F., Sparatore, B., Michetti, M. and Horecker, B.L. (1984) Arch. Biochem. Biophys. 232, 505-512] requires the monomeric form of the inhibitor, and occurs only at the high concentrations of Ca2+ which also cause dissociation of the dimeric 150-kDa proteinase into its 80-kDa subunits. The molecular weight of the inactive proteinase-inhibitor complex was estimated by the equilibrium gel penetration method to be 140 kDa, suggesting that it contains one subunit of proteinase and one of inhibitor. The mechanism of interaction of the inhibitor with the 200-kDa proteinase at high concentrations of Ca2+ is identical to that observed for the 150-kDa proteinase, namely dissociation of both proteinase and inhibitor into subunits and formation of an inactive 160-kDa proteinase-inhibitor complex. However, unlike the 150-kDa proteinase, which does not interact with the inhibitor at low Ca2+ concentrations, the 200-kDa proteinase is also inhibited at low concentrations of Ca2+. Under these conditions, the high-molecular-weight complex (greater than 400 kDa) formed between the tetrameric inhibitor and the dimeric proteinase prevents conversion of the 200-kDa proenzyme to the active, low-Ca2+-requiring form.

Animals↗
PubMed1984

Characterization of the single peptide generated from the amino-terminus end of alpha- and beta-hemoglobin chains by the Ca2+-dependent neutral proteinase.

Human erythrocyte Ca2+-dependent neutral proteinase catalyzes a limited proteolysis of isolated globin chains. The rate of hydrolysis is very rapid using heme-deprived alpha- or beta-globin chains and is reduced to one-fifth with their corresponding native forms. In both cases, the proteinase specifically cleaves a single peptide bond, this resulting in the removal from the amino-terminus end of an octapeptide in beta-globin and of an undecapeptide in alpha-globin. Both peptides have been isolated, their amino acid composition has been characterized and the susceptible site of cleavage has been identified. Hemoglobin variants show a different rate of digestion as compared to that of normal chains. The alpha-Hasharon [alpha 47(CE5) Asp----His] undergoes rapid digestion, while the beta-G San Josè chain [beta 7(A4) Glu----Gly], which carries the mutation near the site of cleavage, reveals a high degree of resistance to proteolytic degradation by the neutral proteinase.

Amino Acid Sequence↗
PubMed1984

Interaction of rabbit liver cathepsin M and fructose 1,6-bisphosphatase converting enzyme with their endogenous inhibitors.

The stoichiometry of complex formation between two lysosomal proteinases from rabbit liver, cathepsin M and fructose 1,6-bisphosphatase converting enzyme (CE), and their respective endogenous inhibitors was studied by the equilibrium gel penetration method. In each case the molecular weight of the complex was found to be the sum of the molecular weights of the proteinase and its inhibitor, indicating the formation of 1:1 complexes. From the reappearance of proteinase activity on dilution, it is concluded that complex formation is reversible. Localization of the proteinase activities on the outer surface of the lysosomes was confirmed in these experiments by the inhibition of this proteinase activity on addition of inhibitors to intact lysosomes. The digestion by subtilisin of rabbit liver aldolase and rabbit liver fructose 1,6-bisphosphatase, the endogenous substrates for the lysosomal proteinases, was unaffected by the inhibitors.

Animals↗
PubMed1984

A comparison of efficacy of photoradiation therapy and other conventional treatment modalities on experimental MS-2 sarcoma.

The therapeutic efficacy of photoradiation therapy (PRT) following hematoporphyrin derivative (HpD) administration was compared in the experimental MS-2 tumour model to that of conventional treatment methods for local control of neoplastic diseases. The therapeutic effects of PRT and surgical removal of primary tumour were comparable in these experiments. However, optimal effects were critically dependent on the stage of tumour development. In addition, the therapeutic advantage of PRT over radiotherapy suggest an interesting role of a new approach in tumours resistant to this conventional treatment.

Animals↗
PubMed1984

Cytosolic Ca2+-dependent neutral proteinases from rabbit liver: activation of the proenzymes by Ca2+ and substrate.

Two neutral Ca2+-dependent proteinases, differing in molecular size, have been isolated from rabbit liver. Both are recovered as inactive proenzymes that can be converted to the active forms by high (0.1-1.0 mM) concentrations of Ca2+ in the absence of substrate or, in the presence of a protein substrate, by low (1-5 microM) concentrations of Ca2+. The activated proteinases required only 1-5 microM Ca2+ for maximal activity. Substrates hydrolyzed were denatured globin, globin, casein, and to a lesser extent, several extracellular proteins; no digestion was observed with several intracellular cytosolic enzymes tested. Only those proteins that served as substrates were capable of promoting conversion of the proenzymes to the active low-Ca2+-requiring proteinases.

Animals↗
PubMed1984

A dual role for the Ca2+-requiring proteinase in the degradation of hemoglobin by erythrocyte membrane proteinases.

Binding of hemoglobin chains to erythrocyte membranes is an obligatory step in the conversion of hemoglobin to acid-soluble products by erythrocyte proteinases. This binding requires limited proteolysis of the hemoglobin chains and also modification of the inner surface of the erythrocyte membrane, both of which result from the action of a soluble Ca2+-requiring neutral proteinase. Final digestion of the bound hemoglobin chains in the membrane complex results from the action of intrinsic membrane endopeptidases. Regulation of the activity of the Ca2+-requiring proteinase by the substrate provides a mechanism for the initiation of selective protein turnover.

Calcimycin↗