Biomedical subjects

G Lupidi

Publications and source records attributed to G Lupidi.

At least 37 records · Page 2Linked to original sources

PubMed1994

Heterotropic modulation of the protease-inhibitor-recognition process. Cations effect the binding properties of alpha-chymotrypsin.

The effect of calcium and lanthanide ions (e.g. terbium) on the binding properties of alpha-chymotrypsin has been studied focussing on the modulation exerted by cations on the interaction of the enzyme with the bovine pancreatic trypsin inhibitor (BPTI or Kunitz inhibitor). The results obtained indicate that the cation binding induces conformational transitions, on the enzyme molecule, which destabilize the enzyme-inhibitor complex formation affecting the interaction of the inhibitor with the secondary specificity site of the proteolytic enzyme. This negative heterotropic effect can be observed only with macromolecular inhibitors (or substrates), displaying an extended interacting surface with the enzyme, and it seems linked to the number of positive charges carried by the cations. Thus, owing to the large conformational changes induced by the binding of trivalent cations, the divalent ones (e.g. calcium) appear to be more suitable for a fine regulation of the enzyme activity. The mutual correlation between inhibitors binding to (and calcium release by) the proteolytic enzymes (and vice versa) could assume an important physiological significance linking parameters, such as calcium concentration and the activity levels of proteolytic enzymes, which are both of great importance for the cell life.

Animals↗

PubMed1994

Adenosine deaminase inhibitors: synthesis and structure-activity relationships of 2-hydroxy-3-nonyl derivatives of azoles.

A series of erythro-1-(2-hydroxy-3-nonyl)azole derivatives have been synthesized and evaluated for adenosine deaminase (ADA) inhibitory activity, in order to introduce simplifications in the ADA inhibitor erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA, 1a). The synthesis of most of the reported compounds was achieved by reaction of 2-bromo-3-nonanone with the suitable azole followed by reduction of the carbonyl group to give a diastereoisomeric mixture of N-substituted (2-hydroxy-3-nonyl)azoles. Separation of diastereoisomers was achieved by HPLC or by preparative TLC plates. The results of the enzymatic test indicate that the nitrogen in the 3-position, and secondly, the nitrogen in the 5-position are very important for the interaction of the azole ring with the inhibitory site on the enzyme. In fact, the pyrazole and the 2-substituted 1,2,3-triazole derivatives (10 and 15, respectively) are nearly inactive, whereas the erythro-1-(2- hydroxy-3-nonyl)-1,2,4-triazole (18e) was the most potent ADA inhibitor in the series with Ki = 0.3 microM.

Adenosine Deaminase Inhibitors↗

PubMed1992

Adenosine deaminase from Saccharomyces cerevisiae: kinetics and interaction with transition and ground state inhibitors.

Several adenosine analogs, such as coformycin, 2'-deoxycoformycin and erythro-9-(3-nonyl-p-aminobenzyl)adenine (EHNA), which are strong inhibitors of mammalian adenosine deaminase, are much weaker inhibitors of the Saccharomyces cerevisiae enzyme. The specificity of the yeast enzyme is more restricted than that of mammalian adenosine deaminase, particularly towards the ribose moiety and around position 6 and 1 of the substrate. The sulphydryl group appears to be more masked in the yeast than in the mammalian enzyme. The kinetic effects of pH with adenosine substrate and with the inhibitor purine riboside are reported. The findings on specificity and pH kinetic effects can be interpreted in a model involving proton transfer from the -SH group of the enzyme to the N-1 atom of the substrate.

Adenine↗

PubMed1992

Binding of hirudin to human alpha, beta and gamma-thrombin. A comparative kinetic and thermodynamic study.

Thermodynamic parameters for the binding of hirudin to human alpha, beta and gamma-thrombin have been determined between pH 5.0 and 9.0, and from 10 degrees C to 40 degrees C; kinetic data for the association and dissociation of the proteinase-inhibitor complex were obtained at pH 7.5 and 21 degrees C. These results have been analysed in parallel with the inhibitor-binding properties of human alpha, beta and gamma-thrombin for the bovine basic pancreatic trypsin inhibitor (Kunitz-type inhibitor; BPTI). For the purpose of an homogeneous comparison, values of the apparent association equilibrium constant for BPTI binding to human gamma-thrombin have been determined between pH 5.0 and 9.0, at 21 degrees C. The different binding behaviour of hirudin and BPTI with respect to human alpha, beta and gamma-thrombin has been related to the inferred stereochemistry of the proteinase-inhibitor contact regions. In particular, whereas the beta and gamma-loops play an appreciable role in the stabilization of the enzyme-hirudin complexes, they contribute to impairment of the adduct formation for the proteinase/BPTI system.

Aprotinin↗

PubMed1992

Adenosine deaminase from bovine brain: purification and partial characterization.

Bovine brain adenosine deaminase cytoplasmatic form was purified about 450 fold by salt fractionation, column chromatography on DEAE-cellulose, octyl-sepharose 4B and affinity chromatography on CH-sepharose 4B 9-(p-aminobenzyl)adenine. The purified enzyme was homogeneous on disc gel electrophoresis; the enzyme had a molecular mass of about 65 kDa with an isoelectric point at pH 4.87. The Km values for adenosine and 2'-deoxyadenosine were 4 x 10(-5) and 5.2 x 10(-5) M, respectively. The enzyme showed a great stability to temperature with a half life of 15 hours at 53 degrees C significantly different compared to that known for other mammalian forms of this enzyme. Aza and deaza analogs of adenosine and erythro-9-(2-hydroxy-3-nonyl) adenine were good inhibitors of the bovine brain enzyme with little difference with respect to those reported for the adenosine deaminases purified from other sources. Kinetic constants for the association and dissociation of coformycin and 2'-deoxycoformycin with the bovine brain adenosine deaminase are reported.

Adenosine↗

PubMed1991

Adenosine deaminase inhibitors: synthesis and structure-activity relationships of imidazole analogues of erythro-9-(2-hydroxy-3-nonyl)adenine.

A series of erythro-1-(2-hydroxy-3-nonyl)imidazole derivatives have been synthesized and evaluated for adenosine deaminase (ADA) inhibitory activity, in order to introduce simplifications in the ADA inhibitors erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA, 1a) and 3-deaza-EHNA (1c). Opening the pyrimidine or pyridine ring of EHNA or 3-deaza-EHNA respectively led to compounds which are still ADA inhibitors. The most potent compound was erythro-1-(2-hydroxy-3-nonyl)imidazole-4-carboxamide (5, Ki = 3.53 x 10(-8) M), which provided potential donor and acceptor sites for hydrogen bonding. Lack of one of this sites could account for the order of potency of all compounds examined in this series. Opening the same ring in adenosine and in 3-deazaadenosine led to fully inactive compounds. These results support the hypothesis of the existence, at or near the enzyme active site, of a hydrophobic region able to bind the erythro-nonyl moiety.

Adenine↗

PubMed1991

Purine and 1-deazapurine ribonucleosides and deoxyribonucleosides: synthesis and biological activity.

A series of 6-(hydroxylamino)purine and -1-deazapurine nucleosides were synthesized and tested for their antitumor and adenosine deaminase inhibitory activity. All the examined molecules displayed an in vitro activity comparable to that of the reference compounds 6-(hydroxylamino)-9-beta-D-ribofuranosylpurine (HAPR) and ara-A, their ID50 ranging from 0.9 microM to approximately 100 microM. The 6-hydroxylamino derivatives of 1-deazapurine 9, 12, and 17 and also the blocked compound 13 are inhibitors of ADA whereas the purine derivatives 4 and 6 and the nitro compounds 11 and 16 are resistant to the enzyme. 7-(Hydroxylamino)-3-(2-deoxy-beta-D-erythro-pentofuranosyl)-3H-imi dazo[4,5- b]pyridine, the less cytotoxic but the most active ADA inhibitor in the series (Ki = 2.7 x 10(-7)), greatly potentiates the antitumor activity of ara-A in vitro.

Adenosine Deaminase Inhibitors↗

PubMed1991

Red blood cells as carriers for delivering of proteins.

The potential use of red blood cells as a carrier system for transport and delivery of pharmacological substances is well documented. Various methods have been attempted for encapsulation of drugs; in this review we evaluate critically all the procedures illustrating their advantages and disadvantages. Moreover, we present kinetic studies of protein encapsulation by moderate hypotonic dialysis, which allows entrapment of molecules with MW less than 50,000 Da with negligible stress of the erythrocyte membrane. Furthermore data reveal that the resealing procedure commonly used is insufficient to completely seal pores of loaded erythrocytes, allowing entrapped proteins with MW less than 12-14,000 Da to escape. However, only 20-30% of the entrapped material is released, depending on the final cytocrit, while the remaining is associated to the inner membrane or to cytosolic components. Although the method of hypotonic dialysis is known to be the one that minimally affects the biophysical and immunological properties of the red blood cell membrane, the interaction of encapsulated material with cell costituents would need to be further assessed when considering red cells as macromolecular carriers.

Cell Membrane Permeability↗

PubMed1990

Encapsulation of proteins into human erythrocytes: a kinetic investigation.

Moderate osmotic shocks of human erythrocytes by hypotonic dialysis (0.06 mosmol/kg) induce cell swelling and formation of pores, without causing apparent lysis. Using 125I-labeled macromolecules of different molecular weight and net charge, we followed the kinetics and efficiency of their encapsulation into erythrocytes. After a 20-30 min period of cell dialysis, macromolecules of up to 50 kDa begin diffusing into the swollen cells by a process which can be described by a first-order two-compartment kinetics. Adsorption to the external cell surface was insignificant, while adsorption to the inner membrane surface was substantial (15-20%) only for positively charged proteins, at physiological pH. After resealing, pores of a 12-14 kDa cut-off might remain open allowing some release of entrapped material (20-30%), depending on the final cytocrit, while the remaining might be associated with inner membrane or cytosolic components. Although the method of hypotonic dialysis is known to affect minimally the biophysical and immunological properties of red blood cell membranes, the interaction of encapsulated material with cell constituents would need to be further assessed when considering red cells as macromolecular carriers.

Cell Membrane Permeability↗

PubMed1990

Precocious puberty and neurofibromatosis of von Recklinghausen. A clinical report.

A case of a 9-year-old boy with neurofibromatosis of von Recklinghausen and precocious puberty is reported. The patient was referred to us because of an unexplained onset of precocious puberty. Clinical manifestations of neurofibromatosis included multiple café-au-lait spots, skeletal anomalies, progressive impairment of vision and precocious sexual development. CT scan and NMR demonstrated the presence of optic gliomas. The correlation between the lesions of retino-hypothalamic projection and production of the neuroendocrinology mechanism of sexual changes is discussed.

Brain↗

PubMed1988

Adenosine deaminase inhibitors. Synthesis and biological activity of deaza analogues of erythro-9-(2-hydroxy-3-nonyl)adenine.

Two new deaza analogues of erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA, 1), 7-deaza-EHNA (6) and 1,3-dideaza-EHNA (11), were synthesized and evaluated for adenosine deaminase (ADA) inhibitory activity and compared with EHNA, 1-deaza-EHNA (2), and 3-deaza-EHNA (3). Substitution of a methine group for a nitrogen atom in the 7-position of the purine moiety of EHNA produces a dramatic drop in the inhibitory activity (Ki = 4 X 10(-4) M) whereas compounds 2 and 3 are still good inhibitors (Ki = 1.2 X 10(-7) M and 6.3 X 10(-9) M respectively). EHNA and its deaza analogues so far synthesized were also tested in vitro for their antiviral and antitumor activity in a range of cellular systems. EHNA and 1-deaza-EHNA are equiactive as inhibitors of human respiratory syncytial virus (HRSV) replication (MIC = 6.25 micrograms/mL) while the other compounds are inactive. On the other hand, all the examined compounds displayed an antitumor activity comparable to that of the reference compound 1-beta-D-arabinofuranosyladenine (ara-A), 7-deaza-EHNA being the most active of all. The results obtained showed that there is no correlation between adenosine deaminase inhibition and antiviral or antitumor activity in this series of compounds. 3-Deaza-EHNA, the most active inhibitor of ADA among the EHNA deaza analogues, greatly potentiates the antitumor activity of ara-A in vitro. In vivo activity was observed only when the two compounds were used in combination.

Adenine↗

PubMed1988

[Bone choristoma of the bilateral choroid and asymmetric microphthalmia].

The authors report a case of associated bilateral asymmetrical microphthalmia and osseous choristoma of the choroid in a seventeen year old young woman. This association, to the author's knowledge, has not been previously reported in the literature. The bone choristoma was present in the eye's posterior poles and the clinical features were studied by electroretinography, fluorescein angiography, A-B scan ultrasonography, computerized axial tomography and nuclear magnetic resonance. The authors hypothesize that a choroid developmental tumor was produced by exposure to the rubella virus during embryonic life.

Adolescent↗

PubMed1987

Associated retinitis pigmentosa and fundus flavimaculatus.

A family is described with 2 members, father and son, affected by associated retinitis pigmentosa and fundus flavimaculatus, whereas 1 other member had a combination of retinitis pigmentosa and unilateral central areolar atrophy, 1 member a fundus flavimaculatus with electroretinographic findings indicative of a subclinical form of retinitis pigmentosa and the last one with electroretinographic findings indicative of a subclinical form of retinitis pigmentosa.

Adult↗

PubMed1987

Adenosine deaminase from Saccharomyces cerevisiae: purification and characterization.

Adenosine deaminase from Saccharomyces Cerevisiae was purified about 1600 fold by salt fractionation, ion exchange and affinity chromatography. Some physico-chemical properties have been determined: the molecular weight of the enzyme by gel filtration is 85,000 daltons; one -SH is readily titrated by paramercuribenzoate per 78,000 mol. weight; optimum pH is 7; Km for adenosine is 40.7 microM; 2'-deoxyadenosine is not a substrate. Deazaadenosine analogues are good inhibitors, while erythro-9-(2-hydroxy-3-nonyl) adenine binds with low affinity. These properties are compared with those of other adenosine deaminases.

Adenosine Deaminase↗

PubMed1986

[Chorioretinal changes in the course of sympathetic ophthalmia].

A case of sympathetic ophthalmitis is reported. A bull's eye chorioretinopathy was observed with electroretinographic changes (augmentation of latencies and disappearance of oscillatory potentials) which regressed in a short time. The authors believe that the retinal changes could be secondary to an autoimmunological reaction, responsible for the sympathetic ophthalmitis.

Adolescent↗

PubMed1985

Recurring bilateral hypopyon in chronic myeloid leukemia in blastic transformation. A case report.

There have been many reports in the literature on keratohypopyon in acute leukemia. We report a case of a 40-year-old-man with chronic myeloid leukemia who developed bilateral, recurring kerato-hypopyon, the first manifestation of which appeared during intrathecal chemotherapeutic treatment just after an episode of leukemic meningiosis. There was no involvement of the CNS at the time of the relapse of kerato-hypopyon.

Adult↗

PubMed1985

Inhibition of adenosine deaminase from several sources by deaza derivatives of adenosine and EHNA.

Deaza analogues of adenosine and EHNA were tested as inhibitors of the enzyme adenosine deaminase (ADA) obtained from several sources including human erythrocytes, calf intestine, Saccaromices cerevisiae, Escherichia coli and Takadiastase. Ki values of the inhibitors suggest differences among the enzymes both at purine and erythro-nonyl binding site. Among the ribofuranosyl derivatives, 1-deazaadenosine is the best inhibitor, its Ki ranging between 3.5 x 10(-7) and 4 x 10(-5) M for ADA from erythrocytes and Takadiastase respectively. Only ADA from erythrocytes and calf intestine bind EHNA and some of deazaEHNA analogues; 3-deazaEHNA behaves very similarly to EHNA both in affinity and slow binding mechanism, whereas 1-deazaEHNA, though less potent, is a good inhibitor.

Adenine↗

PubMed1984

Adenosine deaminase inhibitors. Synthesis of deaza analogues of erythro-9-(2-hydroxy-3-nonyl)adenine.

Structural analogues of erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA), in which the adenine moiety of the molecule was modified, were prepared in order to investigate the structural requirement of EHNA as an inhibitor of adenosine deaminase (ADA). Thus, 1- and 3-deaza-EHNA and their 6-deamino analogues were synthesized and evaluated as inhibitors of ADA from calf intestine. Inhibition studies indicated that isosteric substitution of pyrimidine nitrogens by carbons could be tolerated at the enzymatic binding site. In fact, 3-deaza-EHNA was found to have an inhibitory activity comparable to EHNA itself, and 1-deaza-EHNA, though less potent, is a good inhibitor. The 6-amino group gives an important contribution to the enzymatic binding if the N1 nitrogen is also present, conferring on the compound the characteristic of a semitight inhibitor.

Adenine↗